Nuclear Nonproliferation: A Primer 9781685856564

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NUCLEAR NONPROLIFERATION

Published in association with the Program for Nonproliferation Studies, Monterey Institute of International Studies

NUCLEAR NONPROLIFERATION A PRIMER

Gary T. Gardner

Lynne Rienner Publishers • Boulder & London

Published in the United States of America in 1994 by Lynne Rienner Publishers, Inc. 1800 30th Street, Boulder, C o l o r a d o 80301 and in the United Kingdom by Lynne Rienner Publishers, Inc. 3 Henrietta Street, Covent Garden, London W C 2 E 8LU © 1994 by Lynne Rienner Publishers, Inc. All rights reserved Library of Congress Cataloging-in-Publication Data Gardner, Gary T., 1958Nuclear nonproliferation : a primer / by Gary T. Gardner. Includes bibliographical references and index. ISBN 1-55587-478-9 (alk. paper) ISBN 1-55587-489-4 (pbk. : alk. paper) 1. Nuclear nonproliferation. I. Title. JX1974.73.G374 1994 327.1'74—dc20

93-23571 CIP

British Cataloguing in Publication Data A Cataloguing in Publication record for this book is available from the British Library.

Printed and bound in the United States of America

©

The paper used in this publication meets the requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48-1984.

For Mom, Dad, J e f f , and Clarence, my family

Contents

List of Tables and Figures Preface

ix xi

1

Nuclear Fission and the Nuclear Bomb Fission as a Source of Energy, 1 The Structures of an Atom, 1 Obstacles to Fission, 2 Neutrons and Plutonium Production, 5 The Proliferation Significance of Nuclear Materials, 6 The Basics of an Atomic Bomb, 6 Summary, 8

1

2

The Nuclear Fuel Cycle The Once-Through Versus Plutonium Fuel Cycles, 11 The Fuel Cycle from a Nonproliferation Perspective, 12 A Closer Look at Enrichment Technologies, 21

11

3

Nuclear Reactors Reactor Operation and Purposes, 25 A Proliferation Analysis of Nuclear Reactors, A Taxonomy of Nuclear Reactors, 31

25 27

4

The History of the Nonproliferation Regime Early Approaches to Nonproliferation, 38 Nuclear Promotion Through the Atoms for Peace Program, 39 A Broadening Consensus on Nonproliferation, 41 The Evolution of Nuclear Export Controls, 42 Concern About "Threshold States, " 46 New Recruits and New Strength for the Nonproliferation Regime, 48 Challenges for the Future, 49

37

5

Legal Structures of the Nonproliferation R e g i m e The Concept of a Regime, 53 International Arrangements, 54 Regional Arrangements, 59

53

vii

CONTENTS

v¡¡¡

National Legislation, 62 Other Structures, 64 6

International S a f e g u a r d s The Evolution of Safeguards, 67 General Goals of Safeguards, 68 Specific Goals of Safeguards, 70 What Is Safeguarded? 70 How Is Safeguarding Carried Out ? 73 Safeguarding Authority of the IAEA and Euratom, Limits on IAEA Safeguards, 74

67

74

7

T h e Politics of Proliferation Is the Spread of Nuclear Weapons Inevitable? 79 Incentives for Developing Nuclear Weapons, 80 Disincentives for Developing Nuclear Weapons, 81 Options for Nonproliferation Policy, 82

79

8

The 1995 N P T Extension Conference Purpose and Significance of the Conference, 87 Options Surrounding Treaty Extension, 87 Potential Conference Difficulties, 89 What Would Nonrenewal of the Treaty Mean? 90

87

9

Nations of Proliferation Concern Nuclear and Potential Nuclear States,

93 93

10

Current C h a l l e n g e s to the N o n p r o l i f e r a t i o n R e g i m e The Glut of Fissile Materials, 111 Adequacy of Safeguards, 112 Nuclear Testing and Nuclear Disarmament, 113 Proliferation Potential of the Former Soviet Union, 114 Ineffective Implementation of Export Controls, 114 Drawing New Participants into the Regime, 115 Proliferation of Old Technologies, 116

111

11

Summary On Nuclear Fission, 117 On the Nuclear Fuel Cycle, 117 Regime, 118 On the History of the Nonproliferation On Safeguards, 118 On the Politics of Nonproliferation, 118 On the NPT Review Conference, 118 On Nations of Proliferation Concern, 119 On Current Issues in the Nonproliferation Regime, 119

117

Appendix:

T r e a t y o n the N o n - P r o l i f e r a t i o n o f

Nuclear Weapons

Further Reading Glossary Index About the Book and the Author

121

127 131 137 141

Tables and Figures

TABLES 1.1 1.2 2.1 3.1 3.2 4.1 5.1 5.2 5.3 6.1 9.1

Critical M a s s for U-235, U-233, and Pu-239 Under Various Conditions Comparative Nuclear Yields Global Nuclear Fuel Cycle Facility Capacities Share of Isotopes in Weapons- and Reactor-Grade Plutonium Proliferation-Sensitive Characteristics of Four Reactor T y p e s Key Events in the History of the Nuclear Nonproliferation Regime The Nuclear Suppliers Group and the Zangger Committee: Member-States Safeguards Required by the NPT, the Treaties of Tlatelolco and Rarotonga, and the NSG Legal Characteristics of Selected Institutions of the Nonproliferation Regime Characteristics of I N F C I R C / 6 6 and I N F C I R C / 1 5 3 Model Safeguards A g r e e m e n t s Nuclear Profiles of the Soviet Successor States

7 8 14 30 31 37 57 59 63 68 99

FIGURES 1.1 1.2 1.3 2.1 3.1

Three Possible Destinies of a Neutron in a Reactor Environment A Nuclear Chain Reaction U-235 Defenses The Nuclear Fuel Cycle A Light-Water Nuclear Reactor

¡x

3 3 4 12 26

Preface

T h e e f f o r t to c o n t r o l the s p r e a d of n u c l e a r w e a p o n s has b e e n m o r e s u c c e s s f u l in the past half c e n t u r y than m a n y d a r e d h o p e , a n d is m o r e f i r m l y i n s t i t u t i o n a l i z e d t o d a y t h a n e v e r b e f o r e . Still, n e w c h a l l e n g e s , s t e m m i n g f r o m c h a n g e s in t e c h n o l o g y , g o v e r n m e n t s , a n d i n t e r n a t i o n a l p o l i t i c s , appear c o n s t a n t l y on t h e h o r i z o n . C o m m o n to all t h e s e c h a l l e n g e s is the p r o b l e m of p r o v i d i n g a c c e s s to n u c l e a r t e c h n o l o g y f o r p e a c e f u l p u r p o s e s w h i l e p r e v e n t i n g its d i v e r s i o n to m i l i t a r y u s e . T h e c h a n g i n g f a c e of n o n p r o l i f e r a t i o n c r e a t e d by i n t e r n a t i o n a l e v e n t s s u c h as the G u l f W a r a n d the b r e a k u p of t h e S o v i e t U n i o n c r e a t e s a dem a n d f o r new b l o o d in the f i e l d , i n c l u d i n g b o t h area a n d t o p i c a l s p e c i a l ists, and r e q u i r e s e d u c a t i o n a l r e s o u r c e s g e a r e d to t h e s e n e w c o m e r s . T h i s p r i m e r f o r m s part of that e d u c a t i o n a l e f f o r t . A n initiative of the C I S N o n p r o l i f e r a t i o n P r o j e c t of t h e M o n t e r e y I n s t i t u t e of International S t u d i e s , this b o o k w a s o r i g i n a l l y i n t e n d e d as an i n t r o d u c t i o n to the f i e l d f o r the p r o j e c t ' s c o r e g r o u p of a s p i r i n g n o n p r o l i f e r a t i o n s p e c i a l i s t s in the f o r m e r Soviet U n i o n . T h e e f f o r t h a s g r o w n , h o w e v e r , into a b r o a d - b a s e d i n t r o d u c tion u s e f u l to a m u c h larger a u d i e n c e : s t u d e n t s , j o u r n a l i s t s , a n d o t h e r s new to t h e f i e l d c a n p r o f i t f r o m the i n f o r m a t i o n p r e s e n t e d h e r e . T h i s p r i m e r p r e s u m e s n o p r e v i o u s e x p e r i e n c e w i t h n u c l e a r i s s u e s but p r e s u p p o s e s an interest in s e r i o u s study of the f i e l d . It p r o v i d e s a c o m p r e h e n s i v e o v e r v i e w of n o n p r o l i f e r a t i o n , f r o m the t e c h n i c a l b a s i c s to the history and p o l i t i c s of nonproliferation efforts. B e c a u s e the s c i e n c e of n u c l e a r e n e r g y is at the heart of the n o n p r o l i f e r a t i o n c h a l l e n g e , the p r i m e r b e g i n s w i t h a s i m p l e i n t r o d u c t i o n to n u c l e a r f i s s i o n in C h a p t e r 1, f o l l o w e d by d e s c r i p t i o n s of the n u c l e a r fuel c y c l e and n u c l e a r r e a c t o r s in C h a p t e r s 2 a n d 3. R e a d e r s a v e r s e to s c i e n t i f i c t o p i c s m a y b e g i n their s t u d y later in the b o o k , but are likely to r e t u r n e v e n t u a l l y t o t h e t e c h n i c a l s e c t i o n s as t h e n e e d to c o m p r e h e n d t h e f u n d a m e n t a l s of nuclear power becomes evident. xi

Xil

PREFACE

F o l l o w i n g the technical sections, the b o o k shifts to a look at historical a n d political issues. C h a p t e r 4 d e s c r i b e s the history of e f f o r t s to control the s p r e a d of n u c l e a r m a t e r i a l s and t e c h n o l o g y , a n d C h a p t e r 5 e x a m i n e s the m a j o r legal s t r u c t u r e s e m a n a t i n g f r o m that history. C h a p t e r 6 deals w i t h international n u c l e a r s a f e g u a r d s , a critical c o n f i d e n c e - b u i l d i n g elem e n t of the n o n p r o l i f e r a t i o n r e g i m e . T h e politics of n o n p r o l i f e r a t i o n , inc l u d i n g strategies for dealing with p r o l i f e r a t i o n , is treated in C h a p t e r 7. T h e last three c h a p t e r s deal with the most current issues in the regime. C h a p t e r 8 d i s c u s s e s the critical 1995 N o n - P r o l i f e r a t i o n T r e a t y ( N P T ) extension c o n f e r e n c e , at w h i c h the fate of the N P T will be d e t e r m i n e d . Chapter 9 describes the attitudes t o w a r d n o n p r o l i f e r a t i o n and nuclear capabilities of selected nations of p r o l i f e r a t i o n c o n c e r n . C h a p t e r 10 c l o s e s with a brief d e s c r i p t i o n of c u r r e n t c h a l l e n g e s to the n o n p r o l i f e r a t i o n r e g i m e . A s u m m a r y c h a p t e r , an a p p e n d i x c o n t a i n i n g the text of the N P T , an a n n o tated bibliography, and a glossary p r o v i d e ready r e f e r e n c e i n f o r m a t i o n . It is our h o p e that this e f f o r t will s t i m u l a t e r e a d e r s to p u r s u e f u r t h e r study of the n o n p r o l i f e r a t i o n of n u c l e a r w e a p o n s . Q u e s t i o n s or c o m m e n t s are w e l c o m e and s h o u l d be a d d r e s s e d to: Program for N o n p r o l i f e r a t i o n S t u d i e s Monterey Institute of International S t u d i e s 4 2 5 Van Buren Street Monterey, CA 93940. T h i s educational e f f o r t was m a d e p o s s i b l e by grants f r o m the C a r n e g i e C o r p o r a t i o n , the C o m p t o n F o u n d a t i o n , the J o h n M e r c k F u n d , the P l o u g h s h a r e s F u n d , the W . A l t o n J o n e s F o u n d a t i o n , and the W i n s t o n F o u n d a t i o n . T h e v i e w s e x p r e s s e d herein, h o w e v e r , are those of the author and are not necessarily s h a r e d by these institutions. *

