Transcript
Page 1: Storage Tanks for Liquid Radioactive Wastes: Their Design and Use · 2011. 8. 25. · STORAGE TANKS 4 3.1. General 4 3. 2. Types of tanks and their sizing 4 3.2.1. Collection tanks

TECHNICAL REPORTS SERIES No.

Storage Tanks for Liquid Radioactive Wastes:

Their Design and Use

TOPj! INTERNATIONAL A T O M I C ENERGY AGENCY, V I E N N A , 1 9 7 2

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STORAGE TANKS FOR LIQUID RADIOACTIVE WASTES:

THEIR DESIGN AND USE

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The following Stales ace Members of the International Atomic Energy Agency:

AFGHANISTAN GUATEMALA PAKISTAN ALBANIA HAITI PANAMA ALGERIA HOLY SEE PARAGUAY ARGENTINA HUNGARY PERU AUSTRALIA ICELAND PHILIPPINES AUSTRIA INDIA POLAND BELGIUM INDONESIA PORTUGAL BOLIVIA IRAN ROMANIA BRAZIL IRAQ SAUDI ARABIA BULGARIA IRELAND SENEGAL BURMA ISRAEL SIERRA LEONE BYELORUSSIAN SOVIET ITALY SINGAPORE

SOCIALIST REPUBLIC IVORY COAST SOUTH AFRICA CAMEROON JAMAICA SPAIN CANADA JAPAN SUDAN CEYLON JORDAN SWEDEN CHILE KENYA SWITZERLAND CHINA KHMER REPUBLIC SYRIAN ARAB REPUBLIC COLOMBIA KOREA, REPUBLIC OF THAILAND COSTA RICA KUWAIT TUNISIA CUBA LEBANON TURKEY CYPRUS LIBERIA UGANDA CZECHOSLOVAK SOCIALIST LIBYAN ARAB REPUBLIC UKRAINIAN SOVIET SOCIALIST

REPUBLIC LIECHTENSTEIN REPUBLIC DENMARK LUXEMBOURG UNION OF SOVIET SOCIALIST DOMINICAN REPUBLIC MADAGASCAR REPUBLICS ECUADOR MALAYSIA UNITED KINGDOM OF GREAT EGYPT, ARAB REPUBLIC OF MALI BRITAIN AND NORTHERN EL SALVADOR MEXICO IRELAND ETHIOPIA MONACO UNITED STATES OF AMERICA FINLAND MOROCCO URUGUAY FRANCE NETHERLANDS VENEZUELA GABON NEW ZEALAND VIET-NAM GERMANY, FEDERAL REPUBLIC OF NIGER YUGOSLAVIA GHANA NIGERIA ZAIRE, REPUBLIC OF GREECE NORWAY ZAMBIA

The Agency's Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is "to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world".

© IAEA, 1972

Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Kärntner Ring 11, P.O. Box 590, A-1011 Vienna, Austria.

Printed by the IAEA in Austria

May 1972

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T E C H N I C A L R E P O R T S SERIES No. 135

STORAGE TANKS FOR LIQUID RADIOACTIVE WASTES:

THEIR DESIGN AND USE

A G u i d e b o o k p r e p a r e d by

R . V . A M A L R A J

B h a b h a A t o m i c R e s e a r c h C e n t r e , T r o m b a y , B o m b a y , I n d i a

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 VIENNA, 1972

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S T O R A G E TANKS F O R LIQUID R A D I O A C T I V E W A S T E S : T H E I R DESIGN AND USE

IAEA; VIENNA, 1972 = S T l / D O C / l O / 1 3 5

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FOREWORD

M u c h of t h e r a d i o a c t i v e w a s t e p r o d u c e d a t n u c l e a r e s t a b l i s h m e n t s i s in l i q u i d f o r m . V a r i o u s t y p e s of t a n k s h a v e b e e n d e v e l o p e d f o r t h e s a t i s f a c t o r y l o n g - t e r m s t o r a g e of s u c h w a s t e when i t i s of low o r i n t e r m e d i a t e - l e v e l r a d i o a c t i v i t y .

When l i q u i d w a s t e i s h igh ly r a d i o a c t i v e , a s t h a t r e s u l t i n g f r o m the a q u e o u s r e p r o c e s s i n g of i r r a d i a t e d f u e l to s e p a r a t e f i s s i l e a n d f e r t i l e m a -t e r i a l , t he p r o b l e m s of t r e a t m e n t and u l t i m a t e d i s p o s a l a r e g r e a t e r . T h e on ly p r a c t i c a l m e t h o d a v a i l a b l e a t t he m o m e n t f o r h a n d l i n g t h i s w a s t e i s i t s l o n g - t e r m s t o r a g e in s p e c i a l l y d e s i g n e d t a n k s . N e v e r t h e l e s s , s t o r a g e of t h i s t ype of w a s t e in l i q u i d f o r m h a s s o m e i n h e r e n t d i s a d v a n t a g e s , and m u c h i s h o p e d f r o m c u r r e n t r e s e a r c h and d e v e l o p m e n t w o r k to p r o v i d e t e c h n i q u e s f o r t he s a f e u l t i m a t e d i s p o s a l of t h e s e w a s t e s .

The 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 , c o n s i d e r i n g t h a t a s u m m a r y of p r e s e n t k n o w l e d g e on the d e s i g n of c o n t a i n e r s f o r l i q u i d w a s t e s of v a r i o u s l e v e l s of a c t i v i t y would be u s e f u l , h a v e s p o n s o r e d t h e p r e s e n t g u i d e b o o k . It h a s b e e n p r e p a r e d c h i e f l y f o r t h e b e n e f i t of M e m b e r S t a t e s t h a t a r e d e -v e l o p i n g , a r e a b o u t t o d e v e l o p , o r a r e p l a n n i n g to d e v e l o p in t he f u t u r e , t h e i r own n u c l e a r p r o g r a m s . It a i m s a t a s s i s t i n g t h e m to p r o d u c e s p e c i -f i c a t i o n s f o r t a n k d e s i g n s a n d s u p p o r t i n g a n c i l l a r y s e r v i c e s , and to a d e -q u a t e l y a s s e s s t h e d e s i g n s o f f e r e d a g a i n s t t h o s e s p e c i f i c a t i o n s . T h e book m a y a l s o h e l p p e r s o n n e l in 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 to u n d e r s t a n d s o m e of t h e f a c e t s of t he s a f e m a n a g e m e n t of r a d i o a c t i v e w a s t e s .

T h e gu idebook h a s b e e n w r i t t e n by M r . R . V. A m a l r a j , of t h e B h a b h a A t o m i c R e s e a r c h C e n t r e , B o m b a y , I n d i a . M r . E d w a r d D. H e s p e of t he IAEA o r g a n i z e d and d i r e c t e d t h e w o r k of p r e p a r a t i o n . The IAEA i s a l s o g r a t e f u l t o t h e a t o m i c e n e r g y a u t h o r i t i e s of B e l g i u m , C a n a d a , F r a n c e , I nd i a , t h e Un i t ed K i n g d o m a n d the Uni ted S t a t e s of A m e r i c a f o r p r o v i d i n g the a u t h o r wi th n e c e s s a r y i n f o r m a t i o n on t h e i r r a d i o a c t i v e w a s t e t a n k s t o r a g e s y s t e m s .

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CONTENTS

1. I N T R O D U C T I O N 1

2 . N A T U R E O F R A D I O A C T I V E LIQUID W A S T E S A N D T H E I R S T O R A G E 1

2 . 1 . G e n e r a l 1 2 . 1. 1. R a w m a t e r i a l p r o c e s s i n g 2 . 1. 2. R e a c t o r o p e r a t i o n 2 . 1 . 3 . R e s e a r c h , i s o t o p e p r o d u c t i o n and u t i l i z a t i o n

2 . 2 . R a d i o a c t i v e l i q u i d w a s t e c a t e g o r i e s 3 2 . 3 . F a c i l i t i e s u t i l i z i n g t a n k s t o r a g e 4

3. CONSIDERATIONS F O R DESIGN O F W A S T E S T O R A G E TANKS 4

3 . 1 . G e n e r a l 4 3. 2. T y p e s of t a n k s a n d t h e i r s i z i n g 4

3 . 2 . 1 . C o l l e c t i o n t a n k s 3 . 2 . 2 . T a n k s u s e d in t r e a t m e n t p l a n t s

3 . 3 . C o r r o s i o n c o n s i d e r a t i o n s 9 3 . 4 . A g i t a t i o n 10 3 . 5 . S a m p l i n g 10 3 . 6 . L e a k d e t e c t i o n 11 3 . 7 . D e c o n t a m i n a t i o n 11

4 . DESIGN AND C O N S T R U C T I O N O F W A S T E S T O R A G E TANKS 11

4 . 1 . G e n e r a l 11 4 . 2 . D e s i g n ' • 12

4 . 2 . 1 . S t e e l t a n k s 4 . 2 . 2 . C o n c r e t e t a n k s 4 . 2 . 3 . P r e s t r e s s e d c o n c r e t e t a n k s 4 . 2 . 4 . S t e e l l i n e r s f o r c o n c r e t e t a n k s

4 . 3 . C o n s t r u c t i o n ' 18 4 . 3 . 1 . S t e e l t a n k s 4 . 3 . 2 . C o n c r e t e t a n k s

4 . 4 . I n s p e c t i o n a n d t e s t i n g 18 4 . 4 . 1 . T e s t i n g of r a w m a t e r i a l s 4 . 4 . 2 . T e s t i n g of s t e e l t a n k s 4 . 4 . 3 . T e s t i n g of c o n c r e t e t a n k s

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5. DESIGN O F A C C E S S O R I E S F O R W A S T E S T O R A G E TANKS 19

5 . 1 . G e n e r a l 19 5 . 2 . T r a n s f e r s y s t e m s 19

5 . 2 . 1 . P i p e s and c o n n e c t i o n s 5 . 2 . 2 . V a l v e s 5 . 2 . 3 . P u m p s 5. 2 . 4 . D e s i g n and i n s t a l l a t i o n of t r a n s f e r s y s t e m s

5. 3. G a s - c l e a n i n g s y s t e m s 24 5. 3. 1. C y c l o n e s 5 . 3 . 2 . S c r u b b e r s 5. 3. 3. D e e p - b e d f i l t e r s 5. 3. 4 . H i g h - e f f i c i e n c y f i l t e r s

5 . 4 . A g i t a t o r s 25 5 . 4 . 1 . R e c i r c u l a t i o n p u m p s 5 . 4 . 2 . M e c h a n i c a l a g i t a t o r s . 5 . 4 . 3 . A i r - l i f t c i r c u l a t o r s a n d s p a r g e r s

5 . 5 . S a m p l e r s 28 5 . 6 . L e a k d e t e c t o r s 30 5. 7. I n s t r u m e n t a t i o n 30

5. 7. 1. L e v e l m e a s u r e m e n t 5. 7. 2. D e n s i t y m e a s u r e m e n t 5. 7. 3. T e m p e r a t u r e m e a s u r e m e n t 5. 7. 4 . pH m e a s u r e m e n t 5. 7. 5. P r e s s u r e m e a s u r e m e n t 5. 7. 6. F l o w m e a s u r e m e n t

6. O P E R A T I N G T E C H N I Q U E S 33

6 . 1 . G e n e r a l 33 6 . 2 . T r a n s f e r o p e r a t i o n s 33 6. 3. A n a l y t i c a l c o n t r o l 34 6 . 4 . D e c o n t a m i n a t i o n 34 6 . 5 . O p e r a t i o n a l s a f e t y 35

7. S H I E L D I N G O F W A S T E S T O R A G E TANKS ' 35

7 . 1 . G e n e r a l . . . 35 7 . 2 . F a c t o r s i n f l u e n c i n g s h i e l d i n g d e s i g n 35 7 . 3 . S h i e l d i n g d e s i g n . . . 36

8. E N V I R O N M E N T A L S A F E G U A R D S 37

8 . 1 . G e n e r a l 37 8 . 2 . L o c a t i o n of t a n k s a n d t a n k f a r m s 37

8 . 2 . 1 . G e o l o g i c a l c o n d i t i o n s 8 . 2 . 2 . H y d r o l o g i c a l c o n d i t i o n s ; 8 . 2 . 3 . . M o v e m e n t of r a d i o a c t i v i t y in t h e g r o u n d :

8. 3. E n v i r o n m e n t a l m o n i t o r i n g . . ' 38 8 . 4 . C o n t r o l m e a s u r e s ; . . . . . . 39-8 . 5 . E m e r g e n c y p r o v i s i o n s • - 39

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9. SUMMARY O F E X P E R I E N C E 39

9. 1. G e n e r a l 39 9 . 2 . N u c l e a r p o w e r s t a t i o n s 40

9 . 2 . 1 . Y a n k e e A t o m i c E l e c t r i c Co. (USA) 9 . 2 . 2 . C e n t r a l E l e c t r i c i t y G e n e r a t i n g B o a r d (UK) 9 . 2 . 3 . D o u g l a s P o i n t P o w e r S ta t ion ( C a n a d a )

9 . 3 , R e s e a r c h e s t a b l i s h m e n t s 41 9. 3. 1. O a k R i d g e N a t i o n a l L a b o r a t o r y ,

T e n n e s s e e (USA) 9. 3. 2. A t o m i c E n e r g y R e s e a r c h E s t a b l i s h m e n t ,

H a r w e l l (UK) 9. 3. 3. N u c l e a r C e n t r e , C a d a r a c h e ( F r a n c e ) 9. 3. 4 . B h a b h a A t o m i c R e s e a r c h C e n t r e ,

T r o m b a y (India)

10. COSTS 50

1 0 . 1 . G e n e r a l 50 1 0 . 2 , C o s t i n g p r o c e d u r e s 51

1 0 . 2 . 1 . C a p i t a l c o s t s 1 0 . 2 . 2 . O p e r a t i n g c o s t s

R E F E R E N C E S 53

A P P E N D I X : C o n v e r s i o n T a b l e 55

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1. I N T R O D U C T I O N

T h i s G u i d e b o o k i s i n t e n d e d p r i m a r i l y f o r t h e w a s t e m a n a g e m e n t s p e c i a l -i s t s in t h o s e d e v e l o p i n g c o u n t r i e s t h a t h a v e not t h e a d v a n t a g e of a w e l l d e -v e l o p e d e n g i n e e r i n g a n d t e c h n o l o g i c a l b a c k g r o u n d . T h e i n t e n t i o n of t h e a u t h o r i s t h a t t h e book s h o u l d a s s i s t t he s p e c i a l i s t t o (1) v i s u a l i z e t h e p r o -b l e m s a s s o c i a t e d wi th t h e d e s i g n of s t o r a g e t a n k s , (2) p r e p a r e d e s i g n b r i e f s f o r s u c h s y s t e m s , and (3) e v a l u a t e r e s u l t i n g d e s i g n p r o p o s a l s .

T h u s t h e b o o k d i s c u s s e s m a i n l y t he d e s i g n c r i t e r i a of r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s . S i n c e — f o r s o m e t i m e a t l e a s t — s p e c i a l i s t s i n t h i s c a t e -g o r y a r e u n l i k e l y t o b e f a c e d w i t h t h e p r o b l e m of m a n a g i n g s e l f - h e a t i n g w a s t e s , s t o r a g e f a c i l i t i e s f o r t h i s w a s t e c a t e g o r y a r e not d e a l t w i th .

