Industrial and medical nuclear accidents environmental, ecological, health and socio-economic consequences 9781119629511, 1119629519, 9781119629542, 1119629543

Citation preview

Industrial and Medical Nuclear Accidents

Radioactive Risk Set coordinated by Jean-Claude Amiard

Volume 2

Industrial and Medical Nuclear Accidents Environmental, Ecological, Health and Socio-economic Consequences

Jean-Claude Amiard

First published 2019 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address: ISTE Ltd 27-37 St George’s Road London SW19 4EU UK

John Wiley & Sons, Inc. 111 River Street Hoboken, NJ 07030 USA

www.iste.co.uk

www.wiley.com

© ISTE Ltd 2019 The rights of Jean-Claude Amiard to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. Library of Congress Control Number: 2019933513 British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN 978-1-78630-334-9

Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xv

List of Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xvii

Chapter 1. Classification of Civil, Industrial and Medical Nuclear Accidents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1.1. Nuclear accident or radiological accident? . . . . . . . . . 1.2. Classification of nuclear accidents. Incident or accident?. 1.2.1. Application of the INES in France . . . . . . . . . . . . 1.2.2. Application of the INES at the international level . . . 1.2.3. Other classifications of nuclear accidents . . . . . . . . 1.2.4. The NAMS classification . . . . . . . . . . . . . . . . . 1.3. Classification of radiological accidents . . . . . . . . . . . 1.4. The typology of accidents . . . . . . . . . . . . . . . . . . . 1.4.1. Criticality accidents . . . . . . . . . . . . . . . . . . . . 1.4.2. Accidents in nuclear power reactors . . . . . . . . . . . 1.4.3. Losses of radioactive sources . . . . . . . . . . . . . . . 1.4.4. Radiotherapy accidents . . . . . . . . . . . . . . . . . . 1.4.5. Terrorist attacks . . . . . . . . . . . . . . . . . . . . . . . 1.5. What are the main nuclear accidents? . . . . . . . . . . . . 1.6. Information on nuclear energy. . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

2 3 5 6 6 6 7 9 10 11 11 12 12 12 17

Chapter 2. Accidents Related to Nuclear Power Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19

2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Accidents in the nuclear fuel cycle . . . . . . . . . . . . . . . . . . . . . .

19 19

vi

Industrial and Medical Nuclear Accidents

2.2.1. Uranium mines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2. Milling, conversion, enrichment and fuel manufacturing plants 2.2.3. Nuclear reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4. Spent fuel reprocessing plants . . . . . . . . . . . . . . . . . . . . 2.3. Accidents in laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1. Chalk River laboratories . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2. French study centers . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Other accidents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1. Accidents in civil engineering . . . . . . . . . . . . . . . . . . . . 2.4.2. Accidents in nuclear propulsion . . . . . . . . . . . . . . . . . . . 2.5. Waste management incidents . . . . . . . . . . . . . . . . . . . . . . . 2.6. Incidents in the transport of radioactive packages . . . . . . . . . . . 2.7. Environmental consequences . . . . . . . . . . . . . . . . . . . . . . . 2.7.1. Uranium mines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2. Tokai-Mura . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.3. Saint-Laurent-des-Eaux . . . . . . . . . . . . . . . . . . . . . . . . 2.7.4. Three Mile Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.5. Church Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.6. La Hague . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.7. Chalk River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.8. Simi Valley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8. Health consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.1. Uranium miners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.2. Workers in the nuclear industry . . . . . . . . . . . . . . . . . . . 2.8.3. Simi Valley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.4. Tokai-Mura . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.5. Lucens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.6. Three Mile Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.7. Church Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.8. La Hague . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.9. Chalk River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.10. Ruthenium 106 releases in Russia in September 2017 . . . . . 2.9. The cost of accidents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20 22 22 29 33 33 34 35 35 36 36 37 38 38 39 39 40 41 41 41 42 42 42 44 47 48 49 49 50 50 51 51 52 54

Chapter 3. The Extremely Serious Nuclear Accident at Chernobyl .

57

3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. The facts . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1. The Chernobyl site and the nuclear power plant . 3.2.2. The accident . . . . . . . . . . . . . . . . . . . . . . 3.2.3. The core and the sarcophage . . . . . . . . . . . . 3.2.4. Atmospheric emissions . . . . . . . . . . . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . .

. . . . . .

57 58 58 58 59 59

Contents

3.2.5. The dispersion of radionuclides . . . . . . . . . . . . . . . . . 3.2.6. Radioactive fallout . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.7. Accident management . . . . . . . . . . . . . . . . . . . . . . . 3.2.8. Countermeasures carried out at Chernobyl . . . . . . . . . . . 3.3. Spatial and environmental consequences . . . . . . . . . . . . . . 3.3.1. Atmospheric contamination . . . . . . . . . . . . . . . . . . . . 3.3.2. Soil contamination . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3. Surface water contamination . . . . . . . . . . . . . . . . . . . 3.3.4. Groundwater contamination . . . . . . . . . . . . . . . . . . . 3.3.5. Forest contamination . . . . . . . . . . . . . . . . . . . . . . . . 3.3.6. Contamination of the aquatic environment . . . . . . . . . . . 3.3.7. Contamination of the marine environment . . . . . . . . . . . 3.4. Ecological consequences of the Chernobyl accident . . . . . . . . 3.4.1. The three phases . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2. Effects at molecular level . . . . . . . . . . . . . . . . . . . . . 3.4.3. Genetic effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4. Morphological and physiological effects on individuals . . . 3.4.5. Effects on individual reproduction (sex, sex-ratio, fertility) . 3.4.6. Effects on populations (age, abundance, longevity) . . . . . . 3.4.7. Effects on ecosystem structure and functioning . . . . . . . . 3.4.8. Partial conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5. Health consequences . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1. Implications for large organisms . . . . . . . . . . . . . . . . . 3.5.2. The main contributions to exposure . . . . . . . . . . . . . . . 3.5.3. Population exposure . . . . . . . . . . . . . . . . . . . . . . . . 3.5.4. Cancer pathologies . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.5. Non-cancerous pathologies . . . . . . . . . . . . . . . . . . . . 3.5.6. Mortalities resulting from the Chernobyl accident . . . . . . 3.6. Social consequences. . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1. Psychological disorders among liquidators . . . . . . . . . . . 3.6.2. Psychological disorders in evacuated populations. . . . . . . 3.7. Consequences in Europe and France . . . . . . . . . . . . . . . . . 3.7.1. The impact of Chernobyl in Europe . . . . . . . . . . . . . . . 3.7.2. The impact of Chernobyl in France . . . . . . . . . . . . . . . 3.7.3. Cases of thyroid cancer in France . . . . . . . . . . . . . . . . 3.8. Economic consequences . . . . . . . . . . . . . . . . . . . . . . . . 3.9. Long-term management of the Chernobyl accident . . . . . . . . 3.10. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

60 61 64 67 68 68 69 69 70 71 74 76 76 76 78 80 86 88 89 92 93 94 94 97 97 100 106 112 115 115 116 119 119 123 128 130 131 132

Chapter 4. Fukushima’s Serious Nuclear Accidents . . . . . . . . . . .

135

4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. The course of the Fukushima accidents . . . . . . . . . . . . . . . . . . .

135 136

viii

Industrial and Medical Nuclear Accidents

4.2.1. The facts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2. Atmospheric emissions . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3. Marine discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Actions taken by the Japanese authorities . . . . . . . . . . . . . . . . . . 4.3.1. Evacuation of the populations . . . . . . . . . . . . . . . . . . . . . . 4.3.2. Distribution of iodine tablets to children . . . . . . . . . . . . . . . . 4.3.3. Exposure limits for nuclear workers and the public . . . . . . . . . . 4.3.4. Regulatory values and food monitoring . . . . . . . . . . . . . . . . . 4.3.5. Decontamination tests of crop production . . . . . . . . . . . . . . . 4.3.6. Decontamination and waste management. . . . . . . . . . . . . . . . 4.3.7. The restructuring of the Japanese nuclear industry . . . . . . . . . . 4.3.8. Compensation of victims . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Environmental contamination . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1. Contamination of the atmosphere . . . . . . . . . . . . . . . . . . . . 4.4.2. Contamination of the terrestrial environment . . . . . . . . . . . . . 4.4.3. Forest contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.4. Bird contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.5. Contamination of freshwater environments . . . . . . . . . . . . . . 4.4.6. Contamination of the marine environment . . . . . . . . . . . . . . . 4.4.7. Contamination of agricultural products and foodstuffs . . . . . . . . 4.5. Exposure and effects on flora and fauna . . . . . . . . . . . . . . . . . . . 4.5.1. Exposure and effects on forests. . . . . . . . . . . . . . . . . . . . . . 4.5.2. Exposure and effects on birds. . . . . . . . . . . . . . . . . . . . . . . 4.5.3. Exposure and effects on other terrestrial organisms. . . . . . . . . . 4.5.4. Exposure and effects on freshwater organisms . . . . . . . . . . . . 4.5.5. Exposure and effects on marine organisms . . . . . . . . . . . . . . . 4.6. Health consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1. Consequences for the local human population . . . . . . . . . . . . . 4.6.2. The consequences for nuclear workers . . . . . . . . . . . . . . . . . 4.6.3. Consequences on the world population (excluding Japan) . . . . . . 4.7. Economic consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8. The situation in 2016 and 2017 . . . . . . . . . . . . . . . . . . . . . . . . 4.8.1. The current situation of the Fukushima nuclear facilities . . . . . . 4.8.2. The time course of freshwater contamination . . . . . . . . . . . . . 4.8.3. The first returns and return intentions of the evacuated populations following the accident at the Fukushima Daiichi power plant . . . . . . . 4.9. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

136 139 140 141 141 144 144 145 147 147 149 149 150 150 152 155 158 158 159 165 170 171 172 174 175 175 177 177 184 187 188 189 189 190

Chapter 5. Industrial and Medical Radiology Accidents . . . . . . . .

195

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2. Industrial and medical applications . . . . . . . . . . . . . . . . . . . . . .

195 196

192 192

Contents

5.2.1. Non-destructive industrial testing . . . . . . . . . . . . . . . . . . 5.2.2. Industrial synthesis reactions and mechanical and chemical transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3. Environmental remediation and waste treatment by irradiation . 5.2.4. Agri-food applications . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.5. Medical applications . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3. Radiological criticality accidents . . . . . . . . . . . . . . . . . . . . . 5.4. Radiological accidents related to the loss of radioactive sources . . 5.4.1. Loss of radioactive sources and public exposure . . . . . . . . . 5.4.2. The main causes of loss of radioactive sources . . . . . . . . . . 5.4.3. Nuclear accidents related to the loss of radioactive sources . . . 5.5. Radiological accidents with radioactive sources and industrial accelerators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6. Medical radiological accidents . . . . . . . . . . . . . . . . . . . . . . 5.6.1. Historical accidents involving the use of radiotherapy . . . . . . 5.6.2. Radiological accidents with medicinal radioactive sources . . . 5.6.3. Brachytherapy and brachytherapy accidents . . . . . . . . . . . . 5.6.4. Interventional radiology by fluoroscopy . . . . . . . . . . . . . . 5.6.5. Secondary cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ix

. .

196

. . . . . . . . .

. . . . . . . . .

197 198 199 200 202 203 205 211 212

. . . . . . . .

. . . . . . . .

215 219 219 220 225 226 227 227

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

229

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

239

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

249

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

309

Preface

The danger posed by radioactivity came to light a few days after the discovery of this phenomenon by the very person who discovered “uraniferous salts”, Professor Henri Becquerel himself, when a red mark and then a burn appeared on his skin within the space of a few days when he left a tube of radium in his jacket pocket. This did not prevent radioactivity from becoming a great attraction to the public, since it had amazing virtues. A person apparently just had to drink radioactive waters, consume food and use medicines containing radium, dress in wool containing radium, use radioactive cosmetics and have watches and clocks whose needles were luminous due to this radioactive element. This enthusiasm continued into the 1930s [AMI 13a]. The dangerous nature of radioactivity was confirmed by research scientists, such as Marie Curie, by uranium miners subjected to high levels of exposure to radon and its decay products, and by radiologists who irradiated themselves intensely at the same time as their patients, accumulating their exposure over time. While the danger of radioactivity is well known today, radioactive risk is nevertheless tricky to estimate because it depends on numerous different parameters. Radiosensitivity is mainly a function of the intensity of exposure (dose), and also of the distribution of this dose over time (absorbed dose per unit of time). The effects on organic molecules of various ionizing rays (alpha, beta, gamma, neutron emitters) are very different. In addition, the

xii

Industrial and Medical Nuclear Accidents

radioactive risk depends on which radionuclide is involved, or rather, on the mixture of radionuclides affecting the organism. In addition, some cells are more radiosensitive than others. This is true for both plant and animal species, in addition to sensitivity differences between individuals. In a single species, in most cases, the first stages of life (embryo, fetus, child) are much more radiosensitive than adults and old people [AMI 16]. Nuclear accidents are covered in a series of three volumes. The first volume is dedicated to definitions and classifications of nuclear accidents of military origin. It then tackles the consequences of the actions taken in warfare at Hiroshima and Nagasaki, then atmospheric testing of nuclear bombs and accidents that occurred during underground testing. The use of military force to act as a nuclear deterrent has caused various accidents, in particular among submarines and bomber aircraft. This first volume also considers the various accidents that have occurred during the manufacture of nuclear weapons, in particular those of criticality. This book finishes with estimations of the effects of a possible nuclear war. This book, the second volume in the series, is dedicated to accidents related to civilian use of nuclear technology, from the points of view of civil engineering, the production of electricity and tools for human health (in particular, detection and radiotherapy). Electricity production depends on several stages. Yet, accidents can occur at various stages of the fuel cycle, from mining to reprocessing of the exhausted fuel. Specific chapters are devoted to accidents that occurred in the Chernobyl and Fukushima nuclear reactors. A later chapter evokes the possible consequences of acts of terrorism. For each of the first two volumes, the consequences of nuclear accidents are detailed for the terrestrial, freshwater and marine environments and their flora and fauna, human health, as well as sociological, psychological and economic consequences. The third volume will expand on the future management of nuclear accidents, in particular looking at activities involving decontamination, feedback, post-accident management, risk, perception, Industrial Intervention Plans (PPIs in France) and the need to take potential accidents into account during project design.

Preface

xiii

The book also includes a list of acronyms. Nuclear accidents and disasters have given rise to an abundant literature. Why produce more books on the subject? Many books are openly pro- or anti-nuclear. The intention of the volumes in this series is to provide the reader with a clear, transparent and objective summary of the relevant scientific literature. Jean-Claude AMIARD March 2019

Acknowledgments

Claude Amiard-Triquet (Honorary Research Director, CNRS, France) has taken on the onerous task of re-reading, annotating and casting a critical eye over the French version of this book, and Professor Philip Rainbow (former Keeper of Zoology, Natural History Museum, London, United Kingdom) has done the same for the English version. I warmly thank them both for their time and efforts. A certain number of colleagues have made documents available to me and I am grateful for this. They are in particular Christelle Adam-Guillermin from the IRSN, Pierre-Marie Badot at the Université de Besançon, Mariette Gerber from INSERM in Montpellier, Anders Pape Møller from the CNRS at the Université de Paris Sud (Orsay) and Timothy Mousseau at the University of South Carolina and Jean-Claude Zerbib (radiation protection expert). I hope I have not forgotten anyone. I would also like to thank the members of the GNRC (Nord-Cotentin Radioecology Group), a multi-faceted group, for the remarkable work that they have accomplished, working together in complete harmony.

List of Acronyms

ACRO:

Association pour le Contrôle de la Radioactivité dans l’Ouest (French Association for the Management of Radioactivity in Western France)

AF:

Accumulation Factor

ALPS:

Advanced Liquid Processing System

ARS:

Acute Radiation Syndrome

ASN:

Autorité de Sûreté Nucléaire (French Nuclear Safety Authority)

ASTRAL:

Assistance technique en radioprotection post-accidentel (French Technical Assistance for Post-accident Radiation Protection)

ATSDR:

Agency for Toxic Substances and Disease Registry

BMI:

Body Mass Index

BNFL:

British Nuclear Fuels

BOC:

Bialystok Oncology Center

CEA:

Commissariat à l’Énergie Atomique (French Atomic Energy Commission)

xviii

Industrial and Medical Nuclear Accidents

CI:

Confidence Interval

CLL:

Chronic Lymphocytic Leukemia

CNEVA:

Centre National d’Études Vétérinaires et Alimentaires (National Center for Veterinary and Food Studies)

CR:

Concentration Ratio

CRIIRAD:

Commission de Recherche et d’Information Indépendantes sur la RADioactivité (Commission for Independent Research and Information about RADiation)

CRN:

Commission de Régulation Nucléaire

CSM:

Centre de Stockage des déchets à vie longue et haute activité de la Manche

CTCAE:

Common Terminology Criteria for Adverse Events

EBRD:

European Bank for Reconstruction and Development

EDF:

Electricité de France (Electricity of France)

EEZ:

Exclusive Economic Zone

EHL:

Ecological Half-Life

EIS:

Événements Intéressants la Sûreté (Events of Interest for Safety)

EMEX:

Estonian Metal Export Company

ERR.Gy−1:

Excess Relative Risk per Gray exposure

FA:

Fluctuating Asymmetry

FEPC:

Federation of Japanese Electricians

FNPP:

Fukushima Daiichi Nuclear Power Plant

List of Acronyms

xix

GSH:

Glutathione

HPIP:

Human Performance Investigation Process

IAEA:

International Atomic Energy Agency

ICPR:

International Commission on Radiological Protection

IGAS:

General Inspectorate of Social Affairs

IICPH:

International Institute of Concern for Public Health

INES:

International Nuclear Event Scale

INRS:

Institut National de Recherche et de Sécurité (French National Institute of Research and Safety)

ION:

Instituto Oncológico Nacional

IPPNW:

International Physicians for the Prevention of Nuclear War

IRS:

Incident Reporting System

IRSN:

Institut de Radioprotection et de Sûreté (French Institute for Radiation Protection and Safety)

ISF:

Interim Storage Facility

ISS:

Incidents Significatifs pour la Sûreté (Safety Significant Incidents)

JCO:

Japan Nuclear Fuels Conversion Company

KMPS:

Kurion Mobile Processing System

LCHA:

Laboratoire Central d'Hygiène Alimentaire

LDIR:

Low-Dose Ionizing Radiation

LILW:

Low- to Intermediate-Level Waste

xx

Industrial and Medical Nuclear Accidents

LNT:

Linear No Threshold

LWPE:

Leningrad Regional Waste Processing Enterprise

MAC:

Maximum Allowable Concentration

MAS:

Maximum Acceptable Standard

MEL:

Laboratoire de l’environnement marin (French Marine Environment Laboratory)

MHA:

Medium- and High-Level Waste

MoE:

Ministry of the Environment

MT:

Metallothionein

NAMS:

Nuclear Accident Magnitude Scale

NEA:

Nuclear Energy Agency

NHL:

Non-Hodgkin’s Lymphoma

NISA:

Nuclear and Industrial Safety Agency

NMRD:

Non-Malignant Respiratory Disease

NPP:

Nuclear Power Plant

NRC:

Nuclear Regulatory Commission

NRU:

National Research Universal reactor

NSSA:

Nuclear Safety and Security Agency

OECD:

Organization for Economic Co-operation and Development

OFPP:

Office Fédéral de la Protection de la Population (French Federal Office for the Protection of the Population)

List of Acronyms

xxi

OR:

Odds Ratio

PTSD:

Post-Traumatic Stress Disorder

PUNE:

Peaceful Underground Nuclear Explosion

RDP:

Radon Degradation Product

RER:

Relative Excess Risk

SCPRI:

Service Central de Protection contre les Rayonnements Ionisants (Central Protection Service Against Ionizing Radiation)

SdP:

Pumping Stations

SFRO:

Société Française de Radiothérapie Oncologique (French Society of Oncological Radiotherapy)

SFRP:

Société Française de Radioprotection Society)

SIR:

Standardized Incidence Ratio

SME:

Small and Medium-sized Enterprise

SOL:

Safety through Organizational Learning

SRE:

Sodium Reactor Experiment

SS:

Suspended Solids

SSFL:

Santa Susana Field Laboratory

TEPCO:

Tokyo Electric Power Company

TF:

Transfer Factor

THORP:

Thermal Oxide Reprocessing Plant

Radioprotection

(French

xxii

Industrial and Medical Nuclear Accidents

TMI:

Three Mile Island

TPS:

Treatment Planning System

TSH:

Thyroid-Stimulating Hormone

UAM:

Unit-Alpha-Months

UNSCEAR:

United Nations Scientific Committee on the Effects of Atomic Radiation

WANO:

World Association of Nuclear Operators

1 Classification of Civil, Industrial and Medical Nuclear Accidents

In the first volume of this series [AMI 19], we reviewed the definitions of nuclear incidents and accidents, and provided the American classification for military accidents. The generally accepted definition of an accident is “a fortuitous event that has more or less harmful effects on people or things”. The term accident frequently implies apparent medical damage, morbidity or even mortality [NÉN 01, NÉN 06, NÉN 07]. When the accident is very serious, the terms catastrophe (the event that causes serious disruption and death) or calamity (a public misfortune where misfortune affects a region, a group of individuals) are used. On the contrary, the term incident refers to “an occurrence, a secondary event, generally unfortunate, that occurs during an action and can disrupt its normal course”. Nuclear accidents in the civil, industrial and medical fields occur involuntarily following either a major natural event (earthquake, tsunami, etc.) or human error with serious repercussions, or could result from an act of terrorism. The most serious nuclear accidents cause considerable damage to the environment, flora, fauna and humanity. In addition, their socio-economic impacts can be immense.

Industrial and Medical Nuclear Accidents: Environmental, Ecological, Health and Socio-economic Consequences, First Edition. Jean-Claude Amiard. © ISTE Ltd 2019. Published by ISTE Ltd and John Wiley & Sons, Inc.