*

*

T h e n o n p r o l i f e r a t i o n c o m m u n i t y is a s u p p o r t i v e and g e n e r o u s o n e . M a n y individuals in that c o m m u n i t y w e r e h e l p f u l in r e v i e w i n g p o r t i o n s of the m a n u s c r i p t . I am particularly i n d e b t e d to G e o r g e Bunn, D a v i d Fischer, C h r i s Fitz, L y n n H u i z e n g a , Betsy P e r a b o , W i l l i a m Potter, L e o n a r d Spector, Roland T i m e r b a e v , Frank V o n H i p p e l , a n d Carl W a l t e r s f o r their c o m m e n t s and s u g g e s t i o n s . R o g e r H a n e y p r o v i d e d e x p e r t c o m p u t e r g r a p h i c s a d v i c e . N o n e is in a n y w a y r e s p o n s i b l e for the final p r o d u c t , but all des e r v e a c k n o w l e d g m e n t and a rich note of t h a n k s . Special g r a t i t u d e is in o r d e r f o r t h r e e of the i n d i v i d u a l s m e n t i o n e d a b o v e . W i l l i a m P o t t e r g r a n t e d m e a large b l o c k of u n d i s t u r b e d t i m e to w o r k on the project w h e n he might h a v e p r e f e r r e d that my e n e r g i e s w e r e d i r e c t e d e l s e w h e r e . For his c o n f i d e n c e and s u p p o r t , I am t h a n k f u l . D a v i d F i s c h e r was t r e m e n d o u s l y g e n e r o u s in his r e v i e w of several c h a p t e r s and

Xlll

PREFACE

o f f e r e d highly detailed and i n v a l u a b l e c o m m e n t s on t h e m . His a s s i s t a n c e went far b e y o n d what I c o u l d rightly e x p e c t . Finally, Betsy P e r a b o w a l k e d with m e t h r o u g h the entire p r o c e s s and w a s u n f a i l i n g in her e n c o u r a g e ment of the e f f o r t . Her g o o d cheer, c o n s i s t e n t s u p p o r t , and timely h u m o r m a d e the project a lot of f u n . I am indeed lucky to have such a good friend. Gary T.

Gardner

1 Nuclear Fission and the Nuclear Bomb

N u c l e a r p r o l i f e r a t i o n is a p r o b l e m of g l o b a l p r o p o r t i o n s , but initial a p p r o a c h e s to the s u b j e c t can be m a d e on a m u c h s m a l l e r s c a l e — t h e s c a l e of the a t o m . N u c l e a r p h y s i c s r e v e a l s the e n t i c i n g and p r o b l e m a t i c p o w e r of this f u n d a m e n t a l b u i l d i n g b l o c k of m a t t e r . T h i s c h a p t e r i n t r o d u c e s the basics of n u c l e a r e n e r g y and d i s c u s s e s their r e l a t i o n s h i p to the issue of n u clear proliferation.

FISSION AS A SOURCE OF ENERGY T h e c r u c i a l event in h a r n e s s i n g n u c l e a r e n e r g y , w h e t h e r in a n u c l e a r reactor or a n u c l e a r b o m b , is the s p l i t t i n g of an a t o m . T h i s a c t i o n , k n o w n as n u c l e a r f i s s i o n , r e l e a s e s t r e m e n d o u s e n e r g y — m i l l i o n s of t i m e s m o r e than that of a c h e m i c a l r e a c t i o n . 1 In f a c t , the f i s s i o n i n g of a t o m s in o n e p o u n d of u r a n i u m r e l e a s e s as m u c h e n e r g y as the b u r n i n g of 6 , 0 0 0 b a r r e l s of oil or 1,000 t o n s of c o a l . 2 T h e e n o r m o u s p o w e r of the a t o m m a k e s n u c l e a r e n ergy a t e m p t i n g r e s o u r c e f o r e n e r g y m i n i s t r i e s and m i l i t a r y e s t a b l i s h m e n t s worldwide.3 S p l i t t i n g the a t o m , h o w e v e r , is n o s i m p l e t a s k . M a n y d i f f i c u l t i e s inh e r e n t in the f i s s i o n p r o c e s s m u s t be o v e r c o m e by any n a t i o n or g r o u p int e n d i n g to h a r n e s s the p o w e r of the a t o m , w h e t h e r f o r m i l i t a r y or p e a c e f u l p u r p o s e s . A s i m p l e d e s c r i p t i o n of t h e s e d i f f i c u l t i e s f o l l o w s a brief r e v i e w of the s t r u c t u r e of an a t o m .

THE STRUCTURE OF AN ATOM M o s t a t o m s c o n s i s t of p r o t o n s , n e u t r o n s , a n d e l e c t r o n s . P r o t o n s and n e u trons b o n d t o g e t h e r s t r o n g l y to f o r m a n u c l e u s , a n d e l e c t r o n s orbit a r o u n d t h e m . T h e n u m b e r of p r o t o n s g i v e s an a t o m , or e l e m e n t , its u n i q u e identity

1

NUCLEAR NON PROLIFERATION: A PRIMER

2

a n d f a m i l y n a m e . All u r a n i u m a t o m s , f o r e x a m p l e , h a v e 9 2 p r o t o n s , a n d any a t o m with 9 2 p r o t o n s m u s t b e a u r a n i u m a t o m . If a p r o t o n is a d d e d to an a t o m or t a k e n f r o m it, the a t o m ' s identity c h a n g e s c o m p l e t e l y . N e u t r o n s , o n the o t h e r h a n d , can vary in q u a n t i t y in the s a m e kind of a t o m . S o m e u r a n i u m a t o m s , f o r e x a m p l e , h a v e 143 n e u t r o n s , s o m e 146. If p r o t o n s e s t a b l i s h an e l e m e n t ' s d i s t i n c t i v e i d e n t i t y — i t s s u r n a m e — n e u t r o n s g i v e a twist to that i d e n t i t y , like a first n a m e . A t o m s of t h e s a m e f a m i l y are c a l l e d i s o t o p e s . F o r e x a m p l e , the uran i u m i s o t o p e U - 2 3 5 is m a d e u p of 9 2 p r o t o n s a n d 143 n e u t r o n s , w h e r e a s the m o r e c o m m o n U - 2 3 8 has 9 2 p r o t o n s and 146 n e u t r o n s . ( T h e d e s i g n a tions " 2 3 5 " a n d " 2 3 8 " are o b t a i n e d by a d d i n g t o g e t h e r the n u m b e r s of prot o n s a n d n e u t r o n s in t h e n u c l e u s . ) B o t h U - 2 3 5 a n d U - 2 3 8 b e l o n g to the u r a n i u m f a m i l y , but e a c h has c e r t a i n d i s t i n c t i v e a t t r i b u t e s . U - 2 3 5 is highly u n s t a b l e , w h i c h m a k e s it easier to split t h a n its sister i s o t o p e U - 2 3 8 . In a r e a c t o r , a n e u t r o n f i r e d at a U - 2 3 5 a t o m a t t a c h e s itself to the a t o m , i n c r e a s i n g its i n s t a b i l i t y , w h i c h in t u r n c a u s e s the a t o m to b r e a k apart ( f i s s i o n ) a n d r e l e a s e e n e r g y . T h e s a m e n e u t r o n d i r e c t e d at the m o r e s t a b l e U - 2 3 8 a t o m w o u l d likely be a b s o r b e d w i t h o u t f i s s i o n i n g . M a n y n e u t r o n s are i n t e r c e p t e d b e n i g n l y by U - 2 3 8 a t o m s , a n d o t h e r s are a b s o r b e d by the a t o m s of o t h e r m a t e r i a l s in the r e a c t o r . Still o t h e r s e s c a p e f r o m the r e a c t o r c o m p l e t e l y ( s e e F i g u r e 1.1). In s u m , the f i s s i o n p r o c e s s m i g h t be i m a g i n e d as i n v o l v i n g the f o l l o w i n g c o m p o n e n t s : •

the " t a r g e t s " : U - 2 3 5 a t o m s , w h o s e c a p t u r e a n d f i s s i o n i n g r e l e a s e s the a t o m i c e n e r g y

•

the " a r r o w s " : n e u t r o n s , w h i c h a t t a c k the U - 2 3 5 t a r g e t s or s e e k to escape the " i n t e r c e p t o r s " : U - 2 3 8 a t o m s , w h i c h d e f e n d t h e U - 2 3 5 t a r g e t s by absorbing neutron "arrows"4

•

T h e f i s s i o n i n g of a U - 2 3 5 a t o m in turn r e l e a s e s t w o or t h r e e of its o w n n e u t r o n s . If at least o n e of t h e s e is s u c c e s s f u l in s p l i t t i n g a n o t h e r U - 2 3 5 a t o m , a c h a i n r e a c t i o n is e s t a b l i s h e d , w h i c h p r o d u c e s a s t e a d y o u t p u t of e n e r g y in a n u c l e a r r e a c t o r (see F i g u r e 1.2). If the c h a i n r e a c t i o n i n v o l v e s e n o u g h a t o m s in a f r a c t i o n of a s e c o n d , as in a n u c l e a r b o m b , a t r e m e n d o u s e x p l o s i o n r e s u l t s . B e c a u s e of its e a s y f i s s i b i l i t y , U - 2 3 5 is g e n e r a l l y m o r e v a l u a b l e than U - 2 3 8 to t h o s e i n t e r e s t e d in g e n e r a t i n g n u c l e a r e n e r g y .

OBSTACLES TO FISSION T h e u n s t a b l e U - 2 3 5 a t o m , h o w e v e r , is q u i t e rare, c o n s t i t u t i n g o n l y a tiny f r a c t i o n of the a t o m s in a c h u n k of n a t u r a l u r a n i u m . In fact, the " i n t e r c e p t o r " i s o t o p e U - 2 3 8 is 140 t i m e s m o r e c o m m o n in n a t u r a l u r a n i u m t h a n t h e

NUCLEAR FISSION AND THE NUCLEAR BOMB

Figure 1.1 Three Possible Destinies of a Neutron in a Reactor Environment

Neutrons are absorbed by a U-238 atom (top), by a U-235 atom (middle), or by reactor material (bottom). In the middle case, neutron absorption causes the U235 to become unstable and split.

Figure 1.2 A Nuclear Chain Reaction

Each fissioned atom releases neutrons, some of which go on to split other atoms.