2. N A T U R E O F R A D I O A C T I V E LIQUID W A S T E S AND T H E I R S T O R A G E

2 . 1 . G e n e r a l

A k n o w l e d g e of t h e c h e m i c a l and r a d i o c h e m i c a l c o m p o s i t i o n of t h e w a s t e s i s of p r i m a r y i m p o r t a n c e f o r t h e d e s i g n and o p e r a t i o n of t h e f a c i l i t i e s r e q u i r e d f o r t h e i r m a n a g e m e n t . R a d i o c h e m i c a l c o m p o s i t i o n e s t a b l i s h e s t h e b a s e f o r h a z a r d s c o n t r o l and t h e r e q u i r e m e n t s f o r t h e r e m o v a l of r a d i o -l y t i c g a s e s , w h i l e t h e c h e m i c a l c o m p o s i t i o n d i r e c t l y i n f l u e n c e s c o r r o s i o n r a t e s . P r o c e s s i n g of r a w m a t e r i a l s and n o r m a l o p e r a t i o n of r e a c t o r s g ive r i s e t o l a r g e v o l u m e s of l o w - l e v e l r a d i o a c t i v e l i q u i d w a s t e s . S l i g h t l y h i g h e r r a d i o a c t i v e w a s t e s a r e to b e e x p e c t e d f r o m r e a c t o r s d u r i n g o f f - s t a n d a r d o p e r a t i n g c o n d i t i o n s , r e s e a r c h l a b o r a t o r i e s a n d i s o t o p e p r o d u c t i o n p l a n t s .

2. 1. 1. R a w m a t e r i a l p r o c e s s i n g

T h e w a s t e p r o d u c e d i n u r a n i u m and t h o r i u m p r o c e s s i n g c o n t a i n s l a r g e a m o u n t s of i n a c t i v e c h e m i c a l l o a d . T h e r a d i o a c t i v i t y c o n t e n t of t h e w a s t e i s due t o t h e p r e s e n c e of s m a l l a m o u n t s of u r a n i u m and i t s d e c a y p r o d u c t s . I s o t o p e s of r a d i u m ( s o m e of t h e m g a s e o u s ) a r e t h e m o s t h a z a r d o u s r a d i o -n u c l i d e s p r e s e n t i n t h e s e s t r e a m s . F a b r i c a t i o n of f u e l e l e m e n t s d o e s not g i v e r i s e t o any s i g n i f i c a n t a m o u n t of r a d i o a c t i v i t y i n t h e l i q u i d w a s t e s .

2. 1 . 2 . R e a c t o r o p e r a t i o n

One of t h e c o m m o n l y u s e d c o o l a n t s i n n u c l e a r r e a c t o r s i s d e m i n e r a l i z e d w a t e r w h i c h b e c o m e s t h e m a i n s o u r c e of w a s t e . T h e r a d i o a c t i v e c o n t a m i n a -t i o n of t h e c o o l a n t i s n o r m a l l y due t o t h e n e u t r o n a c t i v a t i o n of t h e i m p u r i t i e s i n t h e c o o l a n t and of t h e c o r r o s i o n p r o d u c t s . F i s s i o n p r o d u c t s a r e a l s o found in t h e c o o l a n t d u e t o t h e c o n t a m i n a t i o n of t h e c l a d d i n g m a t e r i a l by t h e f u e l , o r a s a r e s u l t of c l a d d i n g f a i l u r e . T h e c o o l i n g s y s t e m i s e i t h e r of s i n g l e - p a s s o r of r e c i r c u l a t i n g t y p e . In t h e f i r s t t y p e t h e p r o b l e m of w a s t e h a n d l i n g b e c o m e s m o r e s e r i o u s w h e n the c l a d d i n g r u p t u r e s . In t h e r e -c i r c u l a t i n g s y s t e m t h e c o o l a n t i s r e - u s e d a f t e r n e c e s s a r y f i l t r a t i o n and d e m i n e r a l i z a t i o n . L i q u i d w a s t e s f r o m 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 , b e s i d e s o t h e r i s o t o p e s , l a r g e a m o u n t s of t r i t i u m . L e a k a g e s f r o m p u m p s , v a l v e s , h e a t e x c h a n g e r s , e t c . m u s t a l s o b e t r e a t e d a s w a s t e s . R e g e n e r -a t i o n of i o n - e x c h a n g e c o l u m n s i n t h e w a t e r p u r i f i c a t i o n s y s t e m s p r o d u c e s

1

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T A B L E I . W A S T E F R O M R E A C T O R O P E R A T I O N

Designation Type of reactor Power rating

(MW(e)) Volume collected

(gal/yr)

Activity range before dilution3

(pCi/cm 3)

Percentage re-used

Big Rock Point ( USA) Boiling water 50 1 X 1 0 1 -4 10 - 10~2 . 80

Bradwell (UK) Gas-cooled 300 c b

1 . 2 X 10s 10"' - 2 X 10"1 Nil

Dresden-I (USA) Boiling water 200 11 x iofib 10"5 - lO"2 84

EdF 1 (France) * Gas-cooled 70 About JO8 m 3 / y r

EdF 2 (France) Gas-cooled 180 L for the three I 10"5 - I O - 1 Not applicable

EdF 3 (France) Gas-cooled 475 J reactors J

Hinkley Point (UK) Gas-cooled 500 3 . 6 X 1 0 e b 10- 8 - 2 X 10~3 Nil

Humboldt Bay (USA) Boiling water 52 ~ 7 x io5; 10- 4 - 10~2 Nil

Indian Point-I( USA) Pressurized water 163 8 . 8 X 10s 3 X 10"6 - 2 X 10"3 Nil

Yankee (USA) Pressurized water 163 8 . 5 X 1 0 5 10"6 - 10"5 Nil

a Not including tritium, k Average volume.

Page 14: Storage Tanks for Liquid Radioactive Wastes: Their Design and Use · 2011. 8. 25. · STORAGE TANKS 4 3.1. General 4 3. 2. Types of tanks and their sizing 4 3.2.1. Collection tanks

c h e m i c a l w a s t e s c o n t a i n i n g h igh c o n c e n t r a t i o n s of s a l t s c a r r y i n g s o m e • r a d i o a c t i v e c o n t a m i n a t i o n . O t h e r s o u r c e s of c h e m i c a l and r a d i o a c t i v e w a s t e s a r e l i q u i d s f r o m d e c o n t a m i n a t i o n o p e r a t i o n s , r e s i n s l u i c i n g , e t c .

T h e n a t u r e and q u a n t i t i e s of l i q u i d w a s t e s g e n e r a t e d i n s o m e of t h e o p e r a t i n g p o w e r r e a c t o r s a r e g i v e n in T a b l e I [ 1 ] .

I r r a d i a t e d f u e l e l e m e n t s a r e s t o r e d u n d e r w a t e r in f u e l - s t o r a g e c a n a l s o r p o n d s to a l l o w f o r t h e d e c a y of s h o r t - l i v e d a c t i v i t y . T h i s w a t e r m a y b e c o n t a m i n a t e d wi th f i s s i o n p r o d u c t s f r o m t h e e x p o s e d e n d s of f u e l e l e m e n t s ; d e f e c t i v e o r r u p t u r e d c l a d d i n g m a y a l s o g i v e r i s e t o c o n t a m i n a t i o n . G e n e r -a l l y , a c t i v i t y f r o m t h e c a n a l w a t e r i s c o n t i n u o u s l y r e m o v e d by m e a n s of i o n - e x c h a n g e c o l u m n s to f a c i l i t a t e r e - u s e of t h e d e c o n t a m i n a t e d w a t e r t o t h e m a x i m u m e x t e n t . T h e r e g e n e r a n t f r o m t h e d e m i n e r a l i z i n g c o l u m n s b e c o m e s a s o u r c e of c o n t a m i n a t e d c h e m i c a l r a d i o a c t i v e w a s t e . T h e a c t i v i t y l e v e l in t h e w a t e r and i n t h e r e g e n e r a n t d e p e n d s u p o n t h e n a t u r e of t h e f u e l s t o r e d , t h e n a t u r e and s t a t u s of t h e c l a d d i n g m a t e r i a l , t h e e x t e n t of i r r a -d i a t i o n of t h e f u e l and t h e p e r i o d of s t o r a g e .

2 . 1 . 3. R e s e a r c h , i s o t o p e p r o d u c t i o n and u t i l i z a t i o n

L i q u i d w a s t e s a r i s i n g f r o m t h e p r o d u c t i o n and u t i l i z a t i o n of i s o t o p e s , r e s e a r c h a n d d e v e l o p m e n t a c t i v i t i e s and d e c o n t a m i n a t i o n o p e r a t i o n s a r e u n p r e d i c t a b l e i n n a t u r e a n d a r e l i a b l e to w i d e v a r i a t i o n s d e p e n d i n g on t h e • t y p e of o p e r a t i o n s i n v o l v e d . T h e w a s t e s r e s u l t i n g f r o m i s o t o p e s e p a r a t i o n f a c i l i t i e s a r e g e n e r a l l y s i m i l a r i n c o m p o s i t i o n to t h e r a f f i n a t e s f r o m f u e l r e p r o c e s s i n g p l a n t s , bu t t h e a c t i v i t y l e v e l s a r e l o w e r by s e v e r a l o r d e r s of m a g n i t u d e . W a s t e s p r o d u c e d f r o m h o s p i t a l s and i n d u s t r i e s u s i n g r a d i o -i s o t o p e s g e n e r a l l y c o n t a i n s m a l l q u a n t i t i e s of r a d i o n u c l i d e s , l i k e 3 2 P , 3 5 S , • 1 9 8 A u , 1 3 1 I , e t c . , w h i c h a r e s h o r t - l i v e d . A l a r g e n u m b e r of r a d i o i s o t o p e s i n c l u d i n g a l p h a e m i t t e r s m a y b e p r e s e n t in e f f l u e n t s p r o d u c e d f r o m r e s e a r c h l a b o r a t o r i e s . T h e d i s s o l v e d s o l i d s in t h e w a s t e m a y r a n g e f r o m 0 to 500 p p m d e p e n d i n g upon t h e n a t u r e of t h e w o r k . C o m p l e x i n g a g e n t s , . d e t e r g e n t s , o r g a n i c m a t e r i a l s and o x i d i z i n g a g e n t s a r e i n v a r i a b l y p r e s e n t i n t h e w a s t e s f r o m s u c h l a b o r a t o r i e s . T h e w a s t e s a r e v a r i a b l e w i t h r e g a r d t o v o l u m e , . c h e m i c a l c o m p o s i t i o n and r a d i o a c t i v i t y . L i q u i d w a s t e s r e s u l t i n g f r o m d e -c o n t a m i n a t i o n o p e r a t i o n s m a y c o n t a i n a w ide s p e c t r u m of c h e m i c a l s , d e -t e r g e n t s , s o a p s and o t h e r c l e a n i n g a g e n t s . S u s p e n d e d s o l i d s a n d o x i d i z i n g a g e n t s a r e a l s o l i k e l y t o b e p r e s e n t . F o a m and l a t h e r f o r m a t i o n i s a p a r t i -c u l a r p r o p e r t y a s s o c i a t e d wi th t h e w a s t e s . f r o m t h e o p e r a t i o n of r a d i o a c t i v e l a u n d r i e s . • T h e v o l u m e and a c t i v i t y l e v e l of t h e s e e f f l u e n t s ' W i l l d i f f e r f r o m s i t e to s i t e .

2. 2. R a d i o a c t i v e l i qu id w a s t e c a t e g o r i e s

A m u t u a l l y a g r e e d d e f i n i t i o n of w a s t e c a t e g o r i e s i s v e r y u s e f u l f o r p r o p e r c o m m u n i c a t i o n and d i s s e m i n a t i o n of i n f o r m a t i o n r e g a r d i n g t h e i r ,' m a n a g e m e n t .

T a k i n g in to c o n s i d e r a t i o n t h e d i f f e r e n t v i e w - p o i n t s pu t f o r w a r d by s o m e of t h e d e v e l o p e d and d e v e l o p i n g c o u n t r i e s , t h e 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 h a s m a d e r e c o m m e n d a t i o n s f o r c a t e g o r i z i n g r a d i o a c t i v e l i q u i d w a s t e s a s g i v e n i n T a b l e II [ 2] a n d t h i s c a t e g o r i z a t i o n h a s b e e n a d o p t e d f o r u s e i n t h e s u b s e q u e n t c h a p t e r s .

3

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T A B L E II. P R O P O S E D C A T E G O R I E S O F LIQUID W A S T E S

Category Activity leve l A

(jjCi/ml) Remarks

1 A £ 10"6 Not normally treated

2 10"6 < A s 10"3 Without shielding 1 Treatment

3 10"3 < A S 1 0 " 1 Shielding possible >- by usual

4 10"1 < A « 1 0 4 Shielding necessary J methods

5 104 < A Cooling and shielding necessary

2. 3. F a c i l i t i e s u t i l i z i n g t a n k s t o r a g e

T h e p r o v i s i o n of a d e q u a t e s t o r a g e f a c i l i t i e s i s e s s e n t i a l f o r t h e m a n a g e -m e n t of r a d i o a c t i v e w a s t e s . F i g u r e 1 s h o w s a f e w t y p i c a l t a n k s g e n e r a l l y a s s o c i a t e d w i t h t h e v a r i o u s p h a s e s of n u c l e a r o p e r a t i o n s and 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 .

L i q u i d w a s t e s p r o d u c e d d u r i n g r e f i n i n g of u r a n i u m and t h o r i u m r e q u i r e s t o r a g e p r i o r t o t h e i r d i s c h a r g e f o r s e t t l i n g , t r e a t m e n t and m o n i t o r i n g . In r e a c t o r o p e r a t i o n s t h e a c t i v e n o n - c h e m i c a l w a s t e s a r e s t o r e d i n t a n k s b e f o r e t h e i r t r e a t m e n t f o r r e - u s e o r d i s c h a r g e . T h e c h e m i c a l w a s t e s a r e t r e a t e d a f t e r c o l l e c t i o n i n s i t e s t o r a g e t a n k s .

A l l c a t e g o r i e s of l i q u i d w a s t e s , i r r e s p e c t i v e of t h e i r n a t u r e a n d c o m -p o s i t i o n , r e q u i r e s t o r a g e f o r s o m e l e n g t h of t i m e . T h i s m a y b e s t o r a g e f o r a c t i v i t y d e c a y , o r s t o r a g e f o r e f f e c t i n g d i l u t i o n , o r s t o r a g e b e f o r e a n d a f t e r t r e a t m e n t .

3. C O N S I D E R A T I O N S F O R DESIGN O F W A S T E S T O R A G E TANKS

3 . 1 . G e n e r a l

C o n s i d e r a t i o n s f o r t h e d e s i g n of s t o r a g e s y s t e m s f o r r a d i o a c t i v e l i q u i d w a s t e s a r e v a r i e d a s c o m p a r e d to t h o s e i n c o n v e n t i o n a l i n d u s t r y , i n v i e w of t h e c o m p l e x i t y of t h e p r o b l e m s e n c o u n t e r e d . S o m e of t h e s e w a s t e s c o n t a i n s u f f i c i e n t l y h igh c o n c e n t r a t i o n s of f i s s i o n p r o d u c t s t o c a u s e s p e c i a l p r o b l e m s in t h e d e s i g n of t a n k s f o r t h e i r s a f e s t o r a g e . A l s o , a s t h e s e w a s t e s w i l l be a p o t e n t i a l h a z a r d f o r a l ong p e r i o d of t i m e , t h e s t o r a g e s y s t e m s h o u l d b e s o d e s i g n e d a s to e n s u r e s a f e h a n d l i n g , e f f e c t i v e c o n t a i n m e n t and e n v i r o n -m e n t a l s a f e t y . O n t h e o t h e r h a n d , w a s t e s c o n t a i n i n g s m a l l e r c o n c e n t r a t i o n s of f i s s i o n p r o d u c t s do not p o s e s u c h s e r i o u s p r o b l e m s in t h e i r h a n d l i n g and s t o r a g e .