2

Industrial and Medical Nuclear Accidents

1.1. Nuclear accident or radiological accident? To answer this question, it is necessary to define some essential terms in nuclear physics. An atom, an elementary unit, is made up of a nucleus and electrons that gravitate around it. Each nucleus consists of protons (Z) and neutrons (N), the sum constituting the nucleons (A=Z+N). For the same element, the composition of the nucleus may differ in terms of the number of protons and neutrons, each composition constituting an isotope. Some elements can have many isotopes. The simplest of the elements, hydrogen, consists of a very abundant isotope with a single proton and a single electron. There are two other isotopes: deuterium (nucleus comprising a proton and a neutron) and tritium (nucleus consisting of a proton and two neutrons). The great difference in the constitution of the nucleus explains the exceptional attribution of a particular name. Hydrogen is the most abundant isotope (99.98%), the other two isotopes being very much in the minority. A contrasting example is cesium, where 40 isotopes coexist with a number of nucleons ranging from 112 to 151. For a given element, some isotopes are unstable and therefore radioactive. To regain their atomic stability, they must get rid of an electron, a helium nucleus or a photon. These unstable isotopes are called radionuclides. In hydrogen elements, only the tritium isotope is unstable and radioactive. It recovers its stability by losing an electron and thus transforming into helium. In the case of cesium, only one isotope is stable, cesium 133 (133Cs) containing 78 neutrons. All other isotopes are radionuclides, two of which are important: cesium 134 (134Cs) and cesium 137 (137Cs) because they are fission products of uranium 235 (235U). The return to stability is not always a one-step process. There are often several descendants. For example, there are three main natural families whose leaders are uranium 238 with 14 descendants, uranium 235 and thorium 232 with 11 descendants each. The toxicity of radionuclides is twofold, chemical toxicity resulting from their elementary characteristics and radiotoxicity from their emission of ionizing radiation. With the exception of uranium, which has a high

Classification of Civil, Industrial and Medical Nuclear Accidents

3

chemical toxicity, radiotoxicity is considered, for other radionuclides, to be the most dangerous. As a chemical element, the radionuclide will participate in the usual chemical reactions, disperse into various compartments of the environment and enter living organisms through various pathways (including food). This results in radioactive contamination of the environment and living beings (external and internal contamination). By definition, any event affecting the entire atom will qualify as atomic. When the event takes place at the nucleus level, the event will be nuclear. The distinction between atomic and nuclear events was abandoned in the 1950s because the term atomic had too negative a connotation and only the term nuclear remained for civil activities. An accident involving releases of radionuclides to the environment will therefore be a nuclear accident. When only ionizing radiation reaches the living being, the event qualifies as radiological. This is the case when radioactive contamination remains external and confined. An accident with an intact radioactive source or linear accelerator will therefore be a radiological accident. In the case of a nuclear accident, the International Atomic Energy Agency’s (IAEA) International Nuclear Event Scale (INES) will be used as a calibration to estimate the severity of the accident. In the case of a radiological accident, another scale such as the ASN-SFRO or radiological scale should be used instead. 1.2. Classification of nuclear accidents. Incident or accident? Following the accidents at Three Mile Island in 1979 and Chernobyl in 1986, the IAEA decided to create an INES. This scale was implemented worldwide in 1991. It has eight severity levels rated from 0 to 7. For quantifiable events of a comparable nature, the scale is logarithmic, the change from one level to another corresponding to a factor of 10. Since 1991, the INES has enabled the establishment of a common language for the assessment of an incident or accident in the nuclear sector. The OECD, then the IAEA, drew heavily on a nuclear event severity scale set up by France in 1987 to design the INES. This common international reference makes it easier to understand public opinion. Information on an

4

Industrial and Medical Nuclear Accidents

event is communicated via the IAEA to all countries that have adopted the INES [LEC 04]. The INES is based on several criteria that are taken into account to define the nuclear event’s severity level. The reported events are analyzed according to their consequences at three levels: (1) wider impacts on people or property (worker and/or public health); (2) on-site impacts; and (3) defense-in-depth impacts (presence of several containment barriers). This approach is detailed in Table 1.1. Type

INES Wider impact

Major accident

7

Serious accident

6

Accident 5 (resulting in wider consequences) Accident (not 4 resulting in a significantly wider risk)

Major release: widespread effects on health and the environment Significant release likely to require full implementation of planned countermeasures Limited release likely to require partial application of planned countermeasures Minor release: public exposure within statutory limits

On-site impact

Serious incident

3

Incident

2

Very small release: public exposure represents a fraction of the statutory limits No consequences

Anomaly

1

No consequences

Serious damage to the reactor or radiological barriers Significant damage to the reactor or radiological barriers, or lethal exposure of a worker Serious contamination or acute effects on a worker’s health Significant contamination or overexposure of a worker No consequences

Deviation

0

No consequences

No consequences

Damage to defense-in-depth

Loss of defenses and contamination

Accident narrowly avoided. Loss of defense lines Incident with significant failure of safety provisions Anomaly not included in the authorized modus operandi Insignificant anomaly from a safety point of view

Table 1.1. The severity levels of a nuclear event. The INES

Classification of Civil, Industrial and Medical Nuclear Accidents

5

The transition from incident (levels 1–3) to accident (levels 4–7) is characterized by environmental contamination that can damage public health. Events that occurred before the INES was created were rated retrospectively. In the end, and without being exhaustive, we can note that only two accidents received a rating of 7 (major accident). These are the accidents at Chernobyl (Ukraine) on April 26, 1986 and Fukushima (Japan) on March 11, 2011. One accident was classified as a level 6 accident (serious accident), the Kyshtym disaster in the USSR (Mayak nuclear complex) in 1957. Four events were considered to be level 5 (accident). These were the accident at the Chalk River Laboratories in Canada in 1952, the fire at Windscale (now Sellafield) in the United Kingdom in 1957, the Three Mile Island nuclear accident in the United States in 1979 and the Goiânia nuclear accident in Brazil in 1987 (Table 1.4). This table lists the 10 accidents considered to be the most serious. 1.2.1. Application of the INES in France The INES was adopted in France by the Autorité de Sûreté Nucléaire (ASN) in April 1994. The application of the scale concerned all the basic nuclear installations controlled by the ASN (EDF reactors, Areva plants, CEA laboratories, etc.). The feedback from these industries is based on incidents considered significant, i.e. events that could, in unfavorable circumstances, have combined with others to generate major accidents. In order not to be overwhelmed by the number of events to be recorded and analyzed, the French nuclear manufacturers (EDF, CEA, Orano (previously Areva), etc.) decided to distinguish two groups of events of different severity that are relevant to safety and to apply different methods to them. These two groups are événements intéressants la sûreté (events of interest for safety – EIS) and incidents significatifs pour la sûreté (significant safety incidents – ISS) [LEC 04]. EIS are entered into a national computerized file managed by EDF, called the fichier des événements, “event file”. ISS must be notified to safety organizations and be the subject of a detailed analysis report according to a standard plan. This method should facilitate feedback through broad criteria for recording data in databases.

6

Industrial and Medical Nuclear Accidents

In addition, proactive security methods have been established. This approach to safety has led to technical advances by producing energy more efficiently (fewer cut-offs, shutdowns, reductions of installed capacity) while making financial gains. As in aviation, relevant information is taken into account while ensuring confidentiality and protection for particularly sensitive industrial information [LEC 04]. 1.2.2. Application of the INES at the international level At the international level, three reporting systems are mainly used, namely SOL, IRS and HPIP [LEC 04]. The SOL (Safety through Organizational Learning) system was developed by the Centre for Systems Security Research at the University of Berlin in collaboration with the media outlet TÜV Rheinlandest. It was an approach to event analysis based on the concepts of socio-technical systems and psychological theories of incident genesis (accidents and near accidents). The HPIP (Human Performance Investigation Process) is used by the CRN (Commission de Régulation Nucléaire) to investigate events related to human performance in nuclear power plants. Developed by Paradies et al. [PAR 93], the HPIP structure contains six main human failure modules. The IRS (Incident Reporting System) is used by the IAEA and the NEA (OECD Nuclear Energy Agency), developed by the WANO (World Association of Nuclear Operators). 1.2.3. Other classifications of nuclear accidents The IAEA’s INES classification, while making great progress, is not always satisfactory, and therefore several proposals exist to classify the severity of nuclear accidents. In particular, the three main classification criteria of the INES cannot be applied to radioprotection, i.e. the protection of individuals against ionizing radiation. Similarly, the INES classification does not take sufficient account of the quantities of radionuclides released into the environment. 1.2.4. The NAMS classification Smythe [SMY 11] proposed a new quantitative scale of nuclear accident magnitude (NAMS). To do this, he used the event magnitude approach by

Classification of Civil, Industrial and Medical Nuclear Accidents

7

calculating the magnitude of the accident (M) from wider releases of radionuclides (R). This radioactivity parameter is normalized in iodine 131 equivalents and expressed in TBq. The magnitude is calculated according to the following equation: M = log (20R). Using this NAMS, the distribution between frequency and amplitude has been observed for 33 quantified events over the past 60 years. It follows a reverse power law, as in the case of earthquakes. However, the NAMS shows four exceptional accidents that have values 2–3 orders of magnitude higher than other accidents. These four accidents are, in decreasing order of severity, Chernobyl (NAMS 8.0), Three Mile Island (NAMS 7.9), Fukushima Daiichi (NAMS 7.5) and Kyshtym (NAMS 7.3). According to Smythe [SMY 11], such catastrophic accidents can occur every 12–15 years. 1.3. Classification of radiological accidents Croüail and Lefaure [CRO 03a, CRO 03b] proposed a more radiologically realistic scale for classifying incidents and accidents. This scale makes it possible to take into account radiation protection events affecting patients as part of a radiotherapy procedure. This proposed scale was then discussed at the IAEA. English-speaking countries did not want to use a classification based on the number of people exposed. They only partially gave way on this point by downgrading certain events [ASN 04] by one level. Therefore, since 2007, in France, a specific scale has been created, called the ASN-SFRO scale, which characterizes the severity of radiation protection events. The guide for the application of the new INES for the classification of radiation protection events (excluding patients) relating to radioactive sources and the transport of radioactive materials is currently being developed. Radiotherapy events affecting patients were classified on the ASN-SFRO scale issued by the ASN in July 2008 [ASN 08b, ASN 13]. The criteria for ranking on this scale focus on: (1) the proven consequences of exposure to ionizing radiation; and (2) the potential effects of the events (Table 1.2). Levels 0 and 1 are used to classify events without clinical consequences for the patient. Levels 2 and 3 correspond to events referred to as “incidents”. Levels 4–7 correspond to accidents (Table 1.3). The IRSN [IRS 16a] provides some examples of incidents, such as the level 1 incident where, on October 31, 2008, a practitioner and two

8

Industrial and Medical Nuclear Accidents

manipulators were contaminated with iodine 131 due to inadequate follow-up of cleaning procedures for objects that came into contact with this radioactive element. For level 2 incidents, the IRSN selected three examples. Following an irradiation zone error during radiotherapy performed on December 4, 2008, a patient was re-irradiated in an area after he had already been treated. According to doctors, his condition is now satisfactory. An overexposure of a patient occurred on December 24, 2008 during external radiotherapy during control exposures before a second treatment stage. According to the medical team, the patient’s condition who is receiving special follow-up is currently satisfactory. On June 15, 2007, when a patient was irradiated, the manipulator was still in the treatment room. Based on the effective dose received (approximately 30 mSv), no health effects were expected for this person.

5–7 Accidents

4 Accidents 3 Incidents 2 Incidents

1 Event

O event

Events (unforeseen, unexpected) Death

Causes

Consequences (CTCAE V3.0 grade)

Dose (or volume irradiated) much higher than normal resulting in complications or outcomes not compatible with life Dose or volume irradiated Severe, unexpected or A serious life-threatening much higher than tolerable unpredictable acute or event, complication or late reaction, grade 4 doses or volumes disabling condition An event causing severe Dose or irradiated volume Severe, unexpected or alteration of one or more greater than tolerable doses unpredictable acute or organs or functions or volumes late reaction, grade 3 Dose higher than Moderate, unexpected or An event that causes or is recommended doses or unpredictable acute or likely to cause moderate irradiation of a volume that late effect, grade 2, impairment of an organ or may result in unexpected, minimal or no change in function moderate complications quality of life Event with the dosimetric Dose or volume error: for No symptoms expected consequence but no expected example, dose error or clinical consequence target error during a session that cannot be compensated for over the entire treatment Event without any For example, error in consequences for the patient identifying a patient treated for the same pathology (compensable)

Table 1.2. The ASN-SFRO classification for radiological accidents (adapted from the ASN [ASN 13]. (1) Common Terminology Criteria for Adverse Event, Cancer Therapy Evaluation Program, August 2006, http://ctep.cancer.gov

Classification of Civil, Industrial and Medical Nuclear Accidents

Event

9

Number of individuals and final ranking Minimum ranking

Death or lethal dose received 4

Number of individuals

Final ranking*

> 10

6

>1

5

1

4

Deterministic effect or potential deterministic effect with respect to the 3 dose received

> 10

5

>1

4

1

3

Exposure greater than 1 Sv or 1 Gy

> 100

6

> 10

5

≤ 10

4

> 100

5

4 Exposure greater than 100 mSv 4 Exposure of worker(s) to a dose above the annual regulatory limit or of a 2 member of the public to a dose above 10 mSv Exposure of worker(s) to a dose above the annual regulatory limit or of a member of the public to a dose above 10 mSv

1**

> 10

4

≤ 10

3

> 100

4

> 10

3

≤ 10

2

> 100

3

> 10 ≤ 10

2 1

* The highest ranking should be selected. ** When a dose limit is exceeded as a result of the accumulation of exposure over a certain period of time, the ASN systematically assigns a level 1 classification for lack of a safety culture.

Table 1.3. Procedure for the classification of an event on the basis of exposures or health consequences related to doses received [ASN 08b, IAE 13]

1.4. The typology of accidents Nuclear accidents can be of many different types. Criticality accidents that emit large quantities of neutrons and ionizing radiation are often lethal to workers. Industrial accidents due to fire, lightning, earthquakes, tsunamis

10

Industrial and Medical Nuclear Accidents

and so on can damage any protective measures leading to leaks of radioactive materials. However, radiological protection is rarely broken leading to level 4 accidents. The occurrence of a level 5 accident requires an additional supply of energy. This has already occurred in the case of a core meltdown or could occur during an external attack such as a plane crash or a hollow charge shot (ammunition allowing the armor to be pierced). 1.4.1. Criticality accidents We have seen that criticality accidents (resulting from an unintended chain reaction) were frequent in the military arena between 1945 and 1970 [AMI 19]. This type of accident has also occurred during the manufacture of nuclear fuel for nuclear power reactors, in the latter themselves, and in industrial and medical applications of nuclear technology (linear accelerators, radiotherapy). Accidents can occur in aqueous fissile media, in solid or dry metal media, and in mixed solid/liquid media. On the contrary, no cases have been reported for “powder” media. Most accidents occurred in the United States (Hanford, Idaho Falls, Los Alamos, Oak Ridge and Wood River Junction) and in the former USSR (Obninsk, Electrostal, Mayak, Tomsk and Novosibirsk) [MCL 00] (Figure 1.1). Since 1945, 60 criticality accidents, only six of which occurred after 1978, have occurred worldwide, mainly in research reactors and in laboratories. This means that until the early 1980s, there was more than one accident per year. The last three accidents occurred in Tokai-Mura, Japan (two in 1997 and one in 1999). In a significant number of cases, these accidents resulted in immediate deaths or severe radiation exposure leading to premature death. Criticality accidents resulted in 17 deaths [GAM 07], 19 deaths [IRS 09a] or 20 deaths [MCL 00] depending on the sources. The procedure to be followed in the event of a criticality accident has been detailed by Miele and Lebaron-Jacobs [MIE 05].

Classification of Civil, Industrial and Medical Nuclear Accidents

11

Figure 1.1. Chronology of the main criticality accidents (adapted from [MCL 00]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

1.4.2. Accidents in nuclear power reactors Experimental nuclear reactors or power generators have been the subject of several accidents. The two largest nuclear disasters concern four nuclear power reactors (Chernobyl-4, Fukushima Daiichi-1, 2 and 3). All nuclear facilities were affected by a severe accident of levels 4–7. The economic consequences can be enormous. 1.4.3. Losses of radioactive sources Highly radioactive sources are used for industrial purposes (non-destructive testing, food irradiation, etc.) or medical purposes (radiotherapy, brachytherapy). When these sources are lost, they can be found by the public. Since they are discrete (usually a small plastic cylinder), they can radiate strongly and for a long time, affecting any person in contact with this source, as well as their professional or family entourage. The number of accidents of this type is high, and the number of fatal cases is also relatively high. Among the most serious accidents of this type were those in Mexico City (Mexico) in 1962, Chiba (Japan) in 1971, Algeria in 1978, Brazil in Goiânia in 1987, Istanbul (Turkey) in 1999, Grozny (Russia) in 1999 and Samut Prakan (Thailand) in 2000. Each time several deaths were reported.

12

Industrial and Medical Nuclear Accidents

1.4.4. Radiotherapy accidents Many types of cancers are treated by radiotherapy. The irradiation dose must be carefully calculated to kill all cancer cells. If underexposed, the patient has not been treated adequately and is at risk of dying from cancer. In the event of overexposure, healthy cells are irradiated and the risk of secondary cancer is not negligible. These cases of under- or over-exposure are most often a result of human error, either through the misuse of irradiation equipment (incorrect calculation of the irradiation dose, incorrect adjustment of the irradiation equipment) or through improper transmission of information. 1.4.5. Terrorist attacks The possibilities for terrorists to cause a more or less major nuclear accident are numerous. National and international authorities must be vigilant and develop strategies to combat this risk of terrorism. 1.5. What are the main nuclear accidents? The question is relatively simple but the answer is complex and subject to variation depending on sources [SOV 08, ROG 11, LEL 12, HAD 14, ASN 16]. Some of the discrepancies result from the criteria used to measure the severity of an accident. Is it the number of immediate deaths? Is it the amount of radioactivity released into the environment? Is it the area of land that has been condemned for centuries? In the absence of a comprehensive and public reference list of nuclear accidents, we have reconstructed the history of nuclear accidents in power plants from scientific literature and various public sources. The list of significant events classified at various levels on the INES is similar depending on the source for severity levels 6 and 7. On the contrary, for the lower levels, the lists diverge greatly. For information purposes, we provide in Table 1.4 those from the ASN [ASN 16]. The ASN thus retained two level 7 accidents, one level 6 accident, one level 5 accident, six level 4 accidents and 16 level 3 incidents.

Classification of Civil, Industrial and Medical Nuclear Accidents

Year

13

Site

Country

Case

1986

Chernobyl

Ukraine

Explosion of reactor 4 at the nuclear power plant

2011

Fukushima

Japan

Explosion of reactors 1, 2 and 3 at the nuclear power plant

Kyshtym

USSR

Explosion of a radioactive product tank at the reprocessing plant

Three Mile Island

USA

Partial fusion of the reactor core

1973

Windscale

UK

Release of radioactive materials following an exothermic reaction in a tank during reprocessing

1980

Saint-Laurent-desEaux

France

Damage to the A2 reactor’s core

1999

Tokai-Mura

Japan

Criticality accident in a fuel manufacturing facility

2006

Fleurus

Belgium

Irradiation by a cobalt 60 source of a worker working in an ionizing radiation sterilization facility

2010

New Delhi

India

Discovery of radioactive materials in scrap metal stores and irradiation of a scrap metal dealer

2011

Use of radiography

Bulgaria

Irradiation by a cobalt 60 source of four workers involved in an ionizing radiation sterilization facility

1981

The Hague

France

Fire in a storage silo

1991

Smolensk

Russia

Exceeding the operating boundary conditions during restart tests following a maintenance shutdown of reactor 2 at the nuclear power plant

1992

Sellafield

UK

Nitrated plutonium leak in a containment cell at the Sellafield fuel reprocessing facility

Level 7

Level 6 1957 Level 5 1979 Level 4

Level 3

14

Industrial and Medical Nuclear Accidents

1993

Narora

India

Loss of power supply to reactor 1 at the nuclear power plant

1993

Kola

Russia

Emergency shutdown of reactor 1 at the nuclear power plant

2002

Roissy

France

Incident during the transport of a package by Federal Express between Sweden and the United States via Roissy airport

2002

Davis–Besse

USA

Discovery of a cavity in the vessel cover on the power plant reactor due to boric acid corrosion of the metal

2002

New Orleans

United States

High dose rate measured on a package from Sweden containing iridium 192 sources

2003

Paks

Hungary

Release of radioactive gases from cracked fuel rods stored in a cleaning tank located next to the fuel pool at the plant

2004

Puerto Rico

Puerto Rico Irradiation by a cobalt 60 source of two workers involved in an ionizing radiation sterilization facility

2005

Sellafield

UK

Detection of a radioactive leak on a pipe in the THORP fuel reprocessing facility

2008

Toulouse

France

Irradiation by a cobalt 60 source of a worker working in an irradiation bunker on the ONERA site

2008

Fleurus

Belgium

Abnormal release of iodine 131 from the chimney of the Institut des radioélements building during a transfer of liquid effluent between tanks

2008

São Paulo

Brazil

Irradiation of an American and a Brazilian worker during the replacement of the cobalt 60 source of a cobalt therapy device in a state hospital

Table 1.4. List of nuclear accidents in the civil field classified in order of decreasing severity according to the INES classification (severity 7 to 3). Significant events classified by the ASN [ASN 16] and by the IRSN [IRS 17e]

Level 7 is used by all for the Chernobyl accident [IAE 13] and Fukushima [IRS 17e], level 6 for Kyshtym and level 5 for Three Mile Island [IAE 13]. On the contrary, the ASN [ASN 16] classifies the 1957 Windscale accident as level 4 and the IAEA [IAE 13] as level 5. In its list, the ASN

Classification of Civil, Industrial and Medical Nuclear Accidents

15

ignores the Goiânia accident in Brazil in 1987 [IAE 13] and the accident at the Chalk River nuclear laboratories in Canada in 1952 [MOR 15], classified at level 5. The ASN ignores the accident of October 17, 1969 in Saint Laurent with the fusion of 50 kg of uranium from the Saint-Laurent-A1 nuclear power plant in France during loading [IRS 15a]. Similarly, the ASN ignores the core fusion at the Lucens nuclear power plant in Switzerland on January 21, 1969 [CAN 11], classified at level 5 by the OFPP (Office fédéral de la protection de la population) [OFP 15]. The ASN [ASN 16] classifies the Fleurus accident (Institut national des radioélements) in Belgium in 2006 as level 3 and the IAEA [IAE 13] as level 4. The level 3 incidents reported by the various official sources widely differ. While the ASN retains the Sellafield accident in 2005 [IAE 13] and the silo fire in The Hague in 1981 [FRA 14], several incidents reported by the IAEA [IAE 13], such as the loss of a source causing severe burns in 1999 in Yanango (Peru) or the same year in Ikitelli (Turkey) [IAE 13], are ignored. Further examples are the exposure of a worker to a radioactive source at ONERA in Toulouse (March 18, 2008) and of three temporary employees who entered an industrial accelerator in operation and were heavily irradiated in Forbach (Moselle) in 1991 [IRS 17e]. This was also the case for a radioactive leak (192Ir) from a drum shipped from Sweden to the United States, transiting through Roissy (December 2001–January 2002) [ANO 02]. The most serious nuclear accidents involving reactors are those involving the melting of the fuel contained in their core. From an analysis of the various lists of nuclear accidents [SOV 08, ROG 11], we can consider that at least 12 reactors have been destroyed by this phenomenon since 1952. These are the Windscale plutonium cell (United Kingdom) in 1957 (but which we classified as a military accident), the Chalk River CANDU reactor (Canada) in 1958, the Simi Valley sodium-cooled experimental reactor (California) in 1959, the Monroe sodium-cooled demonstration breeder reactor (Michigan) in 1966, the Chapelcross reactor (United Kingdom) in 1967, the Lucens experimental reactor (Switzerland) in 1969, the pressurized water reactor at Three Mile Island (Pennsylvania) in 1979, the graphite-gas A2 reactor at Saint-Laurent-des-Eaux (France) in 1980, the Chernobyl reactor (Soviet Union) in 1986 and the three reactors at Fukushima (Japan) in 2011.

16

Industrial and Medical Nuclear Accidents

These are not the only reactors whose cores have suffered. For example, according to Wing and Hirsch [WIN 06], at least four of the reactors located at the Santa Susana Field Laboratory (SSFL) site have suffered such accidents. These are the AE6 reactor which suffered a release of gaseous fission products into the environment in March 1959, the SRE which had a power excursion and partial core meltdown in July 1959, the SNAP8ER which in 1964 suffered 80% damage to its nuclear fuel and the SNAP8DR which in 1969 suffered similar damage to one-third of its nuclear fuel. Let us also recall the accident in 1961 of the Idaho Falls SL-1 experimental reactor discussed in the previous volume [AMI 19], or that of the Jaslovske Bohunice reactor (Czechoslovakia) in 1977, but where the consequences were much more limited. For nuclear workers, the number of accidents with clinical consequences is limited and tends to decrease for criticality accidents. On the contrary, the number is greater and tends to increase for accidents with radionuclides and especially for accidents related to sealed sources (Figure 1.2).

Figure 1.2. Trends in the various types of nuclear and radiological accidents with clinical consequences for nuclear workers (adapted from [UNS 00a]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

Classification of Civil, Industrial and Medical Nuclear Accidents

17

1.6. Information on nuclear energy For a long time, public information on radioactive risk has been deficient and even biased, not only in the military field but also in civilian applications of atomic energy. Thus, most of the accidents that occurred in the 1950s and 1960s were kept secret. It was only after the Three Mile Island accident in 1979, and especially the Chernobyl accident in 1986, that public information became more free and taken seriously. The IAEA has mainly developed its communication policy since 1990. In France, public information on nuclear events is provided by the ASN, created only in 2006. Level 0 incidents, about a thousand per year, are not systematically made public. They may be published if they are of particular media interest. All incidents classified at level 1 and above are systematically reported on the ASN website. Annually, there are approximately a hundred level 1 cases in France. Information on incidents at level 2 and above are published and, in addition, brought to the attention of journalists through press releases and telephone contact. In France, they only represent a few cases per year. A follow-up of nuclear incidents was set up in 2001 by the CEPN and the group Personnes Compétentes de la Société Française de Radioprotection (SFRP), in cooperation with the IRSN and INRS. It is the RELIR system (http://relir.cepn.asso.fr/) that brings together the most interesting events for worker training and incident prevention. The selected incidents are presented in the form of descriptive sheets guaranteeing the anonymity of the exposed persons, companies and materials involved.

2 Accidents Related to Nuclear Power Production

2.1. Introduction In the first volume of this series on radioactive risk, we have reviewed nuclear accidents of military origin. We must now address civil nuclear accidents. Atomic energy is mainly used to produce electricity in nuclear reactors and relies on a set of industries capable of extracting, concentrating, transforming, using, reprocessing and reusing nuclear fuel (mainly uranium and plutonium). Nuclear accidents can occur at any stage of the fuel cycle. However, unfortunate experience has shown that nuclear reactors and spent fuel reprocessing plants are the most frequent and most serious locations for accidents. The consequences of accidents remain local when releases are low, regional for medium releases and global only for the most serious accidents. 2.2. Accidents in the nuclear fuel cycle The nuclear fuel cycle is shown in Figure 2.1. To our knowledge, there have been no significant incidents in mines and factories where nuclear fuel is concentrated, converted and enriched. Significant incidents and accidents have occurred in manufacturing plants, nuclear reactors and spent fuel reprocessing plants.