3

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NUCLEAR NONPROLIFERATION: A PRIMER

Figure 1.3 U-235 Defenses

U-236 target atoms are well protected from attacking neutrons.

f i s s i l e " t a r g e t " U - 2 3 5 . T h e rare U - 2 3 5 a t o m s in natural u r a n i u m , then, are w e l l d e f e n d e d a g a i n s t i n c o m i n g n e u t r o n s by the a b u n d a n t U - 2 3 8 a t o m s (see F i g u r e 1.3). In a d d i t i o n , the a t t a c k i n g n e u t r o n s are ill s u i t e d f o r their m i s s i o n : m o s t fly far t o o fast to attach t h e m s e l v e s to a U - 2 3 5 a t o m . W i t h o u t h u m a n i n t e r v e n t i o n , the s i t u a t i o n is not at all f a v o r a b l e f o r s u s t a i n e d f i s s i o n i n g of the U - 2 3 5 a t o m : on the o n e h a n d , f o r m i d a b l e def e n s e s in the f o r m of U - 2 3 8 a t o m s and o t h e r n e u t r o n - a b s o r b i n g m a t e r i a l s k e e p m o s t n e u t r o n s a w a y f r o m the target U - 2 3 5 , and o n the o t h e r , the att a c k i n g n e u t r o n s are largely i n c a p a b l e of p e n e t r a t i n g and splitting an a t o m , e v e n if they can r e a c h it. A n y h o p e of h a r n e s s i n g the t r e m e n d o u s p o w e r of the a t o m r e q u i r e s t h e c r e a t i o n of m o r e f a v o r a b l e c o n d i t i o n s f o r a s u s t a i n able nuclear chain reaction. S e v e r a l a d j u s t m e n t s a r e p o s s i b l e . O n e is to s l o w the a t t a c k i n g n e u t r o n s to a s p e e d w h e r e i n t e r a c t i n g w i t h U - 2 3 5 b e c o m e s p o s s i b l e . ( S l o w n e u t r o n s can m o r e e a s i l y a t t a c h t h e m s e l v e s to an a t o m than f a s t n e u t r o n s c a n . ) In a n u c l e a r r e a c t o r , this is d o n e w i t h the m o d e r a t o r , a m a t e r i a l s u c h as light w a t e r , h e a v y w a t e r , o r g r a p h i t e , w h i c h s u r r o u n d s the n u c l e a r f u e l in t h e r e a c t o r c o r e . 5 W h e n n e u t r o n s c o l l i d e w i t h t h e h e a v y w a t e r or g r a p h i t e a t o m s , t h e n e u t r o n s d e c e l e r a t e to a s p e e d that g r e a t l y i m p r o v e s their c h a n c e s of a t t a c h i n g to a U - 2 3 5 a t o m and c a u s i n g it to b r e a k a p a r t . In r e a c t o r s m o d e r a t e d b y t h e s e m a t e r i a l s , n o o t h e r a d j u s t m e n t s are n e c e s s a r y to m a k e f i s s i o n p o s s i b l e . W h e n light ( o r d i n a r y ) w a t e r is u s e d as a m o d e r a t o r , h o w e v e r , s o m e n e u t r o n s are s l o w e d , but o t h e r s are a b s o r b e d by the n e u t r o n - h u n g r y light-

NUCLEAR FISSION AND THE NUCLEAR BOMB

5

w a t e r a t o m s . T h u s a r e a c t o r m o d e r a t e d b y l i g h t w a t e r is still a n e u t r o n h o s t i l e e n v i r o n m e n t , as t h e n e u t r o n f a c e s p r o b a b l e a b s o r p t i o n e i t h e r b y U - 2 3 8 or l i g h t - w a t e r a t o m s . H o w e v e r , b e c a u s e o r d i n a r y w a t e r is p l e n t i f u l a n d c h e a p c o m p a r e d to h e a v y w a t e r , w h i c h is c o s t l y a n d v e r y d i f f i c u l t to m a k e , l i g h t w a t e r is t h e p r e f e r r e d m o d e r a t i n g m a t e r i a l . T o m a k e u s e of light w a t e r , h o w e v e r , a s e c o n d s t r a t e g y m u s t b e e m p l o y e d to i n c r e a s e t h e c h a n c e of a s u c c e s s f u l f i s s i o n . T h i s s e c o n d s t r a t e g y is to set u p m o r e t a r g e t s , t h a t is, to i n c r e a s e t h e p r o p o r t i o n of U - 2 3 5 f o u n d in u r a n i u m . T h e g r e a t e r t h e s h a r e of

U-235

a t o m s in u r a n i u m f u e l or b o m b m a t e r i a l , t h e m o r e likely a s u c c e s s f u l c h a i n r e a c t i o n c a n be s t a r t e d . A p r o c e s s c a l l e d e n r i c h m e n t is u s e d to r a i s e the p r o p o r t i o n of U - 2 3 5 f r o m its n a t u r a l level of 0 . 7 p e r c e n t to a r o u n d 3 - 5 p e r c e n t f o r use in a l i g h t - w a t e r r e a c t o r , or to a r o u n d 9 0 p e r c e n t f o r use in a n u c l e a r b o m b . W i t h e n r i c h e d u r a n i u m f u e l , e n o u g h U - 2 3 5 is a v a i l a b l e f o r f i s s i o n i n g e v e n a f t e r n e u t r o n l o s s e s to l i g h t - w a t e r a t o m s a r e t a k e n i n t o a c c o u n t . F i n a l l y , in a v a r i a n t o n t h e e n r i c h m e n t o p t i o n , t h e f i s s i o n p r o c e s s m a y b e a s s i s t e d by i n c r e a s i n g t h e p r o p o r t i o n of U - 2 3 5 t a r g e t s s o m u c h t h a t e v e n f a s t n e u t r o n s c a n n o t m i s s t h e m . If t h e p e r c e n t a g e of U - 2 3 5 is inc r e a s e d to 9 0 p e r c e n t or h i g h e r , n e u t r o n s a r e a b l e t o f i s s i o n t h e U - 2 3 5 w i t h o u t b e i n g s l o w e d by a m o d e r a t o r . T h e u s e of f a s t n e u t r o n s a n d h i g h l y e n r i c h e d u r a n i u m ( a l o n g w i t h p l u t o n i u m , d i s c u s s e d s h o r t l y ) is c h a r a c t e r i s t i c of n u c l e a r b o m b s a n d of t h e s o - c a l l e d f a s t r e a c t o r .

NEUTRONS AND PLUTONIUM PRODUCTION A n o t h e r i m p o r t a n t e v e n t in t h e r e a c t o r c o r e t h a t i n c r e a s e s t h e c h a n c e s of s u c c e s s f u l f i s s i o n is t h e t r a n s f o r m i n g a c t i o n of a t t a c k i n g n e u t r o n s .

We

h a v e s e e n that n e u t r o n s t h a t a r e u n s u c c e s s f u l in s p l i t t i n g U - 2 3 5 a t o m s a r e a b s o r b e d by U - 2 3 8 a t o m s o r o t h e r m a t e r i a l s , o r t h e y e s c a p e t h e r e a c t o r e n t i r e l y . T h e n e u t r o n s c a p t u r e d b y U - 2 3 8 a r e not e n t i r e l y w a s t e d , h o w e v e r . H a v i n g f a i l e d to f i n d a n d split a U - 2 3 5 n u c l e u s , t h e s e n e u t r o n s s e r v e a s e c o n d a r y p u r p o s e : to c o n v e r t t h e n o n f i s s i l e U - 2 3 8 i n t o f i s s i l e p l u t o n i u m ( P u 239), a process requiring two steps, w h i c h take a few days. O n c e this t r a n s m u t a t i o n is a c h i e v e d , a n o t h e r f i s s i l e t a r g e t h a s b e e n c r e a t e d f o r o t h e r f l y i n g n e u t r o n s to a t t a c k . In f a c t , a p p r o x i m a t e l y 3 0 p e r c e n t of t h e p o w e r g e n e r a t e d by a n u c l e a r r e a c t o r c o m e s f r o m t h e f i s s i o n i n g of p l u t o n i u m c r e ated through this t r a n s m u t a t i o n process. T h e s a m e process takes place w h e n t h o r i u m , w h i c h is o c c a s i o n a l l y u s e d in n u c l e a r f u e l , a b s o r b s a n e u tron and eventually creates U-233, another fissile element. In s h o r t , n a t u r e s u p p l i e s o n l y o n e f i s s i l e i s o t o p e — U - 2 3 5 — b u t s c i e n t i s t s h a v e c r e a t e d t w o o t h e r s , P u - 2 3 9 a n d U - 2 3 3 . All t h r e e a r e u s e f u l , in v a r y i n g d e g r e e s , f o r g e n e r a t i n g n u c l e a r p o w e r , a n d all t h r e e c a n c o n t r i b u t e to a n u c l e a r e x p l o s i v e c a p a b i l i t y .

6

NUCLEAR NON PROLIFERATION: A PRIMER

THE PROLIFERATION SIGNIFICANCE OF NUCLEAR MATERIALS The preceding discussion of obstacles to successful fission identifies several strategies for assisting the fission process. Four materials used in these strategies are usually safeguarded because of their possible contribution to building a nuclear weapon: •

Plutonium. One of the most proliferation-significant materials in the nuclear fuel cycle, plutonium can be used directly in a nuclear bomb. "Weapons-grade" plutonium, with a high percentage of Pu239, is relatively easy to handle and produces the highest explosive yield per unit of material. "Reactor-grade" plutonium, with levels of Pu-239 lower than that found in weapons-grade material, can be used to build a relatively low-yield (but still quite deadly) nuclear explosive. • Highly enriched uranium. Uranium enriched to 20 percent or more U-235 is considered highly enriched. Enrichment to 93 percent U235 is normally required for use in a bomb. However, even 20 percent U-235 is considered sensitive because relatively little extra work is required for further enrichment to the dangerous 93 percent U-235 level. • Low-enriched uranium. Although low-enriched uranium cannot be used in a nuclear weapon, it is only one step (further enrichment) away from possible use as weapons material. • Heavy water. Although not used in nuclear weapons, heavy water allows natural uranium to be burned in a nuclear reactor, and makes the production of plutonium possible without an expensive and technologically complex uranium enrichment plant. Thus heavy water can be thought of as a substitute for a uranium enrichment plant. 6 Heavy water is also sensitive because it produces tritium when used as a moderator. Tritium can be used as a "booster" for nuclear explosives: it boosts the explosive yield of a given quantity of fissile material. Tritium can also be used to reduce the amount of plutonium or enriched uranium needed to make a nuclear weapon.

THE BASICS OF AN ATOMIC BOMB Although nuclear reactors and atomic bombs both rely on the same fission process for release of energy, their management of the fission is distinctly different. Nuclear reactors are designed to shut themselves off before they exceed their structural capability. Atomic bombs, on the other hand, are designed to keep the fission process going until their materials are so hot

7

NUCLEAR FISSION AND THE N U C L E A R B O M B

that they v a p o r i z e , reach a very high p r e s s u r e , a n d t h e n e x p l o d e . 7 T h e unc o n t r o l l e d f i s s i o n i n g p r o c e s s in a n u c l e a r b o m b is p o s s i b l e o n l y w h e n a certain a m o u n t of fissile material, c a l l e d a critical m a s s , is p r e s e n t . At s u b c r i t i c a l a m o u n t s of f i s s i l e m a t e r i a l , m a n y n e u t r o n s e s c a p e a n d l e a v e t o o f e w n e u t r o n s a v a i l a b l e to f i s s i o n o t h e r a t o m i c n u c l e i . A c r i t i c a l m a s s of n u c l e a r m a t e r i a l , h o w e v e r , is large e n o u g h to m a i n t a i n a n u c l e a r r e a c t i o n e v e n a f t e r n e u t r o n s are lost to the o u t s i d e e n v i r o n m e n t . 8 T h e a m o u n t of fissile m a t e r i a l n e e d e d f o r an a t o m i c b o m b d e p e n d s on several f a c t o r s . First, d i f f e r e n t t y p e s of f i s s i l e m a t e r i a l ( U - 2 3 5 , U - 2 3 3 , or P u - 2 3 9 ) h a v e d i f f e r e n t critical m a s s e s . T h e critical m a s s of P u - 2 3 9 , f o r e x a m p l e , is only o n e - f i f t h that of U - 2 3 5 ; t h e r e f o r e , m u c h less p l u t o n i u m than u r a n i u m is n e e d e d to c o n s t r u c t a b o m b . S e c o n d , c o m p r e s s e d f i s s i l e m a t e r ial has a l o w e r critical m a s s than m a t e r i a l at n o r m a l d e n s i t y . T h u s b o m b m a k e r s can s t r e t c h limited fissile r e s o u r c e s by c o m p r e s s i n g t h e m to critical m a s s l e v e l s . T h i r d , r e f l e c t o r s can be u s e d in the b o m b to d e f l e c t e s c a p i n g n e u t r o n s back into the m a s s of m a t e r i a l a n d i n v o l v e t h e m in the f i s s i o n p r o c e s s . A n d f i n a l l y , tritium c a n b e u s e d in the w e a p o n as a sort of " n e u t r o n s u p p l e m e n t " to p r o v i d e a d d i t i o n a l n e u t r o n s to a c c e l e r a t e the c h a i n r e a c t i o n . T h e critical m a s s f o r the t h r e e f i s s i l e m a t e r i a l s u n d e r v a r i o u s c o n d i t i o n s is s h o w n in T a b l e 1.1.