3. 2. T y p e s of t a n k s and t h e i r s i z i n g

S c h e m e s f o r t h e m a n a g e m e n t of c a t e g o r y - 2 , - 3 and - 4 w a s t e s e m p l o y s t o r a g e t a n k s f o r t h e i r c o l l e c t i o n , t r e a t m e n t and d i s p o s a l . T h e t y p e s and s i z e s of t a n k s u s e d f o r t h e s e w a s t e s a r e v a r i e d and h e n c e on ly a f e w s e l e c -t e d t a n k t y p e s and c o n s i d e r a t i o n s f o r t h e i r s i z i n g a r e d i s c u s s e d i n t h i s s e c t i o n .

4

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F U E L P R E P A R A T I O N P O W E R G E N E R A T I O N F U E L R E P R O C E S S I N G

S O U R C E R E S E A R C H

S I T E S T O R A G E

S T O R A G E F O R

T R E A T M E N T

T R E A T M E N T

S T O R A G E F O R

D I S P O S A L /

L O N G - T E R M

S T O R A G E

CATEGORY— 2 & - 3 W A S T E S

CATEGORY— A W A S T E S

• CATEGORY-S WASTES

y. *

Sr.

C O N C E N T R A T E T A N K

C H E M . T R E A T M E N T I j I O N E X C H A N G E L _ _ j E V A P O R A T I O N S O L I D I F I C A T I O N

a z u j ) DISPERSAL T A N K B O I L I N G T A N K C O O L E D T A N K C O O L E D T A N K

FIG. l . Typical tanks associated with various phases of nuclear operations and radioactive waste management.

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FIG.2 . Genera l a r rangement of typ ica l ho ld -up tanks used for segregat ion and s torage .

3. 2. 1. C o l l e c t i o n t a n k s

C o l l e c t i o n t a n k s a r e p r o v i d e d f o r t h e s e g r e g a t i o n and s t o r a g e of w a s t e s a t p r o d u c t i o n s i t e s p r i o r t o t h e i r m o n i t o r i n g f o r t r e a t m e n t o r d i s p o s a l . T o f a c i l i t a t e g r a v i t y f e e d , t h e t a n k s c a n be a d v a n t a g e o u s l y h o u s e d be low g r o u n d l e v e l i n a b a s e m e n t a r e a o r i n a v a u l t wi th p r o v i s i o n f o r c o l l e c t i o n of l e a k a g e s o r s p i l l s . T h e g e n e r a l a r r a n g e m e n t of a s e t of h o l d - u p t a n k s u s e d f o r s e g r e g a t i o n a n d c o l l e c t i o n of w a s t e s i s s h o w n in F i g . 2.

C o l l e c t i o n t a n k s a r e s i z e d up to p r o v i d e s u f f i c i e n t h o l d - u p c a p a c i t y f o r e a c h t y p e of w a s t e f o r e c o n o m i c m a n a g e m e n t of t r a n s f e r and t r e a t m e n t d e p e n d i n g u p o n t h e q u a n t i t i e s of w a s t e s p r o d u c e d . T h e s e t a n k s a r e f i l l e d on a b a t c h p r i n c i p l e and a m i n i m u m of two t a n k s a r e p r o v i d e d s o a s to a l l ow t i m e f o r s a m p l i n g and a n a l y s i s . T h e s a m e o b j e c t i v e c a n b e a c h i e v e d by p r o v i d i n g c o m p a r t m e n t e d t a n k s .

3. 2. 2. T a n k s u s e d in t r e a t m e n t p l a n t s

C a t e g o r y - 2 and - 3 t y p e s of w a s t e s a r e u s u a l l y t r e a t e d by c h e m i c a l t r e a t m e n t and i o n - e x c h a n g e m e t h o d s . T a n k s a r e u s e d f o r s t o r a g e of w a s t e s b e f o r e and a f t e r t r e a t m e n t . P r e t r e a t m e n t s t o r a g e i s n e c e s s a r y f o r m o n i -t o r i n g and c o n d i t i o n i n g of w a s t e s . S t o r a g e a f t e r t r e a t m e n t f a c i l i t a t e s t he m o n i t o r i n g of w a s t e p r i o r t o d i s p o s a l o r r e c y c l i n g f o r f u r t h e r t r e a t m e n t .

6

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A s e t of t h r e e p r e t r e a t m e n t t a n k s w i t h p r o v i s i o n f o r i n t e r - t r a n s f e r of w a s t e s w i l l f a c i l i t a t e u n i n t e r r u p t e d o p e r a t i o n of t h e p l a n t . W h e n one t a n k i s u s e d f o r f e e d i n g w a s t e s to t h e t r e a t m e n t p l a n t , t h e s e c o n d t a n k , wh ich i s f u l l , i s u s e d f o r s a m p l i n g , a n a l y s i s and c o n d i t i o n i n g of w a s t e s , and t h e t h i r d t a n k i s u s e d f o r r e c e i v i n g w a s t e s . S i m i l a r o p e r a t i o n a l f l e x i b i l i t y c a n b e o b t a i n e d by p r o v i d i n g a n e q u a l n u m b e r of p o s t - t r e a t m e n t t a n k s . T h e s e a r e g e n e r a l l y s i m i l a r to t h e p r e t r e a t m e n t t a n k s in t h e i r d e s i g n and c o n -s t r u c t i o n e x c e p t t h a t a s t i r r i n g a r r a n g e m e n t m a y not be n e c e s s a r y . It i s p r e f e r a b l e t o r o u t e t h e t r e a t e d w a s t e s t h r o u g h a m o n i t o r i n g s t a t i o n b e f o r e d i s c h a r g e w h e r e t h e q u a n t i t y and t h e r a d i o a c t i v i t y of t h e w a s t e s c a n b e d e t e r m i n e d in o r d e r to a c c o u n t f o r t h e t o t a l r e l e a s e i n to t h e e n v i r o n m e n t .

T h e g e n e r a l a r r a n g e m e n t d e t a i l s of a s e t of p r e t r e a t m e n t a n d p o s t -t r e a t m e n t t a n k s a s s o c i a t e d wi th a c h e m i c a l t r e a t m e n t / i o n - e x c h a n g e p l a n t a r e s h o w n in F i g . 3.

In s i z i n g t h e p r e t r e a t m e n t t a n k s , t he f o l l o w i n g a s p e c t s h a v e t o b e e x a m i n e d :

(a) A v e r a g e p r o d u c t i o n r a t e of w a s t e s r e q u i r i n g t r e a t m e n t (b) S u r g e l o a d s of w a s t e s e x p e c t e d d u r i n g o f f - s t a n d a r d o p e r a t i n g c o n -

d i t i o n s and p l a n t d e c o n t a m i n a t i o n (c) P l a n n e d s h u t - d o w n s of t h e t r e a t m e n t p l a n t .

EFFLUENT JOINING CIRUS REACTOR COOLANT DISCHARGE

PRETREATMENT TANKS

CENTRAL DISCHARGE FACILITY WITH PUMPS, FLOW INTEGRATOR AND PROPORTIONAL SAMPLER

POST-TREATMENT TANKS

F I G . 3 . Pre t rea tment and pos t - t r ea tmen t tanks associated with a c h e m i c a l t r e a t m e n t / i o n - e x c h a n g e plant , Bhabha Atomic Research Cent re .

7

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T h e f o l l o w i n g p o i n t s m u s t b e c o n s i d e r e d i n s i z i n g t h e p o s t - t r e a t m e n t t a n k s f r o m w h e r e w a s t e s a r e d i r e c t l y d i s c h a r g e d :

(a) E x p e c t e d v o l u m e of t h e t r e a t e d w a s t e s (b) D i l u t i o n w a t e r a v a i l a b l e , if a n y , i n t h e g e n e r a l p l a n t a r e a (c) T h e m a x i m u m p e r m i s s i b l e c o n c e n t r a t i o n s t i p u l a t e d f o r e f f l u e n t

d i s c h a r g e a t t h e s i t e .

D e p e n d i n g o n t h e i r c o m p o s i t i o n , c a t e g o r y - 3 and - 4 w a s t e s a r e g e n e r a l l y e v a p o r a t e d t o o b t a i n v o l u m e r e d u c t i o n . A s t h e w a s t e v o l u m e s to b e h a n d l e d a r e not l a r g e , s m a l l t a n k s of m e t a l l i c c o n s t r u c t i o n m a y b e u s e d a s e v a p o -r a t o r f e e d t a n k s . P r o v i s i o n s f o r s e c o n d a r y c o n t a i n m e n t , l e a k d e t e c t i o n , l e v e l m e a s u r e m e n t , e t c . a r e n e c e s s a r y . T h e e v a p o r a t o r c o n c e n t r a t e s b e l o n g i n g t o c a t e g o r y - 4 w a s t e s a r e s t o r e d i n l a r g e t a n k s l o c a t e d b e l o w g r o u n d l e v e l to t a k e a d v a n t a g e of e a r t h s h i e l d i n g .

T h e t a n k s s t o r i n g c a t e g o r y - 4 w a s t e s c a n b e b r o a d l y c l a s s i f i e d i n to two t y p e s , i . e . f r e e - s t a n d i n g t a n k s of m e t a l l i c c o n s t r u c t i o n h o u s e d i n a s e c o n d a r y c o n t a i n e r and c o n c r e t e t a n k s w i t h m e t a l l i n e r s .

T h e s t o r a g e t a n k s of t h e f i r s t t y p e a r e c y l i n d r i c a l i n s h a p e , m a d e of e i t h e r s t a i n l e s s s t e e l o r c a r b o n s t e e l d e p e n d i n g on t h e n a t u r e of w a s t e s t o r e d . T h e y a r e g e n e r a l l y of f l a t o r d o m e d roo f c o n s t r u c t i o n . T h e roo f i s d e s i g n e d to m e e t t h e s t r u c t u r a l and s h i e l d i n g r e q u i r e m e n t s . T h e b o t t o m of t h e t a n k r e s t s on a t h i c k c o n c r e t e b a s e . T h e b o t t o m p l a t e i s g e n e r a l l y c u r v e d up to j o i n t h e s h e l l s o a s t o avo id a c c u m u l a t i o n of s l u d g e a r o u n d t h e c o r n e r s . O n e o r m o r e t a n k s a r e h o u s e d i n a n e n c l o s u r e w h i c h i s n o r m a l -ly a c o n c r e t e v a u l t w i th a m e t a l l i n e r . T h e h e i g h t of t h e l i n e r d e p e n d s on t h e c a p a c i t y of t h e l a r g e s t t a n k i n t h e v a u l t .

T h e s e c o n d t y p e , i . e . c o n c r e t e t a n k w i t h m e t a l l i n e r s , i s u s e d t o a l i m i t e d e x t e n t f o r s t o r i n g c a t e g o r y - 4 w a s t e s . T h e s e t a n k s a r e a l m o s t s i m i l a r t o t h e t y p e of t a n k s d e s c r i b e d a b o v e e x c e p t t h a t t h e b o t t o m a n d s i d e w a l l s of t h e t a n k s a r e of r e i n f o r c e d c o n c r e t e w i t h m e t a l l i n e r s .

T h e s i z i n g of a t a n k f o r s t o r i n g c a t e g o r y - 4 w a s t e s i s b a s e d on t h e f o l l o w i n g c o n s i d e r a t i o n s :

(a) Q u a n t i t y of w a s t e t o b e s t o r e d and i t s n a t u r e (b) G e o l o g i c a l and h y d r o l o g i c a l c o n d i t i o n s p r e v a i l i n g a t a s i t e (c) U s e f u l c a p a c i t y and s p a r e c a p a c i t y (d) C o s t .

A f t e r t h e c a p a c i t y of t h e s t o r a g e t a n k s h a s b e e n f i x e d , t h e p r o p o r t i o n i n g of t h e i r d i m e n s i o n s h a s to b e c a r r i e d ou t . F o r t a n k s s t o r i n g c a t e g o r y - 2 a n d - 3 t y p e s of w a s t e s , v a r i o u s s h a p e s a r e b e i n g a d o p t e d d e p e n d i n g on t h e s i t e c o n d i t i o n s . F o r c a t e g o r y - 4 w a s t e s t o r a g e it i s p r e f e r a b l e t o u s e t a n k s of c y l i n d r i c a l s h a p e to h e l p e n s u r e t a n k i n t e g r i t y . C y l i n d r i c a l t a n k s h a v e t h e a d v a n t a g e of m o r e u n i f o r m s t r e s s d i s t r i b u t i o n u n d e r l o a d i n g c o n d i t i o n and l e s s c o r r o s i o n a t c o r n e r s a s a r e s u l t of a c c u m u l a t i o n of s l u d g e s , a s c o m p a r e d to r e c t a n g u l a r t a n k s . M o s t of t h e h i g h - l e v e l r a d i o a c t i v e w a s t e s t o r a g e t a n k s a r e c y l i n d r i c a l i n s h a p e . T h e d i m e n s i o n s of a s t o r a g e t a n k a r e a r r i v e d a t by o p t i m i z i n g t h e d i a m e t e r - t o - h e i g h t r a t i o . T h e v a r i o u s f a c t o r s w h i c h i n f l u e n c e t h e c o s t of t h e t a n k a r e t h e c o s t of t h e f o u n d a t i o n a n d of t h e l a n d a s w e l l a s t h a t of t h e t a n k b o t t o m , s h e l l a n d r o o f . T h e o p t i m u m d i a m e t e r - t o - h e i g h t r a t i o of t h e t a n k i s s e l e c t e d t o g i v e t h e m i n i m u m t o t a l c a p i t a l c o s t . S i n c e v e r y o f t e n t h e c o s t f a c t o r s c a n n o t b e d e t e r m i n e d

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a c c u r a t e l y u n t i l t h e t a n k i s d e s i g n e d , t h e r a n g e of o p t i m u m p r o p o r t i o n s h a s t o b e d e t e r m i n e d by s u c c e s s i v e a p p r o x i m a t i o n s . T h e f i n a l t a n k d i m e n s i o n s h a v e t o b e s e l e c t e d a f t e r c o n s i d e r i n g t h e v a r i o u s a s p e c t s t h a t a r e p e c u l i a r t o t h e s i t e , w h i c h i n c l u d e t h e s h i e l d i n g r e q u i r e m e n t s , t h e l e v e l of t h e f e e d p i p e w h e r e g r a v i t y f low i s u s e d , e t c . M e t h o d s t o b e f o l l o w e d f o r o p t i m i z i n g t h e t a n k d i m e n s i o n s f o r v a r i o u s s h a p e s a r e r e v i e w e d by B r o w n e l l a n d Young [ 3 ] .