Industrial and Medical Nuclear Accidents: Environmental, Ecological, Health and Socio-economic Consequences, First Edition. Jean-Claude Amiard. © ISTE Ltd 2019. Published by ISTE Ltd and John Wiley & Sons, Inc.

20

Industrial and Medical Nuclear Accidents

Figure 2.1. The nuclear fuel cycle (modified from [TUR 97, PAT 02, NAU 08])

2.2.1. Uranium mines Accidents at uranium mines have the same health consequences as those at all other mines and cannot therefore be identified as nuclear accidents. On the other hand, uranium mines, especially underground uranium mines, are areas where radiation sources are significant. This is owing, in particular, to radon concentrations that can exceed 100,000 Bq.m−3 [CCS 11]. This radon comes from the decay of elements of the families of uranium and thorium (mainly uranium 238), which give rise to various radon isotopes (mainly radon 222), which are in a gaseous state and accumulate in mine galleries. Radon isotopes decay in a cascade into various radionuclides that are in a solid state and when inhaled into the lungs are deposited as radioactive dust that may have health consequences (Figure 2.2).

Accidents Related to Nuclear Power Production

21

Figure 2.2. The radioactive family of uranium 238 and its derivatives (according to AMI 13a]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

One of the few accidents with environmental and health impacts is one in Puerco, USA. In 1968, 27 km northeast of the town of Gallup, near the town of Church Rock, New Mexico, United Nuclear began operating the largest underground uranium mine in the United States. The mine waste was stored in three large ponds, each closed off by a dike of earth. Residents near the mine were almost entirely native Navajo and used the Puerco River as a source of water for their livestock. In the early morning hours of July 16, 1979, fewer than 4 months after the high-profile Three Mile Island accident was reported, one of the earth dams gave way near Church Rock Mill. The 6 m-wide dam released approximately 1,100 tons of radioactive waste, and 95 million gallons (360 million liters) of effluent reached the Puerco River in North Fork. In addition to the river, groundwater was affected up to more than 130 km downstream of the dike [BRU 07].

22

Industrial and Medical Nuclear Accidents

2.2.2. Milling, conversion, enrichment and fuel manufacturing plants The most serious accident in a civilian manufacturing plant is the Tokai-Mura accident. This site is a major nuclear complex, with a spent fuel reprocessing plant, a uranium reprocessing plant and experimental reactors. The site is located in Japan 160 km from Tokyo. The plant where the accident occurred is owned by the Japan Nuclear Fuels Conversion Company (JCO), a subsidiary of the Sumitomo Trust. It converts uranium hexafluoride (UF6) enriched in uranium 235 into uranium oxide (UO2) for the manufacture of nuclear fuel. The conversion is carried out by a “wet process”: uranium, initially in the form of gaseous UF6, is transformed in the presence of water and then ammonia before being calcined in a furnace to obtain uranium oxide powder. On Thursday, September 30, 1999, at about 3:30 p.m., following a human error in the quantity of fissile material introduced into the furnace, a so-called criticality accident occurred. The quantity of uranium introduced into a settling tank was indeed abnormally high (16.6 kg) and far exceeded the safety level (2.3 kg). This accident resulted in contamination outside the plant, and three workers were seriously injured. It was classified at level 4 on the INES. In France, the first stages of the fuel cycle are not immune to accidents, and radioactive releases into the environment are not always negligible. This was the case at the Pierrelatte (Comurhex) plant in 1977 (January 1 and November 25) where several tons of uranium hexafluoride leaked into the atmosphere without apparently contaminating the soil away from the plant site. A 30 m3 leak of a solution containing 74 kg of uranium occurred on July 9, 2008 in a plant at the Tricastin nuclear site in Bollène (Vaucluse), part of which spilled into surrounding rivers [AMI 13a]. 2.2.3. Nuclear reactors The largest use of nuclear energy is in the production of electricity. This is the area with the highest number of accidents. Table 2.1 lists accidents classified as severe on the INES with a rating of 3 or more. Subsequently, the three most serious civil accidents (Three Mile Island, Chernobyl and Fukushima Daiichi) will be detailed.

Accidents Related to Nuclear Power Production

23

G Date

Site, country

Type of Type of accident installation (number of years)

3 06/01/1981

La Hague, France

Reprocessing plant (15 years)

Fire in a storage silo

16/08/1989

Gravelines, France

PWR reactor (9 years)

Inadequate screw in the primary circuit’s valve

19/10/1989

Vandellos, Spain

Gas-graphite reactor (17 years)

Fire of a turbo alternator unit

11/03/1997

Tokai-Mura, Japan

Fuel production plant (18 years)

Fire and explosion irradiating 37 people

10/04/2003

Paks, Hungary

PWR reactor (19 years)

Radioactive leakage in the fuel rod cleaning system

21/04/2005

THORP/Sellafield, United Kingdom

Reprocessing plant (8 years)

Leakage of radioactive liquid following a ruptured pipe

Lucens, Switzerland

Heavy water reactor (1 year)

Cooling failure resulting in partial fusion of the reactor

4 21/01/1969

17/10/1969

Saint-Laurent-des-Eaux, Gas-graphite France reactor (1 year)

Uranium smelting Reactor shutdown for 1 year

26/09/1973

Windscale/Sellafield, United Kingdom

Reprocessing plant (22 years)

Explosion and release of radioactive materials (37 people irradiated)

07/12/1975

Lubmin, Germany

PWR reactor (1 year)

Short circuit on the reactor transformer, fire and destruction of cooling pump supply

22/02/1977

Bohunice, Slovakia

Gas-cooled heavy water reactor (5 years)

Core corrosion and power failure during fuel changeover

13/03/1980

Saint-Laurent-des-Eaux, Gas-graphite France reactor (9 years)

30/09/1999

Tokai-Mura, Japan

Fuel fabrication plant (22 years)

Uranium melting and damaged core (corrosion) Uranium dosing error and explosion (three irradiated, two deaths)

24

Industrial and Medical Nuclear Accidents

Windscale

Military reactor (11 years)

Fire

Three Mile Island, United States

PWR reactor (1 year)

Partial fusion of the reactor core

6 1957

Kyshtym, USSR

Reprocessing plant (?)

Explosion (>10 PBq 131 ) I

7 26/04/1986

Chernobyl, USSR (Ukraine)

Pressure tube reactor (3 years)

Explosion and partial melting of the core

Fukushima-Daiichi, Japan

BWR reactors (36–40 years old)

Cooling shutdown and partial core melting of three reactors

5 10/10/1957 28/03/1979

11/03/2011

Table 2.1. The most significant accidents that have occurred in civil nuclear installations. G: severity on the INES

2.2.3.1. Accident at the Simi Valley nuclear power plant The Santa Susana Field Laboratory (SSFL) was a test site used for rockets and nuclear reactors, located 40 km from the geographical center of the Los Angeles metropolitan area (California), near Simi Valley. On July 26, 1959, during the 14th low-power test of the Sodium Reactor Experiment (SRE), following a poor sodium flow, the temperature difference between the various fuel channels was found to be excessively high. After the immediate termination of this test, it appeared that 13 of the 43 fuel elements were damaged [ASH 59, ASH 61]. The Simi Valley accident has remained relatively unknown and continues to be shrouded in mystery today. As a result of corporate and government secrecy, news of the incident came only 20 years later, and the information provided is few and far between [ROG 12]. Thus, while Ashley et al. [ASH 59] claim that no radiological hazards were present in the vicinity of the reactor, subsequent information would estimate radioactive releases 240 times higher than those from Three Mile Island [GRO 15]. Similarly, a controversy over iodine 131 releases arose between those who claimed that no iodine releases had occurred as a result of the accident [CHR 05, DAN 05] and those who believed that substantial quantities of iodine had been released into the atmosphere [MAK 05, MAK 06, LEL 12].

Accidents Related to Nuclear Power Production

25

Iodine 131 releases were estimated at 1,300 Ci (4.81.1013 Bq) by Makhijani [MAK 06]. According to Lelieveld et al. [LEL 12], the radioactive releases from this accident were greater than 200 PBq (without taking into account the supposed substantial emissions of 85Kr and 133Xe but without any available data), making this accident one of the most serious, at level 5 or 6 on the INES. Based on the damaged reactor core fraction (30%), the analytical value of the radioactive iodine and cesium fraction released by the damaged fuel (10%) and an empirical value of the efficiency of the ventilation system (10%), Lochbaum [LOC 06] concluded that the fraction of the total cesium inventory in the SRE reactor core at the time of the July 1959 accident reaching the environment was between 0.3% and 30% and the fraction released of radioactive iodine was between 3% and 30%. This author estimated that the 15% value for the amount of iodine released was the most likely. 2.2.3.2. Accident at the Lucens nuclear power plant Construction of a heavy water reactor at the Lucens site in Switzerland began in 1962 (Figure 2.3). It was constructed completely underground, with the exception of a few storage and operations buildings. At the beginning of 1969, after a period of revision, the Lucens power plant reactor was returned to service. On January 21, 1969, when the power was increasing, the pressure in the primary cooling system dropped sharply. The instruments also reported a significant increase in radioactivity in the facility enclosure and a significant loss of heavy water. This meant that the moderator tank was damaged. An emergency shutdown of the reactor was carried out, and the caverns were isolated from the outside by closing the ventilation ducts. A few hours after the accident, radioactivity in the access tunnel decreased and the reactor continued to be cooled. Measurements taken on the night of the accident itself, and subsequently, showed that the level of radioactivity in the vicinity had hardly changed from a background level. After this incident, the facility was completely dismantled and the caverns decontaminated. The dismantling work, the decontamination, the analyses of the causes of the accident, the various expert reports and the publication of the final report took more than 10 years [CAN 11].

26

Industrial and Medical Nuclear Accidents

Figure 2.3. Diagram of the Lucens experimental nuclear power plant (adapted from [CAN 11]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

2.2.3.3. Nuclear accidents in Saint-Laurent-des-Eaux in 1969 and 1980 During a loading operation of the no. 1 graphite-gas reactor (SLA1) in Saint-Laurent-des-Eaux, France on October 17, 1969, the fuel loading and unloading apparatus in the operating reactor was controlled by a programmable displacement system. By mistake, a flow control valve was introduced over already-loaded fuel elements into one of the reactor core channels. This resulted in a drastic reduction in the cooling circuit of the fuel elements and a subsequent rise in temperature at the level of the magnesium and zirconium alloy sheaths of five fuel elements and their degradation. The reactor was automatically shut down due to the rise of radioactivity in the reactor vessel. These five fuel elements corresponded to about 50 kg of uranium dioxide that melted in the reactor core [IRS 15a]. The contamination would have been limited to the site. But because of its seriousness, it should have been classified at level 4 on the INES. However, EDF described it as an incident because it would not have caused any damage to persons, property or the environment outside of the site. Clean-up operations began 1 year after the accident, while the nuclear fuel cooled and a full-scale model was built. These cleaning operations were

Accidents Related to Nuclear Power Production

27

mainly carried out using remote-controlled means. To finish this operation, several hundred (300–400) “cleaners” were mobilized, each one being able to intervene for only about 10 minutes, even 2 minutes for some. At the end of the clean-up operations, only 47 kg of uranium was recovered and the reactor was restarted on October 16, 1970. The second graphite-gas reactor in Saint-Laurent-des-Eaux (SLA2) was automatically shut down on March 13, 1980 following a sudden increase in radioactivity in the reactor vessel. The next day, EDF estimated that a significant amount of spent uranium had melted. From March 22 to 26, after checking the proper operation of the iodine traps, decompression of the reactor vessel to the atmosphere was carried out in order to return to atmospheric pressure. This same reactor suffered several incidents during the same quarter of 1980 [GUI 16]. Examinations undertaken on March 27, 1980 showed that the accident originated in a total or partial plugging of six channels by a metal sheet detached from the fairing device due to its corrosion. Two fuel elements melted (about 20 kg of uranium) and two others showed significant traces of fusion. The cleaning was very difficult and took more than three and a half years [IRS 15a]. 2.2.3.4. Accident at the Bohunice nuclear power plant The Bohunice nuclear power plant is located 2.5 km from the village of Jaslovské Bohunice in the Trnava district of western Slovakia. On February 22, 1977, the A-1 reactor suffered a major INES 4 accident during reloading. A desiccant bag accompanying the package was inadvertently placed in the core with the nuclear fuel. This limited the circulation of the coolant, causing local overheating and serious damage. As in Simi Valley, this reactor was finally closed in 1978 and is still in the dismantling phase. 2.2.3.5. Accident at the Greifswald or Lubmin nuclear power plant The Greifswald nuclear power plant, also known as the Lubmin nuclear power plant, was located in former East Germany. On December 7, 1975, a short circuit on the transformer of reactor no. 1 caused a small fire that destroyed the supply of five main cooling pumps out of a total of six. If the last pump had not cooled the reactor, core meltdown would have occurred.

28

Industrial and Medical Nuclear Accidents

The rapid intervention of the fire brigade allowed the fire to be extinguished and the power supply to all the pumps to be temporarily restored. The incident was only revealed to the public in 1989 after the fall of the Berlin Wall. The IAEA has classified the accident as a level 4 accident on the INES. 2.2.3.6. Three Mile Island accident On March 28, 1979, one of the two generating station’s reactors at Three Mile Island (TMI-2) in Pennsylvania (United States) suffered serious damage. These were 900 MW-pressurized water reactors. They were located on a small island (3.3 km2) in the Susquehanna River near Harrisburg. The cause of the accident was a result of the leakage of the primary water circuit enclosure (second protective barrier) because of a pressurizer relief valve that remained blocked in the open position. As a result, the core was no longer cooled, resulting in the melting of a substantial part of the fuel. The containment, the third barrier, played its role with the exception of a slight radioactive release that is difficult to quantify [IRS 12c]. This accident was classified as a level 5 accident on the INES. Further analysis [NSA 80] showed that serious damage to the reactor fuel did not begin until about 1 hour and 40 minutes after the accident. During the accident, water containing radioactivity was removed from the reactor building at various times. Some of the radioactive gases dissolved in this water spread into the atmosphere of the auxiliary building and dispersed in the vicinity of the plant through the auxiliary building’s ventilation system. Six years after the accident, it was possible to enter the enclosure, and a camera introduced into the tank showed that a significant portion of the fuel had melted (45%) and that it had partially flowed (20%) to the bottom of the tank but had not passed through it. The corium (the lava-like mixture of material created during the nuclear meltdown) had stratified at the bottom of the tank without causing an explosion. Currently [NRC 11], the damaged core has been completely removed from the tank, including the parts melted during the accident; the containment has also been cleaned, and the plant is awaiting a decision on its future that could potentially be a complete dismantling, making the current right-of-way usable.

Accidents Related to Nuclear Power Production

29

2.2.3.7. Serious incidents at various nuclear power plants Serious incidents of level 3 on the INES occurring at nuclear power plants are relatively numerous. Among these incidents were the discovery in 2002 at the Davis–Besse power plant reactor (United States) of a cavity in the tank cover as a result of corrosion of the metal by boric acid; the loss of power supply in 1993 to Unit 1 of the Narora nuclear power plant (India) caused by a fire in the turbine hall; the emergency shutdown of reactor 1 at the Kola nuclear power plant (Russia) resulting from network disruptions following a tornado; and, in 1991, the exceeding of operating limits during restart tests following a maintenance shutdown of reactor 2 at the Smolensk nuclear power plant (Russia). The same applies to the incident that occurred on April 10, 2003 in reactor no. 2 at the Paks nuclear power plant. This power plant is located in the central region of Hungary, 5 km from Paks and 100 km south of the capital Budapest, on the banks of the Danube. On that day, the reactor was shut down for its annual refueling, and the fuel elements were unloaded and stored temporarily in a cleaning tank located next to the fuel pool. Some of these underwater fuel assemblies were damaged and leaking. The incident initially classified as level 2 was reclassified as level 3 by the authorities because with fuel leaks, there was a risk of reaching the critical mass at the bottom of the cleaning tank. 2.2.3.8. The Chernobyl and Fukushima disasters These two disasters, due to their magnitude and the richness of the literature on them, will be dealt with in two separate chapters (Chapters 3 and 4). 2.2.4. Spent fuel reprocessing plants Spent fuel reprocessing plants routinely represent the most polluting step in the fuel cycle [AMI 13a]. These include significant releases of tritium and rare gases (krypton, xenon, etc.) to the atmosphere and many radionuclides to the freshwater and marine environments: fission and activation products as well as transuranics (plutonium, americium). Thus, the activity rates of 129 I and the ratios 129I/127I in marine samples show the spatial and temporal influence of the La Hague site on its near environment as well as on a regional scale along the Channel coast [FRE 03].

30

Industrial and Medical Nuclear Accidents

Only a few countries, France (La Hague), Japan (Tokai-Mura and then Rokkasho-Mura), United Kingdom (Sellafield) and Russia (Ozersk), have developed this stage and have reprocessing plants. The United States shut down its West Valley plant in 1972. The main accidents or incidents will be described below in chronological order. The largest number of them concerns THORP (Sellafield’s plant). 2.2.4.1. French accidents at La Hague Before the two most serious accidents, a first accident occurred in the La Hague fuel reprocessing plant on October 2 and 3, 1968. It resulted in an atmospheric release of 185.109 Bq of iodine 131 (Scheidhauer et al., 1971, in [AMI 80]). The breakage in the offshore discharge pipeline from the La Hague reprocessing plant The estimated date of this breakage was between early September and late November 1979. This resulted in an increase in radioactivity in the marine environment (seawater, sediments, algae, mollusks, crustaceans, fish) of many radionuclides (90Sr, 106Ru, 137Cs, 238Pu, 239Pu, 244Cm) between 1980 and 1981 [GRN 99, BAR 00]. For example, for 90Sr in 1979, 1980 and 1981 respectively, the concentrations in sediments were 122, 823 and 71 Bq.kg−1 wet weights and those in mollusks were 41, 274 and 24 Bq.kg−1 wet weights. The fire at silo 130 at the La Hague facility On January 6, 1981, a fire broke out in silo 130 of the La Hague plant, where waste from the reprocessing of spent fuel from the “natural uranium-natural graphite-gas” process was stored in the UP2-400 plant, causing cesium 137 to be released into the environment for several hours. It took more than 24 hours to control this fire [JAC 14]. Between 1973 and 1981, silo 130 received a total of 518 tons of waste, mainly graphite, magnesium and uranium. The radioactive substances present in silo 130 were mainly the activation products contained in graphite liners and magnesium caps after their passage through the reactor, and the fission products (in particular cesium 137) contained in uranium metal after their passage through the reactor and uranium metal. In addition, between December 11 and 15, 1980 (a few days before the fire), cotton used for

Accidents Related to Nuclear Power Production

31

decontamination operations (cotton soaked in phosphate degreaser) was dumped into the silo. The last waste container was emptied into silo 130 on January 5, 1981 at 6:30 p.m. It mainly contained magnesium caps and uranium metal. Between recovery and disposal in silo 130, this waste remained dry for several days, but previously the last waste dumped was uranium from a water pit. The most plausible hypothesis is that this uranium, which is most likely present in the form of hydride (UH3) as a result of its prolonged contact with water, is highly pyrophoric, especially when it has been dry for several days, which was the case here. On January 6, 1981, at 4:00 a.m., air contamination was detected approximately 800 meters from silo 130 at the AT1 building. Cesium 137 was mainly present in these discharges, which directed research attention towards the silo. The resulting contamination inside the site on about one hectare affected building 130 overlooking the silo and outside areas. The maximum values recorded were 111.103 Bq. m-² in cesium 137. Off-site, contamination remained low and did not exceed 3.7.102 Bq.m−2 in cesium 137 [JAC 14]. Silo 130 now contains the same substances as those present at the time of the fire, as well as effluents from fire suppression (600 m3) and rainwater infiltration (800 m3). It will be necessary to dismantle this silo despite all the difficulties involved. 2.2.4.2. Accident in Tokai-Mura The first nuclear accident at the Tokai-Mura reprocessing plant occurred on March 11, 1997 at the Dōnen (Power Reactor and Nuclear Fuel Development Corporation) spent fuel reprocessing plant. A small explosion occurred during the night, exposing between 35 and 40 workers to unusual radiation doses. 2.2.4.3. Incidents and accidents in Sellafield The Sellafield site is the main complex of the British nuclear power sector. Originally named Windscale, it was renamed Sellafield following the serious accident at battery 1 involving plutonium for military use in 1957 [AMI 19]. The site borders the Irish Sea in the county of Cumbria in

32

Industrial and Medical Nuclear Accidents

north-west England, near the town of Seascale. It now includes 400 buildings spread over 10 km2 and employs about 10,000 people. Among the facilities is a fuel processing and high-level waste storage plant called THORP (Thermal Oxide Reprocessing Plant). It is designed to process both British and foreign fuels using a different process than the one used at La Hague (PUREX). A first level 3 incident occurred in 1992 with the release of nitrated plutonium into a containment cell in the fuel reprocessing facility. On April 19, 2005, 83,000 liters of radioactive material were discovered in a reinforced concrete enclosure at this plant, which followed a pipeline rupture that had not been detected for several months. About 200 kg of plutonium in nitric acid solution had flowed along a tank and accumulated in a drip pan (large collection tank for flow fluids) with a risk of criticality accident. The investigation concluded that the uranium and plutonium had flowed for about 9 months on the ground and then into a sump. The British Safety Council (HSE/ND4) has published a 28-page report [HSE 05]. The company, prosecuted for non-compliance with three authorizations concerning “safety, mechanisms, devices and circuits”, “operating instructions” and “leaks and losses of radioactive materials or radioactive waste”, had to pay £500,000 in fines plus approximately £68,000 in procedural costs. About 19 tons of uranium and 160 kg of plutonium (out of 200 kg according to the IRSN [IRS 12a]) dissolved in nitric acid were recovered by pumping into the reservoir’s sump outside the plant. According to the IRSN ([IRS 12a]), these failures were caused by “excessive confidence in the plant design” and “an insufficient safety culture”. The accident was classified as a level 3 accident on the INES. A similar plant in La Hague has modified its procedures to prevent this type of accident. As a result of this accident, the THORP was closed from April 2005 to July 2007 and will be finally closed in 2018 after the completion of contracts, and then dismantled. 2.2.4.4. Accident in Russia in September 2017 The IRSN [IRS 17c], as well as several Western European networks, have detected high concentrations of ruthenium 106 in the air. In France, the maximum concentration was measured in Nice between October 2 and 9,

Accidents Related to Nuclear Power Production

33

2017 (46 µBq.m−3). By reverse modeling, the IRSN estimated that the accident site was located between the Volga and the Urals rivers and the date was the last week of September 2017. The quantity released was significant, in the range of 100–300 TBq. With 106Ru being an artificial fission product, three accidental sources are possible: first, leakage came from a spent fuel reprocessing plant; second, leakage came from a ruthenium-based radioactive source manufacturing plant; third, it could even be from the possible fall of a satellite powered by a nuclear reactor based on this radionuclide. With the final hypothesis being refuted by the IAEA, one of the other two possibilities is the most likely. The accident site is close to the Mayak complex, where the Kyshtym military accident occurred [AMI 19]. 2.3. Accidents in laboratories 2.3.1. Chalk River laboratories Of the nuclear accidents that have occurred in research laboratories, those at the Chalk River Laboratories are the most serious. The nuclear laboratories at Chalk River, Ontario, Canada, were established in 1942 as a result of British-Canadian collaboration. Their main activity is research in the field of nuclear reactions. In 1947, the first nuclear reactor outside the United States was commissioned. This nuclear research reactor, NRX (1947–1992), is moderated by heavy water and cooled by light water and was originally designed for military applications. Today, the Chalk River Laboratories are of great importance in the medical applications of nuclear energy. The first accident occurred on December 12, 1952 in the NRX reactor. While the reactor was operating at full power, it experienced a partial loss of coolant. Operators made several bad decisions, causing a chain reaction that more than doubled the nuclear reactor’s power. In particular, operators opened valves in the cooling system to lower the containment pressure. Inexplicably, the descent of the control rods into the reactor core was not complete. This triggered an explosion that destroyed the nuclear reactor’s core and caused a nuclear fuel leak. A series of hydrogen explosions raised the four-ton dome into the air. About 370 TBq of fission products were released into the atmosphere with 4,500 tons of contaminated water. The