Table 1.1

Critical Mass for U-235, U-233, and Pu-239 Under Various Conditions (in kilograms) U-235

Normal density, unreflected Compressed to double density Using reflectors

U-233

Pu-239

52

16

10

13 13-25

4 5-10

2.5 5-10

Sources: Nuclear Weapons Databook, Volume I: U.S. Nuclear Forces and Capabilities (Cambridge, Mass.: Ballinger Publishing Co., 1984), p. 24; F. Von Hippel, personal correspondence, July 25, 1992, p. 1.

T h e p l u t o n i u m r o u t e to d e v e l o p m e n t of a n u c l e a r w e a p o n h a s b e e n t a k e n by the U n i t e d K i n g d o m , F r a n c e , I n d i a , and p r o b a b l y Israel, w h e r e a s S o u t h A f r i c a , B r a z i l , A r g e n t i n a , Iraq, a n d P a k i s t a n h a v e all p u r s u e d ( a n d in the last c a s e is still p u r s u i n g ) the e n r i c h e d u r a n i u m r o u t e to a b o m b . F i s s i o n b o m b s a r e of t w o t y p e s . T h e g u n - b a r r e l d e s i g n u s e s c o n v e n tional e x p l o s i v e s to propel a s u b c r i t i c a l m a s s of u r a n i u m d o w n a barrel f o r collision with another subcritical mass. T h e b o m b dropped on Hiroshima w a s of this t y p e . 9 ( T a b l e 1.2 c o m p a r e s the n u c l e a r y i e l d s of v a r i o u s b o m b t y p e s w i t h that of the H i r o s h i m a b o m b . )

8

NUCLEAR NONPROLIFERATION: A PRIMER

T h e o t h e r f i s s i o n b o m b d e s i g n is a n i m p l o s i o n d e v i c e , in w h i c h c o n v e n t i o n a l e x p l o s i v e s a n d r e f l e c t o r s s u r r o u n d a s u b c r i t i c a l m a s s of n u c l e a r m a t e r i a l . W h e n the e x p l o s i v e s are d e t o n a t e d s i m u l t a n e o u s l y , the p r e s s u r e o n t h e c e n t r a l c o r e of n u c l e a r m a t e r i a l is s o g r e a t t h a t it c o m p r e s s e s t h e m a t e r i a l to c r i t i c a l i t y . I ( ) U n d e r a p p r o p r i a t e c o n d i t i o n s , t h e r a t e at w h i c h f i s s i o n s o c c u r t h e n i n c r e a s e s g r e a t l y a n d e n e r g y is r e l e a s e d s o r a p i d l y that a nuclear explosion results.

Table 1.2

Comparative Nuclear Yields Yield

Hiroshima bomb

12-15 Kt

Limit imposed by "TTB Treaty

150 Kt

Relation to Hiroshima b o m b —

11.1 times larger

First hydrogen bomb test

10.4 Mt

770 times larger

Largest nuclear test (USSR)

58 Mt

4296 times larger

Smallest U.S. nuclear weapon

0.25 Kt

54 times smaller

.Source: Compiled from Nuclear Weapons Databook, Volume 1 : U.S. Nuclear Forces and Capabilities (Cambridge, Mass.: Ballinger Publishing Co., 1984), pp. .12-34 Notes: Kt = kiloton, mt = megaton, T T B = Threshold Test Ban. Last column is calculated using 13.5 Kt as the estimated size of the Hiroshima bomb.

SUMMARY F r o m t h e p e r s p e c t i v e of a t o m i c p h y s i c s , n u c l e a r p r o l i f e r a t i o n is s i m p l y the s p r e a d of p a r t i c u l a r m a t e r i a l s a n d t e c h n o l o g i e s that f a c i l i t a t e t h e f i s s i o n of a t o m i c n u c l e i . A n y e l e m e n t o r t e c h n o l o g y that i n c r e a s e s t h e n u m b e r of f i s sile U - 2 3 5 a t o m s in n u c l e a r f u e l , c r e a t e s P u - 2 3 9 or U - 2 3 3 , or i m p r o v e s t h e c h a n c e s of f r e e - f l y i n g n e u t r o n s h i t t i n g a f i s s i l e a t o m is of c o n c e r n . T h e d i f f i c u l t i e s in m a n a g i n g t h e s e m a t e r i a l s a n d t e c h n o l o g i e s a r e e s p e c i a l l y great because most can be used for both military and peaceful purposes. B e c a u s e a t o m i c p h y s i c s p r o v i d e s no m e a n s to distinguish f i s s i o n for p e a c e f u l p u r p o s e s f r o m f i s s i o n f o r m i l i t a r y e n d s , s o l u t i o n s to t h i s d i l e m m a h a v e b e e n s o u g h t in t h e p o l i t i c a l a n d l e g a l r e a l m ; t h e s e a r e d i s c u s s e d in l a t e r c h a p t e r s of this b o o k .

NOTES 1. Anthony Nero, A Guidebook to Nuclear Reactors (Berkeley: University of California Press, 1979), p. 4. 2. Ibid. 3. Even more energy is released if very light atoms can be fused together. This process—nuclear fusion—is the basis for thermonuclear explosives (the hydrogen

NUCLEAR FISSION AND THE NUCLEAR BOMB

9

b o m b ) , which are many times m o r e p o w e r f u l than fission b o m b s . Although fusion, or h y d r o g e n , b o m b s are an integral part of the arsenals of the m a j o r n u c l e a r w e a p o n states, the e c o n o m i c and industrial r e s o u r c e s necessary and the level of technological complexity involved m a k e them impractical and unobtainable in almost every other case. In fact, d e v e l o p m e n t of a fission reaction is necessary in order to "trigger" fusion. Because civilian uses of fusion energy are still only a distant prospect, and f u s i o n - b a s e d w e a p o n s can only follow the d e v e l o p m e n t of fission, this book will focus on the nonproliferation threat from nuclear fission. 4. O n e important c h a r a c t e r i s t i c of the neutron does not fit the a n a l o g y : the neutron does not split an atom by force in the way an arrow would split an apple. In fact, a slow neutron is m o r e likely than a fast one to fission an atom. This is bec a u s e the slow neutron is able to attach itself to the atom and m a k e it u n s t a b l e e n o u g h to break apart. T h e fast neutron is likely to be d e f l e c t e d f r o m the target atom. 5. Heavy water is m a d e up, in part, of hydrogen atoms that contain one neutron, w h e r e a s the h y d r o g e n in light ( o r d i n a r y ) water has no n e u t r o n s . This gives each different m o d e r a t i n g properties. 6. H o w e v e r , another t e c h n o l o g i c a l l y c o m p l e x f a c i l i t y — a p l u t o n i u m reproc e s s i n g p l a n t — i s necessary to extract p l u t o n i u m from spent fuel for use in a nuclear b o m b . Thus, heavy water is of m u c h greater proliferation concern w h e n coupled with a reprocessing capability than when it is not. Chapter 3, Nuclear Reactors, considers this question further. 7. C. Walter, personal c o r r e s p o n d e n c e , July 15, 1992. 8. C o c h r a n , Arkin, and H o e n i g , Nuclear Weapons Databook, Volume I, p. 24. 9. Ibid., p.26. 10. Ibid.

2 The Nuclear Fuel Cycle

T h e d i v e r s i o n of n u c l e a r m a t e r i a l f r o m p e a c e f u l to m i l i t a r y use is m o r e likely at s o m e t y p e s of n u c l e a r f a c i l i t i e s than at o t h e r s . T h i s c h a p t e r g i v e s an o v e r v i e w of the life c y c l e of n u c l e a r f u e l , f r o m its o r i g i n as natural uranium to its final state as n u c l e a r w a s t e , a n d a s s e s s e s the p r o l i f e r a t i o n risks associated with each stage.

THE ONCE-THROUGH VERSUS PLUTONIUM FUEL CYCLES A s i m p l i f i e d v e r s i o n of the fuel c y c l e , w i t h m o d i f i c a t i o n s f o r d i f f e r e n t rea c t o r t y p e s , is s h o w n in F i g u r e 2.1. In the b a s i c c y c l e , u r a n i u m is m i n e d , r e f i n e d , p r o c e s s e d into an a p p r o p r i a t e c h e m i c a l f o r m , c o n v e r t e d into f u e l r o d s , f i s s i o n e d ( b u r n e d ) in a r e a c t o r , a n d s t o r e d as w a s t e . H o w e v e r , variations o n this c y c l e a r e n e c e s s a r y to a c c o m m o d a t e d i f f e r e n t r e a c t o r types, and t h e s e v a r i a t i o n s i n t r o d u c e p r o l i f e r a t i o n c o n c e r n s . T h e u r a n i u m e n r i c h m e n t s t a g e , f o r e x a m p l e , is n e e d e d to p r e p a r e f u e l f o r use in l i g h t - w a t e r rea c t o r s , w h e r e a s h e a v y - w a t e r p r o d u c t i o n is n e e d e d to s u p p l y the m o d e r a t o r f o r h e a v y - w a t e r r e a c t o r s . In a d d i t i o n , b o t h r e a c t o r t y p e s m a y o p e r a t e on a o n c e - t h r o u g h fuel c y c l e , in w h i c h s p e n t r e a c t o r f u e l is not r e c y c l e d , or on a p l u t o n i u m f u e l c y c l e , w h i c h p r o v i d e s f o r e x t r a c t i o n a n d r e u s e of p l u t o n i u m f r o m s p e n t f u e l r o d s . T h i s e x t r a c t i o n p r o c e s s is an a d d i t i o n a l sensitive s t a g e in the f u e l c y c l e k n o w n as r e p r o c e s s i n g . T h e p l u t o n i u m f u e l c y c l e is c o n t r o v e r s i a l . Its p r o p o n e n t s a r g u e that it r e q u i r e s far less f r e s h u r a n i u m f u e l and p r o d u c e s l o w e r q u a n t i t i e s of nuclear w a s t e t h a n a o n c e - t h r o u g h f u e l c y c l e . O p p o n e n t s c l a i m that w a s t e levels u n d e r the t w o s y s t e m s are similar. M o r e s i g n i f i c a n t l y , o p p o n e n t s w o r r y that the vast quantities of r e c y c l e d p l u t o n i u m m a d e a v a i l a b l e at p o w e r plants all o v e r the w o r l d w o u l d s i g n i f i c a n t l y increase the c h a n c e s of diversion to illicit p u r p o s e s . T h e y p o i n t o u t that all f i s s i l e m a t e r i a l in t h e o n c e - t h r o u g h fuel cycle r e m a i n s in a f o r m not directly u s a b l e f o r n u c l e a r w e a p o n s . '

11

12

NUCLEAR NON PROLIFERATION: A PRIMER

Figure 2.1 The Nuclear Fuel Cycle

ffiïiièS

un

Fu«t Fabrication

Ccnvarsian to U F S Gas

0

Bum-up h Reactor

©

O

S Spsnt Fuel Storage

©

Uranium Mining and Milling

C S

• — Waata Disposa]

O

G Uranium Enrichment (Isotope Separation)

©

Reprocessing (Plutonium Extraction)

©

Steps shown on the top line are part of the basic fuel cycle. Uranium enrichment and reprocessing, shown under the basic cycle, are optional steps. Source: Based on William Sweet, The Nuclear Age (Washington, D.C.: Congressional Quarterly, 1984) p. 47

In the United States, o p p o n e n t s of the p l u t o n i u m fuel c y c l e c a r r i e d the day in the 1970s, p r o s c r i b i n g c o m m e r c i a l p l u t o n i u m r e p r o c e s s i n g f o r b o t h d o m e s t i c use and e x p o r t a n d s e v e r e l y c u r t a i l i n g U.S. d e v e l o p m e n t of the b r e e d e r r e a c t o r , w h i c h is d e s i g n e d to g e n e r a t e r e u s a b l e p l u t o n i u m f u e l . S i n c e then, d e v e l o p m e n t of the b r e e d e r r e a c t o r e l s e w h e r e in the w o r l d has s l o w e d f o r e c o n o m i c r e a s o n s . T o d a y , o n l y a h a n d f u l of n a t i o n s p o s s e s s rep r o c e s s i n g p l a n t s , and f e w e r still p l a n to b a s e their n u c l e a r p o w e r p r o g r a m s on the r e c y c l i n g of n u c l e a r f u e l .