3. 3. C o r r o s i o n c o n s i d e r a t i o n s

A s c a t e g o r y - 2 and - 3 w a s t e s t o r a g e t a n k s s h o u l d b e c a p a b l e of r e c e i v i n g l i q u i d s of d i v e r s e c h e m i c a l n a t u r e , t h e e f f e c t s of t h e s e on c o n s t r u c t i o n m a t e r i a l s h a v e t o b e p r o p e r l y e v a l u a t e d . T h e c o r r o s i o n r e s i s t a n c e of s t a i n -l e s s s t e e l i s w e l l known. H o w e v e r , w a s t e s c o n t a i n i n g f l u o r i d e s and c h l o r i d e s w i l l d e s t r o y t h e p r o t e c t i v e o x i d e l a y e r and b r i n g abou t r a p i d a t t a c k . At n o r m a l t e m p e r a t u r e , c a r b o n s t e e l i s q u i t e r e s i s t a n t to a l k a l i n e s o l u t i o n s . A l t h o u g h g e n e r a l c o r r o s i o n i n a l k a l i n e w a s t e s t o r a g e t a n k s i s q u i t e l ow , p i t t i n g and s t r e s s c o r r o s i o n m a y a f f e c t t h e t a n k i n t e g r i t y .

A s h igh r a d i a t i o n and t e m p e r a t u r e p r o b l e m s do not e x i s t wi th t h e s t o r a g e of t h e s e w a s t e s , s u i t a b l e c h e m i c a l l y r e s i s t a n t p a i n t s c a n b e a d v a n t a g e o u s l y u s e d , w h e r e v e r n e c e s s a r y , t o m i n i m i z e c o r r o s i o n . E f f l u e n t s c o n t a i n i n g h i g h l y c o r r o s i v e c o n s t i t u e n t s , s u c h a s c h l o r i d e s a n d f l u o r i d e s , c a n b e s a f e l y s t o r e d i n t a n k s by p r o v i d i n g p r o t e c t i v e l i n i n g s l i k e i s o m e r i c r u b b e r , p o l y v i n y l c h l o r i d e (PVC) and epoxy f i b r e g l a s s . It i s d e s i r a b l e t o s e g r e g a t e c h e m i c a l a n d n o n - c h e m i c a l w a s t e s a n d s t o r e t h e m s e p a r a t e l y .

In s e l e c t i n g t h e c o n s t r u c t i o n m a t e r i a l s f o r t h e s t o r a g e of c a t e g o r y - 4 w a s t e s s p e c i a l c o n s i d e r a t i o n i s r e q u i r e d f o r a c i d w a s t e s c o n t a i n i n g s u l -p h a t e s o r f l u o r i d e s . S p e c i a l s t a i n l e s s s t e e l a n d a l s o c a r b o n s t e e l l i n e d w i t h l e a d o r p l a s t i c m a t e r i a l s c a n b e u s e d f o r s t o r i n g t h e s e w a s t e s . T h o u g h n e u t r a l i z a t i o n of t h e a c i d i c w a s t e s r e d u c e s c o r r o s i o n , t h e c o n s e q u e n t p r e -c i p i t a t i o n , if any , and v o l u m e i n c r e a s e m a y h a v e t o b e c o n s i d e r e d . A l s o , t h e d e s i g n of m e t a l l i c c o n t a i n e r s f o r s t o r i n g c a t e g o r y - 4 w a s t e s s h o u l d t a k e in to a c c o u n t t h e l o n g - t e r m c o r r o s i o n e f f e c t s d u r i n g s t o r a g e . P i t t i n g c o r -r o s i o n i s p o s s i b l e i n t a n k s ho ld ing s t a g n a n t s o l u t i o n s and i t i s e n h a n c e d by s u r f a c e d e f e c t s . S t r e s s c o r r o s i o n i s m a i n l y r e s p o n s i b l e f o r c o n s i d e r a b l y r e d u c i n g t h e l i f e of t h e s e t a n k s . R e s i d u a l s t r e s s p r e s e n t i n f i n i s h e d t a n k s n e a r t h e h e a t - a f f e c t e d a r e a s , u n s t a b l e t h e r m a l c o n d i t i o n s d u r i n g s t o r a g e a n d s u r f a c e d i s c o n t i n u i t i e s s h o u l d b e a v o i d e d a s f a r a s p o s s i b l e , a s t h e s e a r e r e s p o n s i b l e f o r i n c r e a s e d s t r e s s e s w h i c h m a y l e a d t o s t r e s s - c o r r o s i o n c r a c k i n g . S t u d i e s o n t h e c h o i c e of s u i t a b l e c o n s t r u c t i o n m a t e r i a l s f o r c a t e g o r y - 4 w a s t e s t o r a g e t a n k s h a v e b e e n c a r r i e d out by M a r c u s a n d O m a y [ 4 ] .

It i s d e s i r a b l e t o c a r r y out c o r r o s i o n s t u d i e s on m a t e r i a l s l i k e l y t o b e u s e d f o r t a n k c o n s t r u c t i o n , s i m u l a t i n g t h e c o n d i t i o n s p r e v a i l i n g a t a p a r t i c u l a r p l a n t . B a s e d o n t h e d a t a c o l l e c t e d , i t s h o u l d b e p o s s i b l e t o s e l e c t t h e c o n s t r u c t i o n m a t e r i a l a n d to p r o v i d e t h e r e q u i r e d c o r r o s i o n a l l o w a n c e . S u c h s t u d i e s shou ld i n c l u d e t h e f o l l o w i n g :

(a) E v a l u a t i o n of a l l p r o m i s i n g m a t e r i a l s ; t h e w e l d e d s a m p l e s r e p r e -s e n t i n g t h e c r i t i c a l j o i n t s in t h e t a n k h a v e to b e i n c l u d e d .

(b) T a k i n g in to a c c o u n t t h e s t o r a g e c o n d i t i o n s , s u c h a s w a s t e c o m -p o s i t i o n and t e m p e r a t u r e .

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(c) C o l l e c t i o n of d a t a f o r t h e l iqu id p h a s e , t h e i n t e r p h a s e a n d t h e v a p o u r p h a s e , if any .

T h e i n f o r m a t i o n s h o u l d b e b a s e d on p r o l o n g e d t r i a l r u n s wi th p e r i o d i c e v a l u a t i o n . C a r e s h o u l d b e t a k e n t o m a i n t a i n t h e p r o p e r t i e s of t h e t e s t s o l u t i o n c o n s t a n t t h r o u g h o u t t h e t e s t p e r i o d .

A c t u a l c o r r o s i o n d a t a u n d e r o p e r a t i n g c o n d i t i o n s c a n b e c o l l e c t e d by u s i n g t e s t p i e c e s in t h e t ank ; s u c h da t a c a n b e u s e f u l f o r p r e d i c t i n g t h e t a n k l i f e and a l s o f o r t h e d e s i g n of f u t u r e t a n k s .

3. 4 . A g i t a t i o n

A g i t a t i o n i s n e c e s s a r y t o e n s u r e u n i f o r m m i x i n g of d i f f e r e n t w a s t e s t r e a m s c o l l e c t e d i n t a n k s and t h e i r c o n d i t i o n i n g b e f o r e t r e a t m e n t o r d i s -c h a r g e . Good m i x i n g of t a n k c o n t e n t s i s e s s e n t i a l to o b t a i n r e p r e s e n t a t i v e s a m p l e s f o r m o n i t o r i n g p u r p o s e s .

A s t h e m a j o r p o r t i o n of r a d i o a c t i v i t y m a y b e a s s o c i a t e d wi th t h e s e t t l i n g s l u d g e , i t s n o n - u n i f o r m d i s t r i b u t i o n i n a t a n k m a y g ive r i s e to p r o b l e m s in s a m p l i n g and t r e a t m e n t . T h e s e p r o b l e m s c a n b e r e d u c e d by d i s p e r s i n g t h e s l u d g e in t h e t a n k by e m p l o y i n g d e v i c e s f o r a g i t a t i o n .

T h e s e l e c t e d a g i t a t i o n d e v i c e shou ld b e s u c h t h a t i t p r o v i d e s a n e f f e c t i v e , s t e a d y and m i l d m i x i n g p a t t e r n in t he t a n k . T h e e n t r a i n m e n t of l i qu id d r o p l e t s f o r a g i v e n m i x i n g s h o u l d b e kep t to a m i n i m u m . It s h o u l d be p o s s i b l e , to o p e r a t e t h e a g i t a t i o n d e v i c e s c o n t i n u o u s l y s o a s to a v o i d m a i n -t e n a n c e p r o b l e m s .

F o r m i x i n g c a t e g o r y - 2 and - 3 t y p e s of w a s t e s , r e c i r c u l a t i n g p u m p s a n d m e c h a n i c a l a g i t a t o r s m a y b e u s e d . R e c i r c u l a t i o n by p u m p s i s n o r -m a l l y p r o v i d e d f o r s m a l l - c a p a c i t y t a n k s . R e c i r c u l a t i o n i s i n e f f e c t i v e w h e n f a s t - s e t t l i n g s u s p e n d e d s o l i d s a r e p r e s e n t i n t h e w a s t e . If m e c h a n i -c a l a g i t a t o r s a r e u s e d , t h e y h a v e t o b e r u n a t l ow s p e e d and t h e r e s h o u l d not b e any s p l a s h i n g of w a s t e s . T h e d e s i g n and l o c a t i o n of t h e s t i r r e r b l a d e s s h o u l d be s u c h a s to e n s u r e good and u n i f o r m m i x i n g of t h e e n t i r e t a n k c o n t e n t s .

A i r - l i f t a g i t a t o r s and s p a r g e r s c a n b e a d v a n t a g e o u s l y u s e d f o r a g i t a t i n g c a t e g o r y - 4 w a s t e s i n t a n k s .

3. 5. S a m p l i n g

It i s e s s e n t i a l , w h e n s a m p l i n g , to o b t a i n t h e m o s t r e p r e s e n t a t i v e s a m p l e s in o r d e r t o a s s e s s t h e c h a r a c t e r i s t i c s of w a s t e s f o r s t o r a g e t r e a t m e n t o r d i s p o s a l . S a m p l i n g w i l l e n a b l e t h e c o m p o s i t i o n and a c t i v i t y l e v e l t o b e d e t e r m i n e d . If a l a r g e n u m b e r of r a d i o n u c l i d e s a r e to b e i d e n t i f i e d , o r if t h e w a s t e s c o n t a i n v e r y low c o n c e n t r a t i o n s of r a d i o a c t i v i t y , it m a y b e n e c e s s a r y to c o l l e c t a l a r g e q u a n t i t y of a g i v e n s a m p l e . T h o r o u g h m i x i n g of t h e t a n k c o n t e n t s b e f o r e s a m p l i n g i s n e c e s s a r y and i t s h o u l d b e p o s s i b l e t o w i t h d r a w s a m p l e s f r o m d i f f e r e n t l o c a t i o n s . F u r t h e r , t h e c o n s t r u c t i o n m a t e r i a l s of t h e s a m p l i n g s y s t e m shou ld b e s u c h t h a t t h e y do not c h e m i c a l l y r e a c t w i t h t h e c o n s t i t u e n t s of t h e s a m p l e .

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3. 6. L e a k d e t e c t i o n

In t h e even t of a f a i l u r e of a t a n k ho ld ing h i g h e r - l e v e l r a d i o a c t i v e w a s t e s it i s e s s e n t i a l to p r o m p t l y d e t e c t t h e l e a k m o r d e r to t a k e i m m e d i a t e c o r -r e c t i v e m e a s u r e s . T h i s m a y b e done by p r o v i d i n g l e v e l g a u g e s i n s i d e t h e t a n k and by i n s t a l l i n g r a d i a t i o n d e t e c t i o n d e v i c e s in a d j a c e n t b o r e h o l e s o r a t c o l l e c t i o n p o i n t s c o n n e c t i n g t h e l a t e r a l c h a n n e l s c o n s t r u c t e d b e n e a t h t h e t a n k .

A s w a s t e t r a n s f e r o p e r a t i o n s in t a n k s ho ld ing c a t e g o r y - 2 and - 3 w a s t e s a r e c a r r i e d out f r e q u e n t l y , s p i l l a g e and o v e r f l o w i n g m a y o c c u r . T h e r o o m s o r p l a t f o r m s w h e r e c a t e g o r y - 2 , - 3 and - 4 w a s t e s t o r a g e t a n k s a r e l o c a t e d a r e g e n e r a l l y p r o v i d e d wi th c u r b s and c o l l e c t i o n s u m p s and s u c h o t h e r s e c o n d a r y c o n t a i n m e n t d e v i c c s a s a r e u s e f u l t o d e t e c t l e a k a g e s . F o r u n d e r -g r o u n d s t o r a g e t a n k s , w h e r e no s e c o n d a r y c o n t a i n m e n t i s p r o v i d e d , m e a s u r e -m e n t of t h e l i qu id l e v e l in t h e t a n k and w a s t e i n v e n t o r y c o n t r o l w i l l i n d i c a t e l e a k a g e s . T h e l e v e l g a u g e s shou ld be v e r y s e n s i t i v e when l a r g e -s i z e d t a n k s a r e u s e d , a s i s g e n e r a l l y t h e c a s e w h e n s t o r i n g c a t e g o r y - 4 w a s t e s . A l s o , t h e r a d i a t i o n m e a s u r i n g i n s t r u m e n t s e m p l o y e d s h o u l d be s e n s i t i v e to e v e n s m a l l c h a n g e s of r a d i a t i o n l e v e l s a b o v e t h e b a c k g r o u n d . A s t a t i c m o n i t o r , if not p r o p e r l y l o c a t e d , m a y b e c o m e i n e f f e c t i v e a s t h e r e a r e c h a n c e s of t he l i qu id b y p a s s i n g t h e i n s t r u m e n t . F u r t h e r , t h e d e t e r m i n a t i o n of t h e n a t u r e and t h e a c t i v i t y l e v e l of t h e l e a k a g e i s not p o s s i b l e if s u c h d e t e c t o r s a r e u s e d . A n a n a l y s i s of g r o u n d - w a t e r s a m p l e s , p e r i o d i c a l l y c o l l e c t e d f r o m m o n i t o r i n g w e l l s a r o u n d t h e t a n k , w i l l p r o v i d e t h e m o s t r e l i a b l e i n f o r m a t i o n on t h e s e f a c t o r s .

3. 7. D e c o n t a m i n a t i o n

D e c o n t a m i n a t i o n of t a n k s i s n e c e s s a r y t o f a c i l i t a t e m a i n t e n a n c e and a l s o to b r i n g down t h e g e n e r a l r a d i a t i o n l e v e l , w h e r e v e r n e c e s s a r y . A s t h e t a n k s p l a c e d b e h i n d s h i e l d i n g w a l l s o r be low g r o u n d l e v e l m a y not be r e a d i l y a c c e s s i b l e f o r d e c o n t a m i n a t i o n i t i s d e s i r a b l e , p a r t i c u l a r l y f o r h i g h e r - l e v e l w a s t e s , t o p r o v i d e r e c i r c u l a t i o n j e t s f o r t h e i n t r o d u c t i o n of a m e a s u r e d q u a n t i t y of d e c o n t a m i n a t i n g s o l u t i o n s wi th p r o v i s i o n s f o r h e a t i n g . T h e a c t i o n of d e c o n t a m i n a t i n g s o l u t i o n s on t h e c o n s t r u c t i o n m a t e r i a l of t a n k s h a s to be t a k e n in to c o n s i d e r a t i o n w h e n s e l e c t i n g t h e c l e a n i n g r e a g e n t s .