34

Industrial and Medical Nuclear Accidents

contaminated water had to be pumped out of the subsoil and into shallow trenches near the Ottawa River. The core of the NRX reactor that could not be decontaminated had to be buried like other radioactive wastes. This accident was classified as a level 5 accident according to the INES. The Atomic Energy of Canada Company restarted the site within the year. A second accident in 1958 involved a fuel failure and fire in the 135 MWt National Research Universal reactor (NRU) building (1957–2018). Some fuel rods had overheated. Using a robotic crane, one of the uranium metal rods was removed from the reactor vessel. But when the crane arm moved away from the core, the uranium caught fire, the rod broke and most of the stem fell into the containment. This led the whole building to be contaminated. The ventilation system valves were opened and a large area of the building’s exterior was contaminated. The fire was extinguished by scientists and cleaners wearing protective clothing by throwing buckets of wet sand. 2.3.2. French study centers France has more than 70 basic civil nuclear facilities (INBs): “Laboratories, Plants, Dismantling Facilities and Waste Treatment, Storage or Storage Facilities” called LUDDs. Unlike the nuclear power plants operated by EDF, LUDD-type installations are very diverse (nature of activities, nature of risks) and are operated by many companies, the main ones being Areva (now Orano), CEA, ANDRA and EDF [IRS 09b]. The safety of nuclear installations is never definitively established and it should be aimed at continuous improvement, taking into account new knowledge and feedback. The IRSN also regularly capitalizes, using appropriate tools, on the feedback from the analysis of events that occurred in France in LUDD-type installations as well as the most significant incidents that occurred abroad in installations of the same type. From the overall examination of the events reported for the years 2005–2008, it first appears that there was a significant increase (approximately 45%) in the number of events reported to the ASN in 2008 compared to that in the previous 3 years. In terms of consequences, it appears first of all that no events reported to the ASN for the years 2005–2008 had any serious consequences for workers, the public or the

Accidents Related to Nuclear Power Production

35

environment [IRS 09b]. ASN [ASN 12] has devoted an issue of the journal Contrôle to this subject. Among the incidents that have occurred in nuclear study centers (CENs), some can pollute the aquatic environment. Thus, in 1974, the Grenoble center contaminated the groundwater with radioactive antimony, but the expertise that established that the maximum allowable concentration (MAC) had been exceeded is disputed by the center’s management. The use of radioactive sources gives rise to too many incidents or even accidents resulting from their escape into the environment and their recovery by the public, unaware of their danger. For example, the ASN was informed by a letter dated September 7, 2007 by the CEN in Saclay of the loss of a source of promethium 147 as part of a dust measuring device, the dismantling of which had been initiated in June 2006. Accidents related to radioactive sources will be discussed in more detail in Chapter 5. When the CEN plutonium technology workshop (ATPu) at Cadarache (Bouches-du-Rhône) was dismantled in 2009, the French Atomic Energy Commission (CEA) considered that the residual dust deposits at the end of operation were significantly underestimated. Indeed, this workshop contained some 39 kg of plutonium, and not 8 kg, as initially assessed by the CEA. The ASN was only informed of this undervaluation on October 6, 2009, although the facts had been known since June of the same year. It classified the incident as a level 2 and suspended the dismantling of the ATPu for several months [AMI 13a]. 2.4. Other accidents 2.4.1. Accidents in civil engineering Accidents in the field of civil engineering are varied. Of the 81 civilian underground nuclear explosions (PUNE – Peaceful Underground Nuclear Explosions) carried out by the Soviets from 1965 to 1988, four (Globus-1, Taiga, Crystal and Kraton-3) resulted in accidents with long-term environmental contamination. The most dramatic and severe is the “Kraton-3” carried out in 1978 near the Arctic Circle (65.9°N, 112.3°E) in Yakutia (Republic of Sakha). Two radionuclides (137Cs and 90Sr) were particularly monitored in the environment, particularly in plants [RAM 09].

36

Industrial and Medical Nuclear Accidents

2.4.2. Accidents in nuclear propulsion Propulsion using nuclear reactors is not limited to military applications. Various ships and civilian satellites are equipped with various types of engines in order to move. Accidents have also occurred. Thus, spacecraft equipped with radioisotope power reactors or generators can contaminate aquatic environments directly by intact re-entry into the atmosphere and loss at sea, such as the generator of the lunar module used in the Apollo 13 lunar program (238Pu – 1.6.1015 Bq), which fell back in April 1970 into the South Pacific Ocean to a depth of about 6,100 m (USAEC, 1971, in [EIS 73]). Contamination of aquatic environments can be indirect, as in the case of the SNAP 9A series satellite, which vanished when it re-entered the atmosphere in 1964. Its power generator consisted of 629.1012 Bq of 238Pu. Up until then, 238Pu in the upper atmosphere (33,000 m) had been generated solely by earlier nuclear explosions, but 4 months after the accident, this 238Pu had increased significantly. By the end of 1970, 95% (592.1012 Bq) of the 238Pu from this satellite had fallen to the surface of the land and oceans. Previously, two other American satellites carrying a power generator (SNAP-3A – 238Pu – 59.2.1012 Bq series) launched in 1961 had vanished into the atmosphere. Similarly, the Soviet Cosmos-954 satellite was destroyed on January 24, 1978, and radioactive debris was introduced into part of Canada’s Far North into certain bodies of water such as Great Slave Lake in Fort Reliance Bay. Fission products were sought in lichens growing on the debris fallout zone (900 km x 45 km corridor) in the northern Canadian territories. The environmental impact was minimal [TAY 79]. 2.5. Waste management incidents Waste management incidents are few and far between. Among these, let us mention the explosion that occurred on Monday, September 12, 2011 at around 12 p.m. in the CENTRACO facility located in Marcoule, in the Gard, France (30). Operated by SOCODEI, this facility is dedicated to the processing and conditioning of low and very low level radioactive waste. The explosion occurred in the metallurgical furnace used to melt metal waste. One employee was killed and three others burned to varying degrees by a violent projection of molten metal in the facility’s hall. IRSN measurements confirmed the absence of radioactive releases to the environment off-site [IRS 12b].

Accidents Related to Nuclear Power Production

37

There are also some risks associated with waste storage, such as leaks in tanks containing high-level liquid waste (e.g. Hanford mild steel tanks) [DET 74], which could lead to groundwater contamination. In the case of waste dumped at sea, contamination could result from a barrel crack (manufacturing defect) or corrosion, resulting in the release of radioactive materials. In France, at the Centre de Stockage des déchets à vie longue et haute activité de la Manche (CSM), stored tritium escaped into groundwater. Thus, between 1977 and 1992, tritium contamination reached values of 1.4.104–6.105 Bq.L−1 at different points from the slick to the center (ANDRA, 1992, in [GAZ 10]). In 2008, tritium concentrations in these waters reached values in the order of 103–105 Bq.L−1 at the site boundary (IRSN, 2008, in [GAZ 10]). In the waters of the St. Helena stream, tritium values were in the order of 5.104 Bq.L−1 in 1982, and concentrations reduced in 1992 to several hundred Bq.L−1 [GAZ 10]. 2.6. Incidents in the transport of radioactive packages Prior to the 1970s, some accidents during the transport of radioactive materials by sea, air, rail and especially road led to local contamination of various aquatic environments [EIS 73]. In France, approximately 96% of radioactive substance packages are exclusively transported by road and the rest by a combination of several modes of transport (3% by road and air, 1% by road, sea and rail). Rail transport is mainly used by the nuclear industry. In 2014 and 2015, 139 and 122 events, respectively, were reported to the French Nuclear Safety Authority, corresponding to approximately one reported event for every 7,500 packages transported. To date, in France, there is an average of one to two transport accidents per year, resulting in a release of radioactivity into the environment. These events have had limited consequences on human health and the environment, as most of them are ranked 1 on the INES. In the most serious cases in France, classified 3 on the INES, low levels of contamination were detected and could be treated by specific decontamination operations [IRS 16b]. The IRSN regularly identifies the various incidents affecting the transport of radioactive packages [IRS 11a, IRS13a, IRS13b]. Thus, the IRSN [IRS 16b] lists 16 significant transport incidents from 1983 to 2007, but with no consequences for the environment or health impacts.

38

Industrial and Medical Nuclear Accidents

Incidents of level 3 on the INES concerning parcels are few and far between. In France, only one case was noted in December 2001 when Federal Express transported an incoming package with a dose rate above the regulatory limit between Sweden and the United States via Roissy airport. This incident was classified by the Swedish Competent Authority as a level 3 incident. Similarly, in 2004, the dose rate measured in New Orleans (United States) on a package from Sweden containing sources of iridium 192 was too high. Following a collision with the car ferry Olau Britannia 10 nautical miles from the Belgian coast, the cargo ship Mont-Louis sank in the North Sea 10.5 nautical miles north of the port of Ostend on Saturday, August 25, 1984 at around 7 p.m. This cargo carried 350 tons of uranium hexafluoride (UF6) in 30 48-Y containers. The uranium 235 content varied from 0.67% to 0.88% depending on the batch. In addition, two batches contained recycled uranium in varying proportions. The recovery of the 30 containers began on September 1 and ended on October 4, 1984. Only one small leakage was found on a single container, so the Mont-Louis maritime accident had no radiological or chemical consequences [AUG 85]. 2.7. Environmental consequences 2.7.1. Uranium mines Active uranium mines pose generally minimal environmental problems. On the other hand, abandoned mines often cause environmental damage. Waste rock from uranium ore that is too depleted to be economically viable still contains radionuclides from the uranium (or thorium) families which, if poorly controlled, can be leached and returned to the aquatic environment. The G@zette du Nucléaire dossier no. 111/112 deals with this subject [ANO 91]. In France, uranium ore exploration, production, processing and storage activities have been carried out at more than 200 sites in 27 departments. These activities have sometimes led to a change in the natural environment’s radiological state. This change may be significant from a measurement point of view without necessarily being significant from a health point of view. The IRSN [IRS 17b] has carried out several expert assessments of the impact

Accidents Related to Nuclear Power Production

39

of former French mining sites and proposes an environmental guide value for uranium equal to 0.3 μg.L−1 [IRS 15b]. 2.7.2. Tokai-Mura Approximately 160 TBq of noble gases and 2 TBq of gaseous iodine were reportedly released to the environment. Following the Tokai-Mura accident, the soils near the plant were contaminated with 24Na, 140La, 122Sb, 59 Fe, 124Sb, 46Sc, 65Zn, 134Cs and 60Co [NAK 00]. 2.7.3. Saint-Laurent-des-Eaux The atmospheric emissions associated with the 1980 accident were estimated by EDF at 29.6 TBq in rare gases and 0.37 GBq in iodine and aerosols on the basis of the measurements made [IRS 15a]. Following the accident that occurred in March 1980 at one of the UNGG reactors in Saint-Laurent-des-Eaux, the fusion of two fuel elements from Unit 2 resulted in the release of a small quantity of plutoniums 239 and 240 into the Loire. This quantity was estimated at 10–20 mCi, or 535–740.106 Bq, by Martin and Thomas ([MAR 88]). This represents between 0.063 and 0.322 g of 239,240Pu [GUI 16]. Thomas ([THO 82]) measured Pu activities in sediments and suspended solids (SS) from the Loire. The results show that the ratio of 238Pu/239.240Pu in particle matter is consistent with that of the overall deposition (about 0.05) upstream of the plants and in a single sandy sample taken downstream of the Dampierre plant, but this ratio reaches 0.15–0.42 downstream of St. Laurent. At the entrance to the estuary (Montjean), it is still 0.05–0.28 (Figure 2.4). The IRSN [IRS 15a] states that the traces of the 1980 releases have no longer been perceptible in the Loire since 1994 and specifies that “the traces of plutonium measured in the soil as part of the monitoring near EDF’s nuclear sites are the result of the fallout from nuclear tests, with no discernible influence from releases from nuclear power plants”.

40

Industrial and Medical Nuclear Accidents

Figure 2.4. Isotopic composition of plutonium in sediments (full circles) and suspended solids (empty circles) in the Loire River between 1980 and 1983 [THO 82]. For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

2.7.4. Three Mile Island Despite the partial melting of the reactor core and the significant release of radioactivity into the containment, the immediate radiological consequences to the environment were minimal. The containment has indeed fulfilled its role. The low releases to the environment were caused by the continued operation of a primary circuit effluent pumping system. Due to leaky circuits, hot contaminated water escaped into the building and vaporized, releasing the iodine and xenon it contained. These gases and vapors were sucked into the general ventilation of the building, through insufficiently efficient iodine filters, and released into the environment [IRS 12c]. The continuous radioactive releases consisted almost entirely of radioactive gases, with very small quantities of radioactive iodine. The highest measured ground dose rate was 1.3.102 C.kg−1 (50 mR.h−1) and the highest concentration of 131I was less than 3.7.10-6 Bq.cm−3 [HUL 89]. For example, honey samples were collected in the summer and fall of 1979 from hives within 16 km of the Three Mile Island generating station. None of the seven samples showed overall radioactivity significantly different from that of the control samples collected at a distance of more than 250 km [MOR 80]. These results confirm the findings of previous studies

Accidents Related to Nuclear Power Production

41

suggesting that only minimal quantities of 137Cs escaped from the damaged Three Mile Island station after the accident. In contrast, Field [FIE 93] found that the tongues of white-tailed deer (Odocoileus virgianus) caught in the 10 counties of Pennsylvania more than 88 km from Three Mile Island had levels 137Cs higher than those of deer tongues tested in the counties surrounding the nuclear power plant. Similarly, in the thyroid glands of meadow voles (Microtus pennsylvanicus) trapped near the Three Mile Island nuclear power plant (1.9 km from the reactor) between April 6 and 16, 1979, the amounts of 131I were significantly higher than those in voles captured further away [FIE 81]. 2.7.5. Church Rock Following the failure of the Church Rock uranium mine dike, the total mass of uranium and gross alpha activity released into the Puerco River was estimated at 560.106 g or 260 Ci. The accidental spill into the water on July 16, 1979 was 1.5.106 g of uranium and 46 Ci (1,7 TBq) of gross activity [VAN 92]. 2.7.6. La Hague The fire at the La Hague silo led to air contamination during the fire. All air contamination measurements made during the event revealed only the release of cesium 137 with maximum concentrations of 48.1 GBq.m−3 of air. After detailed studies, total cesium 137 releases were estimated to be between 740 and 1,850 GBq. The fire also caused soil contamination with very low contamination areas. This contamination was found inside the site on about one hectare; it affected building 130 overlooking the silo and the surrounding areas. The maximum values recorded were 111.103 Bq.m−2 cesium 137 at the site, and contamination remained low off-site and did not exceed 3.7.102 Bq.m−2 of cesium 137. 2.7.7. Chalk River Gamma-emitting radionuclides from discharges from the Chalk River Laboratories were only present in the sediments of the Ottawa River in the immediate vicinity of the outfall and were no longer detected 2 km

42

Industrial and Medical Nuclear Accidents

downstream. These detected anthropogenic radionuclides were 60Co, 137 Cs, 152Eu, 154Eu, 155Eu and 241Am [ROW 12].

94

Nb,

2.7.8. Simi Valley Apparently, no radioactive contamination studies around the Simi Valley site were conducted after the 1959 nuclear accident or at least made public. Some data still appear about the situation 40 years later. Rogers [ROG 12] discussed a 1999 report by Foster Wheeler Environmental Company in Costa Mesa that found that soils contained strontium 90 concentrations 27 times higher than normal. 2.8. Health consequences Health consequences affect two distinct populations: nuclear workers and the general population. Unfortunately, although health data concerning the professional nuclear sector are provided, for some accidents, data are limited. 2.8.1. Uranium miners Historically, people working in uranium mines have suffered very high doses of radiation. The exposure doses of miners are mainly due to radon degradation products (RDPs). These doses are often expressed in unit-alphamonths (UAM) and one UAM is equivalent to 5 mSv, based on an average of 2,000 hours worked per year. As before 1950, workers were exposed to high doses of RDP, and their mortality rate from lung cancer was much higher than that of the rest of the male population. In Canada, average doses of RDPs have decreased from more than 400 UAM (2000 mSv) in 1940 to less than 2.3 UAM (11.5 mSv) in 1970. Exposure to RDPs was reduced more than four times from 1970 (≤2.3 UAM or 11.5 mSv) to 2000 (≤0.5 UAM or 2.5 mSv). Exposure to the RDPs from 1975 to 2000 for all Saskatchewan mining facilities ranged from 0.2 to 1 UAM. Starting in 1979, the average RDP dose (due to radon alone) was kept below 0.2 UAM (1 mSv) at all times. The average external dose since 1975 has been kept below 2 mSv and has been reduced to less than 1 mSv since 1994 [CCS 14a, CCS 14b].

Accidents Related to Nuclear Power Production

43

According to Roscoe et al. [ROS 83], the main reason for the overall increase in mortality in the American white miner cohort was higher rates of lung cancer deaths, accidents and non-malignant respiratory diseases (NMRDs). Canadian studies have linked lung cancer in uranium miners to exposure to ionizing radiation [CCS 15, HOW 15]. According to the CCSN [CCS 14a], workers at the Port Radium mine in the Northwest Territories have received the highest doses of RDPs, approximately 900 mSv, during their careers. The RDP doses reported for the Port Radium mine in the 1940s were in the order of 450 UAM or 2,250 mSv, while those reported in 2013 for Saskatchewan mines were in the range of 0.05 UAM or 0.25 mSv. These doses are also below the radon threshold recommended by Santé Canada in its guideline for domestic radon, 200 Bq.m−3 (i.e. nearly 2 mSv). Among the 8,487 miners in Saskatchewan from 1948 to 1980, 65 lung cancers were detected, which is significantly higher than testimonies report [HOW 86]. The lung cancer mortality rate in the uranium miners cohort in Ontario was 34% higher than that in the Canadian population (SMR = 1.34, 95% CI 1.27–1.42), as concluded by the OCRC report, and the incidence of lung cancer among uranium miners in Ontario was 30% higher than that in the Canadian population (SIR = 1.30, 95% CI 1.23–1.37) [KUS 93, OCR 15]. In the United States, as early as 1964, Wagener et al. [WAG 64] considered that from the evidence available, the start of the increase in respiratory cancer among American uranium miners necessarily involved radiation from the mining atmosphere. Among the 459 residents who had worked in American underground uranium mines (Uravan, Colorado), a significant increase in lung cancer was found (SMR 2.00; 95% CI 1.39–2.78). This community cohort study revealed a significant excess of lung cancer in men who had been employed as underground miners. Similarly, increased mortality was observed among the 1,735 underground uranium miners in Grants, New Mexico, from 1955 to 1990. This was a result of respiratory diseases, either malignant (SMR 2.17; 95% CI 1.75–2.65; n = 95) or non-malignant (SMR 1.64; 95% CI 1.23–2.13; n = 55), cirrhosis of the liver (SMR 1.79; n = 18) and external causes (SMR 1.65; n = 58). The likely excess lung cancer level was down to historically high levels of radon in uranium mines on the Colorado Plateau combined with intensive use of tobacco products [BOI 07, BOI 08].

44

Industrial and Medical Nuclear Accidents

In France, the miners cohort has a statistically significant excess mortality rate for liver cancers (SMR = 1.75; 95% CI 1.01–2.80) [BOV 16]. As Tomasek et al. [TOM 08] in a study of Czech and French uranium miners concluded: “There have been excessive reports of lung cancer, reduced lung function and emphysema. This excess has mainly been attributed to the irradiation of the tracheobronchial epithelium by particles emitted during the radioactive decay of radon and its derivatives”. An epidemiological study [AMA 09] among French miners reveals a significant association between the relative risk of lung cancer and silicosis (OR silicosis = 3.6; 95% CI 1.4–8.9), and the relationship between radon and lung cancer persists after adjustment for smokers and silicotic status (ERR radon per working month = 1.0%; 95% CI 0.1–3.5%). Radon, smoking and silicotic status appear to be three factors that each have a specific effect on lung cancer risk. A multi-analysis concerning miners was carried out by Lublin et al. [LUB 95]. It involved 11 cohorts of miners who had worked underground and included more than 27,000 lung cancer deaths among the 68,000 miners studied and almost 1.5 million person-years observed. This study found that the relative excess risk (RER) per UAM for lung cancer death was directly proportionate to the cumulative dose of PDR (ERR/UAM = 0.49%; 95% CI 0.2–1.0%). Many questions remain about the risks of extra-pulmonary cancers (as the study by Bouet et al. above shows for liver cancer) and non-malignant diseases and about the health impact of other occupational radiological exposures [DRU 15]. 2.8.2. Workers in the nuclear industry In the absence of a nuclear accident, chronic exposure to ionizing radiation can have health consequences. For this reason, worker cohorts in the nuclear industry are being followed up medically. In Oak Ridge, the observed number of 1,017 deaths from all causes was 74% of what was expected. This finding, which has been repeated several times, is based in particular on the cohort’s relatively high socio-economic status, associated with good health [CHE 83]. Among workers at a spent fuel reprocessing plant (Tennessee Eastman Corporation, USA), the relative risk of lung cancer increased with increasing

Accidents Related to Nuclear Power Production

45

exposure even after controlling age and smoking, but only for those over 45 years of age at first exposure [COO 83]. Among the 999 workers exposed to atmospheric uranium from 1943 to 1947 at the Tennessee reprocessing plant, the doses received were as high as 74 rads or 740 rems if a quality factor of 10 is used [BEC 83]. Among female watchmakers who used radium-based light dials, a tripling of the risk of multiple myeloma occurred in the cohort working before 1930. However, analyses of body burdens and duration of use suggest that external radiation due to radium was more likely to be responsible than internal radium [STE 83]. The impact of working in a nuclear environment is understood in France thanks to the TRACY cohort. This cohort of French fuel cycle workers was the subject of a reconstruction of occupational exposures [SAM 12, SAM 16]. According to the IRSN [IRS 17a], during the follow-up period (1968–2008) and with an average follow-up period of 27 years, 2,130 deaths (17% of workers) occurred. The mortality analysis shows a strong effect of the statistically significant “healthy worker” with an under-mortality of 35% compared to the national general population. Significant under-mortality is also observed for deaths by cancer pathology, non-cancer pathology and external causes. A single location presented a significant excess compared to the French population: pleural cancer (17 cases) with a standardized mortality ratio (SMR) of 2.04 (95% CI 1.19–3.27). UNSCEAR [UNS 00b] reported 136 nuclear accidents with clinical consequences causing serious injuries to 90 nuclear workers, at least 40 of whom died within a few days. In addition, the same organization recorded 13 other accidents with clinical consequences for 368 workers, 13 of whom died. The normalized annual effective doses per unit of energy production were significantly higher for miners operating uranium mines. These doses decreased steadily from 1975 to 1994 due to radiation protection measures taken over time (Figure 2.5). The number of nuclear workers monitored for radiation increased from 1975 to 1989 and then stabilized, while the annual effective doses to workers steadily decreased (Figure 2.6).

46

Industrial and Medical Nuclear Accidents

Figure 2.5. Standardized collective effective dose per unit of energy production for various stages of the nuclear fuel cycle (mining, conversion, enrichment and fuel production) and for various time periods (adapted from [UNS 00b]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

Figure 2.6. Changes in the number of workers (in thousands) under surveillance (A) and of effective doses received (in mSv) by nuclear fuel cycle workers (B) according to four periods (adapted from [UNS 00b])

Accidents Related to Nuclear Power Production

47

2.8.3. Simi Valley Beyea [BEY 06] tried to estimate the exposure of residents around the Santa Susana Field Laboratory (Simi Valley, USA) to help epidemiologists improve the effectiveness of their studies on radiation-induced diseases. This has been extremely complex, particularly from a meteorological point of view as a result of the particular climate of this region. In addition, the information available on radioactivity releases in the 1950s and 1960s is very limited. Exposures were dominated by the inhalation of radioactive iodine and ground deposition of radiocesium, since milk was a relatively minor source at this location. Out of the 20,000 simulations performed by Beyea, the average number of excess cancers was 260 (95% CI 0–1,800). In 25% of simulations, there were eight or fewer excess cancers; in half of the scenarios, the number of cancers was 50 or more, and in 2.5% of them, the number of cancers expected was 1,800 or more. Nine specific or “radiosensitive” cancers revealed high incidence rates between 1988 and 1995 in people living within 2 miles of the SSFL. Specifically, the standardized incidence rate was greater than 1.6 for cancers of the blood and lymphatic tissues, bladder, thyroid and upper aerodigestive tract. Between 1996 and 2002, the prevalence rate among people living within 2 miles of the STPE was greater than 1.6 for thyroid cancer [MOR 07]. For his part, summarizing the various epidemiological studies of this site, Weitzberg [WEI 14] considers that no evidence of an increase in cancer in the population around Santa Susana has been scientifically demonstrated. It should be noted that the author probably had conflicts of interest with the company responsible for the accident, while the article by Morgenstern et al. (2007) was commissioned by the Agency for Toxic Substances and Disease Registry (ATSDR). Epidemiological studies on workers at the SSFL site indicate a trend towards an increase in cancer mortality rate associated with an increase in the cumulative radiation dose to workers when this dose was external [RIT 99a, RIT 99b]. When this exposure was internal, Ritz et al. [RIT 00] also observed a trend between cumulative radiation exposure and cancer mortality (all types), mortality due to lymphopoietic cancers and of the upper aerodigestive tract, but not with lung cancer. On the other hand, Boice et al. [BOI 06] did not confirm this significant increase in cancer mortality in general or to a specific cancer among employees who worked at the SSFL site between 1948 and 1999.