THE FUEL CYCLE FROM A NON PROLIFERATION PERSPECTIVE T h e f u e l c y c l e s t a g e s illustrated in F i g u r e 2.1 are d e s c r i b e d b e l o w . H e a v y w a t e r p r o d u c t i o n , w h i c h is not strictly a part of the f u e l c y c l e , is a d d r e s s e d last.

• Mining and Milling U r a n i u m ore is f o u n d in the e a r t h ' s c r u s t and m u s t be m i n e d like any o t h e r m i n e r a l . E x c a v a t e d o r e is m i l l e d to s e p a r a t e u r a n i u m f r o m f o r e i g n m a t t e r ; the u r a n i u m is then p r o c e s s e d into a c h e m i c a l f o r m ( U 3 O x ) c a l l e d y e l l o w c a k e , n a m e d f o r its a m b e r c o l o r .

13

THE NUCLEAR FUEL CYCLE

Facility locations. T h e w o r l d l e a d e r s in u r a n i u m m i n i n g a n d m i l l i n g are Canada, the United States, Australia, France, Niger, Namibia, and South A f r i c a . 2 V i r t u a l l y all c o u n t r i e s c o n t a i n m i n a b l e u r a n i u m d e p o s i t s , a l t h o u g h e x t r a c t i o n of the u r a n i u m o r e m a y not be c o s t e f f e c t i v e .

Nuclear material's

vulnerability

to theft (by persons

unconnected

A b o u t 5 , 0 0 0 k i l o g r a m s ( k g ) of n a t u r a l u r a n i u m a r e with the facility). n e e d e d to p r o d u c e t h e 25 kg of w e a p o n s - g r a d e u r a n i u m r e q u i r e d f o r o n e a t o m i c b o m b . 3 D i v e r s i o n of this q u a n t i t y of n a t u r a l u r a n i u m w i t h o u t detection by f a c i l i t y a u t h o r i t i e s w o u l d be h i g h l y d i f f i c u l t .

Nuclear material's vulnerability to diversion (by persons

connected

with the facility). D i v e r s i o n by f a c i l i t y a u t h o r i t i e s w o u l d not be d i f f i c u l t , p a r t i c u l a r l y b e c a u s e m o s t u r a n i u m m i n e s a n d p r o c e s s i n g c e n t e r s are not s u b j e c t to i n t e r n a t i o n a l s a f e g u a r d s . risk. V e r y l o w . In i s o l a t i o n , t h i s s t a g e p o s e s v i r t u a l l y n o Proliferation p r o l i f e r a t i o n risk b e c a u s e n a t u r a l u r a n i u m c a n n o t be u s e d to m a k e an atomic weapon.

• Conversion At the c o n v e r s i o n s t a g e , t h e p r o c e s s e d n a t u r a l u r a n i u m is c o n v e r t e d to a f o r m u s a b l e in a n u c l e a r r e a c t o r . If the m a t e r i a l is i n t e n d e d f o r use in a h e a v y - w a t e r reactor, w h i c h b u r n s natural ( n o n e n r i c h e d ) u r a n i u m , it is c o n v e r t e d to u r a n i u m m e t a l or u r a n i u m d i o x i d e ( U 0 2 ) . U r a n i u m d e s t i n e d f o r l i g h t - w a t e r r e a c t o r s is c o n v e r t e d to u r a n i u m h e x a f l u o r i d e , a g a s s u i t a b l e for e n r i c h m e n t . Facility locations. T h e n a t i o n s w i t h the h i g h e s t u r a n i u m c o n v e r s i o n capacity are C a n a d a , F r a n c e , the U n i t e d S t a t e s , and the U n i t e d K i n g d o m . 4 A c o m p l e t e list of s u c h n a t i o n s is g i v e n in T a b l e 2.1

Nuclear material's

vulnerability

to theft. Same as for mining and

milling.

Nuclear material's

vulnerability to diversion.

At an unsafeguarded

f a c i l i t y , m a t e r i a l c o u l d b e d i v e r t e d e a s i l y to m i l i t a r y p u r p o s e s . At a s a f e g u a r d e d f a c i l i t y , d i v e r s i o n w o u l d likely be d e t e c t e d . Proliferation risk. V e r y l o w . B e c a u s e t h e p e r c e n t a g e of U - 2 3 5 in t h e c o n v e r t e d u r a n i u m is still e x t r e m e l y l o w , t h e m a t e r i a l c a n n o t b e u s e d dir e c t l y in the p r o d u c t i o n of n u c l e a r w e a p o n s . H o w e v e r , I n t e r n a t i o n a l A t o m i c E n e r g y A g e n c y ( I A E A ) s a f e g u a r d s t a k e e f f e c t at this s t a g e .

14

N U C L E A R N O N P R O L I F E R A T I O N : A PRIMER

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16

NUCLEAR NON PROLIFERATION: A PRIMER

• Enrichment T h e e n r i c h m e n t s t a g e is p a r t i c u l a r l y s e n s i t i v e : it is t h e f i r s t m o m e n t at w h i c h u r a n i u m t a k e s o n t h e f i s s i l e p r o p e r t i e s n e e d e d f o r use in a n u c l e a r b o m b . E n r i c h m e n t is a p r o c e s s d e s i g n e d to raise the s h a r e of the d e s i r e d f i s s i l e U - 2 3 5 in u r a n i u m f r o m its natural level of 0.7 p e r c e n t to the m u c h h i g h e r levels n e e d e d f o r use in a n u c l e a r reactor or a n u c l e a r b o m b . ( T h e s e l e v e l s r a n g e f r o m 1.8 p e r c e n t f o r use in s o m e R u s s i a n - b u i l t r e a c t o r s to 3 p e r c e n t f o r m o s t l i g h t - w a t e r r e a c t o r s to m o r e t h a n 9 0 p e r c e n t f o r use in a nuclear bomb.) A l t h o u g h w e a p o n s - g r a d e u r a n i u m has thirty t i m e s m o r e U - 2 3 5 t h a n l i g h t - w a t e r r e a c t o r - g r a d e u r a n i u m , it is not thirty t i m e s m o r e d i f f i c u l t to m a n u f a c t u r e . O n c e an e n r i c h m e n t c a p a c i t y is in place, it c a n be m o d i f i e d to p r o d u c e h i g h l y e n r i c h e d u r a n i u m , a l t h o u g h this is m o r e d i f f i c u l t f o r s o m e t y p e s of e n r i c h m e n t t e c h n o l o g y than for o t h e r s . 5 ( S e e the e l a b o r a t i o n on the e n r i c h m e n t p r o c e s s that f o l l o w s this o v e r v i e w . ) Facilities locations. P r i n c i p a l n a t i o n s i n v o l v e d in u r a n i u m e n r i c h m e n t are the U n i t e d S t a t e s , F r a n c e , R u s s i a , the N e t h e r l a n d s , a n d the U n i t e d K i n g d o m . N a t i o n s of p r o l i f e r a t i o n c o n c e r n that p o s s e s s an e n r i c h m e n t cap a c i t y i n c l u d e A r g e n t i n a , B r a z i l , and P a k i s t a n . See T a b l e 2.1 f o r a c o m plete listing of s u c h n a t i o n s .

Nuclear material's

vulnerability to theft. As noted in the previous

c h a p t e r , an a t o m i c e x p l o s i v e r e q u i r e s as little as 13 kg of u r a n i u m e n r i c h e d to m o r e t h a n 9 0 p e r c e n t U - 2 3 5 , a m a s s of m a t e r i a l e a s i l y h a n d l e d by o n e p e r s o n . S e c u r i t y at e n r i c h m e n t p l a n t s , h o w e v e r , is e x t r e m e l y tight.

Nuclear material's

vulnerability

to diversion.

Material from un-

s a f e g u a r d e d e n r i c h m e n t p l a n t s c a n be d i v e r t e d easily to m i l i t a r y p u r p o s e s . M a t e r i a l u n d e r I A E A s a f e g u a r d s can also be easily d i v e r t e d to p r o s c r i b e d uses, but not w i t h o u t a high l i k e l i h o o d of d e t e c t i o n . Proliferation risk. H i g h . E n r i c h m e n t facilities h a v e the p o t e n t i a l to p r o duce weapons-grade uranium. (However, even highly enriched uranium h e x a f l u o r i d e c a n n o t b e u s e d d i r e c t l y in an a t o m i c b o m b . It m u s t first be c o n v e r t e d to u r a n i u m o x i d e or u r a n i u m m e t a l . 6 ) T h e high p r o l i f e r a t i o n p o tential of t h e e n r i c h m e n t s t a g e h a s led N u c l e a r S u p p l i e r s G r o u p ( N S G ) m e m b e r - s t a t e s to p l a c e an u n o f f i c i a l e m b a r g o on the e x p o r t of e n r i c h m e n t technology.

• Fuel Fabrication B e f o r e e n r i c h e d u r a n i u m or p l u t o n i u m can be u s e d in a n u c l e a r r e a c t o r , it m u s t b e f a b r i c a t e d into f u e l r o d s . T h e e n r i c h e d u r a n i u m , p l u t o n i u m , or

THE NUCLEAR FUEL CYCLE

17

natural u r a n i u m ( u s e d in h e a v y - w a t e r r e a c t o r s ) is s h a p e d into c y l i n d r i c a l pellets, w h i c h are then s t a c k e d in t u b e s c a l l e d f u e l r o d s . T h e r o d s are t h e n b u n d l e d t o g e t h e r into f u e l a s s e m b l i e s . Facilities locations. T h e l e a d i n g n u c l e a r f u e l f a b r i c a t i o n plants are loc a t e d in the U n i t e d S t a t e s , C a n a d a , F r a n c e , t h e U n i t e d K i n g d o m , J a p a n , and G e r m a n y . N a t i o n s of p r o l i f e r a t i o n c o n c e r n that h a v e f a b r i c a t i o n p l a n t s i n c l u d e A r g e n t i n a , B r a z i l , a n d India. S e e T a b l e 2.1 f o r a c o m p l e t e listing of s u c h n a t i o n s .

Nuclear material's

vulnerability

to theft. Light-water reactor fuel

a s s e m b l i e s e a c h w e i g h f r o m 4 4 0 to 1 , 1 0 0 p o u n d s . T h e y a r e s h i p p e d o n o p e n trailer trucks, w i t h e a c h pair of a s s e m b l i e s e n c l o s e d in steel c o n t a i n ers to p r e v e n t d a m a g e . T h e total w e i g h t of t w o a s s e m b l i e s and their c o n t a i n e r is a b o u t t h r e e t o n s . 7 D i v e r s i o n of f u e l a s s e m b l i e s w o u l d r e q u i r e heavy-duty transport and handling equipment.