4. DESIGN AND C O N S T R U C T I O N O F W A S T E S T O R A G E TANKS

4. 1. G e n e r a l

T h e s p e c i a l f e a t u r e s in t h e d e s i g n and c o n s t r u c t i o n of r a d i o a c t i v e l i qu id w a s t e s t o r a g e t a n k s a r e t h e e x t r a s a f e t y and t h e r i g o r o u s i n s p e c t i o n and t e s t i n g r e q u i r e m e n t s to e n s u r e q u a l i t y c o n t r o l . A s t h e s e f e a t u r e s i n c r e a s e t h e c o s t , t h e d e g r e e of s a f e t y of t h e s y s t e m s h o u l d be j u s t i f i e d by t h e s e r v i c e r e q u i r e m e n t s . D e p e n d i n g on t h e n a t u r e of t h e s e r v i c e s r e q u i r e d , p r o p e r d e s i g n , c o n s t r u c t i o n , i n s p e c t i o n and t e s t i n g p r o c e d u r e s h a v e to b e a d o p t e d .

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4. 2. D e s i g n

S t r e s s e v a l u a t i o n p l a y s a p r e d o m i n a n t r o l e i n t h e a s s e s s m e n t of t a n k i n t e g r i t y . T h e b a s i c r e q u i r e m e n t f o r t h e d e s i g n i s t o e n s u r e t h a t t h e s t r e s s e s i n d u c e d i n t h e m a t e r i a l do not e x c e e d t h e m a x i m u m a l l o w a b l e s t r e s s f o r t h a t m a t e r i a l . Shou ld t h e y e x c e e d a v a l u e w h i c h i s s a f e f o r a p a r t i c u l a r d e s i g n , m o d i f i c a t i o n s have to b e i n c o r p o r a t e d by c h a n g i n g t h e d i m e n s i o n s , g e o m e t r y , l o a d i n g p a t t e r n , e t c .

T h e v a r i o u s t y p e s of l o a d i n g t h a t h a v e t o b e c o n s i d e r e d c a n be l i s t e d a s f o l l o w s :

(a) Sta t ic , h y d r a u l i c l o a d i n g (b) R e a c t i o n s a t s u p p o r t s and p ip ing s y s t e m s (c) E a r t h p r e s s u r e and h y d r o s t a t i c p r e s s u r e f r o m g r o u n d - w a t e r (d) S e i s m i c and o t h e r e x t e r n a l l o a d s

, (e) T r a n s i e n t l o a d s , if a n y .

I n c a l c u l a t i n g t h e e x p e c t e d m a x i m u m h y d r o s t a t i c p r e s s u r e , p o s s i b l e c h a n g e s in s p e c i f i c g r a v i t y h a v e to b e t a k e n in to a c c o u n t . T h e e a r t h p r e s -s u r e w i l l d e p e n d on t h e s i t e c o n d i t i o n s . S u p p o r t r e a c t i o n s a r e p r e d o m i n a n t i n t h e c a s e of l ong , h o r i z o n t a l t a n k s r e s t i n g on s a d d l e s , and v e r t i c a l t a n k s i n s t a l l e d on lug s u p p o r t s . T h e e x t e r n a l l o a d i n g on t h e t a n k c a n b e h igh w h e n s h a l l o w g r o u n d - w a t e r c o n d i t i o n s p r e v a i l . T h e m a x i m u m e x p e c t e d g r o u n d - w a t e r p r e s s u r e c a n b e e s t i m a t e d by u s i n g h y d r o g r a p h s p e r t a i n i n g to t h e s i t e . If t a n k s a r e l o c a t e d in s e i s m i c r e g i o n s , t h e d e s i g n s h o u l d a c c o u n t f o r t h e e x p e c t e d e a r t h q u a k e l o a d s . S i m i l a r l y , e x t e r n a l l o a d s due to w ind p r e s s u r e , i c e l o a d , e t c . have t o be c o n s i d e r e d w h e r e v e r a p p l i c a b l e . T h e d a t a r e q u i r e d f o r s u c h c o n s i d e r a t i o n s m a y b e o b t a i n e d t h r o u g h t h e l o c a l m e t e o r o l o g i c a l c e n t r e s . T r a n s i e n t l o a d s due t o t e m p e r a t u r e v a r i a t i o n s o f t e n c a l l f o r t h e p r o v i s i o n of a d d i t i o n a l s a f e t y f a c t o r s . In e v a l u a t i n g t h e r m a l s t r e s s e s , i n d e t e r m i n a t e s s u c h a s t h e a c t u a l t e m p e r a t u r e g r a d i e n t s , t h e e f f e c t of t h e r m a l e x p a n s i o n , t h e m a g n i t u d e of s e c o n d a r y s t r e s s e s d e -v e l o p e d in w a l l s due t o r e s t r a i n t s , h a v e to b e c o n s i d e r e d .

T h e s t r e s s e s t o b e c o n s i d e r e d a r e t h e p r i m a r y s t r e s s e s d e v e l o p e d by t h e i m p o s e d l o a d i n g and t h e s e c o n d a r y s t r e s s e s d e v e l o p e d due t o t h e c o n -s t r a i n t s of a s t r u c t u r e . S o m e n a t i o n a l c o d e s s t i p u l a t e t h a t a d e t a i l e d s t r e s s a n a l y s i s of s t r u c t u r a l c o m p o n e n t s h a s t o be c a r r i e d ou t in o r d e r t o e n s u r e t h a t t h e i n d u c e d s t r e s s e s do not e x c e e d t h e a l l o w a b l e l i m i t s . In c a s e s w h e r e c o d e s and s t a n d a r d s do not c a l l f o r a r i g o r o u s s t r e s s a n a l y s i s , t h e d e s i g n e r h a s t o u s e h i s j u d g e m e n t f o r c a r r y i n g out s t r e s s a n a l y s i s f o r a l l c r i t i c a l c o m p o n e n t s b a s e d on t h e r e q u i r e m e n t s of t h e s e r v i c e c o n d i t i o n s .

4 . 2. 1. S t e e l t a n k s

C y l i n d r i c a l t y p e s of t a n k s u s e d f o r s t o r i n g h i g h e r - l e v e l r a d i o a c t i v e w a s t e s p o s s e s s g r e a t e r s t r u c t u r a l s t r e n g t h . T h e s t r e s s e s t h a t m a y o c c u r i n t h e s h e l l a n d w h i c h h a v e t o b e d e t e r m i n e d a r e t h e l o n g i t u d i n a l and c i r c u m -f e r e n t i a l s t r e s s e s . T h e s t r e s s f r o m s u p e r i m p o s e d l o a d s s h o u l d a l s o b e c o n s i d e r e d .

L o n g i t u d i n a l a n d c i r c u m f e r e n t i a l s t r e s s e s m a y b.e c a u s e d by h y d r o s t a t i c l o a d , i n t e r n a l v a p o u r p r e s s u r e , e x t e r n a l l o a d s and t h e r m a l g r a d i e n t s . A p a r t f r o m t h e s e , s t r e s s e s a t t h e k n u c k l e p l a t e s and s h e l l - h e a d j u n c t i o n s h o u l d

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b e d e t e r m i n e d . F o r l a r g e - s i z e t a n k s , s t r e s s e s a t t h e k n u c k l e p l a t e s c a n b e q u i t e h igh . S u p p o r t s and o p e n i n g s m a y i m p o s e d e t r i m e n t a l l o a d i n g . M e t h o d s f o r e v a l u a t i n g s t r e s s e s i n d u c e d i n t h e s h e l l by t h e s u p p o r t s a r e i n d i c a t e d by B r o w n e l l and Young (Ref . [ 3 ] , p . 203).

In d e a l i n g wi th s i t u a t i o n s w h e r e d e s i g n u n c e r t a i n t i e s e x i s t i t m a y b e d i f f i c u l t t o d e c i d e t h e s a f e t y f a c t o r t o b e p r o v i d e d . C o n s i d e r a t i o n s f o r a s s u m i n g r e a s o n a b l e s a f e t y f a c t o r s s h o u l d t a k e in to a c c o u n t t h e m e t h o d of d e s i g n e m p l o y e d , t h e q u a l i t y of m a t e r i a l s u s e d and t h e s t a n d a r d s f o l l o w e d f o r f a b r i c a t i o n i n c l u d i n g t h e s e r v i c e c o n d i t i o n s of t h e t a n k .

A s t h e w e l d e d j o i n t s i n t a n k s a r e m o r e s u s c e p t i b l e t o f a i l u r e , t h e i n t e g r i t y of s u c h j o i n t s h a s t o b e e n s u r e d . W h e n e v e r p o s i t i o n w e l d i n g i s r e q u i r e d , h i g h - q u a l i t y d e s i g n and w e l d i n g a r e e s s e n t i a l . F o r c r i t i c a l s e r v i c e r e q u i r e m e n t s , a s m a y b e t h e c a s e i n c a t e g o r y - 4 w a s t e s t o r a g e , i t i s d e s i r a b l e t o c a r r y out 100% r a d i o g r a p h i c e x a m i n a t i o n of w e l d s .

T h e s a l i e n t s t r u c t u r a l d e t a i l s of a t y p i c a l h o r i z o n t a l s t e e l t a n k f o r a v o l u m e of 1500 m 3 of c a t e g o r y - 2 l i q u i d w a s t e s a s s o c i a t e d w i t h a p o w e r r e a c t o r i n s t a l l a t i o n a r e s h o w n i n F i g . 4 .

4. 2. 2. C o n c r e t e t a n k s

B a r e c o n c r e t e t a n k s a r e not g e n e r a l l y u s e d f o r s t o r i n g r a d i o a c t i v e w a s t e s , a s l e a k - t i g h t n e s s and c o r r o s i o n r e s i s t a n c e c a n n o t b e a s s u r e d . C o n c r e t e t a n k s a r e i n v a r i a b l y l i n e d w i t h s u i t a b l e m a t e r i a l s f o r p r e v e n t i n g a l e a k p a t h .

R e i n f o r c e d c o n c r e t e t a n k d e s i g n t a k e s i n to a c c o u n t t h e f a c t t h a t t e n s i o n c r a c k s w i l l d e v e l o p . T h e r e i n f o r c i n g s t e e l c o n t r o l s t h e s i z e of t h e c r a c k s w h i l e t h e s t r u c t u r e i s u n d e r t e n s i o n .

A p a r t f r o m t h e s t r e s s e s due t o t h e i m p o s e d l o a d i n g , s t r e s s e s t h a t a r e i n d u c e d in c o n c r e t e p r o d u c e ' s h r i n k a g e c r a c k s ' . T h e c o n c r e t e s h r i n k s a g a i n s t t h e a c t i o n of s t e e l d u r i n g t h e c u r i n g p e r i o d . Bu t i n c o u r s e of t i m e t h e p l a s t i c f low e l i m i n a t e s t h i s s t r e s s .

C y l i n d r i c a l t a n k s , t h o u g h i n v o l v i n g m o r e c u m b e r s o m e f o r m - w o r k , a r e a d v a n t a g e o u s a s c o m p a r e d to r e c t a n g u l a r t a n k s , a s r e g a r d s b o t h t he s t r u c t u r e a n d t h e m a t e r i a l e c o n o m y . A s t h e c o n c r e t e w a l l s a r e r i g i d , b o t h t h e r i n g t e n s i o n and t h e v e r t i c a l b e a m a c t i o n u n d e r h y d r o s t a t i c h e a d h a v e to b e c o n -s i d e r e d . T h e d i m e n s i o n s of t h e t a n k and t h e t y p e s of r e s t r a i n t s a t t h e e d g e s d e t e r m i n e t he p r o p o r t i o n of t h e l o a d r e s i s t e d by r i n g t e n s i o n and b e a m a c t i o n . W h e n t h e w a l l c a n n o t d e f l e c t f r e e l y u n d e r t h e l o a d , t h e m a x i m u m r i n g t e n s i o n i s f o u n d to o c c u r no t a t t h e po in t of m a x i m u m h y d r o s t a t i c p r e s s u r e b u t a t s o m e p o i n t a b o v e t h i s [ 5 ] . T h e c i r c u m f e r e n t i a l s t r e s s e s a r e c a u s e d by t h e i n t e r n a l h y d r o s t a t i c p r e s s u r e , e a r t h p r e s s u r e , e x t e r n a l w a t e r p r e s s u r e , and t h e s u r c h a r g e f r o m e q u i p m e n t u s e d d u r i n g c o n s t r u c t i o n a n d a l s o t h e r m a l s t r e s s e s , if a n y . T h e v e r t i c a l s t r e s s e s a r e due t o t h e r o o f l o a d , w a l l b e n d i n g m o m e n t , t e m p e r a t u r e g r a d i e n t , e t c . T h e w e i g h t of t h e l i q u i d i s c a r r i e d t h r o u g h t h e f l o o r s l a b t o t h e s u b g r a d e . T h e l i q u i d l o a d d o e s not c a u s e b e n d i n g of t h e s l a b if t h e s u b g r a d e i s q u i t e f i r m . R e i n -f o r c e m e n t s h a v e t o b e p r o v i d e d a g a i n s t any s e t t l e m e n t of s o i l c a u s i n g b e n d i n g of t h e s l a b . If h y d r o s t a t i c p r e s s u r e due t o g r o u n d - w a t e r i s e x -p e c t e d , t h e b a s e s l a b h a s to b e d e s i g n e d t o w i t h s t a n d t h i s u n i f o r m u p w a r d p r e s s u r e w h e n t h e t a n k i s e m p t y . A n e l l i p s o i d a l d o m e i s a good s h a p e t o r e s i s t e a r t h l oad a n d i n t e r n a l v a p o u r p r e s s u r e . It a l s o r e d u c e s t h e a m o u n t

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W E L D I N G D E T A I L S FOR

M A N - H O L E

T Y P I C A L W E L D I N G

D E T A I L S FOR N O Z Z L E S

\ 7 \ * y ^ / / / / / / / / / f y V / / / / / / ^

W E L D I N G D E T A I L S FOR V E R T I C A L A N D H O R I Z O N T A L

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BE m : SECTION A-A

a l l d i m e n s i o n s i n mm

FIG-4. Structural details of a steel tank to hold category-2 liquid waste, Rajasthan Atomic Power Plant.

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of e x c a v a t i o n and a v o i d s t h e u s e of a h e a v y d o m e r i n g , a s i s n e c e s s a r y i n t h e c a s e of a s e g m e n t a l s p h e r i c a l s h a p e .

T h e d e s i g n of r e c t a n g u l a r r e i n f o r c e d c o n c r e t e t a n k s i s g e n e r a l l y b a s e d on s i m i l a r c o n s i d e r a t i o n s a s d i s c u s s e d f o r c y l i n d r i c a l t a n k s . H o w e v e r , t h e u n c e r t a i n t y i n e v a l u a t i n g r e s t r a i n t s a t c o r n e r s and t h e r m a l s t r e s s e s p o s e d e s i g n p r o b l e m s . T h e r e f o r e , r e c t a n g u l a r t a n k s a r e not r e c o m m e n d e d f o r u s e i n c r i t i c a l s e r v i c e .

In g e n e r a l , t h e d e s i g n of c o n c r e t e s t r u c t u r e s i s o f t e n c o m p l i c a t e d s i n c e t h e s t r e s s e s d e v e l o p e d i n t h e s t r u c t u r e a r e not n e c e s s a r i l y d i r e c t l y p r o -p o r t i o n a l t o t h e l o a d . T h e p r o b l e m s h a v e t o b e s o l v e d by t r i a l and e r r o r m e t h o d s . H o w e v e r , a r o u g h a p p r o x i m a t i o n c a n b e m a d e by s i m p l i f i e d a s s u m p t i o n s .