48

Industrial and Medical Nuclear Accidents

Many class actions have been initiated by the population living around the SSFL site. After 7 years of litigation, 100 local residents received a US$30 million settlement following a trial. Information about the verdict and the conclusions found remains elusive, with only the settlement as proof of the conclusion [ROG 12]. In a study on clusters (disease outbreaks), Ingber and Ross [ING 11] consider that the Santa Susana site lacks evidence to be included in a first analysis. 2.8.4. Tokai-Mura Four hours after the accident began, approximately 50 families were evacuated within a radius of 350 m, 161 people living in 39 houses, and the area was closed to traffic [TAK 05a, TAK 05b]. In addition, approximately 320,000 residents residing within a 10 km radius were notified by loudspeakers, starting at 12:30 p.m. (2 hours after the onset of the chain reaction), to stay at home and close their windows. At 7 p.m., more than 5,000 families were still confined to their homes. A Tokai-Mura city official said the same day that the rain was facilitating the high radiation level in the vicinity of the accident site. Three plant employees who had been exposed to radiation were transported by helicopter to hospital. The two most affected workers, aged 35 and 39, who reportedly received doses of 16,000–20,000 and 6,000–10,000 mSv, respectively, had symptoms of high radiation that are difficult to treat. About half of those who have suffered radiation at this level face death within 30 days. The two most seriously injured died after 12 weeks and 7 months. The third worker (54 years old) received a lower dose of 1,000–5,000 mSv. According to experts, the chances of this patient’s survival (who was suffering from severe pain) were reasonable, subject to possible complications in the short or long term from severe burns to the arm, head and neck. The quality of care provided to victims has made it possible to prolong their survival beyond what had ever been achieved in accidents of this type and has thus revealed complex and new pathologies [IRS 02]. It was only around 3 a.m. on Friday morning that employees tried to stop the reaction by pumping cooling water around the container and pouring sodium borate to absorb the neutrons. Twenty-four of these employees were seriously irradiated and reportedly received doses above 48 mSv and even up

Accidents Related to Nuclear Power Production

49

to 120 mSv for one of them. Of the accidentally exposed workers in the plant, 56 were exposed to a dose of 0.1–23 mSv and 21 other workers received high doses when the tank was drained. For members of the public, estimates are highly variable with one receiving 24 mSv, four receiving 10–15 mSv and 15 receiving 5–10 mSv. 2.8.5. Lucens Staff at the Lucens power plant was examined at hospital (Hôpital Cantonal de Berne), which revealed that they had not been put at risk. The Atlas of Cancer Mortality in Switzerland prepared by Professors Schüler and Bopp shows an increase in intestinal cancer in the Broye region between 1970 and 1990. Professor Bopp interviewed in “Le Temps” on this subject mentions that “In men, the general excess mortality in the Broye region has the same components as in neighboring regions, namely diseases related to alcohol consumption, accidents and lung cancer. In women, heart disease was the cause of additional deaths. It is therefore impossible to deduce a link with the nuclear damage of 1969, especially since intestinal cancer is not one of the cancers suspected of being caused by radiation” [CAN 11]. 2.8.6. Three Mile Island Several authors [BRO 82, DEW 87] point out that populations near Three Mile Island (TMI) have developed mental trauma due to anxiety created by unnecessary and careless publicity. The excess percentage of morbidity caused by the accident for the period 1981–1984 (after a latency of 2 years) was estimated per unit dose (associated with the standard deviation). These percentages were 0.020 ± 0.012 for all cancers, 0.082 ± 0.032 for lung cancer and 0.116 ± 0.067 for leukemias. Adjustments for socio-economic variables increase the percentage estimates to 0.034 ± 0.013, 0.103 ± 0.035 and 0.139 ± 0.073, respectively, for all cancers, lung cancers and leukemias [WIN 97]. According to Talbott et al. [TAL 00], standardized mortality ratios are significantly raised for men and women (SMR 109 and 118, respectively). They also found a significant linear trend between breast cancer risk in women and increasing levels of exposure associated with the TMI accident (p = 0.02). In a subsequent study, the same authors [TAL 03] were more

50

Industrial and Medical Nuclear Accidents

reserved about cancer and radioactivity relationships caused by the TMI accident than in their first article. In a synthesis conducted 25 years after the accident, Osif et al. [OSI 04] estimated that the health effects resulting from the radiation emitted by the reactor accident were minimal. The only significant effects were on the mental health of local populations. However, the studies carried out only concern a part of the population and over a short period of time. Some effects may appear years or even decades later. For example, 30 years after the TMI accident, an increased incidence of thyroid cancer was observed in counties south of the plant and in high-risk age groups. Average incidence rates between 1990 and 2009 were higher than expected in the counties of York, Lancaster, Adams and Chester [LEV 13]. Despite these findings, a direct correlation with the accident remains uncertain, as incidence rates may coincide with other factors, and the original data were limited [LEV 13]. 2.8.7. Church Rock Following the accident at the Church Rock mine retention basin in New Mexico, the dose for the general population over 50 years is estimated at 2.04 mSv for the inhalation of sediment particles from the river. The same dose is estimated at 0.01 mSv in the liver and 0.79 mSv in the bones when eating wild meat. This suggests that the major contribution to human exposure comes from mine dehydration effluent that has been continuously released into the river system for many years [RUT 84]. 2.8.8. La Hague The incident involving the breach of radioactive effluents in the sea at La Hague was the subject of a reconstruction of the radiological impact, based on the consumption of marine products by the GRNC [GRN 99]. The calculations were based on two assumptions, and the differences between the results were in the order of a factor of 7 for the collective ex utero dose and a factor of 8 for the collective risk. Whatever the calculation hypothesis considered, the predicted number of leukemia cases, which was in the order of 0.0014 cases between 1978 and 1996 (taking into account only the consumption of marine products), increases to 0.002 if we look at all the exposure routes to discharges from nuclear installations in North Cotentin. This result illustrates the significant sensitivity of the risk of leukemia down

Accidents Related to Nuclear Power Production

51

to discharges from nuclear installations, particularly with regard to the incident of pipe breakage [BAR 00]. The consequences on exposure ex utero of the two major incidents that occurred at the site of the La Hague spent fuel reprocessing plant (breaking of the offshore discharge pipe in 1979–1980 and fire at silo 181 containing high-level waste on January 6, 1981) were estimated and are presented in Table 2.2. Incident

Type of exposure

Dose (myear.Sv)

Percentage

Breaking of the pipe

Ingestion (90Sr, 106Ru)

0.04

48

External (106Ru, 125Sb)

25

244

Inadvertence ( Cm)

16 90

Spray and spreading ( Sr) Silo fire

Ingestion (

137

137

Cs)

External ( Cs, Inhalation

11 0.14

134

Cs)

64 35 1

Table 2.2. Type and level of exposure of the population of Beaumont-Hague caused by incidents at the La Hague spent fuel reprocessing plant (modified according to [GRN 99]. For each of the accidents, the percentages of the various causes are provided

2.8.9. Chalk River The two accidents at the Chalk River Laboratories in Canada required a major clean-up effort involving many civilians and military personnel (approximately 850). Health surveillance of these workers did not seem to reveal any negative impact of the two accidents [WER 82]. However, some cleaning workers who were part of the military contingent assigned to the NRX reactor applied unsuccessfully for a military disability pension as a result of health damage. 2.8.10. Ruthenium 106 releases in Russia in September 2017 Contamination of the food chain by ruthenium 106 is known, with the contamination of laverbread (made from the seaweed Porphyra sp.) around Windscale and beyond in the Irish Sea causing a partial exposure of the

52

Industrial and Medical Nuclear Accidents

population in 1959 of 7 mSv [AMI 13a]. The risk in the case of this Russian accident (Mayak) would be the consumption of mushrooms. The maximum acceptable standard (MAS) for this radionuclide in mushrooms is 1,250 Bq.kg−1. The transfer factor from soil to fungal mycelium is about 102 m2.kg−1. Therefore, to exceed the MAS, it is necessary that the soil be contaminated to more than 2,000,000,000 Bq.m−2, which in this accident represents about a 2 km radius. In addition, for a child (2–7 years old) to exceed the committed effective dose by ingestion of 1 mSv, they would have to eat 32 kg of mushrooms in 1 year [IRS 17c]. 2.9. The cost of accidents For the Simi Valley accident, dismantling costs for the period 1974–1983 amounted to US$16.6 million. This represents about 11% of the cost of the liquid sodium cooled test reactor (estimated at US$150 million, 1982 value) [CAR 83]. For Three Mile Island (TMI), the initial construction cost was US$400 million. In Marc Haumont’s blog, a text is summarized by Cousteau [COU 81] on the cost of the TMI accident. “In 1975, Congress passed the Anderson Act, according to which the American state insured itself against nuclear accidents to the tune of US$560 million. After the accident, the decontamination and reconditioning of the defective reactor was estimated at more than US$500 million. A few months after the accident, 14 law firms representing people living within a 40 km radius of the TMI plant filed lawsuits for ‘negligence or wilful mismanagement’ against the responsible electricity company (Metropolitan Edison). This was the largest trial ever undertaken and the sums claimed amounted to US$560 million. Finally, the expenses generated by the TMI accident, classified at level 5 on the INES, will prove to be more than 1 billion dollars, excluding the storage of radioactive waste for which no definitive solution exists”. The cleaning of TMI Unit 2 ended in December 1993, 14 years after the accident, but the reactor will remain under permanent control until it is completely dismantled. Located within the Sellafield complex, the THORP for reprocessing spent nuclear fuel ceased operations in 2010. This site, which cost €2.35 billion to build and was considered the spearhead of the British nuclear industry, operated for only 9 years. British Nuclear Fuels (BNFL) decided that the

Accidents Related to Nuclear Power Production

53

plant, following the dismantling of the reprocessing plants, will become a nuclear waste storage center. But how much will this conversion cost? “45 billion euros of clean-up work will be required”, predicted Brian Watson, the director of the Sellafield complex [BRO 03]. In the case of France, many questions remain about the costs of nuclear power in the field of safety, decommissioning and waste. With regard to safety, following the Fukushima accident, the ASN launched additional safety assessments in 2011 and 2012. These assessments demonstrate the need for many developments in operating facilities to be carried out as quickly as possible. Under ASN’s terms, this would lead to a massive investment that could be in the order of €50 billion or more. However, only 40 have been provisioned by EDF [LEG 13]. An increasing number of nuclear installations will be dismantled in the future, and it will be inevitably necessary to manage their waste. Cost estimates have been put forward: will the dismantling require 20, 25 billion euros or more? For waste management, the sum of more than 30 billion has been proposed [LEG 13]. After Three Mile Island, Chernobyl and Fukushima, Leglu et al. [LEG 13] have several questions. Where and when will the next disaster take place? How big will it be and who will sacrifice themselves to contain it? How many people will have to be evacuated, and how much territory will become a restricted area? If this perspective is not unthinkable, as the authors have tried to show, in France the consequences would be catastrophic, particularly because of the population density near some reactors. In the end, these authors wonder whether staying in the nuclear industry would not be more expensive, in both human and financial terms, than leaving it. A serious accident would cost France several hundred billion dollars! Ultimately, Leglu et al. [LEG 13] believe that there is only one solution: to develop an energy plan that will save money and further diversify primary sources. By using the definition of a nuclear accident as the death of a human being or the cost of the accident exceeding US$50,000, Sovocool [SOV 10] identifies no less than 99 nuclear accidents from 1952 to 2010. The total cost of legal damages for these accidents is US$20.5 billion, representing one accident and US$330 million in damages each year over the past six decades.

54

Industrial and Medical Nuclear Accidents

2.11. Conclusions Environmental impacts are not necessarily related to a nuclear accident. Thus, the abandonment of uranium mines is often synonymous with radioactive contamination by uranium. However, the most serious environmental and health impacts result from accidents at nuclear reactors or spent fuel reprocessing plants. The health impacts, out of any accident, were significant for miners working in the period from 1940 to 1970. Since then, precautions have been taken to extract as much radon as possible from mine galleries. Until 1995, the number of accidents involving nuclear reactors was two to three accidents per year (Figure 2.7).

Figure 2.7. Number of accidents involving nuclear reactors or causing high irradiation over 5-year periods from 1945 to 1995 (modified from Sanderson et al., 1997 in [MAC 00])

The 99 nuclear accidents, fatal and/or costing more than US$50,000, between 1952 and 2010 resulted in 4,100 deaths (including 4,056 from the Chernobyl accident alone). Compared to deaths caused by other energy sources, nuclear energy is the second most deadly source of energy supply (after hydroelectric dams, including the failure of the Shimantan hydroelectric plant in China causing 171,000 deaths on August 8, 1975) and above oil, coal and natural gas production systems [SOV 08]. A total of

Accidents Related to Nuclear Power Production

55

57 accidents (as defined by Sovacool [SOV 10]) have occurred since the Chernobyl disaster in 1986 and nearly two-thirds (56 out of 99) of all nuclear accidents have occurred in the United States, refuting the notion that serious accidents are consigned to the past or to non-American countries that have neither the control of modern technology nor the effective supervision of the nuclear industry [SOV 10].

3 The Extremely Serious Nuclear Accident at Chernobyl

3.1. Introduction The accident at the Chernobyl nuclear power plant on April 26, 1986 at 00:23 is the biggest disaster in the civil nuclear industry, at least until a final assessment of the Fukushima nuclear power plant accident is made in a few years’ time. Literature on this accident is much more extensive than that on previous accidents. This is down to several reasons, such as the scale of the accident, the need for transparency with regard to the other states concerned, in particular the European countries, the end of the Soviet regime, which occurred less than 4 years after the accident, and the cooperation of scientists from all over the world in understanding the consequences of the accident. Our knowledge is important even though many gray areas remain, such as the monitoring of affected human populations given the lack of a serious census in place as soon as the accident occurred. Following the accident, the IAEA’s expertise was called upon to study the consequences. The main results were presented in conferences. They focused on environmental contamination, estimation of radiation exposure of various populations, health impacts and protective countermeasures. All this has been the subject of two publications [IAE 91a, IAE 91b].

Industrial and Medical Nuclear Accidents: Environmental, Ecological, Health and Socio-economic Consequences, First Edition. Jean-Claude Amiard. © ISTE Ltd 2019. Published by ISTE Ltd and John Wiley & Sons, Inc.

58

Industrial and Medical Nuclear Accidents

The IAEA, in collaboration with the WHO and the European Community, launched two major research programs: “International Chernobyl Project: Health effects” and “Chernobyl: Environmental Impact Assessment”. A first assessment of the results obtained was presented at the conference “One Decade after Chernobyl. Summing up the Consequences of the Accident” [IAE 96c]. The first conclusions on acute syndromes, thyroid cancers, long-term effects, population stress and the perspectives for this accident were drawn. Many other reports and publications will follow. 3.2. The facts 3.2.1. The Chernobyl site and the nuclear power plant The Chernobyl site is in northern Ukraine in an environment of forests and wetlands on the banks of the Pripyat River, a tributary of the Dnieper River. The cities around the site are Pripyat, a city that served to house workers (49,000 inhabitants) 3 km to the northwest, Chernobyl (12,000 inhabitants) 12 km to the southeast and Kiev (3 million inhabitants) 110 km to the south. The Chernobyl nuclear power plant consisted of two 1,000 MWe RMBK reactors No. 3 and No. 4) moderated with graphite and cooled by boiling water circulating in pressure tubes containing fuel, with uranium enriched to 2%. This type of reactor had no retention system nor containment. The Chernobyl reactor in question started up in September 1977 and was to operate for 30 years. 3.2.2. The accident Following a poorly controlled experiment, reactor No. 4 overheated on April 25, 1986 in the evening, which caused an immediate explosion in the upper part of the reactor. The core collapsed, and the lid (a 2,000-ton slab) lifted vertically under the impact of the explosion. All pressure tubes containing the fuel bundles broke. Graphite explosions and fires lasted 10 days, and the release of radioactive materials continued for 5 months. During the explosion, the most volatile elements (iodine, tellurium, cesium) and fine dust were thrown up to an altitude of 1,200 m. A total of 659 Chernobyl firefighters from Pripyat and Kiev fought the fire, 108 of whom received high doses of radiation. Three hours after the fire was

The Extremely Serious Nuclear Accident at Chernobyl

59

contained (a graphite fire resumed and lasted several days), the releases rose to only 200–400 m. Thousands of tons of materials (lava, sand) were spilled on the reactor core. The core temperature rose to 2,000°C, causing iodine to volatilize and corium to flow into the lower parts of the reactor. 3.2.3. The core and the sarcophage The molten core represented 130–150 tons and a radioactivity of 7.4.1017 Bq. It was porous and about 30 tons were in the form of dust with a radioactivity of 1017 Bq (47% from 90Sr and 30% from 137Cs). In addition, approximately 3,000 m3 of water was present in the core. Annual particulate emissions were limited to 1010 Bq as a result of the periodic injection of polyvinyl acetate into the core. The main risk was related to groundwater contamination. The period of atmospheric emissions was followed by the clean–up work by thousands of liquidators (clean-up workers). Often, their work could not exceed a few minutes; otherwise, the exposure would have become fatal. Then, the first sarcophagus was constructed, which trapped the rest of the radioactivity from the core, preventing the leaching of radioactive isotopes by rainwater and allowing the restarting of reactor No. 3. In 1997, the principle of a second sarcophagus was adopted, the cost of which was estimated at 760 million euros. The project was managed by the European Bank for Reconstruction and Development (EBRD). The second sarcophagus, called the Chernobyl Arch, was built by Bouygues and Vinci (France) in 2016 to isolate reactor No. 4 and its first damaged sarcophagus from the environment. It is an arch-shaped metal structure 108 m high and 162 m wide with a span of 257 m. It is designed for a service life of 100 years. 3.2.4. Atmospheric emissions The reactor core contained 190 tons of 2% 235U-enriched fuel distributed in 1,659 elements. The combustion rate after 715 days of operation was 10,300 MWD.t−1. About 3–4% of the 190 tons of fuel was released into the atmosphere in 10 days. Releases of radionuclides with a physical half-life greater than 1 year represented 12.1018 Bq (12 billion billion Bq), including

60

Industrial and Medical Nuclear Accidents

6.5.1018 Bq for noble gases alone (xenon and krypton). About 60% of the iodine and 30% of the cesium in the fuel were released. On the contrary, only 4% of strontium radioisotopes and 3% of plutonium and neptunium radioisotopes were expelled from the core. The atmospheric emissions estimated by the IAEA in 1997 were 3.7.1016 Bq of 137Cs, 2.6.1017 Bq of 131I, 8.1015 Bq of 90Sr and 9.1013 Bq of Pu-α. To these must be added volatile noble gases such as krypton and xenon. The maximum discharge occurred from day 1 to day 10. Release estimates have since been revised upwards and would represent about 33% (± 10%) of the cesium present in the reactor core. Plutonium release would be 15–23 kg. Thus, Magill and Galy [MAG 05] provide a relatively accurate inventory of radionuclides dispersed in the environment following the Chernobyl accident. Releases vary greatly depending on the physical half-life of the radionuclides. Thus, those with a period of less than 1 month represent 84%, more than 1 year 16%, more than 30 years 1% and more than 50 years only 0.001% [POI 01]. 3.2.5. The dispersion of radionuclides The clouds of radioactive elements rose to an altitude of more than 1,000 m and were carried away by the winds. As the release took place over several days under changing weather conditions, three main radioactive clouds formed contaminating northwest, central and southwestern Europe. The initial cloud, driven by a southeast to northwest wind, first headed towards the Baltic and Scandinavia; then, particles were emitted to the southwest (Central and Western Europe); towards the end of the discharge, the radioactive materials moved south (Greece, Turkey). It was during May that this large quantity of radioactive isotopes fell back on Europe. In Europe, the trajectory of the radioactive cloud was analyzed by ApSimon et al. [APS 89] showing a passage over Scandinavia on April 26, 1986 and then on April 27, a change of direction towards Central Europe, Northern Italy and Eastern France. Deposition levels reached several hundred kBq.m−2. UNSCEAR offered a figure summarizing the radioactive cloud’s displacement (Figure 3.1).

The Extremely Serious Nuclear Accident at Chernobyl

61

Figure 3.1. Displacement of the radioactive plume over time (A April 26, B April 27–28 and C April 29–30, 1986). The figures represent the radioactive cloud’s day of arrival (1, April 26; 2, April 27; 3, April 28; 4, April 29; 5, April 30; 6, May 1; 7, May 2 and 8, May 3) (adapted from [UNS 88, MOU 00]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

3.2.6. Radioactive fallout Radioactive fallout onto the ground is mainly explained by rainfall (intensity and homogeneity), with upper winds guiding only the cloud trajectory. Thus, the quantity dropped onto a site reflects the coincidence between a rainy episode and the passage of the radioactive cloud. The distance from the accident site was not a determining factor. The consequence was that the amount of radioactivity released varied greatly over short distances. The distribution of radioactive contamination is a “contamination task”. On a European scale, the most significant activities were located near the accident site in Ukraine, Russia and Belarus, where contamination in 1986 was over 185,000 Bq.m−2 of 137Cs. Then came the

62

Industrial and Medical Nuclear Accidents

places with heavy rain in the Alps, the Vosges, Wales and Scandinavia with levels between 40,000 and 100,000 Bq.m−2. For the rest of Europe, the fallout from 137Cs was between 0 and 40,000 Bq.m−2. The heterogeneity and brevity of radioactive deposits were characteristic of the Chernobyl accident. In the 30 km zone around the plant, the estimated soil deposition in 1986 was 930.1015 Bq, which fell to 230.1015 Bq in August 1996 as a result of the disappearance of short-lived radionuclides. At the end of 2000, most of the radioactivity was down to two radionuclides, 137Cs and 90Sr. The total activity of the α emitters in the soils of this area was about 80.1012 Bq. The share of americium 241 increased from 3 to 40.1012 Bq as a result of the decrease in plutonium 241. The area around the plant was mainly contaminated with 137Cs, 90Sr, 241Am, 238Pu, 239Pu, 240Pu and 241Pu (Table 3.1). Ninety percent of the external exposure was caused by 137Cs [POI 01]. Area

137

Cs (Bq)

90

Sr (Bq)

239+240

Pu (Bq)

1.14.10

14

1–3 km

5.92.10

14

3–5 km

1.44.1015

7.40.1014

3.70.1012

5–15 km

3.18.1015

3.07.1015

1.33.1013

> 15 km

4.07.1015

3.70.1015

2.96.1013

0–1 km

1.11.10

14

11

2.59.10

6.29.10

14

1.37.1012

Table 3.1. Inventory of 137Cs, 90Sr and 239,240Pu deposits in the 30 km Chernobyl area at the end of 2000 (modified from [POI 01])

Deposits in the three republics of Belarus, Russia and Ukraine are significant and affect a large population. Thus, cesium 137 deposits in soils on January 1, 1995 are reported in Table 3.2. In Belarus, cesium deposits were significant and exceeded 37 kBq.m−2 over 46,450 km2, where 2.2 million people were living at the time of the accident and 1.6 million at the beginning of 1995. In Ukraine, the territory with a contamination greater than 37 kBq.m−2 was 41,840 km2 inhabited by 2.4 million people. The same area for Russia was 56,930 km2 inhabited by 5.6 million people. The three areas (A, B and C shown in Figure 3.2) particularly contaminated with 137Cs were around the plant, in Bryansk and Kaluga (Figure 3.2.).