Nuclear material's

vulnerability to diversion.

Unsafeguarded fuel

a s s e m b l i e s c o u l d easily be d i v e r t e d to military uses. T h e d i v e r s i o n of s a f e g u a r d e d a s s e m b l i e s w o u l d likely be d e t e c t e d , but not p r e v e n t e d , by international s a f e g u a r d s . Proliferation risk. L o w to h i g h . Fuel r o d s f a b r i c a t e d f o r use in h e a v y w a t e r r e a c t o r s c o n t a i n natural ( n o n e n r i c h e d ) u r a n i u m , w h e r e a s t h o s e d e s tined f o r use in l i g h t - w a t e r r e a c t o r s c o n t a i n l o w - e n r i c h e d u r a n i u m . N e i t h e r t y p e of u r a n i u m can b e d i r e c t l y d i v e r t e d to a n u c l e a r w e a p o n . Fuel r o d s f a b r i c a t e d f o r use in a b r e e d e r r e a c t o r c o n t a i n v a r i o u s i s o t o p e s of p l u t o n i u m , b u t with s u f f i c i e n t P u - 2 3 9 and P u - 2 4 1 c o n t e n t to b e of high p r o l i f eration concern.K

• Fuel Burn-up O n c e in t h e r e a c t o r c o r e , the f u e l r o d s a r e i r r a d i a t e d as a c o n t r o l l e d f i s s i o n r e a c t i o n p r o c e s s is b e g u n . A p p r o x i m a t e l y 1 8 0 f u e l a s s e m b l i e s c o n t a i n i n g a b o u t 1 1 0 t o n s of u r a n i u m a r e n e e d e d to f u e l a t y p i c a l 1 , 0 0 0 m e g a w a t t ( M W ) l i g h t - w a t e r r e a c t o r f o r t h r e e y e a r s . 9 T h e q u a n t i t y of f i s s i l e u r a n i u m is r e d u c e d a s t h e f u e l is b u r n e d up, b u t p l u t o n i u m is p r o d u c e d in its p l a c e . Facility locations. At the e n d of A u g u s t 1991, 431 p o w e r reactors w e r e in o p e r a t i o n and 71 w e r e u n d e r c o n s t r u c t i o n a r o u n d the w o r l d . 1 0

Nuclear material's vulnerability to theft. Fissile material is probably less v u l n e r a b l e to t h e f t d u r i n g r e a c t o r o p e r a t i o n t h a n at any o t h e r point

18

NUCLEAR NONPROLIFERATION: A PRIMER

in the fuel c y c l e b e c a u s e the f u e l a s s e m b l i e s a r e i n a c c e s s i b l e (in all but the Canadian heavy-water reactor) and radioactive period." Most reactors m u s t be shut d o w n to r e m o v e the f u e l r o d s ; this cannot be d o n e w i t h o u t attracting attention.

Nuclear material's

vulnerability

to diversion.

In an unsafeguarded

r e a c t o r , material easily c o u l d be d i v e r t e d to military uses. In a s a f e g u a r d e d reactor, d i v e r s i o n w o u l d likely be d e t e c t e d . risk. L o w to high. In i s o l a t i o n , a nuclear r e a c t o r u s i n g natProliferation ural or l o w - e n r i c h e d u r a n i u m is not a p r o l i f e r a t i o n d a n g e r ; it c o n t a i n s no n u c l e a r m a t e r i a l that c o u l d be d i v e r t e d directly to p r o d u c t i o n of a n u c l e a r e x p l o s i v e . In c o m b i n a t i o n w i t h a r e p r o c e s s i n g c a p a b i l i t y , h o w e v e r , the f u e l in a n u c l e a r r e a c t o r is of p r o l i f e r a t i o n c o n c e r n . R e a c t o r s u s i n g highly e n r i c h e d u r a n i u m are of g r e a t c o n c e r n .

• Spent-fuel

Storage

A f t e r b u r n - u p , t h e f u e l r o d s m u s t be r e p l a c e d w i t h f r e s h f u e l . D e p l e t e d of U - 2 3 5 but rich in p l u t o n i u m , t h e r o d s are r e m o v e d f r o m t h e r e a c t o r a n d c o o l e d f o r s e v e r a l m o n t h s in p o o l s of f r e s h w a t e r . A l t h o u g h this s t o r a g e is i n t e n d e d to be t e m p o r a r y , n o p e r m a n e n t w a s t e disposal site has b e e n c h o sen a n y w h e r e in the w o r l d . Facility locations. T e m p o r a r y s p e n t - f u e l s t o r a g e p o n d s are g e n e r a l l y loc a t e d on the g r o u n d s of the n u c l e a r r e a c t o r f r o m w h i c h the spent f u e l w a s t a k e n . S o - c a l l e d " a w a y f r o m r e a c t o r " s p e n t - f u e l s t o r a g e sites are f o u n d in the United K i n g d o m , France, S w e d e n , G e r m a n y , Finland, the United S t a t e s , the f o r m e r C z e c h o s l o v a k i a , and J a p a n . 1 2 Nuclear material's vulnerability to theft. A l t h o u g h laden w i t h p l u t o n i u m , s p e n t f u e l r o d s a r e not a t t r a c t i v e t a r g e t s for thieves. T h e r o d s are h i g h l y r a d i o a c t i v e a n d u n w i e l d y . M o r e o v e r , s p e n t f u e l is of u s e in the m a n u f a c t u r e of n u c l e a r e x p l o s i v e s only if there is a r e p r o c e s s i n g plant, a n d m o s t n a t i o n s w i t h r e p r o c e s s i n g p l a n t s h a v e their o w n s u p p l y of s p e n t f u e l . Nuclear material's vulnerability to diversion. F r o m an u n s a f e g u a r d e d s p e n t - f u e l s t o r a g e p l a n t , m a t e r i a l c o u l d be d i v e r t e d to m i l i t a r y u s e s ( a s s u m i n g a c c e s s to a r e p r o c e s s i n g f a c i l i t y ) w i t h n o p r o b l e m . In a s a f e g u a r d e d f a c i l i t y , d i v e r s i o n w o u l d likely be d e t e c t e d . Proliferation risk. M e d i u m . In i s o l a t i o n , a s p e n t - f u e l s t o r a g e f a c i l i t y is not a great p r o l i f e r a t i o n risk. O n l y in c o m b i n a t i o n with a r e p r o c e s s i n g c a pability is s p e n t f u e l of p r o l i f e r a t i o n c o n c e r n .

19

THE NUCLEAR FUEL CYCLE

• Reprocessing S p e n t - f u e l r o d s are r e m o v e d f r o m s t o r a g e p o o l s a n d s e n t t o a r e p r o c e s s i n g p l a n t f o r p l u t o n i u m e x t r a c t i o n . T h e r o d s are c u t i n t o p i e c e s a n d d i s s o l v e d in a c i d . 1 3 U s i n g t h e P l u t o n i u m U r a n i u m R e c o v e r y b y

Extraction

( P U R E X ) m e t h o d , m o r e t h a n 9 0 p e r c e n t o f the u r a n i u m a n d p l u t o n i u m in the spent-fuel s o l u t i o n can be r e c o v e r e d . 1 4 U r a n i u m e m e r g i n g f r o m this process

typically

contains

only

1 percent

U-235,

far b e l o w

the

level

n e e d e d f o r a n u c l e a r b o m b , a n d e v e n t o o w e a k f o r u s e in a l i g h t - w a t e r reactor. T h e p l u t o n i u m e x i t i n g a r e p r o c e s s i n g plant, h o w e v e r , can be conv e r t e d to a f o r m u s a b l e for n u c l e a r w e a p o n s .

Facility locations.

R u s s i a , F r a n c e , and the U n i t e d K i n g d o m are the

w o r l d l e a d e r s in r e p r o c e s s i n g . J a p a n h a s a s t r o n g i n t e r e s t in r e p r o c e s s i n g a n d is c u r r e n t l y

constructing

a large r e p r o c e s s i n g

p l a n t at

Rokkasho-

M u r a . I n d i a h a s s e v e r a l s m a l l r e p r o c e s s i n g p l a n t s , a n d A r g e n t i n a is c o n s t r u c t i n g o n e . S e e T a b l e 2 . 1 f o r a c o m p l e t e list o f n a t i o n s w i t h r e p r o c e s s ing capabilities.

Nuclear material's vulnerability to theft.

R e p r o c e s s i n g o f the h i g h l y

r a d i o a c t i v e s p e n t f u e l is d o n e b y r e m o t e c o n t r o l f r o m b e h i n d t h i c k w a l l s ; the s e p a r a t e d p l u t o n i u m a n d u r a n i u m are v i r t u a l l y i n a c c e s s i b l e d u r i n g t h i s o p e r a t i o n . 1 5 F o l l o w i n g r e p r o c e s s i n g , the m a t e r i a l s e n t e r a m o r e a c c e s s i b l e p a c k a g i n g area w h e r e 1 0 - l i t e r c y l i n d e r s a b o u t o n e m e t e r l o n g are f i l l e d w i t h 2.5 kg of plutonium solution. Each cylinder weighs

14 kg w h e n

filled.

Their stainless steel shipping containers, h o w e v e r , w e i g h about 1 8 0 kg.16

Nuclear material's vulnerability to diversion.

Unsafeguarded mate-

rial in a r e p r o c e s s i n g p l a n t c o u l d e a s i l y b e d i v e r t e d t o a n u c l e a r w e a p o n s program. D i v e r s i o n of s a f e g u a r d e d material w o u l d likely be detected.

Proliferation

risk.

High. Plutonium extracted from low burn-up fuel

( e . g . , f r o m a p r o d u c t i o n reactor or a h e a v y - w a t e r , natural-uranium research r e a c t o r ) is d i r e c t l y u s a b l e in a n u c l e a r w e a p o n . P l u t o n i u m d e r i v e d f r o m t h e h i g h b u r n - u p f u e l o f the s t a n d a r d l i g h t - w a t e r reactor is not the p r e f e r r e d m a t e r i a l f o r n u c l e a r w e a p o n s , b u t it c o u l d b e u s e d a s a n u c l e a r e x p l o s i v e b y a p a r t y n o t c o n c e r n e d w i t h o b t a i n i n g t h e h i g h e s t p o s s i b l e e f f i c i e n c y or y i e l d . 1 7 ( S e e also Chapter 3, N u c l e a r Reactors.) P l u t o n i u m

reprocessing

t e c h n o l o g y i s a n o t h e r h i g h l y s e n s i t i v e t e c h n o l o g y ; its e x p o r t is u n o f f i c i a l l y e m b a r g o e d by the N u c l e a r S u p p l i e r s Group.

• Waste Disposal A f t e r t h e u r a n i u m a n d p l u t o n i u m are r e m o v e d , t h e f u e l r o d r e s i d u e , w h i c h c o n t a i n s m o r e than forty r a d i o a c t i v e i s o t o p e s , must be s a f e l y d i s p o s e d of.