T h e s t r u c t u r a l d e t a i l s of a t y p i c a l u n d e r g r o u n d r e i n f o r c e d c o n c r e t e t a n k w i t h a m e t a l l i n e r u s e d f o r c o l l e c t i n g c a t e g o r y - 3 w a s t e s f r o m a r e s e a r c h r e a c t o r a r e s h o w n in F i g . 5.

4 . 2 . 3 . P r e s t r e s s e d c o n c r e t e t a n k s [6 ]

C r i t i c a l d e s i g n s f o r p r e s t r e s s e d c o n c r e t e t a n k s a r e g e n e r a l l y b a s e d o n m o d e l t e s t i n g a n d s t u d i e s on p r o t o t y p e s t r u c t u r e s . T h e p r i n c i p l e i n -v o l v e d i n t h e d e s i g n of p r e s t r e s s e d c o n c r e t e s t r u c t u r e s i s t h a t t h e p r e -s t r e s s i n g p e r m i t s t h e c o n c r e t e t o b e u s e d a s a t e n s i o n m e m b e r w h i l e m a i n -t a i n i n g t h e c o n c r e t e i t s e l f u n d e r c o m p r e s s i o n . T h e t e n s i o n - l o a d e d s t e e l i s e f f i c i e n t l y u t i l i z e d and t e n s i l e c r a c k s i n c o n c r e t e a r e v i r t u a l l y e l i m i n a t e d .

T h e a d v a n t a g e s of u s i n g p r e s t r e s s e d c o n c r e t e m a y b e s u m m a r i z e d a s f o l l o w s :

D u c t i l e m o d e of f a i l u r e a n d r e s e a l i n g c a p a c i t y of t h e s t r u c t u r e U n d e r l o a d i n g c o n d i t i o n s , t h e e f f e c t i v e s t r e s s on t h e c o n c r e t e i s kep t ! a t a m i n i m u m and h e n c e d e f o r m a t i o n c a n b e r e d u c e d C a b l e r e p l a c e m e n t a n d r e s t r e s s i n g a r e e a s y S u b s t a n t i a l s a v i n g s i n c o s t a r e p o s s i b l e f o r l a r g e s t r u c t u r e s .

H o w e v e r , f o r p r e s t r e s s e d c o n c r e t e t a n k s t h e d e s i g n h a s to t a k e i n to a c c o u n t t h e f o l l o w i n g :

(a) E f f e c t s of t e m p e r a t u r e t r a n s i e n t s , if any (b) S t r e s s c o n c e n t r a t i o n due t o b u n c h i n g of c a b l e s a t p e n e t r a t i o n s (c) N e c e s s i t y of s p e c i a l p r o t e c t i o n f o r h i g h - t e n s i l e s t e e l c a b l e s i m -

m e d i a t e l y a f t e r t e n s i o n i n g s o t h a t s t r e s s c o r r o s i o n i s a v o i d e d . In p l a c e s l i a b l e t o s t r e s s c o r r o s i o n , t h e u s e of c o l d - d r a w n h i g h -t e n s i l e s t e e l w i r e s i s r e c o m m e n d e d .

In v i e w of t h e i n h e r e n t a d v a n t a g e s w i t h r e s p e c t to c o s t and s t r u c t u r a l i n t e g r i t y , p r e s t r e s s e d c o n c r e t e s t r u c t u r e s a r e b e i n g u s e d f o r s t o r i n g n o n -h e a t i n g r a d i o a c t i v e l i q u i d w a s t e s , d e s p i t e t h e d i s a d v a n t a g e s m e n t i o n e d a b o v e .

F i g u r e 6 g i v e s t h e d e t a i l s of a t y p i c a l p r e s t r e s s e d c o n c r e t e t a n k u s e d f o r s t o r i n g l o w - l e v e l r a d i o a c t i v e w a s t e s o l u t i o n s [ 7 ] ,

(a) (b)

(c) ( d )

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FIG. 5. Structural details of an underground reinforced concrete tank with a metal liner for category-3 wastes, Bhabha Atomic Research Centre.

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DOME L I V E L O A D = SO l b / f t '

. 4 ) O N E - I N C H - D I A M E T E R T Y P E "P" RODS

^ G R A D I E N T 1 5 °

2f t 9 in. E A R T H S H I E L D I N G

(MAXIMUM WATER T A B L E : 230.0)

FIG. 6 . Details of a prestressed concrete tank used for storing low- leve l radioactive waste at Savannah River Plant.

4. 2. 4. S t e e l l i n e r s f o r c o n c r e t e t a n k s

Bo th r e i n f o r c e d c o n c r e t e a n d p r e s t r e s s e d c o n c r e t e t a n k s a r e g e n e r a l l y p r o v i d e d w i t h a m e t a l l i n e r w h i c h i s c o m p a t i b l e w i t h t h e w a s t e t o b e s t o r e d . T h e l i n e r c a n b e u s e d a s a n i n s i d e f o r m f o r t h e c o n c r e t e .

D e s i g n and c o n s t r u c t i o n p r o c e d u r e s to b e f o l l o w e d f o r l i n e r s a r e b a s i -c a l l y s i m i l a r t o t h o s e a d o p t e d f o r s t e e l t a n k s .

It i s t h e u s u a l p r a c t i c e t o c h o o s e t h e t h i c k n e s s of t h e l i n e r o n t h e b a s i s of t h e c o r r o s i o n c h a r a c t e r i s t i c s of t h e w a s t e s t o r e d a n d a l s o t a k i n g in to a c c o u n t t h e d i f f e r e n t t y p e s of l o a d s i m p o s e d on t h e l i n e r .

T h e l o a d s t o b e c o n s i d e r e d a r e [ 8 ] :

(a) H y d r o s t a t i c l o a d d u r i n g t e s t (b) E x t e r n a l l o a d f r o m t h e c o n c r e t e , if t h e l i n e r i s u s e d a s a n i n s i d e

f o r m d u r i n g c o n s t r u c t i o n (c) S h r i n k a g e s t r e s s t r a n s f e r r e d f r o m t h e c o n c r e t e c a u s i n g c i r c u m -

f e r e n t i a l c o m p r e s s i o n (d) C i r c u m f e r e n t i a l c o m p r e s s i o n due t o p r e s t r e s s i n g , if a n y .

T h e l i n e r i s a n c h o r e d t o t h e c o n c r e t e by p r o v i d i n g h o l d f a s t s a t r e g u l a r i n t e r v a l s . T h e b u c k l i n g s t r e n g t h of e a c h s e c t i o n of t h e l i n e r s h o u l d b e e v a l u a t e d a n d c o m p a r e d w i t h t h e i m p o s e d l o a d on t h a t s e c t i o n . Y i e l d i n g of t h e l i n e r u n d e r c o m p r e s s i v e s t r e s s m a y not p o s e p r o b l e m s , a s l o c a l a d j u s t m e n t w i t h i n t h e s e c t i o n i s p o s s i b l e .

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4. 3. C o n s t r u c t i o n

4 . 3 . 1 . S t e e l t a n k s

W i t h i n c r e a s i n g s t r u c t u r e d i m e n s i o n s a n d w e i g h t , a c o m b i n e d f a b r i c a t i o n i n s h o p and f i e l d a p p e a r s t o b e a d v a n t a g e o u s . In s u c h a c a s e , t h e s i t e s h o u l d h a v e f a c i l i t i e s f o r w e l d i n g , m a c h i n i n g , s t r e s s - r e l i e v i n g , i n s p e c t i o n , e t c . T h e m a t e r i a l s u s e d s h o u l d b e p r o p e r l y i d e n t i f i e d w i t h t h e n e c e s s a r y m i l l -t e s t r e p o r t s and c o d e d m a r k i n g s t o e n a b l e p r o p e r m a t e r i a l s e l e c t i o n and s i t e a s s e m b l y . A s f a b r i c a t i o n p r o g r e s s e s , t h e e d g e s of p l a t e s , o p e n i n g s a n d f i t t i n g s h a v e t o b e c a r e f u l l y e x a m i n e d f o r l a m i n a t i o n s , c r a c k s o r s i m i l a r f l a w s . It i s q u i t e p o s s i b l e t h a t t h e i n s p e c t i o n of w e l d s m a y not r e v e a l s o m e of the< r o o t - s u r f a c e d e f e c t s , and t h e r e f o r e t h e w e l d i n g p r o c e d u r e s f o l l o w e d f o r t h e f a b r i c a t i o n s h o u l d b e c l e a r l y s p e c i f i e d t o avo id s u c h d e f e c t s . T h e b e s t m e t h o d t o g u a r d a g a i n s t e f f e c t s of co ld w o r k and r e s i d u a l s t r e s s e s i n h e a t - a f f e c t e d a r e a s i s s t r e s s - r e l i e v i n g by h e a t t r e a t m e n t . If t h e s t a i n l e s s s t e e l u s e d i s not s t a b i l i z e d , c o r r o s i o n in t h e - w e l d - a f f e c t e d a r e a s of t h e t a n k i s p o s s i b l e due t o c a r b i d e p r e c i p i t a t i o n and d e p l e t i o n of c h r o m i u m . H e a t t r e a t m e n t i s t h e c o m m o n l y a c c e p t e d p r a c t i c e t o r e s t o r e c h r o m i u m b a c k t o t h e i m p o v e r i s h e d z o n e s .

4. 3. 2. C o n c r e t e t a n k s

F o r t h e p r e p a r a t i o n of a good c o n c r e t e - m i x it. i s n e c e s s a r y t o f i nd out t h e p r o p e r p r o p o r t i o n s of t h e i n g r e d i e n t s t o e n s u r e a w o r k a b l e , d e n s e and s t r o n g c o n c r e t e . No u n i f o r m p r o c e d u r e c a n b e l a i d down b e c a u s e of t h e l a r g e n u m b e r of v a r i a b l e s i n v o l v e d . T h e q u a l i t y c o n t r o l p r o c e d u r e s a d o p t e d f o r m a t e r i a l , m i x a n d c o n s t r u c t i o n m u s t b e v e r y r i g o r o u s t o e n s u r e t h e s t r u c t u r a l i n t e g r i t y of t h e t a n k s .

T h e m e t h o d s e m p l o y e d f o r t h e c o n s t r u c t i o n of c o n c r e t e t a n k s h a v e a m a r k e d e f f e c t on t h e i n t e g r i t y of t h e s t r u c t u r e . It i s e s s e n t i a l t o c l e a r l y s p e c i f y all- c o n s t r u c t i o n p r o c e d u r e s in o r d e r t o e n s u r e h o m o g e n e i t y of t h e s t r u c t u r e . P r o p e r p l a c e m e n t , c o m p a c t i o n and f o r m a t i o n of j o i n t s a r e s o m e of t h e m o s t i m p o r t a n t r e q u i r e m e n t s . I n t h e c a s e of l a r g e - c a p a c i t y t a n k s , w h e r e m o n o l i t h i c p o u r m a y b e d i f f i c u l t , it i s n e c e s s a r y t o c a r e f u l l y p r e -p a r e t h e c o n c r e t e s u r f a c e s b e f o r e s u c c e s s i v e p o u r s to e n s u r e good c o n -s t r u c t i o n j o i n t s .

4. 4. I n s p e c t i o n and t e s t i n g

4 . 4. 1.- T e s t i n g of r a w m a t e r i a l s

I n h e r e n t d e f e c t s i n t h e r a w m a t e r i a l a n d d e f e c t s i n t r o d u c e d d u r i n g t r a n s p o r t , s t o r a g e and f a b r i c a t i o n m a y c a u s e f a i l u r e c o n d i t i o n s . V a r i a t i o n s i n t h e q u a l i t y of r a w m a t e r i a l s u sed : g ive r i s e t o s o m e u n c e r t a i n t i e s i n p r e d i c t i n g t h e p e r f o r m a n c e of t a n k s t r u c t u r e s u n d e r s e r v i c e . R i g o r o u s i n s p e c t i o n f o r f l a w d e t e c t i o n , d e t e r m i n a t i o n of t h e c h e m i c a l c o n s t i t u e n t s a n d p r o p e r h a n d l i n g of t h e m a t e r i a l d u r i n g t r a n s p o r t and s t o r a g e a r e s o m e of t h e r e q u i r e m e n t s f o r a v o i d i n g t a n k f a i l u r e due t o m a t e r i a l d e f e c t s ;

S o m e of t h e c o m m o n t e s t s r e c o m m e n d e d f o r d i f f e r e n t c o n s t r u c t i o n m a t e r i a l s a r e a s f o l l o w s :

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S t e e l p l a t e s and s t r u c t u r a l s : v i s u a l i n s p e c t i o n , r a d i o g r a p h y , m a g n e t i c p a r t i c l e and s o n i c t e c h n i q u e s , l i q u i d p e n e t r a n t t e s t s , e t c .

C e m e n t : t e s t f o r s o u n d n e s s , s e t t i n g t i m e , t e n s i l e s t r e n g t h and c o m p r e s s i v e s t r e n g t h .

Sand : a n a l y s i s f o r d e l e t e r i o u s m a t e r i a l s , s i e v e a n a l y s i s and vo id t e s t . A g g r e g a t e : t e s t s f o r d e l e t e r i o u s m a t e r i a l s , p h y s i c a l p r o p e r t i e s a n d a l k a l i

r e a c t i v i t y . C o n c r e t e : c o n s i s t e n c y t e s t , c o m p r e s s i o n a n d e x p a n s i o n t e s t s , e s t i m a t i o n

of w a t e r / c e m e n t r a t i o and t e s t f o r s e t t i n g s h r i n k a g e . R e i n f o r c i n g and p r e s t r e s s i n g c a b l e s : v i s u a l i n s p e c t i o n , d e t e r m i n a t i o n

of y i e l d and u l t i m a t e s t r e n g t h and c r e e p t e s t .

4 . 4. 2. T e s t i n g of s t e e l t a n k s

A h y d r o s t a t i c t e s t c a n b e done on t a n k s w h i c h a r e s u p p o r t e d o r a n c h o r e d s a f e l y . T h e c o r r o s i o n a l l o w a n c e p r o v i d e d h a s to b e t a k e n in to a c c o u n t f o r a r r i v i n g a t t he t e s t p r e s s u r e . T h e p r e s s u r e - h o l d i n g t i m e s h o u l d b e s u f f i -c i e n t t o e n a b l e i n s p e c t i o n f o r l e a k a g e of a l l t h e p a r t s .

A l m o s t a l l t h e t e s t s s p e c i f i e d f o r t h e i n s p e c t i o n of s t e e l p l a t e s and s t r u c t u r a l s a r e g e n e r a l l y a p p l i c a b l e f o r t he i n s p e c t i o n of w e l d s .

4. 4. 3. T e s t i n g of c o n c r e t e t a n k s

C o n c r e t e t a n k s a r e t e s t e d f o r l e a k a g e by f i l l i n g t h e m w i t h w a t e r to t h e d e s i r e d l e v e l . If t h e t a n k h a s a l i n e r , t h i s h a s t o b e t e s t e d h y d r o s t a t i -c a l l y b e f o r e t h e c o n c r e t e f o r m s a r e p l a c e d i n p o s i t i o n .