The Extremely Serious Nuclear Accident at Chernobyl

Figure 3.2. Areas highly contaminated in 1986 with cesium 137 (>555 kBq.m−2) (C zone around the Chernobyl power plant, B zone Bryansk and Belarus and K zone of Kaluga-Tula-Orel) (adapted from [MOU 00]). For a color version of the figure, see www.iste.co.uk/amiard/industrial.zip

Deposit (in Bq.m−2)

Population on January 1, 1995

Surface area (in km2) Ukraine

37–185

37,200

1,732,000

185–555

3,180

653,000

555–1,480

880

19,200

>1,480

270

Sum

41,480

37–185

48,800

2,249,000

185–555

5,720

347,000

555–1,480

2,100

91,000

>1,480

310

Sum

56,930

2,405,000 Russian Federation

2,687,000

63

64

Industrial and Medical Nuclear Accidents

Belarus 37–185

29,920

1,300,000

185–555

10,170

300,000

555–1,480

4,210

20,000

>1,480

2,150

Sum

46,450

1,620,000

Total

145,220

6,712,000

Table 3.2. Surface area in km2 and populations affected on January 1, 1995 137 −2 according to soil contamination by Cs in Bq.m (modified from [POI 01])

More than 60% of the iodine in the core spread. Deposits were abundant at the beginning of the accident with a maximum for iodine 131 of 18,500,000 Bq.m−2 as of May 10, 1986. Releases of 89Sr and 90Sr were abundant, respectively 83.1015 and 8.1015 Bq, but the physical periods were very different (2 and 28 years respectively), and 15 years after the accident, only 90Sr was still present. Deposits of plutonium 239 and 240 were lower than those of iodine and cesium. Outside the exclusion zone, the maximum deposit was 3,700 Bq.m−2 [POI 01]. 3.2.7. Accident management In the countries of the former Soviet Union, trapping radioactive particles has been attempted to avoid secondary contamination. Forests in the vicinity of the site were felled to prevent possible fires, and trees were buried in shallow trenches. About 800 interim waste disposal sites have been created, containing 4.106 m3 of waste. In 1989, to protect the water supply to cities such as Kiev, 130 dams and dikes were built. During this phase, interventions were carried out when soil contamination exceeded 555 kBq.m−2 as 137Cs. Three maps of soil contamination in 1989 were published by the IAEA for 137Cs, 90Sr, 239Pu and 240Pu [IAE 91c]. The administrative organization of contaminated areas has evolved over time. At the beginning, a prohibited zone (known as the 10 km zone) was defined according to 137Cs isotope concentrations greater than 1,480 Bq.m−2 and an exclusion zone (known as the 30 km zone) when 137Cs concentrations exceeded 555 kBq.m−2, or 90Sr 74 kBq.m−2 or Pu 3.7 kBq.m−2. The exclusion zone is divided into several parts. It includes the 30 km zone itself

The Extremely Serious Nuclear Accident at Chernobyl

65

(2,800 km2) around the site where the population was evacuated, as well as various other evacuated settlements and also areas where agriculture is prohibited. The entire exclusion zone covers an area of 4,000 km2, including 2,100 km2 in Belarus, 2,040 km2 in Ukraine and 170 km2 in Russia. Since 1991, the Ukrainian territory has been divided into three zones according to the soil contamination in 137Cs. If the 137Cs surface activity is greater than 555 kBq.m−2, then housing, industrial and agricultural activities are prohibited and entry and exit into the area are regulated. Relocation becomes mandatory as soon as the surface activity exceeds 1,480 kBq.m−2. If the 137Cs surface activity is between 185 and 555 kBq.m−2, then no new activity can be created and this second area is called voluntary relocation, because only the inhabitants requesting it will be relocated. When the 137Cs surface activity is between 37 and 185 kBq.m−2, the restrictions are the same as in the second zone, but industrial activities can be established there, while health centers cannot [POI 01]. The management of the territory in Belarus is slightly different. In 1991 (February 22), the country enacted a law defining four zones according to soil contamination with various radionuclides (137Cs, 90Sr and plutonium isotopes). Depending on the area today, people may or may not stay there, and may or may not be entitled to resettlement (Table 3.3). Soil contamination in kBq.m−2

Zones

Cesium 137

Zone 1: periodic radiological inspection

37–185

Strontium 90 Plutonium 238, 239 and 240 5.55–18.5

0.37–0.74

Zone 2: migration rights 18.5–74

18.5–74

0.74–1.85

Zone 3: right to relocation

555–1,480

74–111

1.85–3.7

Zone 4: mandatory and immediate relocation

>1,480

>111

>3.7

Table 3.3. Definition of the contamination zones in −2 Belarus in kBq.m (modified from [ACR 15])

After the accident, 116,000 people were evacuated during the first week, including those living within 30 km of the plant, which became an “exclusion zone”. These populations were reported to have received a dose

66

Industrial and Medical Nuclear Accidents

between 50 and 140 mSv. In total, the displaced populations in Chernobyl were about 135,000 in Belarus, 175,000 in Ukraine and 50,000 in Russia. Contaminated soils were about 25% in Belarus, 5% in Ukraine and 1.5% in Russia. The economically affected population was estimated at 4.5 million inhabitants [MAS 04]. From 1987 to 1989, food control and consumption bans took the value of 350 mSv as an irradiation dose limit. After 1990, more stringent limits were introduced with various problems, particularly in private dairy production, peaty or swampy soils and forests. Other problems arose in some areas (West and South of Chernobyl) where the solubilities of particles containing plutonium and strontium 90 were initially low, but this solubility increased over time leading to significant transfers to plants, while the solubility of cesium 137 has decreased over time (Figure 3.3). Transfer factors to prairie grasses were 18 in 1986 and less than 5 for 1987–1994 for cesium 137. They were 15 in 1986, then decreased to less than 5 in 1987 and regularly increased to 10 in 1994 for strontium 90 (Arkhipov et al., 1998, in [COU 01]).

Figure 3.3. Extractibilities of 90Sr and 137Cs from the surface soils of the Chernobyl exclusion zone (modified from Arkhipov et al., 1998, in [COU 01])

The Extremely Serious Nuclear Accident at Chernobyl

67

3.2.8. Countermeasures carried out at Chernobyl Several countermeasures were put in place at Chernobyl. These were mainly in the agricultural sector: immediate plowing (allowing dilution of the highly contaminated surface with the less contaminated underlying land) of arable land and grasslands; correction of the land’s calcium deficiency with, in particular, the contribution of fertilizers, mainly potassium and phosphorus, and the change of use (outside the exclusion zone) if the two previous measures were insufficient [IAE 94]. In the aquatic domain, the measures taken from 1986 to 1989 were the construction of dikes several kilometers long along the Pripyat River to trap runoff from the cities of Chernobyl and Pripyat, without this operation being fully effective. In the same river, the bed was dredged in the summer of 1986 in order to reduce the flow velocity and thus increase the sedimentation of suspended solids. Again, the operation was not successful because the majority of particles were too fine to sediment quickly. The isolation of the pond containing the cooling water from the Chernobyl reactors of the Pripyat River was a major issue in the early years. It was associated with a drainage system for the water infiltration of the pond, although unfortunately never completed as a result of its construction and maintenance costs. In 1986 and 1987, more than 100 zeolite dikes were built on small rivers to retain radionuclides and thus purify water. They retained only 5–10% of the 90 Sr carried by the water. In addition, to temporarily contain radioactive waste, a large number of trenches, without any particular protection from groundwater, were dug. The consequence was groundwater contamination. In a second phase, a dike was built on the east bank of the Pripyat River. Completed in 1992, it retained a significant fraction of the 90Sr during the spring 1994 flood. The countermeasures taken since 1993 have been aimed at maintaining an acceptable level of radioactivity in the waters of the Dnieper basin, estimated at 2 Bq.L−1 of 90Sr. For this criterion to be met, various measures to reduce radioactivity had to be taken, such as the construction of dikes around the floodplain and sediment cleaning operations in the cooling pools of the Chernobyl reactors. In addition, several environmental quality-monitoring programs around Chernobyl (water, soil, etc.), including transuranic monitoring, were set up [COU 01]. Many decontamination works and storage sites were created, particularly in the exclusion zone. Thus, in some areas, the soil surface was stripped off

68

Industrial and Medical Nuclear Accidents

or covered by uncontaminated soil. This was effective, reducing surface contamination by up to a factor of 100. Three large radioactive waste repositories were created (Pidlinskii, Kompleksnii and Bouriakivka), totaling 3 PBq of 137Cs and 90Sr; however, there were also 800 landfill sites created in 1986 and 1987 in a 10 km zone around the plant representing 1,000,000 m3 and 13.1015 Bq [POI 01]. 3.3. Spatial and environmental consequences Before the accident, radioactivity in the environment resulted from atmospheric deposition and the operation of local reactors. Thus, the total air radioactivity was 7–20 mBq.m−3 in the vicinity of the plant, 0.4–1.3 mBq.m−3 in 2–5 km of the plant and only 0.04 mBq.m−3 in 10–40 km of the plant site. Between 1977 and 1984, 137Cs deposits ranged from 100 to 1,000 Bq.m−2 and for 90Sr from 40 to 400 Bq.m−2. The dose rate at the plant site was four times higher than that down to the natural radioactivity component (400 nSv.h−1) [POI 01]. The spatial consequences of the fallout of radionuclides at Chernobyl have recently been reviewed and modeled [EVA 13, EVA 16]. 3.3.1. Atmospheric contamination Air contamination in the vicinity of the plant was high. In the first days following the accident, total radioactivity was extremely high at 1.5.106 Bq.m−3 in the city of Chernobyl from April 30 to May 1 and 20.106 Bq.m−3 in Pripyat on April 27 and 28. This contamination was divided by 10 in 24 hours and by 10,000 in 6 days. By the end of June, radioactivity in the city of Chernobyl had stabilized at between 1 and 3 Bq.m−3. Once the releases had stopped, the radioactivity of the air was caused by the resuspension of radioactive particles in the air itself. This phenomenon was highly variable over time depending on climatic conditions (humidity, precipitation rate, wind). The average resuspension rate in the cities of Chernobyl and Pripyat was 1–3.10−7.m−1 at the beginning and then dropped to between 3.10−11 and 3.10−10.m−1. However, exceptional situations lead to high levels of contamination. Thus, in April 1987, a very strong storm resumed the suspension of deposits

The Extremely Serious Nuclear Accident at Chernobyl

69

and in Pripyat, the radioactivity of the air was 300 Bq.m−3. Similarly, forest fires increased the radioactivity of the air and in 1992, 20 Bq.m−3 of radioactivity was measured, 70 mBq.m−3 of which was down to plutonium isotopes [POI 01]. 3.3.2. Soil contamination As mentioned earlier (see section 3.2.7), atmospheric deposition contaminated the soil mainly with three radionuclides (137Cs, 90Sr and plutonium), and the accident zoning was based mainly on the contamination levels of 137Cs. After the accident, the contaminated soil and vegetation were buried in shallow trenches dug directly on site in an eolian sand deposit. These trenches are sources of radionuclide pollution, particularly for groundwater. Thus, only between 2% and 21% of the activity of 90Sr is associated with weather-resistant fuel particles [KAS 04]. Several studies using sophisticated equipment and involving several international teams have been initiated to better estimate leaching [KAS 12, LEG 12, VAN 12]. 3.3.3. Surface water contamination Contamination of surface water, both running and stagnant, was significant during the critical phase of the accident [POI 01]. During the discharge period, the total activity in running water was 100,000 Bq.L−1 in the Pripyat River, 70–90% of which was down to iodine 131. This activity decreased rapidly from 200 Bq.L−1 in June 1996 to 40 Bq.L−1 in early 1997. Cesium is much less soluble than strontium in water. 137Cs concentration had stabilized at 0.1–0.2 Bq.L−1, 10 times the value before the accident. 90Sr concentration varied according to the state of the river; during flood periods, the concentration could reach 10 Bq.L−1 and 10 times less during low water periods. 90Sr contribution to the Pripyat and Kiev reservoir resulted in years of high floods and ice jams. The highest contributions occurred just after the accident from May to September 1986 with 67 TBq of 137Cs and 28 TBq of 90 Sr in the city of Chernobyl. 90Sr contributions to Dnieper were estimated at 66 TBq. For stagnant water, many water points exist in the exclusion zone and are a risk of contamination to the Pripyat River in the event of a flood, resulting

70

Industrial and Medical Nuclear Accidents

in the construction of many dikes. For example, these waters contained 17.1012 Bq of 137Cs, 20.1012 Bq of 90Sr and 0.45.1012 Bq of 238,239,249Pu in 1996–1998. The cooling basin of the plant contained the largest quantities with 150.1012 Bq of 137Cs and 30.1012 Bq of 90Sr. The behavior of strontium 90 in the waters of the Dnieper River system, and the various cascade reservoirs near Chernobyl, is highly dependent on the volume of water in each component. About 43% of the dissolved 90Sr that entered the Dnieper system from 1987 to 1993 reached the Black Sea. On the contrary, cesium 137 seems to be less dependent on surface hydrology and the main accumulation was upstream in the first reservoir [SAN 96]. 3.3.4. Groundwater contamination Groundwater contamination is possible. Indeed, following the migration of radionuclides deposited on the ground, radioactivity reached the groundwater table. The authorities have also created and are monitoring various wells. It appears that 90Sr migrates relatively quickly to groundwater. Thus, in 1991, its concentration in water was 0.2 Bq.L−1; it increased to several dozen becquerels per liter in 1998. On the contrary, in 2000, 137 Cs concentrations were only 0.02–0.1 Bq.L−1 and 239+240Pu 5 mBq.L−1. Faybishenko et al. [FAY 15] draw attention to the consequences of the Chernobyl accident on groundwater. To this end, they carry out long-term modeling of radionuclide transport in soil and groundwater in the Ukrainian part of the Dnipro basin. Their synthesis also includes the assessment of the effect of preferential and episodic flow on the transport of radionuclides to aquifers and the assessment of groundwater vulnerability risks. The majority of the study area is characterized by an average vulnerability of groundwater with surface contamination densities in 137Cs of 0.01–0.1 Ci.km−2 and a concentration in groundwater of 1–10 mBq.dm−3. In the Chernobyl exclusion zone, the many trenches containing radioactive waste are likely to contaminate groundwater. Several international radioecological projects have also been developed to study this phenomenon. These include the Chernobyl pilot project (1999–2003) and the Chernobyl experimental platform (2004–2008). This platform studied the 22T trench (Chernobyl pilot site) which was located in the Red Forest

The Extremely Serious Nuclear Accident at Chernobyl

71

radioactive waste disposal site in the Chernobyl exclusion zone. It was 70 m long, 6–8 m wide on average and 2–2.5 m deep. The total inventory of the trench estimated that the quantity of 137Cs was 600 ± 200 GBq and 290 ± 140 GBq for 90Sr [BUG 05]. Microscopic analyses of the waste and leaching experiments showed that 10–30% of the radioactive inventory was associated with chemically extra-stable Zr–U–O particles. The largest fraction of 90Sr activity in the trench (30–60%) is associated with relatively slow-dissolving unoxidized UO2 matrix fuel particles [DEW 04]. Bugai et al. [BUG 12a, BUG 12b] provide groundwater geochemical monitoring data collected in 1998–2008 from the international experimental radioecological study site, with a high 90Sr content (of an order of n.(1,000−n).10,000 Bq.L−1). Groundwater had high concentrations of Ca, K, NO3, SO42− and some trace elements (in particular, stable Sr). Bugai et al. [BUG 12a, BUG 12b] estimate that if a decrease (4–8 times) in the concentration of major cations (Ca and Sr) occurs, then it will have three consequences: an increase in the distribution coefficient Kd (ratio of concentrations between dissolved phase and particulate phase) of 90 Sr (trench and aquifer), a decrease in the concentration of 90Sr in interstitial water and a reduction in the migration process at depth. It is possible to suspect a reverse trend for transfer to vegetation for two reasons: biomass development and a favorable chemical environment. 3.3.5. Forest contamination In Chernobyl, the forest covers 40% of the surface area of areas contaminated by more than 37 kBq.m−2, or 40,000 km2. During the accident, the forest acted as a filter for radioactive particles. Thus, the foliage on the edges of the forests was contaminated by 10–20% more than that in the center of the massive forest. One month after the accident, more than half of the contamination was found on the ground in the forest litter. Less than 2% of the cesium migrates from this litter deep into the soil each year. Cesium accumulates more in deciduous leaves, and its presence in the first few centimeters of soil leads to its concentration in wood, especially for young shoots; hence the need for regulations to market this wood according to its contamination. The distribution of radiocesium was determined in two populations of Scots pine (Pinus sylvestris L.), aged 17 and 58 years respectively, and also

72

Industrial and Medical Nuclear Accidents

affected by Chernobyl fallout. For both age classes, concentrations were always lowest in barrelwood, highest in inner bark and intermediate levels were observed for outer bark. Due to the cumulative nature of its biomass, stem wood is an important long-term storage site of 137Cs [THI 02]. Fifteen years after the accident, 90Sr contamination was about 10 times higher than 137Cs contamination; 80% of 90Sr was contained in woody organs and 46% of 137Cs in foliage. The extraction of radionuclides from the ground by vegetation was evident, particularly of 90Sr. Indeed, the net transfer of 90 Sr related to root sampling appeared to be higher than that of losses by leaching. Dewiere et al. [DEW 04] estimated that in 2001, 2–7% of the initial inventory of radioactivity was present in the underlying groundwater. Annual leaching migration is 0.14–0.5% per year, and root sampling is 0.8% per year. This difference could increase with the growth of forest populations. Some pine plantations are located above the trenches (2–3 m) that served as repositories for radioactive waste. These trenches are highly contaminated (600 GBq of 137Cs and 300 GBq of 90Sr), while around the trenches, the soils are less contaminated (20–30 cm outside the trench, 125 kBq/kg of 137Cs and 56 kBq/kg of 90Sr). Two essential questions arise: what is the ability of trees to extract contamination from trenches? What is the long-term impact of these new forests on radionuclide recycling? The planting of Scots pine trees in a landfill site has strongly influenced the long-term redistribution of radioactivity in underground trenches. After 15 years of growth, the above-ground biomass of the average 22T trench tree accumulated 1.7 times more 137Cs than that of trees growing outside the trench, and 5.4 times more than 90Sr (Table 3.4) [THI 09]. Out of the trench (GBq.ha−1)

Above the trench (GBq.ha−1)

Ratio above/below

137

1.4

2.3 (0.024%)

1.6

90

21.7

115.8 (2.52%)

5.3

Cs

Sr

Table 3.4. Concentrations in 137Cs and 90Sr in Scots pine trees growing above and outside a radioactive waste trench and the relationship between these two locations (adapted from [THI 09])

The Extremely Serious Nuclear Accident at Chernobyl

73

After the accident, the interception of radioactive atmospheric fallout by forest trees was mainly at the foliar level. Leaching from the foliage depended at an early stage on the frequency of rainfall events, and 60% of the initial contamination was lost in 70 days. The elimination half-life of the intercepted radiocesium was 25 days. At the end of the growing season, 30% of the initial deposits were relocated to different parts of the trees, including organs such as stemwood (5%) and roots (6%) not directly exposed to the repository [THI 16]. Contamination of forests has led to contamination of harvested products (fungi, berries, etc.) and game. In some areas, this contamination was very high, as in 1995 in the Bryansk district for cesium 137 (30,000 Bq.kg−1 for game, 340,000 Bq.kg−1 for dried fungi, 4,500 Bq.kg−1 for berries). Contamination of higher fungi by 137Cs depended on the level of soil contamination, the location of the mycelium in the soil (especially depth) and the species of fungus, in particular its membership of a particular ecological group. In addition, the value of the specific activity of 137Cs in mushrooms of a given species could vary more than 10 times during a growing season [ZAR 16]. Many studies have been carried out in the Chernobyl exclusion zone, particularly during the chronic phase. The dynamics of cesium in forest components in the 30 km zone around the Chernobyl nuclear power plant (NPP) between 1986 and 1994 were mainly associated with the size of radioactive particles in the fallout, tree age, ecosystem moisture and soil type. The influence of particle size was particularly significant between 1986 and 1987. This was demonstrated by the low biological availability of radionuclides in the area closest to the plant (in the 10 km radius around the reactor) compared to more remote areas (in the 30 km radius circle). Later, this influence decreased and the transfer factor (the ratio of 137Cs activity contained in above-ground plant biomass to soil activity) became approximately the same for all plots with similar ecological characteristics and fallout. Environmental humidity and soil type determined the vertical migration rate of radionuclides in the soil and the biological availability of 137 Cs. These parameters were highest for hydromorphic (water-saturated) soils in wetlands enriched with organic matter and soils low in clay minerals. The accumulation of 137Cs in the above-ground biomass of trees according to their age was higher in the structural parts of young trees compared to that of old trees [MAM 97].

74

Industrial and Medical Nuclear Accidents

In an unburned forest (white spruce), the highest concentration of 137Cs was identified in epiphytic lichens and mosses, while in burned forests, the highest concentration was measured in surface organic soil. 137Cs was redistributed in the burned forest on the surface of the soil, as well as part of this 137Cs was lost as a result of the fire, leaving it in the atmosphere and likely contaminating other ecosystems [PAL 95]. The resuspension factor of 137 Cs and 90Sr was between 10−6 and 10−5 m−1, and that of plutonium was from 10−7 to 10−6 m−1 [YOS 06a]. During forest fires, up to 4% of 137Cs and 90 Sr and up to 1% of Pu isotopes were released from forest litter according to calculations in Yoschenko et al.’s model [YOS 06b]. From 1993 to 2012, there were 841 forest fires devastating 239,688 ha in the Chernobyl exclusion zone. More than 10% of these areas were difficult for firefighters to access (more than 1 hour) or even inaccessible [ZIB 15]. The forests of Ukraine and Belarus are heavily affected by radioactive contamination, particularly in 137Cs. In addition, carbon storage has been increased by the mass of dead trees and the decrease in litter decomposition. The rate of forest litter degradation is significantly reduced when irradiation increases; up to 40% for sites 2,600 times more contaminated [MOU 14b]. Intense and spontaneous fires were observed in 2002, 2008 and 2010, causing an 8% re-dispersion of the 137Cs deposited after the accident [EVA 15]. 3.3.6. Contamination of the aquatic environment The first studies of the fallout from the Chernobyl accident were carried out in the cooling pool of the Chernobyl nuclear power plant, the Pripyat River and the Dnieper reservoirs. Concentrations in the dissolved phase of the water of the Pripyat River in Chernobyl on May 1, 1986 were 250 Bq.L−1 for 137Cs and 30 Bq.L−1 for 90Sr. The 137Cs concentration increased to reach 1,591 Bq.L−1 on May 6, 1986. Concentrations in the sediments of the cooling pool were 600 kBq.kg−1 for 137Cs and 110 kBq.kg−1 for 90Sr [SMI 05b]. Maximum levels of contamination of predatory fish with cesium radionuclides appeared in 1987–1988, while in “non-predatory” fish, cesium concentrations were generally highest in the first year following the accident (1986). Perch, zander and pike seemed to be the best candidates to serve as bioindicators of radioactive contamination of food chains [KRY 93].