20

NUCLEAR NON PROLIFERATION: A PRIMER

B e c a u s e a p e r m a n e n t w a s t e d i s p o s a l s o l u t i o n h a s not b e e n f o u n d for this h i g h - l e v e l w a s t e ( H L W ) , m o s t o f it i s " t e m p o r a r i l y " s t o r e d in p o o l s at the f a c i l i t i e s that p r o d u c e d it. P e r m a n e n t w a s t e d i s p o s a l s i t e s in o u t e r s p a c e , in t h e s e a b e d , or u n d e r g r o u n d h a v e b e e n p r o p o s e d . Facility

Currently, a permanent nuclear waste disposal facil-

locations.

ity is b e i n g c o n s i d e r e d in N e v a d a f o r U . S . w a s t e , a n d a n o t h e r f a c i l i t y is p l a n n e d in G e r m a n y . P e r m a n e n t w a s t e d i s p o s a l

facilities for

low-level

w a s t e ( L L W , i n c l u d i n g r a g s , g l o v e s , f i l t e r s , a n d s i m i l a r m a t e r i a l s that h a v e b e e n e x p o s e d to r a d i a t i o n b u t d o n o t r e q u i r e s p e c i a l s h i e l d i n g ) a n d i n t e r mediate-level waste (ILW, including solidified sludges, equipment, m e t a l f r a g m e n t s w h o s e l e v e l o f r a d i o a c t i v i t y is l o w e r t h a n that o f

and

HLW,

b u t still r e q u i r e s p e c i a l s h i e l d i n g ) a r e o p e r a t i n g in F r a n c e , S w e d e n , G e r m a n y , a n d the U n i t e d S t a t e s . I X

Nuclear material's

vulnerability

to theft.

H L W ' s v u l n e r a b i l i t y to

t h e f t is l i k e l y to b e s i m i l a r to that o f s p e n t f u e l . If the w a s t e h a s b e e n rep r o c e s s e d , h o w e v e r , it is a m u c h l e s s a t t r a c t i v e t a r g e t f o r t h e f t b e c a u s e the p l u t o n i u m h a s b e e n r e m o v e d f r o m it.

Nuclear material's Proliferation

risk.

vulnerability

to diversion.

Same as for spent fuel.

L o w . T h e h i g h l e v e l o f r a d i o a c t i v i t y c o u p l e d w i t h the

d e p l e t e d s t a t e o f u r a n i u m a n d p l u t o n i u m l e f t in t h e w a s t e m a k e d i v e r s i o n o f the material for the c o n s t r u c t i o n o f a n u c l e a r b o m b u n a t t r a c t i v e .

• Heavy-water Production A l t h o u g h t e c h n i c a l l y not a p a r t o f a f u e l c y c l e , h e a v y - w a t e r p r o d u c t i o n d e s e r v e s m e n t i o n a s a n i m p o r t a n t a u x i l i a r y c o m p o n e n t o f the h e a v y - w a t e r reactor fuel cycle. B e c a u s e reactors m o d e r a t e d by heavy water can fission n a t u r a l u r a n i u m , t h e e x p e n s i v e a n d d i f f i c u l t s t e p o f e n r i c h i n g u r a n i u m is u n n e c e s s a r y . H e a v y - w a t e r p r o d u c t i o n is i t s e l f a d i f f i c u l t p r o c e s s , b u t is n o t b e y o n d the c a p a b i l i t y o f m o s t i n d u s t r i a l i z e d n a t i o n s . Facility

locations.

I n d i a is t h e w o r l d l e a d e r in h e a v y - w a t e r p r o d u c t i o n

c a p a c i t y , a l t h o u g h its p l a n t s a r e p l a g u e d b y f r e q u e n t b r e a k d o w n s . 1 9 T h e United States, Canada, Russia, and N o r w a y also produce heavy water. Argentina has a l o n g - d e l a y e d plant under construction. ( S e e T a b l e 2.1 for a listing of heavy-water production capacities.)

Heavy water's vulnerability to theft.

Several hundred cubic meters

o f h e a v y w a t e r a r e u s e d to m o d e r a t e a m e d i u m - s i z e d h e a v y - w a t e r

reac-

t o r . 2 0 P r e s u m a b l y , theft o f s u c h a m a s s i v e q u a n t i t y o f m a t e r i a l is

more

THE NUCLEAR FUEL CYCLE

21

likely in t r a n s i t , w h e n t h e m o d e of t r a n s p o r t itself c o u l d be c o m m a n d e e r e d , than at the reactor site. Heavy water's vulnerability to diversion. Unsafeguarded heavy w a t e r c o u l d easily be d i v e r t e d . D i v e r s i o n of s a f e g u a r d e d h e a v y w a t e r p r e s u m a b l y w o u l d b e d e t e c t e d , a l t h o u g h s e v e r a l i n s t a n c e s of l o n g - h i d d e n h e a v y - w a t e r d i v e r s i o n s to third p a r t i e s h a v e b e e n r e v e a l e d . A G e r m a n trader, f o r e x a m p l e , is k n o w n to h a v e b o u g h t S o v i e t - o r i g i n heavy w a t e r in q u a n t i t i e s of less than o n e t o n — t h e level that t r i g g e r s I A E A s a f e g u a r d s . T h e material w a s then s h i p p e d to India. Proliferation risk. H i g h . H e a v y w a t e r , like a u r a n i u m e n r i c h m e n t p l a n t , can s e r v e as a critical link in the c h a i n of p r o c e s s e s n e e d e d to c o n v e r t natural u r a n i u m into p l u t o n i u m , and the t r i t i u m e x t r a c t e d f r o m h e a v y w a t e r can be used to r e d u c e the a m o u n t of f i s s i l e m a t e r i a l n e e d e d to c r e a t e a nuclear e x p l o s i v e .

A CLOSER LOOK AT ENRICHMENT TECHNOLOGIES U r a n i u m c a n b e e n r i c h e d in s e v e r a l w a y s . C o m m o n to all m e t h o d s is t h e e f f o r t to s e p a r a t e s o m e of t h e n o n f i s s i l e U - 2 3 8 a t o m s f r o m t h e rest of t h e u r a n i u m s t o c k , so t h a t w h a t r e m a i n s h a s a h i g h e r p e r c e n t a g e of the desirable U - 2 3 5 a t o m s . T h e four most c o m m o n l y used u r a n i u m enr i c h m e n t m e t h o d s are g a s e o u s d i f f u s i o n , g a s c e n t r i f u g e , a e r o d y n a m i c , and laser.

• Gaseous

Diffusion

T h e most w i d e l y used e n r i c h m e n t m e t h o d , g a s e o u s d i f f u s i o n d a t e s b a c k to the M a n h a t t a n P r o j e c t . U r a n i u m in a g a s e o u s f o r m c a l l e d u r a n i u m h e x a f l u o r i d e is f o r c e d t h r o u g h a s e r i e s of m e m b r a n e s , e a c h of w h i c h a l l o w s t h e l i g h t e r U - 2 3 5 a t o m s to p a s s t h r o u g h m o r e e a s i l y t h a n the h e a v i e r U - 2 3 8 a t o m s . A f t e r p e n e t r a t i n g e a c h m e m b r a n e , the g a s is r i c h e r in U - 2 3 5 t h a n it w a s o r i g i n a l l y , but only s l i g h t l y : 1 , 2 5 0 p a s s e s a r e n e e d e d to e n r i c h t h e g a s to 3 p e r c e n t U - 2 3 5 , the e n r i c h m e n t level used in m o s t l i g h t - w a t e r n u c l e a r p o w e r plants, w h e r e a s 4 , 0 0 0 p a s s e s a r e r e q u i r e d to e n r i c h the m a t e rial to the w e a p o n s g r a d e of 9 0 p e r c e n t U - 2 3 5 . 2 1 Proliferation significance. G a s e o u s d i f f u s i o n is a t e c h n i c a l l y c o m p l e x p r o c e s s that r e q u i r e s m a s s i v e a m o u n t s of e l e c t r i c i t y . ( T h e t w o U.S. e n r i c h m e n t facilities still in o p e r a t i o n each use a b o u t 5 , 0 0 0 M W of electricity, as m u c h as is c o n s u m e d by a city of several m i l l i o n p e o p l e . 2 2 ) T h e s e b a r r i e r s m a k e c l a n d e s t i n e a c q u i s i t i o n of a g a s e o u s d i f f u s i o n plant d i f f i c u l t . 2 3 In

22

NUCLEAR NONPROLIFERATION: A PRIMER

a d d i t i o n , it is d i f f i c u l t , a l t h o u g h not i m p o s s i b l e , to m o d i f y a g a s e o u s diff u s i o n p l a n t that p r o d u c e s l o w - e n r i c h e d u r a n i u m to p r o d u c e h i g h l y enr i c h e d u r a n i u m . 2 4 Still, as w i t h all e n r i c h m e n t f a c i l i t i e s , g a s e o u s d i f f u s i o n p l a n t s a r e of p r o l i f e r a t i o n c o n c e r n b e c a u s e of t h e i r c a p a c i t y to p r o d u c e weapons-grade uranium.

• Gas Centrifuge T h e g a s c e n t r i f u g e u s e s c e n t r i f u g a l f o r c e to d r a w U - 2 3 8 a t o m s a w a y f r o m the d e s i r e d U - 2 3 5 . W h e n u r a n i u m g a s is s p u n in a c e n t r i f u g e , the h e a v i e r U - 2 3 8 a t o m s g r a v i t a t e t o w a r d the o u t e r w a l l s , w h e r e a s the lighter U - 2 3 5 a t o m s r e m a i n in the c e n t e r . T h e c e n t r i f u g e m e t h o d r e q u i r e s only 3 5 repet i t i o n s to a c h i e v e w e a p o n s - g r a d e u r a n i u m , a n d a plant w i t h 1 , 0 0 0 c e n t r i f u g e s c a n s u p p l y the u r a n i u m s t o c k f o r s e v e r a l n u c l e a r w e a p o n s p e r y e a r . 2 5 O n the d o w n s i d e , the t e c h n o l o g y r e q u i r e s a high level of t e c h n i c a l p r e c i s i o n , and it is d i f f i c u l t to m a i n t a i n . Proliferation significance. T h e r e l a t i v e l y low p o w e r r e q u i r e m e n t s of t h e g a s c e n t r i f u g e m e t h o d of e n r i c h m e n t , c o u p l e d w i t h its r e l a t i v e e f f i c i e n c y , m a k e it an e n r i c h m e n t p r o c e s s of high p r o l i f e r a t i o n c o n c e r n .

• Aerodynamic Methods Like the g a s c e n t r i f u g e e n r i c h m e n t m e t h o d , a e r o d y n a m i c m e t h o d s use c e n t r i f u g a l f o r c e to s e p a r a t e s o m e U - 2 3 8 f r o m the b u l k of the u r a n i u m s t o c k . U r a n i u m g a s is b l o w n o v e r a c u r v e d s u r f a c e , w h i c h has the e f f e c t of s e p a r a t i n g the h e a v i e r U - 2 3 8 f r o m the lighter U - 2 3 5 . Six h u n d r e d r e p e t i t i o n s of this p r o c e s s are n e e d e d to a c h i e v e 3 p e r c e n t U - 2 3 5 e n r i c h m e n t , a n d 2 , 0 0 0 s t a g e s are n e e d e d f o r 9 0 p e r c e n t e n r i c h m e n t . A l t h o u g h a e r o d y n a m i c m e t h o d s s u c h as the B e c k e r n o z z l e a n d H e l i k o n are less t e c h n o l o g i c a l l y c o m p l e x than g a s e o u s d i f f u s i o n or the g a s c e n t r i f u g e , they r e q u i r e the m o s t e n e r g y of all the p r o c e s s e s u n d e r c o n s i d e r a t i o n . 2 6 Proliferation Significance. B e c a u s e of the t r e m e n d o u s e n e r g y r e q u i r e m e n t s of a e r o d y n a m i c m e t h o d s a n d their r e l a t i v e l y i n e f f i c i e n t o p e r a t i o n , o t h e r m e t h o d s of e n r i c h m e n t a r e likely to b e p r e f e r r e d . 2 7

• Laser Still in t h e d e v e l o p m e n t s t a g e s , t h e l a s e r m e t h o d of e n r i c h m e n t u s e s d i f f e r e n t light w a v e s to e x c i t e p a r t i c u l a r a t o m s w h i l e l e a v i n g o t h e r s u n a f f e c t e d . T h e e x c i t e d a t o m s c a n t h e n be s e p a r a t e d f r o m t h e o t h e r s . T h i s m e t h o d is s o p r e c i s e that o n l y o n e p a s s is n e c e s s a r y to c o m p l e t e t h e e n r i c h m e n t p r o c e s s , a n d it c a n b e u s e d o n " t a i l i n g s , " or w a s t e s r e m a i n i n g from other plants.28

THE NUCLEAR FUEL CYCLE

23

Proliferation significance. Laser enrichment technology appears to be out of the reach of most nations of current proliferation concern. However, its high e f f i c i e n c y and relatively low energy requirements could make it the enrichment method of choice as it b e c o m e s more widely available.