5. DESIGN O F A C C E S S O R I E S F O R W A S T E S T O R A G E TANKS

5 . 1 . G e n e r a l

T o f a c i l i t a t e t h e p r o p e r s t o r a g e and h a n d l i n g of r a d i o a c t i v e l i q u i d w a s t e s it i s e s s e n t i a l t o p r o v i d e s u i t a b l e a c c e s s o r i e s . In a c c o r d a n c e w i t h t h e v a r i o u s c o n s i d e r a t i o n s d i s c u s s e d in s e c t i o n 4, s p e c i a l f e a t u r e s h a v e to b e i n c o r p o r a t e d i n t h e d e s i g n of a c c e s s o r i e s to p r o v i d e s a f e o p e r a t i n g c o n d i t i o n s .

5. 2. T r a n s f e r s y s t e m s

T h e t r a n s f e r s y s t e m s a s s o c i a t e d wi th r a d i o a c t i v e l i qu id w a s t e s t o r a g e t a n k s e s s e n t i a l l y c o n s i s t of p i p e s , p ipe f i t t i n g s and v a l v e s . P u m p s a r e g e n e r a l l y u s e d to p r o v i d e t h e r e q u i r e d e n e r g y f o r t h e t r a n s f e r of w a s t e s . T h e d e g r e e of s a f e t y r e q u i r e d f o r t r a n s f e r s y s t e m s w i l l b e d e p e n d e n t u p o n t h e s p e c i f i c a c t i v i t y of t h e l i q u i d , t h e l o c a t i o n of t h e e q u i p m e n t and t h e p o s s i b l e o f f - s t a n d a r d o p e r a t i n g c o n d i t i o n s .

5. 2. 1. P i p e s and c o n n e c t i o n s

T h e m a t e r i a l s f o r p i p e s a n d c o n n e c t i o n s h a v e t o b e s e l e c t e d p r i m a r i l y w i t h r e g a r d to t h e c h e m i c a l n a t u r e of t h e l i q u i d to b e h a n d l e d . C o n s i d e r a -t i o n s l i k e t h o s e of m a i n t e n a n c e and d e c o n t a m i n a t i o n s h o u l d a l s o b e t a k e n

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i n to a c c o u n t . T h e u s e of c a r b o n s t e e l i s l i m i t e d i n t h e n u c l e a r i n d u s t r y , a s it e a s i l y c o r r o d e s and i t s d e c o n t a m i n a t i o n i s d i f f i c u l t . C a r b o n s t e e l m a y , h o w e v e r , b e u s e d i n t r a n s f e r s y s t e m s c a r r y i n g l o w - l e v e l r a d i o a c t i v e w a s t e s u n d e r a l k a l i n e c o n d i t i o n s , w h e r e m a i n t e n a n c e and p e r i o d i c r e p l a c e -m e n t of t h e p ip ing do not p o s e p r o b l e m s . S t a i n l e s s s t e e l i s t h e m o s t v e r -s a t i l e m a t e r i a l t h a t c a n b e u s e d f o r p ip ing s y s t e m s , p a r t i c u l a r l y for , c a s e s w h e r e l a r g e v a r i a t i o n s i n t h e c h e m i c a l c o m p o s i t i o n of w a s t e s a r e e x p e c t e d . A l s o , i t i s a d v a n t a g e o u s t o u s e s t a i n l e s s s t e e l b e c a u s e t h e n e e d f o r m a i n -t e n a n c e i s r e d u c e d and d e c o n t a m i n a t i o n i s e a s i e r . B e c a u s e of t h e i r c o r r o -s i o n - r e s i s t a n c e p r o p e r t i e s c o p p e r p i p e s a r e c o m m o n l y u s e d in t h e f o r m of e m b e d d e d p ip ing f o r t r a n s f e r r i n g l o w - l e v e l r a d i o a c t i v e w a s t e s . P o l y e t h y l e n e i s c h e a p , l i g h t , f l e x i b l e a n d c h e m i c a l l y i n e r t and i t i s t h e r e f o r e a n i d e a l m a t e r i a l f o r d r a i n p i p e s c a r r y i n g l a b o r a t o r y w a s t e s . U n p l a s t i c i z e d p o l y v i n y l c h l o r i d e (PVC) , w h i c h i s t h e m o s t r i g i d v a r i e t y , i s c o m m o n l y u s e d f o r r a d i o a c t i v e w a s t e p i p i n g , p r o v i d e d t h e r e c o m m e n d e d t e m p e r a t u r e l i m i t s a r e not e x c e e d e d . P V C i s r e s i s t a n t t o c h e m i c a l a c t i o n and i t c a n b e e a s i l y d e c o n t a m i n a t e d .

T h e p i p e f i t t i n g s s h o u l d . b e s u i t a b l e t o f o r m p e r f e c t l y l e a k - t i g h t j o i n t s . It i s p r e f e r a b l e t o u s e a l l - w e l d e d f i t t i n g s f o r p i p e s c a r r y i n g r a d i o a c t i v e w a s t e s . F l a n g e d f i t t i n g s a r e u s e d f o r e q u i p m e n t c o n n e c t i o n s a n d on p i p e s e c t i o n s w h i c h r e q u i r e d i s m a n t l i n g . F l a n g e d c o n n e c t i o n s s h o u l d b e kep t to t h e m i n i m u m and t h r e a d e d c o n n e c t i o n s h a v e t o b e a v o i d e d , e x c e p t in t h e c a s e of v e r y l o w - l e v e l r a d i o a c t i v e w a s t e s .

5. 2. 2. V a l v e s

T h e v a l v e s u s e d f o r r a d i o a c t i v e s e r v i c e a r e g e n e r a l l y a d a p t a t i o n s of t h e s t a n d a r d v a l v e s u s e d in c h e m i c a l p l a n t s . T h e s e s p e c i a l a d a p t a t i o n s a r e f o r t h e p u r p o s e of p r e c l u d i n g t h e p o s s i b i l i t y of t r a p p i n g r a d i o a c t i v e m a t e r i a l s i n t h e body of t h e v a l v e and t o f a c i l i t a t e r e m o t e o p e r a t i o n , w h e r e v e r r e q u i r e d .

T h e g a t e - v a l v e i s m a i n l y u s e d a s a n o n - o f f d i s t r i b u t i o n v a l v e b e c a u s e i t d o e s not p e r m i t e a s y c o n t r o l of f low. T h e g a t e - v a l v e p r o v i d e s a c l e a r , u n r e s t r i c t e d f l o w - o p e n i n g , r e s u l t i n g i n a v e r y low p r e s s u r e d r o p . It i s n o r m a l l y u s e d on l a r g e - s i z e p i p e s c a r r y i n g w a s t e s wi th low s u s p e n d e d s o l i d s . T h e g l o b e - v a l v e i s u s e d f o r c o a r s e t h r o t t l i n g s e r v i c e i n t h e c a s e of w a s t e s c o n t a i n i n g low s o l i d s . T h e b a l l - v a l v e i s a q u i c k - o p e n i n g v a l v e ' w h i c h c a n b e u s e d a s a n o n - o f f d i s t r i b u t i o n v a l v e i n p i p e s hand l ing w a s t e s c o n t a i n i n g v e r y low s u s p e n d e d s o l i d s and s l u d g e s . T h e b u t t e r f l y - v a l v e i s w i d e l y u s e d i n l a r g e - s i z e d r a d i o a c t i v e w a s t e p i p i n g b e c a u s e of i t s e c o n o m i c d e s i g n and e a s e of r e m o t e o p e r a t i o n . H o w e v e r , t h i s v a l v e c a n n o t c o n t r o l t h e f l ow a c c u r a t e l y . T h e d i a p h r a g m - v a l v e i s u s e d in r a d i o a c t i v e w a s t e s y s t e m s f o r f l ow c o n t r o l b e c a u s e t h e r e i s no l e a k a g e a t t h e v a l v e s t e m . It c a n a l s o b e u s e d i n p i p e - l i n e s c a r r y i n g s l u r r i e s .

A d i v e r s i o n box (F ig . 7) i s c o m m o n l y u s e d i n t r a n s f e r s y s t e m s f o r h a n d l i n g c a t e g o r y - 4 w a s t e s . It c o n s i s t s of a r e c t a n g u l a r c o n c r e t e box w i t h r e m o v a b l e c o v e r s . A t y p i c a l d i v e r s i o n box h a s a n u m b e r of l i n e s e n t e r i n g t h r o u g h o n e f a c e of t h e box w i t h n o z z l e s on t h e i n s i d e f a c e . O n t h e o p p o s i t e f a c e , a n u m b e r of n o z z l e s a r e l o c a t e d l e a d i n g t h r o u g h t h e w a l l of t h e box to v a r i o u s t a n k s . T h e n o z z l e s on t h e o p p o s i t e f a c e s of t h e b o x c a n b e c o n n e c t e d t o p r o v i d e d i f f e r e n t r o u t i n g s by j u m p e r s ( r i g i d s e c t i o n s of p i p e s t e r m i n a t e d in c o n n e c t o r s ) w h e n w a s t e t r a n s f e r t o a s p e c i f i c t a n k

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W A S T E PIPING FROM REPROCESSING PLANT

FIG. 7. Typical diversion box used in transfer systems for handling high-level radioactive liquid wastes.

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i s r e q u i r e d , o r t h e y c a n b e b l a n k e d off w h e n not in u s e . T h e box s h o u l d c o n t a i n a s u m p o r a n o v e r f l o w l e a d i n g to a c a t c h t a n k f r o m w h i c h i t c a n b e r e t u r n e d to a s t o r a g e t a n k by m e a n s of a s u i t a b l e j u m p e r c o n n e c t i o n .

5. 2. 3. P u m p s

T h e i d e a l m e t h o d of e f f e c t i n g r a d i o a c t i v e l i qu id t r a n s f e r i s by g r a v i t y f l ow. S i n c e t h i s m e t h o d i s not a l w a y s p r a c t i c a b l e , p u m p s a r e u s e d to p r o v i d e t h e m o t i v e f o r c e f o r t r a n s f e r r i n g l i q u i d s . T h e c h a r a c t e r i s t i c s of p u m p s s h o u l d s a t i s f y t h e p r o c e s s r e q u i r e m e n t s . T h e t h e o r y and c o m p l e t e d e t a i l s of d e s i g n , s e l e c t i o n a n d p e r f o r m a n c e of p u m p s c a n b e found in R e f s [ 9 , 1 0 ] .

N u m e r o u s t y p e s of p u m p s a r e be ing u s e d f o r h a n d l i n g r a d i o a c t i v e l i q u i d s . A f ew of t h e m o s t c o m m o n l y u s e d t y p e s a r e d i s c u s s e d b e l o w .

P o s i t i v e d i s p l a c e m e n t p u m p s a r e not g e n e r a l l y u s e d f o r t r a n s f e r r i n g r a d i o a c t i v e l i q u i d w a s t e s , s i n c e t h e f low i s not u n i f o r m and t h e m a i n t e n a n c e p o s e s p r o b l e m s . In c e r t a i n c a s e s , d i a p h r a g m p u m p s c a n b e u s e d , p a r t i c u -l a r l y f o r s l u r r i e s . T h e s e p u m p s c a n b e e a s i l y pu t i n to s e r v i c e and m a i n -t a i n e d . C e n t r i f u g a l p u m p s g ive e x c e l l e n t s e r v i c e w h e r e f l o o d e d s u c t i o n c o n d i t i o n s a r e a v a i l a b l e . S e l f - p r i m i n g p u m p s c a n b e u s e d wi th a d v a n t a g e i n l o w - a c t i v i t y w a s t e s e r v i c e w h e r e f l o o d e d s u c t i o n c o n d i t i o n s c a n n o t b e p r o v i d e d .

T h e p u m p b e s t s u i t e d f o r hand l ing h i g h e r - l e v e l r a d i o a c t i v e w a s t e s i s a c o m p l e t e l y s u b m e r s i b l e p u m p . A s s u c h p u m p s m a y not b e c o m m o n l y a v a i l a b l e , a r e a s o n a b l e a l t e r n a t i v e i s a s u b m e r g e d p u m p , p o w e r e d by a m o t o r w h i c h i s i n s t a l l e d o u t s i d e t h e t a n k . A v e r t i c a l s u b m e r s i b l e r e g e n e r -a t i v e t u r b i n e p u m p c a n d e v e l o p m u c h h i g h e r h e a d s t h a n a c e n t r i f u g a l p u m p and i s g e n e r a l l y u s e d f o r p u m p i n g s m a l l q u a n t i t i e s of l i q u i d s . D e e p - w e l l t u r b i n e p u m p s a r e u s e d f o r t r a n s f e r r i n g s o l u t i o n s a t h i g h f l ow r a t e s . T h e y a r e c o m m o n l y u s e d f o r t r a n s f e r o p e r a t i o n s f r o m d e e p u n d e r g r o u n d t a n k s .

E j e c t o r s a r e i n c r e a s i n g l y b e i n g u s e d f o r t r a n s f e r r i n g h i g h e r - l e v e l w a s t e s f r o m s t o r a g e t a n k s , a s m a i n t e n a n c e and l e a k a g e p r o b l e m s a r e m i n i -m i z e d d u e t o t h e a b s e n c e of m o v i n g p a r t s . T h e y a r e of s t a n d a r d t y p e s u s i n g s t e a m , a i r o r w a t e r a s m o t i v e f l u i d s . D e s i g n da t a and g e n e r a l c h a r a c t e r -i s t i c s of e j e c t o r s c a n b e o b t a i n e d f r o m m a n u f a c t u r e r s and h a n d b o o k s ( s e e R e f . [ 1 1 ] ) .

I n p u m p i n g i n s t a l l a t i o n s i t m a y b e n e c e s s a r y t o u s e c o n t r o l s y s t e m s . S o m e s u c h c o n t r o l s a r e :

(a) A u t o m a t i c p u m p t r i p i n c o n d i t i o n s l i k e low l i q u i d l e v e l i n t h e t a n k , l e a k a g e of a c t i v e l i q u i d a:nd h igh d i s c h a r g e p r e s s u r e .

(b) A u t o m a t i c p u m p s t a r t a t h igh l i qu id l e v e l i n t h e v e s s e l . T h i s s h o u l d b e c o n s i d e r e d p a r t i c u l a r l y f o r u n m a n n e d c o l l e c t i o n t a n k s a n d s u m p s to avo id o v e r f l o w i n g .

(c) A u t o m a t i c c h a n g e - o v e r of s t a n d - b y p u m p s . T h i s i s o f t e n done to r e g u l a t e w e a r and t e a r of p u m p s .