The Extremely Serious Nuclear Accident at Chernobyl

75

On May 30, 1986, in the Chernobyl plant’s cooling reservoir, the concentrations of 137Cs in water and sediment were 40 ± 27 Bq.L−1 and 2.3 ± 1.0 MBq.m−2 respectively and for 90Sr, the corresponding values were 400 ± 200 Bq.L−1 and 2.7 ± 1.8 MBq.m−2. In the same reservoir in 1986, 137 Cs concentrations in fish muscles were 100, 110, 140, 180 and 30 kBq.kg−1 fresh weight for carp, bream, silver carp, perch and pike respectively. In the Kiev reservoir in 1986, 137Cs concentrations were 2.0 Bq.L−1 in water, 670 Bq.kg−1 fresh weight in zebra mussels (mollusks), 960 Bq.kg−1 fresh weight in bream and 220 Bq.kg−1 fresh weight in pike. For the same site on the same date, 90Sr concentrations were 0.85 Bq.L−1 in water, 1,000 Bq.kg−1 fresh weight in zebra mussels, 60 Bq.kg−1 fresh weight in bream and 220 Bq.kg−1 in pike-perch. Predatory fish bioaccumulated more 137 Cs than herbivorous fish [KRY 95]. Koulikov [KOU 96] monitored the bioaccumulation of cesium 137 in fish from 1987 to 1992 in the Kiev water reservoir near Chernobyl. Predatory fish, perch (Perca fluviatilis) and pike (Esox lucius), were the most heavily contaminated with maximum average activities of 1,658 and 1,773 Bq.kg−1 dry weight of 137Cs respectively in the muscles. Samples of sediment and carp (Carassius carassius) were collected from 14 ponds located outside or within the Chernobyl 30 km exclusion zone. The concentration of radioactive cesium in sediments was highly variable from 1 Bq.g−1 dry weight to 11 Bq.g−1 dry weight. In fish muscles, the cesium concentration was less than 8.2 Bq.g−1 dry weight, but with great variability depending on the site [JAG 97]. During the period 1991–1994, in the Techa River, the average annual water content of 90Sr ranged from 6 to 20 Bq.L−1. The average annual content of 137Cs in the river water ranged from 0.06 to 0.23 Bq.L−1, two orders of magnitude lower than 90Sr. The concentration of 239.240Pu in the water ranged from 0.004 to 0.019 Bq.L−1 [KRY 98a]. In 2004, the γ activity of mollusks (Lymnaea stagnalis), taken from the Pripyat River and Lake Perstock located in the Belarusian region and the Chernobyl area, amounted to 39.2 and 567.8 Bq kg−1 respectively and β activity to 123.4 and 7,055 Bq kg−1 respectively [GOL 05]. In May 2017, the highest levels of water contamination were found in canal waters at the nuclear power plant (8.0 Bq.kg−1 for 137Cs, 4.1 Bq.kg−1

76

Industrial and Medical Nuclear Accidents

for 90Sr). The concentrations of 90Sr and 137Cs in water generally decreased with increasing distance. However, at the same time, Querfeld et al. [QUE 18] found that the activity ratio of 90Sr/137Cs was increasing. 3.3.7. Contamination of the marine environment Many marine radioecologists studied the impact of the Chernobyl accident on the marine environment, such as the IAEA’s Marine Environment Laboratory (MEL) in Monaco. The Chernobyl accident had a measurable effect on the marine environment as a result of atmospheric fallout. Radionuclide concentrations (mainly cesium 137) were two to three orders of magnitude higher than before the accident. However, public doses resulting from cesium 137 in seafood were at least one order of magnitude lower than those caused by natural polonium 210 [POV 96]. 3.4. Ecological consequences of the Chernobyl accident In Chernobyl, the ecological consequences were felt mainly in two ecosystems: the forest ecosystem and the aquatic ecosystem. Although few studies were undertaken immediately after the accident, a few years later, a large number of Russian, Ukrainian, Belarusian and Western teams came to work on this site. There were also many publications. Two conferences summarized the principal results of long-term research on the accident’s environmental and health consequences [IAE 97, KAR 97]. Many European reports bring together the results of the work carried out by researchers from many countries. Several books and reports also summarize radioecological studies [SMI 05a, ADA 16, IRS 16c]. 3.4.1. The three phases Following the Chernobyl accident, living organisms were subjected to various exposures, broken down into three successive phases. The effects on species living in the exclusion zone were therefore variable. Phase I lasted for the first 20–30 days and was called the acute phase. Phase II continued until the following spring season and was referred to as the transitional phase. Phase III extends to the present day and is called the chronic phase.

The Extremely Serious Nuclear Accident at Chernobyl

77

Several general observations should be highlighted. First of all, living organisms have been exposed to different radionuclides. As noted above, there was enormous spatial heterogeneity in deposition and environmental parameters governing the dynamics of radionuclide concentration dynamics in habitats and organisms. Finally, the accident occurred at the time of biological productivity in early spring [HIN 07]. Exposure during phase I was characterized by the presence of a large amount of short-lived radionuclides (99Mo, 132Te/I, 133Xe, 131I, 140Ba/La). The dose rate reached up to 20 Gy.d−1 while the dose rates from β emitters were occasionally higher, with a ratio β/γ of about 6 and very high thyroid doses. During phase I, acute deleterious effects were observed within 10 km around the accident reactor with mortality of the most radiosensitive species. This included increased mortality in conifers, leading to the red forest phenomenon. Mortality also increased in soil invertebrates and mammals [GAR 12]. During the initial phase, the only work carried out was that by Soviet scientists and most of it was published in Russian. Sazykina and Kryshev [SAZ 06] summarized this Russian work on ecological consequences. Studies were conducted on various terrestrial vertebrates (rodents, cows, dogs, pigs, birds, squirrels, beavers). The pathologies concerned many organs. Some authors noted in particular that in the most contaminated cows, the thyroxine concentration decreased significantly. In frogs, the authors found infertility of eggs. Exposure during phase II was characterized by a decrease in short-lived radionuclides and a redistribution within the different compartments of deposited radionuclides (transport, transfers). The contribution of internal contamination of living organisms gradually dominated external irradiation. During the first 3 months after the accident, 80% of the total dose (estimated on a lifetime scale) was delivered to plants and animals, and more than 95% of this dose was caused by radiation with a ratio of about 30. During the second phase, reproduction was affected in mammals with increased embryonic resorption. The cumulative dose for the first 5 months was 12–110 Gy (γ) and 580–4,500 Gy (β) [GAR 12]. During the intermediate phase, the data mainly concerned rodents, where a significant population decline was observed in several studies [SAZ 06]. However, radiosensitivities are very variable according to the species [GRI 09]. As for the other terrestrial vertebrates (wild boars, foxes, wolves, beavers), their abundance was the subject of scientific controversy, with some noting that their number increased considerably after the accident (thus for wild boars,

78

Industrial and Medical Nuclear Accidents

the number increased eight times) and others claiming that their number decreased significantly. In frogs, egg infertility decreased during the intermediate phase, but chromosomal aberrations increased, as did bone tumors [SAZ 06]. During phase III, exposure is chronic and dose rates are generally less than 1% of the initial rates (but still high, up to about 100–200 μGy.h−1). The contribution of β versus γ radiation to total dose is a function of the accumulation capacities of Cs and Sr specific to each species on the one hand, and of environmental parameters on the other. 137Cs and 90Sr are the main contributors to the dose, followed by transuranics (Pu, Am). Indirect and subtle effects dominate. This is the phase of all scientific controversies concerning the interpretation of observed effects [GAR 12]. The consequences of biological responses in the acute and transient phases have led to a drastic change in ecosystems in the Chernobyl exclusion zone. Originally there was a pine forest between 30 and 40 years old, characterized overall by mature and stable ecosystems. The accident induced lethal doses in the 30 km zone for a number of species causing a drastic alteration of this balance, with the gradual creation of new ecological niches open to species migrating to the zone [GAR 12]. Beyond the exclusion zone, Ellegren et al. [ELL 97] report an increase in abnormalities in swallows in Belarus. The radio-ecological effects of ionizing radiation on aquatic organisms are manifested in a dose rate range from 0.002 to 800 Gy. d−1 [KRY 98b]. 3.4.2. Effects at molecular level The first biological effects of ionizing radiation occur at the molecular level. An individual undergoing radiation exposure will trigger defense mechanisms against this stress. Two main types of mechanisms are used. The first is the induction of metallothioneins, proteins specialized in the detoxification of certain metallic elements including various radionuclides [CAI 99, AMI 06]. The second category of detoxification mechanisms for stable trace metals and radionuclides includes the various molecules involved in combating oxidative stress. Metallothioneins and oxidative stress molecules are biomarkers indicating that an organism is defending itself [AMI 13b, AMI 17].

The Extremely Serious Nuclear Accident at Chernobyl

79

While metallothioneins significantly reduce metal toxicity by trapping metals, their effect during radiation exposure heads in the wrong direction since they tend to increase the duration of the irradiation. Metallothioneins are strongly induced in freshwater mollusks (Anodonta anatina) living in the reservoir of a nuclear power plant [FAL 14]. In contrast, Lymnaea stagnalis pulmonate mollusks collected near the Chernobyl plant and chronically irradiated are clearly distinguished by the lowest levels of metallothioneins (MT), Mn-superoxide dismutase and lactate dehydrogenase and the highest level of glutathione [GNA 12]. Ionizing radiation induces oxidative stress by the formation of free radicals. This frequently results in the induction of antioxidant molecules in the fight against oxidative stress and, at the same time, a decrease in their availability for other functions (immunity, pigment synthesis, gamete production). Other molecules are linked to oxidative stress such as carotenoid-based pigments in birds [GAL 11]. Pheomelanin is a pink to red version of melanin pigment deposited in the skin and its productions such as hair and feathers. As a result of its bright color, pheomelanin plays a crucial role in signaling, particularly sexual signaling. However, the production of pheomelanin, as opposed to its darker alternative, eumelanin, involves costs in terms of consumption of important antioxidants otherwise available for the protection of DNA against naturally produced reactive oxidative species. In bats (Myodes glareolus), the production of pheomelanin is affected by the level of radiation prevailing in Chernobyl [BOR 14]. Similarly, this pheomelanin pigment, which colors bird feathers black (lighter than eumelanin) and can protect the individual from oxidative stress, is much less produced in highly irradiated birds [BOR 14]. The same is true for various crystalline proteins in birds and rodents [MOU 13a]. Galván et al. [GAL 14] analyzed the levels of the most important intracellular antioxidant glutathione (GSH), its redox state, DNA damage and body condition in 16 bird species exposed to ionizing radiation at Chernobyl. The authors found that GSH levels and body condition increased and oxidative stress and DNA damage decreased with increased irradiation. This adaptive response to radiation allows birds not to be negatively affected by chronic exposure and even produces beneficial hormonal effects. Analysis of the phylogenetic signal supports the existence of adaptation in

80

Industrial and Medical Nuclear Accidents

the traits studied, particularly in GSH levels and DNA damage. This phenomenon has not been observed in swallows or great tits. Radiation due to the Chernobyl accident has had an impact on other biomarkers. Various Soviet authors, reported by Sazykina and Kryshev [TSA 06], found abnormalities in blood count and histological changes in the spleen, liver and endocrine system in various vertebrates, including rodents. 3.4.3. Genetic effects Genetic effects can be observed at various levels of biological organization (molecular on DNA, chromosomal, cytological, morphological, etc.). Soon after the accident, several Soviet radioecologists looked for genetic modifications in plant and animal species. The results are mixed. 3.4.3.1. Effects on flora Thus, for flora, the cytogenetic damage of Scots pines was significant. In 1993, with exposures of 5–15 Gy, cytological aberrations were eight times greater than those observed in controls and 50–60% of young conifers showed abnormal morphogenesis [ZEL 05, YOS 11]. Some of the pine needles remained dwarfed and appeared on the same tree. A total of 12 genes were significantly (p 555 kBq.m−2

270,000

50

Deposits 137Cs > 37.5 kBq.m−2

5,000,000

10

Belarus, Ukraine and contaminated areas of Russia

66,500,000

2.5

Europe

570,000,000

0.5

Table 3.6. Main exposed populations and average effective dose (mSv) (based on [LAU 16])

The Extremely Serious Nuclear Accident at Chernobyl

97

3.5.2. The main contributions to exposure Contaminated food and the atmosphere were the two main contributors to the exposure of people living around Chernobyl. Fifteen years after the accident, the vast majority of agricultural products complied with the permissible limits of contamination. In Ukraine, since June 25, 1987, these limits have been 100 Bq.L−1 for dairy products, 200 Bq.kg−1 for meat and 20 Bq.kg−1 for potatoes and bread. In the 2000s, there was a major distortion in the quality of agricultural products depending on the status of collective or private farms. For the latter, the products were always more contaminated because they did not comply with the instructions and did not strictly apply the recommendations of the countermeasures. As a result, 90% of the dose received by the local population was down to the ingestion of agricultural products. Since 1991, half of the internal doses delivered have been due to milk ingestion, hence the implementation of countermeasures such as soil amendment to limit the transfer of cesium from the soil to the grass and then to the milk [POI 01]. In Ukraine, 8.6 million hectares of agricultural land contaminated with cesium are subject to agronomic measures. We mentioned earlier (see section 3.3.1) the very high spatial and temporal variability of air contamination. This makes the determination of exposure doses from inhaled air excessively complex. 3.5.3. Population exposure 3.5.3.1. Exposure of intervention personnel The operators of the accident site, firefighters, military personnel and helicopter pilots, 658 people, responded very quickly after the accident and received high doses of radiation. As of April 26, 1986 at 2 p.m., 108 people were hospitalized for burns and severe radiation. Of the total 237 patients hospitalized, 134 had symptoms of acute radiation (vomiting, dizziness, skin burns), 28 of whom died. Later, about 600,000 people participated in the clean-up operations. It should be noted that the number of liquidators is not precisely known and varies greatly from one source to another. A register of liquidators was set

98

Industrial and Medical Nuclear Accidents

up in 1986, but its monitoring has been problematic since the number was only 284,000 in 1986 and only 168,000 in 1996. The causes are probably multiple, such as the individuals’ relocation and their lack of response to letters. Dosimetric analysis shows that these liquidators suffered doses ranging from 50 to 250 mSv with an average of 108 mSv. However, figures are not very credible [POI 01]. After the publication of the report by the Chernobyl Forum [IAE 05], which was very optimistic on the health of liquidators, scientists from the three countries concerned, assisted by many Western scientists, organized themselves to set up a serious medical follow-up. Three major new epidemiological investigations have been published, a cohort study and two overlapping case–control studies [TAN 16]. All the studies reviewed conclude that there is an increased incidence of leukemia in Chernobyl liquidators [KES 08, ROM 08a, ROM 08b, IVA 12]. 3.5.3.2. Exposure of evacuated populations According to Soviet standards, population evacuation must be carried out at doses of 250–750 mSv. This was the case in Pripyat on April 26 (estimated at 300–400 mSv). However, the evacuation did not begin until 48 hours after the accident. The evacuation of 46,614 people, including 10,000 children, was carried out with 1,350 buses, 2 trains and 3 boats. From May 2 to 7, 1986, an additional 10,000 people were evacuated within an additional 10 km radius. The authorities’ policy changed a few months after the accident and evacuations followed one another as soon as the dose rate exceeded 50 µSv.h−1 and the dose exceeded 100 mSv. A total of 90,784 people were evacuated on May 7 from 76 Ukrainian villages and 50 villages in Belarus. The boundaries were further extended, and by August of the same year, 116,000 people had been evacuated from 188 villages. In the fall of 1986, 3,000 people from 15 villages were removed. By the end of the first year, 135,000 people had been evacuated in Ukraine, Russia and Belarus, including 115,000 in the first week, including those living within 30 km of the plant, which would become an “exclusion zone”. These populations were reported to have received a dose of between 50 and 140 mSv. Between 1990 and 1995, 50,000 people in Ukraine, 135,000 in Belarus and 30,000 in Russia were evacuated [POI 01]. In 1996, 270,000 people lived in areas where 137Cs activity exceeded 0.6 million Bq.m−2 (corresponding to doses of 80–440 mSv) and 3,700,000 people in areas

The Extremely Serious Nuclear Accident at Chernobyl

99

between 40,000 and 600,000 Bq.m−2 (corresponding to doses of 70–200 mSv). The inhabitants of these areas are continuously exposed through external radiation and ingestion of contaminated food. For example, two human groups in the village of Khristinovka (Narodichi district in the Zhytomyr region) were monitored for their diet. This area is highly contaminated with cesium 137 (>100 Ci.km−2). Group A was made up of the elderly, the sick and isolated who are unable to support themselves financially and who feed on forest products, including fresh or dried mushrooms. They received an irradiation dose of 14.65 mSv.y−1. In Group B, which consisted of young families with children and low consumption of forest products, the internal dose was about 1.5 mSv.y−1. Total abstinence from consumption of forest products would lead to an internal dose of 0.56 mSv.y−1 [ORL 07]. 3.5.3.3. Exposure of populations in the Chernobyl region The radiological situation in the vicinity of the sarcophagus was problematic with high dose rates. In the molten core, the activity of 137Cs and 90 Sr is estimated at 370.1015 Bq and that of plutonium at 3.7.1015 Bq. From the molten core and all the waste distributed in the plant, dose rates in 1999 were 300–500 µSv.h−1 near the sarcophagus, 20 mSv.h−1 near the turbine hall and 390 mSv.h−1 on the roof of the sarcophagus. Three main storage facilities exist 20 and 50 m from the west wall, and dose rates vary from 10 to 50 mSv.h−1. External exposure in the 30 km zone around the plant was also intense. The contaminated area around Chernobyl with contamination levels above 555 kBq.m−2 largely exceeds the 30 km exclusion zone centered on the destroyed reactor and covers 10,300 km2, spread over three countries (Ukraine, Russia and Belarus). This represents 4.7 times the area of Tokyo [TAK 05]. Dose rates at the beginning of the accident reached 10 Gy.y−1 near the plant and several hundred mGy.y−1 in Pripyat. As a result of the penetration of some of the radionuclides into the soil, 1 year after the accident, the dose rate decreased twice as quickly as the activity deposited onto the soil [POI 01].

100

Industrial and Medical Nuclear Accidents

More recently, the average doses received by the populations were 3.0 and 0.56 µSv.h−1 in Belarus and Ukraine respectively. The highest radiation doses were in Belarus between the villages of Perki and Kryki (19.9 µSv.h−1). The population was prohibited from living in the exclusion zone. However, there was a couple including a man aged 45 who had been living in this area since 1991. Similarly, 56 inhabitants lived in the village of Opatiti, including a woman who had returned in 1994. They had electricity at their disposal, which proves that the authorities were turning a blind eye. In Russia, the most contaminated area was around Zaborie, where populations had been evacuated when the concentration in the soil was greater than 555 kBq.m−2 in 137Cs. However, 10,000 people continued to live there voluntarily in 1997 [TAK 05]. 3.5.4. Cancer pathologies The appearance of different cancers following exposure to ionizing radiation has been observed for two Japanese populations who have been subjected to wartime exposure from Hiroshima and Nagasaki. Depending on the type of cancer, the onset is caused by a more or less long latency period. Leukemias appear quite quickly, unlike cancers of the digestive tract, which were triggered several decades after the atomic explosions [AMI 19]. However, unlike the events in Japan, where the exposure was unique and intense, the exposure suffered by the populations of Ukraine, Belarus and Russia was chronic. Early on, experts and international authorities recognized that the consequences of the Chernobyl disaster on people and the environment would last for several decades. However, far from all the consequences are known with precision, since it was only late – in early 1990 – that epidemiological studies were carried out. The effects of the early years were therefore not observed. 3.5.4.1. Iodine 131 and thyroid pathologies It is the radioactive isotopes of iodine and, in particular, iodine 131 that have harmed populations. Iodine 131 intake was mainly from food products. Thus, one liter of milk provided an infant with 100,000 Bq of iodine 131 and a dose of 370 mSv to the thyroid gland. Populations in northern Ukraine and southern Belarus have been subjected to thyroid doses of about 100 mGy to several dozen grays. As early as 1990, this resulted in a significant increase

The Extremely Serious Nuclear Accident at Chernobyl

101

in thyroid cancer, particularly among children below 5 years of age at the time of the accident. This increase was a factor of 10–100. Thus, in the three countries, the number of thyroid cancers was 1,400 in 1997 and 1,792 in 1999 [POI 01]. Unquestionably linked to the Chernobyl accident, a significant increase above the natural rate of thyroid cancer has been observed since 1990, with an increased frequency especially among children below 15 years of age, in Belarus, northern Ukraine and southern Russia. 3.5.4.1.1. Thyroid cancer in children In the Gomel region of Belarus, the incidence increased from 0.3 per 100,000 children between 1981 and 1985 to 9.6 between 1991 and 1994. In Ukraine, in the five most contaminated regions, it fell from 0.01 between 1981 and 1985 to 1.1 between 1991 and 1994. Within a radius of 150 km around Chernobyl, no thyroid cancer has been detected in the 9,472 children born after the accident (1987–89), while among the 12,129 children born before the Chernobyl accident, 32 thyroid cancers have been recorded (January 1, 1983 to December 31, 1986) [SHI 01, SHI 02]. In Ukraine, after the Chernobyl accident (1986–2000), 472 cases of thyroid cancer were noted among children below 15 years of age. Of these, 431 were born before the accident, 11 were in utero at the time of the accident and 30 were born after the Chernobyl accident [TRO 02]. The number of cases of thyroid cancer is similar for children born between 1968 and 1985 in Belarus and Ukraine. On the other hand, the age at the time of exposure (1986) has a major impact [JAC 02]. It is now well documented that children and adolescents exposed to radioactive isotopes of iodine from the radioactive fallout from Chernobyl have shown a fairly significant increase in thyroid cancer in relation to the radiation dose. The risk increases in inverse relationship to age at exposure, with younger people being the most radiosensitive and it appears that the lack of stable iodine may increase the risk [CAR 02, CAR 11]. Ostroumova et al. [OST 13] found positive and significant associations of iodine 131 exposure doses in Belarusian children with hypothyroidism and serum thyroid-stimulating hormone (TSH) concentration. The excess odds ratio (OR) per 1 Gy for hypothyroidism was 0.34 (95% CI: 0.15–0.62) and varied significantly with age at exposure and examination, presence of goiter and urban or rural residence.

102

Industrial and Medical Nuclear Accidents

The various forms of thyroid cancer in children appear mainly in girls (11 boys and 71 girls) [AST 04]. Girls living in Bryansk and exposed between 0 and 4 years of age had a relative excess risk per 1 Gy of 45.3 (95% confidence interval from 5.2 to 9,953) between 1991 and 2001 [IVA 07]. 3.5.4.1.2. Explanations for the increased sensitivity of children Radioactive iodine binds preferentially to thyroid cells, causing a decrease in the gland’s ability to function (hypothyroidism). Three iodine isotopes are concerned: 132I (2.4 hour half-life in equilibrium with its ascendant 132Te of a 3.3 day half-life), 133I (20.8 hour half-life) and 131I (8 day half-life). Thyroid contamination with iodine is particularly significant in areas of iodine deficiency, resulting in a much higher dose to the thyroid than to the whole body. For iodine 131 for example, the thyroid dose is 350 mGy.MBq−1, for a whole body dose of 200 Gy.MBq−1. However, according to the WHO, 30% of the world’s population lives in a state of iodine deficiency. The contamination of children is much more serious than that of adults for three reasons. First of all, the low mass of the thyroid and the significance of iodine uptake lead to greater irradiation than for adults (about eight times more at 1 year old, four times more at 5 years old for the same iodine 131 intake). Second, milk contamination can be significant. Finally, the children’s thyroid glands can be affected by radiation-induced cancer, which is more rarely the case in adults. The responsible dose varies according to the functioning of the thyroid gland, which is particularly intense in children (rapid development of cancers). A dose of 100 mSv is considered likely to cause cancer 5–10 years after exposure. The radiation doses suffered by Chernobyl children are poorly known. For residents of Pripyat, the average thyroid dose in children was 991 mGy for the 0–7 year age group and 275 mGy for adults at the time of the accident. Among the evacuees, individual doses are very variable and some are as high as 40,000 Gy [BOU 07]. There has been a gradual decrease in cases since 1995 in relation to a decrease in the proportion of children aged 0–14 years exposed in 1986 (they were not yet born). On the other hand, for the 15–29 age group, the increase continues. These are subjects who were between 2 and 16 years old in 1986.