NOTES 1. A n t h o n y N e r o , A Guidebook to Nuclear Reactors ( B e r k e l e y : U n i v e r s i t y of C a l i f o r n i a P r e s s , 1 9 7 9 ) , p. 191. 2. N u c l e a r E n g i n e e r i n g I n t e r n a t i o n a l , World Nuclear Industry Handbook, 1992, p. 127. 3. F. V o n H i p p e l , p e r s o n a l c o r r e s p o n d e n c e , July 25, 1 9 9 2 , p. 2. 4. N u c l e a r E n g i n e e r i n g I n t e r n a t i o n a l , World Nuclear Industry Handbook, 1992, p. 127. 5. W i l l i a m C . P o t t e r , Nuclear Power and Nonproliferation: An Interdisciplinary Perspective (Cambridge, Mass.: Oelgeschlager, G u n n & Hain, Publishers, 1982), p. 8 1 . 6. M a s o n W i l l r i c h and T h e o d o r e B. T a y l o r , Nuclear Theft: Risks and Safeguards ( C a m b r i d g e , M a s s . : B a l l i n g e r P u b l i s h i n g C o . , 1 9 7 4 ) , p. 18. 7. I b i d . , p. 3 4 . 8. C . W a l t e r , p e r s o n a l c o r r e s p o n d e n c e , July 15, 1 9 9 2 . 9. W i l l r i c h a n d T a y l o r , p. 3 4 . 10. N u c l e a r E n g i n e e r i n g I n t e r n a t i o n a l , p. 11. 11. W i l l r i c h a n d T a y l o r , p. 3 5 . 12. N u c l e a r E n g i n e e r i n g I n t e r n a t i o n a l , p. 128. 13. W i l l r i c h a n d T a y l o r , p. 3 5 . 14. P o t t e r , p. 7 8 . 15. W i l l r i c h a n d T a y l o r , p. 3 5 . 16. I b i d . , p. 3 6 . 17. D. F i s c h e r , p e r s o n a l c o r r e s p o n d e n c e , J u l y 15, 1 9 9 2 , p. 3. 18. I n t e r n a t i o n a l A t o m i c E n e r g y A g e n c y , " R a d i o a c t i v e W a s t e M a n a g e m e n t " ( V i e n n a : I A E A D i v i s i o n of P u b l i c I n f o r m a t i o n ) , p. 3. 19. D . F i s c h e r , p e r s o n a l c o r r e s p o n d e n c e , J u l y 15, 1 9 9 2 , p. 3. 2 0 . T h i s f i g u r e is b a s e d o n d a t a f r o m a s a m p l e of C A N D U ( C a n a d i a n d e u t e r i u m u r a n i u m ) r e a c t o r s l i s t e d in N u c l e a r E n g i n e e r i n g I n t e r n a t i o n a l , World Nuclear Industry Handbook, p p . 9 1 , 9 3 , and 1 0 4 . 21. Potter, pp. 7 1 - 7 2 . 2 2 . F. V o n H i p p e l , p e r s o n a l c o r r e s p o n d e n c e , J u l y 2 5 , 1 9 9 2 , p. 3. 2 3 . P o t t e r , p. 7 2 . 2 4 . I b i d . , p. 8 1 . 2 5 . I b i d . , p. 7 2 . 2 6 . I b i d . , pp. 7 2 - 7 3 . 2 7 . I b i d . , p. 7 3 . 2 8 . Ibid., pp. 7 3 - 7 4 .

3 Nuclear Reactors

Although reactors are not the most proliferation-prone facilities in the nuclear fuel cycle, the assorted reactor types worldwide do present a variety of proliferation concerns. Following a brief description of the operation of a nuclear reactor and a review of reactor functions, this chapter discusses the proliferation significance of various reactors in operation today.

REACTOR OPERATION AND PURPOSES Nuclear reactors are made in many types and sizes, but the basic elements and processes involved are similar in most models (see Figure 3.1). Fuel in the form of uranium, plutonium, or a mixture of these is placed in the reactor core, where neutrons from these materials are used to split, or fission, the fuel's atoms. A moderator, usually water or graphite, surrounds the fuel and slows down (moderates) neutrons in the fuel to increase the chances of a successful fission. Control rods filled with neutron-absorbing substances such as boron are inserted into the core to regulate the fission process and to shut down the reactor if necessary. Finally, a coolant, which is sometimes the same material as the moderator, is flushed through the hot fuel rods of power reactors to carry away heat. In a power reactor the coolant is run through a heat exchanger, which generates steam to spin a turbine. The turbine generates electricity. Nuclear reactors are commonly associated with electricity production, but they have a variety of other uses as well. The first clue to the proliferation significance of a nuclear reactor is found by examining the declared purpose of the unit. Power reactors. Most reactors are used to produce electricity through the process described above. No single characteristic of a power reactor makes it a proliferation concern; its proliferation danger depends on the 25

26

NUCLEAR NONPROLIFERATION: A PRIMER

Figure 3.1 A Ught-Water Nuclear Reactor

Etectictty

BOILER

TURBINE

Source: William Sweet, The Nuclear Age (Washington, D.C.: Congressional Quarterly, 1984) p. 36 t y p e o f f u e l a n d m o d e r a t o r u s e d , the a m o u n t o f p l u t o n i u m p r o d u c e d , a n d the r e f u e l i n g p r o c e s s u s e d for the r e a c t o r . Plutonium

production

reactors.

All reactors w h o s e fuel contains U-

238 produce weapons-usable plutonium as a by-product. A plutonium prod u c t i o n r e a c t o r , h o w e v e r , is d e s i g n e d to p r o d u c e m a t e r i a l i d e a l l y s u i t e d f o r u s e in w e a p o n s . 1 T h u s a p l u t o n i u m p r o d u c t i o n r e a c t o r is o b v i o u s l y o f h i g h p r o l i f e r a t i o n c o n c e r n . T h e U n i t e d K i n g d o m o n c e u s e d the p l u t o n i u m p r o d u c t i o n r e a c t o r f o r p o w e r p r o d u c t i o n ; h o w e v e r , it is i n e f f i c i e n t a n d u n e c o n o m i c a l f o r this p u r p o s e . Research

reactors.

R e s e a r c h r e a c t o r s are u s e d f o r training p u r p o s e s or

f o r the p r o d u c t i o n o f r a d i o a c t i v e i s o t o p e s with m e d i c a l or b i o l o g i c a l

ap-

p l i c a t i o n s . R e s e a r c h r e a c t o r s a r e t y p i c a l l y 1 - 5 M W — a s i z e that y i e l d s l o w quantities of plutonium-laden

spent fuel. Despite

these apparently

in-

n o c u o u s c h a r a c t e r i s t i c s , s o m e r e s e a r c h r e a c t o r s e n c o m p a s s the m o s t d a n g e r o u s p r o l i f e r a t i o n c h a r a c t e r i s t i c s o f a l l : a h e a v y w a t e r - m o d e r a t e d , natu r a l u r a n i u m - f u e l e d , l o w f u e l b u r n - u p r e s e a r c h r e a c t o r is o f

particular

concern (see b e l o w ) . C o u p l e d with a r e p r o c e s s i n g capability, a research reactor can be a dangerous, proliférant technology. Materials

test

reactors.

B e c a u s e m a t e r i a l s u s e d in a r e a c t o r c o r e u n -

d e r g o great stress from constant neutron b o m b a r d m e n t , new materials are r e g u l a r l y t e s t e d to d e t e r m i n e t h e i r s u i t a b i l i t y f o r u s e in a n u c l e a r r e a c t o r .

NUCLEAR REACTORS

27

T h e s e m a t e r i a l s are best t e s t e d in a r e a c t o r e n v i r o n m e n t , a n d a m a t e r i a l s test r e a c t o r is d e s i g n e d f o r this p u r p o s e . T h e s p e n t f u e l f r o m a m a t e r i a l s test r e a c t o r y i e l d s small a m o u n t s of p l u t o n i u m , w h i c h c o u l d be used in a nuclear b o m b . Submarine reactors. N u c l e a r s u b m a r i n e s are p r o p e l l e d by small lightw a t e r r e a c t o r s , the kind of r e a c t o r used to g e n e r a t e e l e c t r i c p o w e r . U n l i k e m o s t l i g h t - w a t e r p o w e r r e a c t o r s , h o w e v e r , s u b m a r i n e r e a c t o r s are f u e l e d by h i g h l y e n r i c h e d u r a n i u m ( H E U ) , w h i c h c a n be u s e d in a n u c l e a r w e a p o n . For this reason they are of great p r o l i f e r a t i o n s i g n i f i c a n c e . It s h o u l d be s t r e s s e d that in isolation most r e a c t o r s p r e s e n t no p r o l i f e r a t i o n p r o b l e m unless they are f u e l e d with p l u t o n i u m or highly e n r i c h e d u r a n i u m . 2 If the n u c l e a r f u e l e n t e r i n g t h e r e a c t o r is not w e a p o n s - u s a b i e , and if a nation has no c a p a c i t y to extract p l u t o n i u m f r o m s p e n t f u e l , the reactor itself can d o little to a d v a n c e a n u c l e a r w e a p o n s c a p a b i l i t y . Still, in c o m b i n a t i o n w i t h o t h e r facilities, r e a c t o r s can b e c o m e an integral part of a n u c l e a r w e a p o n s p r o g r a m . S e e C h a p t e r 2. T h e N u c l e a r Fuel C y c l e , f o r a d e s c r i p t i o n of t h e s e other f a c i l i t i e s .

A PROLIFERATION ANALYSIS OF NUCLEAR REACTORS T h e d e c l a r e d p u r p o s e of a n u c l e a r r e a c t o r g i v e s a p r e l i m i n a r y idea of its p r o l i f e r a t i o n s i g n i f i c a n c e , but o t h e r r e a c t o r c h a r a c t e r i s t i c s r e v e a l m o r e a b o u t the r e a c t o r ' s potential for use in a n u c l e a r b o m b p r o g r a m . T h e f i v e q u e s t i o n s d i s c u s s e d b e l o w help to c l a r i f y f u r t h e r the p r o l i f e r a t i o n p o t e n t i a l of a n u c l e a r r e a c t o r .

• What Kind of Fuel Does the Reactor Use? First, a r e a c t o r ' s p r o l i f e r a t i o n s i g n i f i c a n c e can be a s s e s s e d by l o o k i n g at the t y p e of f u e l it uses. S o m e of the n u c l e a r f u e l s d e s c r i b e d b e l o w w e r e d i s c u s s e d in C h a p t e r 1. Natural uranium. N a t u r a l u r a n i u m is not u s a b l e in a n u c l e a r w e a p o n , a n d p o s e s no d i r e c t p r o l i f e r a t i o n t h r e a t . ( H i s t o r i c a l l y , h o w e v e r , m o s t rea c t o r - g e n e r a t e d w e a p o n s m a t e r i a l h a s c o m e f r o m r e a c t o r s f u e l e d by n a t ural u r a n i u m , e s p e c i a l l y the h e a v y - w a t e r reactor, d e s c r i b e d b e l o w . 3 ) Low-enriched uranium. n u c l e a r w e a p o n . It is no m o r e n i u m , unless z z z

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