The Extremely Serious Nuclear Accident at Chernobyl

103

3.5.4.1.3. Thyroid cancers in the adult population Cancers induced by ionizing radiation are most often aggressive and frequently accompanied by cervical lymph node metastases. Nevertheless, in its differentiated form, papillary type (70% of thyroid cancers), definitive cure occurs in 85% of cases. Other non-cancerous thyroid pathologies may be related to irradiation (benign nodules or inflammation called thyroiditis), but no data are available. In addition, in adults, the observed increase in the number of thyroid cancers in the most contaminated areas (incidence multiplied by 3) may be related to the deterioration of tumors present before the accident. The WHO in its 2006 report [WHO 06] predicted an increase in thyroid cancer. After 30 years, 11,000 cancers have been reported, a fraction of which are down to the Chernobyl accident and radioactive iodine releases [BOG 15, WHO 16]. Thus, in an American-Ukrainian cohort, Bogdanova et al. [BOG 15] found, by examining the histopathology of papillary thyroid carcinomas, a significant linear-quadratic limit association (P = 0.063) between the iodine 131 dose and overall tumor invasion. In contrast, Peters et al. [PET 17] found no evidence of significant associations between the thyroid dose of iodine 131 and serum thyroglobulin (Tg) concentration in an exposed Ukrainian cohort. The increase in the number of thyroid cancers persists for more than 20 years after the accident and is now observed in adults. The dose–risk relationship for thyroid cancer in children (0–17 years of age) for external exposure (ERR.Gy−1, excess relative risk per Gray exposure) is 7.7 (1.1–32) and for internal exposure, the OR at 1 Gy ranges from 5.5 to 8.4 (ERR.Gy−1, 1.9–19) [YAM 14b]. 3.5.4.1.4. Thyroid cancers in liquidators The incidence of thyroid cancer among liquidators is clear. A cohort of 150,813 Ukrainian liquidators was followed from 1986 to 2010 and 196 cases of thyroid cancer were diagnosed and compared to the total cohort of the national cancer registry. The standardized incidence ratio (SIR) is 3.5 (3.0–4.0) for the total cohort and 3.9 (3.3–4.6) for the 1986 liquidators [OST 14]. For the Belarusian, Russian and Baltic liquidators who worked at the Chernobyl site between April 1986 and December 1987, a nested

104

Industrial and Medical Nuclear Accidents

case–control study was carried out on a large number of 107 cases and 423 controls who received a median thyroid dose between 50 and 70 mGy. The relative excess risk per 100 mGy is 0.38 (0.1–1.09) [KES 12]. 3.5.4.1.5. A molecular sign of radiation-induced thyroid cancers A specific molecular sign for thyroid cancers induced by ionizing radiation would have obvious benefits [CHE 16]. Therefore, since 2004 ([CHE 04]), there has been a search for new genes that can be targeted as diagnostic and clinical markers of differentiated thyroid tumors. Ory et al. [ORY 11] showed that some specific molecular pathways are deregulated in tumors induced by ionizing radiation. The specificities of radiation-induced thyroid tumors (studied with transcriptomic, proteomic and comparative genomic hybridization approaches, and taking into account the analytical constraints required to analyze such small tumor series) suggested that such a molecular signature could be found [ORY 12]. Finally, all of this team’s work suggested that thyroid tumors that develop following high external exposure (post-radiotherapy) or internal contamination by iodine 131 (post-Chernobyl) share common molecular characteristics related to DNA repair, oxidative stress and endoplasmic reticulum, allowing them to be classified as radiation-induced tumors, regardless of dose and dose rates. Ory et al. [ORY 13] also believe that there may be a “general” sign of thyroid tumors induced by radiation. 3.5.4.2. Leukemia In children below 5 years of age residing in the most contaminated areas of Ukraine, a case–control study, with 492 controls, found 246 cases of leukemia between 1987 and 1997. The reconstituted doses range from 0 to 313 mGy (92% < 10 mGy), and the significant increase in the risk of leukemia (OR) is 2.4 (1.4–4.0) for a dose greater than 10 mGy [NOS 10]. In Ukraine, between 1998 and 2009, out of 13,203 individuals, the SIR was 1.9 (0.7–4.1) [HAT 15b]. In Belarus, between 1997 and 2011, out of 11,847 individuals, the SIR was 1.8 (0.7–3.6) [OST 16]. For example, in children below 18 years of age in 1986, the SIRs for leukemia were calculated and none was significant. Among the Belarusian–Russian–Baltic liquidators (66,000, 65,000 and 15,000 respectively) receiving an average dose of 13 mGy, 70 cases of leukemia were detected (40 leukemias, 20 non-Hodgkin’s lymphomas (NHL) and 10 various others) with a matched control population of

The Extremely Serious Nuclear Accident at Chernobyl

105

287 individuals. The number of leukemias excluding chronic lymphocytic leukemias (CLL) was 0.5 ERR per 100 mGy (−0.4; 5.7) [KES 08]. The increase in leukemia in liquidators seems to be confirmed, but the studies have limitations such as low statistical power, high uncertainties in dose reconstitution and significant confounding factors [GLU 11]. In the Ukrainian liquidators (117 cases and 716 controls) who received an average dose of 132 and 82 mGy respectively for cases and controls, the number of non-CLL leukemias was 2.4 ERR per Gy (0.5–5.9) and the number of CLLs was 2.6 ERR per Gy (0.1–8.4) [ROM 08a, ROM 08b, ZAB 13]. 3.5.4.3. Breast cancer in women Breast cancers in women have been quantified in Ukraine [PRY 14]. The SIRs do not provide an indication of excess breast cancer in the general population and a possible excess among liquidators in the early years (Table 3.7). Number of cases observed Residents of contaminated areas (1990–2011)

1,168

Evacuated from Pripyat 314 and 30 km zone (1990–2011) Liquidators in 1986–87 (1994–2011)

303

Number of cases expected

SIR (95% CI)

1,835.7

0.63 (0.60, 0.67)

411.9

0.76 (0.68, 0.85)

18.7

1.63 (1.44, 1.82)

Table 3.7. Breast cancer incidence rate among women in the main population groups affected by the Chernobyl accident (SIR: standardized incidence ratio) (adapted from [PRY 14])

3.5.4.4. Other solid non-thyroid cancers Among Belarusian adults, the trend in mortality from solid cancers increased from 1991 to 2002 [GRI 13]. In Ukraine, there is no evidence of excess solid cancer in the general population and possible excess among liquidators in the early years [PRY 14] (Table 3.8).

106

Industrial and Medical Nuclear Accidents

Number of employees in 1986

Number of cases observed

Number of cases expected

SIR (95% CI)

Residents of contaminated areas (1990–2011)

360,000

15,389

19,226.8

0.80 (0.79, 0.81)

Evacuated from Pripyat and 30 km zone (1990–2011)

50,000

3,360

3,968

0.85 (0.82, 0.88)

Liquidators in 1986–87 (1994–2011)

85,000

9,764

9,063.2

1.08 (1.05, 1.10)

SIR: standardized incidence ratio; CI: 95% confidence interval

Table 3.8. Cancer incidence rates in the main population groups affected by the Chernobyl accident (modified from [PRY 14])

The risk of solid cancer in Russian liquidators was estimated using the cohort of Russian liquidators itself (National Chernobyl Registry) where the individual dose for 67,568 individuals is available. This dose ranges from 0.0001 to 1.24 Gy (median, 0.102 Gy). In this cohort, 4,002 solid cancers were observed and 2,422 deaths from solid cancer between 1992 and 2009 were reported. The excess relative risks of cancer incidence and mortality for 1 Gy (ERR Gy−1) are 0.47 (95% CI 0.03, 0.96; p = 0.034) and 0.58 (95% CI 0.002; p = 0.049) respectively, a difference which is statistically significant [KAS 15]. 3.5.5. Non-cancerous pathologies The pathologies concern the whole population, but it is mainly children who are affected by the effects of radiation. Fushiki [FUS 13], in light of previous accidents, considers that the main risks for children are related first to the ingestion of radioactive iodine (risk of thyroid cancer) and then to exposure to longer-lived radionuclides such as cesium 134 and especially 137. Another risk is delayed brain development for exposures greater than 100 mSv for the fetus. Thus, in Chernobyl, children exposed in utero have a statistically lower IQ than children who were not exposed during gestation [IGU 00].

The Extremely Serious Nuclear Accident at Chernobyl

107

3.5.5.1. Genetic and hereditary effects 3.5.5.1.1. Chromosomal aberrations Lazutka et al. [LAZ 99] note a sharp increase in chromosomal aberrations among nuclear workers and Chernobyl liquidators. Studies of damage in the genome of children exposed to ionizing radiation in their environment show, particularly after nuclear tests and the Chernobyl accident, that environmental radioactive pollution and accidental internal contamination cause chromosome aberrations and an increased frequency of micronuclei compared to children in reference areas [FUC 08]. In situ studies on children exposed to chemicals or radiation at an early age, or in utero, show that chromosomal aberrations increase and that they are a precursor of cancer outbreaks in adulthood [MER 07]. Similarly, the micronucleus test has been shown to be effective in detecting and monitoring the health of children exposed to various environmental stresses such as radiation [NER 03]. Thus, Zotti-Martelli et al. [ZOT 99] find that children highly exposed to radiation in Gomel (Belarus) develop more micronuclei in lymphocytes than children living in Pisa (Italy). This increase is correlated with the increase in cesium 137 contamination in children. 3.5.5.1.2. Congenital malformations The Belarusian national register was set up thanks to the Franco-German Chernobyl Initiative. This register makes it possible to quantify mutagenic anomalies (trisomy 21, polydactyly, esophageal atresia, anal atresia) as well as teratogenic anomalies (cleft lip, anencephaly, spina bifida, shortening of limbs) [LAZ 03]. The Ukrainian register of congenital malformations in Rivne province showed that mothers in the Polissia region had accumulated concentrations of 137Cs (28,500 measurements) three to five times higher than the rest of the province over the period 2000–2009. The frequency of neural tube closure failure (spinal cord precursor) (n = 319) is 160% higher [WER 14, WER 16]. This study, which is only descriptive, has various limitations, such as the data are aggregated, there are no individual doses, the numbers are small and several possible confounding factors exist (rural population, lifestyle, alcohol).

108

Industrial and Medical Nuclear Accidents

Sperling et al. [SPE 12] observed an increase in trisomy of chromosome 21 (Down syndrome) in January 1987 in Belarus and western Berlin at a time when the fallout of radionuclides from Chernobyl was most intense. Given that maternal meiosis is an error-prone process, the hypothesis of a causal relationship between low-dose irradiation and non-disjunction is the most likely explanation for the observed increase in trisomy after the Chernobyl reactor accident. Wertelecki [WER 10] notes that births in Polissia in the Rivne province of Ukraine have some of the highest malformation rates in Europe, such as 22.2 per 10,000 live births for neural tube defects. 3.5.5.2. Sensory organs and cataracts The relationship between irradiation and the occurrence of cataracts has been known since the effects of the atomic bomb in Hiroshima and Nagasaki at doses of 5–8 Gy. However, recent studies conducted by Hammer et al. [HAM 13] report that in atomic bomb survivors exposed as children, doses of 0.6–1 Sv were thresholds for the appearance of various types of cataracts. For the Chernobyl liquidators, the dose of 0.34 Sv (95% CI 0.19–0.68 Sv) caused a significant onset of a stage 1 cataract. The Ukrainian liquidators received a dose spread over 20 months. The doses received were relatively low (33% < 0.1 Gy; 77% < 0.2 Gy; median = 0.12 Gy). These liquidators had a large staff of 8,607 people who benefited from two ophthalmological evaluations 12 and 14 years after the exposure. After various adjustments (on age, sex, smoking status, diabetes, etc.), the prevalence of posterior or cortical subcapsular opacities is 25%. For a dose of 1 Gy, the OR is 1.65 (all non-nuclear opacity, grade 1–5). The estimated dose threshold is 0.50 Gy (95% CI 0.17–0.65 Gy) [WOR 07]. 3.5.5.3. Cardiovascular diseases Among the Russian cohort, 61,017 liquidators were followed from 1986 to 2000. The average dose received was 109 mGy. Only individuals who received a dose greater than 150 mGy had significantly higher cerebrovascular pathologies than controls (Table 3.9) [IVA 06].

The Extremely Serious Nuclear Accident at Chernobyl

Pathology

Number of people

ERR.Gy−1

Circulatory diseases

32,189

0.18 (−0.03 to 0.39)

Ischemic heart disease

10,942

0.41 (0.05 to 0.78)

Essential hypertension

11,910

0.36 (0.01 to 0.71)

Cerebrovascular pathology

12,832

0.45 (0.11 to 0.80)

Cerebrovascular pathology (average dose > 150 mGy)

109

1.10 (1.00 to 1.40)

Table 3.9. Cardiovascular diseases and relationship with dose received (modified according to [IVA 06]). ERR: excess relative risk

Using a meta-analysis, Little et al. [LIT 12] examined information on the risks of circulatory disease associated with exposure to whole-body ionizing radiation at low and moderate doses. The estimated excess risk to the population for all circulatory diseases combined ranged from 2.5% per Sv [95% confidence interval, 0.8 to 4.2] for the French population to 8.5% per Sv (95% CI 4.0 to 13.0) for the Russian population. If these results were confirmed, this would mean that the overall radiation-related mortality is about twice as high as currently estimated. 3.5.5.4. Other pathologies In 2006, Greenpeace [GRE 06] published a report on the consequences of the Chernobyl accident written by a large number of scientists. In this report, several other pathologies resulting from excessive irradiation are reported. These include, in particular, the length and weight of babies at birth, premature aging, hormonal status, abnormalities of immune function, as well as disorders of the respiratory, digestive, urogenital and reproductive systems, musculo-skeletal and skin disorders, and neurological and psychological disorders. Prenatal exposure to external radiation has been linked to stunting in adolescence among survivors of the Hiroshima and Nagasaki atomic bombs. What about the exposure of fetuses to iodine 131 in Chernobyl? In utero exposure of 2,460 fetuses to radioactive fallout from the Chernobyl nuclear accident in 1986 with an average 131I dose of 72 mGy had no effect on height, weight and body mass index (BMI) per 100 mGy dose increase unit [NET 14]. But what about exposure doses above 500 mGy?

110

Industrial and Medical Nuclear Accidents

Accelerated aging is one of the well-known consequences of exposure to ionizing radiation. This phenomenon occurs more or less in all populations contaminated by Chernobyl radionuclides [YAB 09d]. The increase in the incidence of type I diabetes appears to be sensitive to the effects of radiation since the incidence is higher in children and adolescents living in Gomel than those living in Minsk (139 and 407 km from Chernobyl respectively) [ZAL 04]. About 100 children exposed in utero during the Chernobyl accident and about 50 unexposed children between the ages of 11 and 13 were examined using neuropsychiatric tests. Loganovsky et al. [LON 08b] found that the exposed children had more neuropsychiatric disorders, including neurological signs of the left brain and lower verbal IQ. Tables 3.10–3.12 provide the incidence of various diseases for liquidators and morbidity for children, adolescents and adults living near Chernobyl. Morbidity in the liquidators’ group for 2008, particularly exposed in 1986–1987, was 79% down to cardiovascular diseases, 10% to diseases of the digestive system, 5% to diseases of the respiratory system and 6% to various other diseases [UKR 11]. In 2008, 33% of the liquidators exposed in 1986–1987 were unable to work as a result of cardiovascular diseases, 28% of diseases of the digestive system, 17% of diseases of the nervous system and sensory organs, 11% of diseases of the respiratory system and 11% of various other diseases [UKR 11]. Disease

1986

1993

Multiplicative factor

Blood and bloodforming organs

15

218

14.5

Circulation

183

4,250

23.2

Endocrine system

96

4,300

45.1

Respiratory system

645

7,110

11.0

Urogenital tract

34

1,410

41.4

Nervous system and sensory organs

232

9,890

42.6

Psychological changes

621

4,930

7.9

Digestive system

82

6,100

74.4

The Extremely Serious Nuclear Accident at Chernobyl

46

726

15.8

Infections and parasites 36

414

11.5

Neoplasms

20

621

31.1

Malignant growths

13

184

14.2

Skin and subcutaneous tissue

Table 3.10. Incidence (per 100,000) of the 12 disease groups among liquidators (modified from [PFL 11])

Disease/organism

1987

1992

Increasing

Endocrine system

631

16,404

25.8

Psychological disorders

249

13,145

52.8

Neurological system

2,641

15,101

5.7

Circulatory system

2,236

98,363

44.0

Digestive system

1,041

62,920

60.4

Skin and subcutaneous tissue

1,194

60,271

50.5

Muscles and bone tissue

768

73,440

96.9

Table 3.11. Incidence (per 100,000) of morbidity among adults and adolescents in northeastern Ukraine between 1987 and 1992 (modified from Pflugbeil et al., 2006 reported by [YAB 09b])

Disease

1985

Total primary diagnosis

9,771.2

Blood and blood-forming organs Circulatory diseases

1997

Multiplicative factor

124,440.6

12.8

54.3

1,146.9

20.9

32.3

425.1

13.2

Endocrine and immune systems

3.7

1,111.4

300.4

Respiratory system

760.1

82,688.9

108.8

Urogenital tract

24.5

1,198.8

48.9

Digestion organs

26.0

5,547.9

213.3

Muscles, bones and connective tissue

13.4

1,035.9

77.3

Mental disorders

95.5

867.6

9.1

Neural and sensory system

644.8

7,040.0

10.9

111

112

Industrial and Medical Nuclear Accidents

Skin and subcutaneous tissue

159.0

7,100.4

44.7

Parasitic infections and diseases

4,761.1

8,694.2

1.8

Birth defects

50.8

339.6

6.7

Neoplasias

1.4

134.5

99.4

Accidents and intoxication

2,590.2

4,343.0

1.7

Table 3.12. Impacts (per 100,000) of juvenile morbidity in Gomel province, Belarus (modified from [PFL 11])

3.5.6. Mortalities resulting from the Chernobyl accident Specialists consider that there are no clinical symptoms below 200 mSv. Up to 1 Sv, there is a decrease in white blood cells; then, between 1 and 2.5 Sv, early vomiting is accompanied by a decrease in blood cell count. Beyond 2.5 Sv, the consequences are more serious, and during an irradiation of 5 Sv, one person out of two dies. It is difficult to make an unambiguous statement about the health consequences of the Chernobyl accident given the confusing nature of scientific information, the lack of comprehensive epidemiological studies and uncertainty about the exact exposure to radioactive particles. In 1990, 590,000 people were on the official registers, of whom 200,000 were liquidators, about half of whom had received an irradiation dose of more than 10 rem (0.1 Sv). In 1991, among the liquidators, about 10% received a dose of 250 mSv and 30–50% received doses between 100 and 250 mSv (compared to 150 natural mSv over a lifetime). The liquidators represent a complex group because they are now scattered throughout the former republics of the Soviet Union, which makes medical surveillance difficult. In 1995, no excess mortality (death rate) was observed in this population. In Chernobyl, immediate deaths were reported. At the time of the accident, one plant employee died from shock and two others from their burns. Among rescuers and firefighters, 237 people were hospitalized, including 134 for acute radiation syndrome (ARS) (high doses received over a short period of time). Of these, 28 died quickly within a few months despite treatment (Table 3.13).

The Extremely Serious Nuclear Accident at Chernobyl

Degree of ARS

Dose (Gy)

Number of patients treated

Number of deaths

Low (I)

0.8–2.1

41

0

Moderate (II)

2.2–4.1

50

1

Severe (III)

4.2–6.4

22

7

Very severe (IV) 6.5–16

21

20

134

28

Total

0.8–16

113

Table 3.13. The number of acute radiation syndromes among liquidators (adapted from [KEN 05])

Perinatal mortality rates in the regions of Ukraine and Belarus surrounding the Chernobyl site increased in 1987, the year following the Chernobyl accident. In the same year, increases in perinatal mortality were also observed in Germany and Poland. This effect may be associated with cesium loading in pregnant women. After 1989, there was a second unexpected increase in perinatal mortality in Belarus and Ukraine. This increase is correlated with strontium levels in pregnant women. Although the effect of cesium is essentially limited to 1987, the effect of strontium persists until the end of the study period in 1998. The cumulative effect of strontium around Chernobyl on perinatal mortality outweighs the effect of cesium by at least a factor of 10 [KÖR 03]. While five million people live in the accident-contaminated areas of Belarus, Ukraine and Russia, the level of exposure is currently generally lower than in areas with high levels of naturally occurring radioactivity in India, Iran, Brazil and China. However, the report points out that 100,000 people in the contaminated areas receive a dose greater than 1 mSv.y−1. Vigilance is required since cesium 137 will remain present in the food chain, through milk and meat, for decades to come. However, in terms of health, the contamination caused an epidemic of thyroid cancer, which affected about 4,000 children, 99% of whom were cured. The report also mentions, without dwelling too much, that there is “a slight increase in cardiovascular diseases due to radiation”. The assessment of cancer deaths due to the Chernobyl disaster since 1986 varies widely by source (Table 3.14), with Greenpeace’s assessment being significantly higher than the others. The latter figure is very similar to that proposed in 2006 by Khudoley et al. and reported by Yablokov [YAB 09b]

114

Industrial and Medical Nuclear Accidents

(Table 3.15). For the whole world, the excess of global mortality is estimated at 985,000 deaths between April 1986 and the end of 2004 [YAB 09a]. According to Yablokov [YAB 09c], the number of fatal cancers ranges from 212,000 to 245,000 in Europe and 19,000 in the rest of the world. Approximately 112,000–125,000 liquidators died before 2005, representing 15% of the 830,000 people who could be associated with this group according to Yablokov [YAB 09a]. Using a conservative methodology based on external ionizing radiation risk factors derived from Japanese studies on the A-bomb, Bertell [BER 06] from the International Institute of Concern for Public Health (IICPH) estimates that the final outcome of the Chernobyl disaster would be more likely for the world population to be 290 deaths directly induced by radiation damage, 899,310–1,786,657 from deadly cancers, for a total of 899,600–1,787,000 deaths. Experts from several agencies (e.g. IAEA, WHO, UNDP) gathered in the Chernobyl Forum (created in 2002) identified 56 deaths directly attributable to exposure to high levels of radiation immediately after the explosion, 28 rescuers in the months that followed, 19 in subsequent years and 9 children who died from thyroid cancer [IAE 05]. Overall, experts estimate that nearly 4,000 people died from cancers induced by the radiation from the accident, among the 600,000 “liquidators” who intervened on the site after the disaster and among the inhabitants of the affected areas. Source

Population taken into account

Number of deaths from cancer

IAEA, 2005; press release

Liquidators and evacuees

4,000

WHO, 2006 (aide-memoire)

Liquidators, evacuees and inhabitants of contaminated areas

9,000

IARC, 2006 (study, Cardis, ed.) European population

16,000

TORCH, 2006 (report)

World population

30,000–60,000

Greenpeace, 2006 (report)

Russia, Ukraine and Belarus

200,000

Table 3.14. Assessment of cancer deaths caused by the Chernobyl disaster since 1986. Assessed by various agencies (sources: [IAE 05, OMS 06, CIR 06, TOR 06, GRE 06])

The Extremely Serious Nuclear Accident at Chernobyl

European Russia Population living in highly 1,789,000 contaminated areas Number of additional deaths due to Chernobyl

67,000

Belarus

Ukraine

115

Total

1,571,000

2,290,000

5,650,000

59,000

86,000

212,000

Table 3.15. Number of additional deaths in Belarus, Ukraine and European Russia from 1990 to 2004 that can be attributed to the Chernobyl disaster (modified from Khudoley et al., 2006; in [YAB 09a])

3.6. Social consequences Unlike the Japanese populations exposed to ionizing radiation (“Hibaku”) who were stigmatized after the wartime bombings in Hiroshima and Nagasaki (Amiard, 2019), the Slavic populations living around Chernobyl did not feel any aversion from other populations. On the other hand, a disaster such as Chernobyl necessarily induces psychological disorders. This usually begins with anxiety on the part of the liquidators and individuals in the displaced populations. Anxious individuals try to fight this feeling by taking legal drugs (tobacco, alcohol, etc.), or even illegal drugs. This leads to mild morbidity, which in turn leads to anxiety and then psychological disorders. It is a rather classic vicious circle. 3.6.1. Psychological disorders among liquidators The population of liquidators was the most exposed to ionizing radiation. It therefore seems logical that these individuals raised the question of the consequences on their health and that their anxiety was high. Between 1986 and 1993, an increase in suicides (50% compared to the population) was reported for Estonian liquidators (4,833 men), representing the third cause of death after accidents and diseases of the circulatory system.

116

Industrial and Medical Nuclear Accidents

After the Chernobyl accident, the percentage of depressive episodes was higher among Ukrainian liquidators (295 liquidators) and 397 control individuals than among control individuals overall (18.0% vs. 13.1%). The same is true for suicide (9.2% vs. 4.1%). In the year preceding the interview, conducted 18 years after the accident, the rates of depression (14.9% vs. 7.1%), post-traumatic stress disorder (4.1% vs. 1.0%) and headaches (69.2% vs. 12.4%) were high. The affected workers lost more working days than the control population [LON 08a]. Twenty-four years after the Chernobyl accident, Estonian liquidators had significantly more sleep problems, somatization and symptoms of agoraphobia than the control population, even after the maximum number of adjustments taking into account ethnicity, education, marital status and employment status [LAN 15]. 3.6.2. Psychological disorders in evacuated populations Populations exposed to stress following the Chernobyl accident were identified according to the contamination of their living environment and the exposure dose (Table 3.16). The first epidemiological study carried out in Chernobyl was reported by Dutch scientists (Nijenhuis et al., [NIJ 95]) in 1992 in the highly contaminated region of Gomel (Belarus). This study highlights the increase in the frequency of psychological disorders in the population (mood disorders, anxiety). In Chernobyl, a significant increase in psychological distress, poorer subjective health and higher medicine consumption in the exposed population were observed as early as 1992 [HAV 96]. The results were more pronounced in at-risk groups such as evacuees and mothers with children. However, no significant differences in overall levels of psychiatric or physical morbidity were found. Radiation-related diseases could not explain the poor perception of health in the sample studied. These results indicate that psychological factors after the Chernobyl disaster had a significant effect on psychological well-being, perceived health and subsequent disease progression [HAV 96].

The Extremely Serious Nuclear Accident at Chernobyl

Contamination of soils by 137Cs (kBq.m−2)

Estimated exposure (Sv.y−1)

Exposed population

117

Actions taken

>1,480

>5

115,000

Almost total evacuation

555–1,480