5. 2. 4. D e s i g n a n d i n s t a l l a t i o n of t r a n s f e r s y s t e m s

T h e c a l c u l a t i o n of p r e s s u r e d r o p s i n p i p e - l i n e s i s i m p o r t a n t f o r t h e s i z i n g of p i p e s and t h e s e l e c t i o n of p u m p s to p e r f o r m t h e r e q u i r e d s e r v i c e . Such c a l c u l a t i o n s a r e a l s o n e c e s s a r y f o r g r a v i t y f low p i p i n g f o r d e t e r m i n i n g t h e r e q u i r e d g r a d i e n t s and t h e p i p e d i a m e t e r s . T h e m e t h o d s f o l l o w e d f o r

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e s t i m a t i n g t h e p r e s s u r e d r o p s i n p i p e - l i n e s a r e c o n v e n t i o n a l a n d c a n b e o b t a i n e d f r o m s t a n d a r d h a n d b o o k s ( s e e R e f s . [ 1 1 , 1 2 ] , p . 3 7 7 - 9 0 , . 1 4 3 0 - 3 5 ) . T h e p i p e d i a m e t e r s f o r t r a n s f e r o p e r a t i o n s s h o u l d be s e l e c t e d t o p r o v i d e t h e m o s t e c o n o m i c a l d e s i g n , wi th m i n i m u m t o t a l c a p i t a l and o p e r a t i n g c o s t s . T h e c a p i t a l c o s t of t h e p i p e s and f i t t i n g s i s d i r e c t l y p r o p o r t i o n a l t o t h e p ipe d i a m e t e r , w h e r e a s t h e c o s t of p u m p i n g , w h i c h i s d e p e n d e n t on t h e f l ow r a t e s a n d p r e s s u r e d r o p s , i s i n v e r s e l y p r o p o r t i o n a l to t h e p i p e . d i a m e t e r . T h e e c o n o m i c p i p e d i a m e t e r c a n b e d e t e r m i n e d by o p t i m i z i n g t h e a b o v e c o s t f a c t o r s . M e t h o d s f o r o p t i m i z i n g p i p e d i a m e t e r s a r e g i v e n in R e f . [ 1 3 ] .

A p a r t f r o m c o n v e n t i o n a l d e s i g n p r a c t i c e s f o r p ip ing s y s t e m s , t h e . • f o l l o w i n g p o i n t s h a v e t o b e t a k e n in to a c c o u n t p r i o r t o d e s i g n i n g r a d i o a c t i v e w a s t e t r a n s f e r s y s t e m s :

(a) C o n t a i n m e n t of p o s s i b l e l e a k a g e s (b) S h i e l d i n g r e q u i r e m e n t s (c) P r o v i s i o n of s p a r e p ip ing a n d e m b e d m e n t s (d) P o s s i b i l i t y f o r i s o l a t i o n of a c t i v e s t r e a m s (e) F a c i l i t y f o r f l u s h i n g and d e c o n t a m i n a t i o n of p ip ing (f) E a s e of m a i n t e n a n c e and r e p l a c e m e n t s (g) P r o v i s i o n s f o r r e m o t e o p e r a t i o n (h) S a f e t y a n d e n v i r o n m e n t a l c o n t a m i n a t i o n .

T h e e x t e n t of s a f e t y p r e c a u t i o n s a p p l i e d i n t he d e s i g n of r a d i o a c t i v e w a s t e p i p i n g l a r g e l y d e p e n d s on t h e h a z a r d p o t e n t i a l of t h e w a s t e and t h e c o s t c o n s i d e r a t i o n s w h i c h v a r y f r o m s i t e t o s i t e . T h e p ip ing s y s t e m s f o r h a n d l i n g l o w - a c t i v i t y w a s t e s a r e r e l a t i v e l y s i m p l e i n d e s i g n and a r e s i m i l a r to t h e p i p i n g s y s t e m s e m p l o y e d i n c o n v e n t i o n a l c h e m i c a l p l a n t s . T h e p ip ing d e s i g n i s m o r e i n v o l v e d f o r h i g h e r - l e v e l r a d i o a c t i v e w a s t e t r a n s f e r , w h e r e e v e n m i n o r l e a k a g e s c a n b e v e r y h a z a r d o u s and the c o s t of r e c t i f i c a t i o n h igh . T h e f o l l o w i n g g e n e r a l l y a c c e p t e d m e t h o d s of i n s t a l l a t i o n a r e r e c o m m e n d e d f o r p i p i n g s y s t e m s hand l ing h i g h e r - l e v e l r a d i o a c t i v e w a s t e s :

(a) P i p e - l i n e s w i t h i n b u i l d i n g s s h o u l d b e i n s t a l l e d i n p i p e t r e n c h e s o r p i p e g a l l e r i e s w i t h p r o v i s i o n f o r s e c o n d a r y c o n t a i n m e n t .

(b) P i p i n g s y s t e m s o u t s i d e t h e b u i l d i n g shou ld b e u n d e r g r o u n d and r u n in r e i n f o r c e d c o n c r e t e t r e n c h e s l i n e d wi th a s p h a l t on t h e i n s i d e . A l t e r -n a t i v e s , l i k e c o n c e n t r i c c a r b o n s t e e l p i p e s o v e r w a s t e l i n e s a n d s t e e l - l i n e d c o n c r e t e c o n d u i t s , c a n be u s e d w i t h d i s c r e t i o n . E x h a u s t i v e s t u d i e s on t h i s s u b j e c t h a v e b e e n c a r r i e d out a t H a n f o r d [ 1 4 - 1 6 ] a n d i t h a s b e e n r e c o m -m e n d e d t h a t e n c a s e m e n t s n e e d to b e p r o v i d e d only a t b u i l d i n g s a n d h e a v y t r a f f i c a r e a s ; i s o l a t e d p i p e s shou ld b e r u n i n c o n c e n t r i c p i p e s a n d t h e r e m a i n i n g p i p i n g p r o v i d e d w i t h c a t h o d i c p r o t e c t i o n . T h e s e r e c o m m e n d a t i o n s a p p e a r to m e e t t h e r e q u i r e m e n t s w i t h r e s p e c t to s a f e t y and e c o n o m y and m a y b e s u i t a b l e f o r m o s t s i t e s .

(c) In g e n e r a l , p i p e - l i n e s s h o u l d b e i n s t a l l e d a t a n i n c l i n e t o f a c i l i t a t e e a s y g r a v i t y d i s c h a r g e of t h e c o n t e n t s w h e n t h e l i n e s a r e not i n u s e .

(d) T h e t r e n c h e s and o t h e r e n c a s e m e n t s f o r p i p e s s h o u l d b e s l o p e d t o w a r d s low p o i n t s l o c a t e d a t i n t e r v a l s a long t h e p i p e - l i n e s t o f a c i l i t a t e t h e c o l l e c t i o n of a c t i v e w a s t e f r o m l e a k a g e . T h e low p o i n t s s h o u l d b e p r o - , v i d e d w i t h l e a k d e t e c t o r s , s a m p l e r s a n d a r r a n g e m e n t s f o r r e m o v i n g t h e c o l l e c t e d l i q u i d .

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(e) S i n c e t h e r a d i o a c t i v i t y p r e v e n t s e a s y m a i n t e n a n c e of t he p i p e s , i t m a y b e n e c e s s a r y t o d u p l i c a t e p i p e s o r t o p r o v i d e a l t e r n a t i v e r o u t i n g s . In p a r t i c u l a r , t h e e m b e d d e d p i p e s shou ld b e d u p l i c a t e d .

(f) P i p i n g s wi th r a d i o a c t i v e l i qu id w a s t e s s h o u l d b e c l e a r l y i s o l a t e d f r o m n o n - r a d i o a c t i v e p a r t s . S e a l - p o t s s h o u l d b e i n s t a l l e d i n p i p e s w h i c h a r e r o u t e d f r o m r a d i o a c t i v e t o n o n - r a d i o a c t i v e s e c t i o n s t o p r e v e n t c r o s s -c o n t a m i n a t i o n .

(g) F l u s h i n g f a c i l i t i e s s h o u l d b e p r o v i d e d , p a r t i c u l a r l y f o r p i p e - l i n e s w h i c h c a r r y l i q u i d s w i t h s u s p e n d e d s o l i d s . T h e f l u s h i n g l i qu id s h o u l d b e t r e a t e d a s a c t i v e w a s t e .

(h) A r e g u l a r m o n i t o r i n g and i n s p e c t i o n p r o g r a m s h o u l d be l a i d down to e n s u r e p r o m p t d e t e c t i o n of l e a k a g e s .

F a i l u r e of p i p e - l i n e s c a n g e n e r a l l y b e a t t r i b u t e d t o i n e f f e c t i v e s u p p o r t s , n e g l e c t e d v i b r a t i o n and t h e r m a l e x p a n s i o n e f f e c t s , i n a c c e s s i b i l i t y of i n s i d e s u r f a c e s f o r i n s p e c t i o n , e t c . T o e n s u r e t h e i n t e g r i t y of t h e p ip ing s y s t e m s i t i s e s s e n t i a l to i n s p e c t and t e s t t h e m p e r i o d i c a l l y .

5. 3. G a s - c l e a n i n g s y s t e m s

T h e s e l e c t i o n of g a s - c l e a n i n g s y s t e m s f o r w a s t e s t o r a g e t a n k s l a r g e l y d e p e n d s u p o n t h e n a t u r e of t h e w a s t e s s t o r e d . In g e n e r a l , t h e g a s - c l e a n i n g s y s t e m s f o r t h e w a s t e s t o r a g e t a n k s c o n s i s t of d e v i c e s f o r r e m o v i n g l i q u i d d r o p l e t s a n d p a r t i c u l a t e m a t t e r . S a l i e n t d e t a i l s of s o m e of t he c o m m o n l y u s e d g a s - c l e a n i n g e q u i p m e n t a r e b r i e f l y c o v e r e d b e l o w .

5 . 3 . 1 . C y c l o n e s

C y c l o n e s a r e c o m m o n l y u s e d a s p r e c l e a n i n g d e v i c e s f o r r e m o v i n g l i q u i d d r o p l e t s e n t r a i n e d in to t h e o f f - g a s s y s t e m . In a c y c l o n e , t h e g a s t a n g e n t i a l l y e n t e r s a c y l i n d r i c a l o r c o n i c a l c h a m b e r w h e r e t h e d r o p l e t s c o l l e c t a t t h e p e r i p h e r y due to c e n t r i f u g a l a c t i o n , and t h e c l e a n g a s l e a v e s t h r o u g h a c e n t r a l o p e n i n g . A c y l i n d r i c a l c y c l o n e i s m o r e s u i t a b l e a s r e g a r d s t h e p r o b l e m of r e - e n t r a i n m e n t of t h e l i q u i d d r o p l e t s t h a t i s l i k e l y to o c c u r i n a c o n i c a l c y c l o n e ; t h e d e s i g n d e t a i l s of s u c h a c y l i n d r i c a l c y c l o n e w i t h p r o v i s i o n f o r d e - e n t r a i n m e n t a r e c o v e r e d i n R e f . [ 1 7 ] . S m a l l - d i a m e t e r c y c l o n e s a r e b e t t e r s u i t e d f o r a c h i e v i n g h igh c o l l e c t i o n e f f i c i e n c y .

5. 3. 2. S c r u b b e r s

T h e s c r u b b e r s a r e m a i n l y u s e d f o r r e m o v i n g and n e u t r a l i z i n g c o r r o s i v e v a p o u r s a n d m i s t . T h e d e s i g n of a s c r u b b e r a i m s a t e f f e c t i n g a n i n t i m a t e c o n t a c t b e t w e e n t h e s c r u b l i q u o r and t h e o f f - g a s e s . C e n t r i f u g a l s p r a y s c r u b b e r s a r e f o u n d to b e v e r y e f f e c t i v e f o r r e m o v i n g t h e c o n t a m i n a n t s [ 1 8 ] . A s t h e s c r u b b i n g l i q u i d i s g e n e r a l l y r e c i r c u l a t e d , t h e n o z z l e s in t h e s c r u b b e r s m u s t b e c a p a b l e of h a n d l i n g l i q u i d s w i t h a f a i r l y h igh s o l i d c o n c e n t r a t i o n . A l s o , t h e s c r u b l i q u o r s h o u l d b e f i l t e r e d to o v e r c o m e t h i s p r o b l e m .

5. 3. 3. D e e p - b e d f i l t e r s

A d e e p - b e d f i l t e r c o n s i s t s of a n a s s e m b l y of f i b r o u s m e d i a p a c k e d i n t h e f o r m of a b e d . M a t e r i a l s s u c h a s g l a s s , a s b e s t o s a n d t h e i r c o m b i n a t i o n s

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i n s u i t a b l e p r o p o r t i o n s a r e g e n e r a l l y u s e d . G l a s s - f i b r e f i l t e r s a r e w i d e l y e m p l o y e d i n g a s - c l e a n i n g s y s t e m s a s s o c i a t e d w i t h t a n k s b e c a u s e of t h e i r c h e m i c a l i n e r t n e s s . T h e e f f i c i e n c y of s u c h f i l t e r s d e p e n d s u p o n t h e p a c k i n g d e n s i t y , t h e t h i c k n e s s of t h e b e d , t h e m e a n f i b r e d i a m e t e r and t h e f a c e v e l o c i t y of t h e g a s . T h e d e c o n t a m i n a t i o n f a c t o r t h a t c a n b e o b t a i n e d w i t h t h e s e f i l t e r s c a n b e e v a l u a t e d by u s i n g e m p i r i c a l m e t h o d s [19 J .

5. 3. 4 . H i g h - e f f i c i e n c y f i l t e r s

F i b r o u s m a t e r i a l s a r e f o r m e d in to a l a p and p l e a t e d t o m a k e a h i g h -e f f i c i e n c y f i l t e r . T h i s t y p e of c o n s t r u c t i o n p r o v i d e s a l a r g e s u r f a c e a r e a t o t h e a i r f l o w , t h u s r e d u c i n g t h e o v e r a l l p r e s s u r e d r o p a c r o s s t h e f i l t e r . S u c h f i l t e r s , h a v i n g a c o l l e c t i o n e f f i c i e n c y of 99. 99% f o r p a r t i c l e s of 0. 3 ;um, a r e c o m m e r c i a l l y a v a i l a b l e and c a n b e u s e d i n t h e f i n a l s t a g e f o r r e m o v i n g t h e f i n e p a r t i c l e s i n t h e o f f - g a s e s . T h e s e l e c t i o n and i n s t a l l a t i o n of s u c h f i l t e r s s h o u l d b e b a s e d on t h e fo l l owing c o n s i d e r a t i o n s :

(a) T h e f i l t e r m e d i a and a l l t h e o t h e r c o m p o n e n t s of t h e f i l t e r s h o u l d b e c a p a b l e of w i t h s t a n d i n g t h e h u m i d a n d c o r r o s i v e c o n d i t i o n s e x -p e c t e d i n t h e s y s t e m

(b) T h e c a p a c i t y s h o u l d b e s u c h a s t o m e e t t h e m a x i m u m g a s f l ow d u r i n g a d v e r s e o p e r a t i n g c o n d i t i o n s

(c) T h e f i l t e r s s h o u l d b e s o m o u n t e d i n t h e f i l t e r f r a m e a s t o p r o v i d e a p e r f e c t l y l e a k - p r o o f a s s e m b l y a n d to e n a b l e e a s y r e p l a c e m e n t w i t h o u t s p r e a d of c o n t a m i n a t i o n .

5 . 4 . A g i t a t o r s

A g i t a t i o n w i l l b e n o r m a l l y r e q u i r e d i n m o s t of t h e r a d i o a c t i v e w a s t e s t o r a g e t a n k s . T h e e q u i p m e n t s u s e d f o r a g i t a t i o n i n t a n k s a r e : r e c i r c u l a t i n g p u m p s , m e c h a n i c a l a g i t a t o r s , a i r - l i f t c i r c u l a t o r s and s p a r g e r s .

5. 4. 1. R e c i r c u l a t i o n p u m p s

A g i t a t i o n by r e c i r c u l a t i o n of w a s t e s u s i n g p u m p s o r e j e c t o r s i s n o r m a l l y done i n s m a l l - c a p a c i t y t a n k s s t o r i n g c a t e g o r y - 2 and - 3 w a s t e s . T h i s i s a m e t h o d w h i c h c a n b e c o n v e n i e n t l y u s e d w h e n s i m u l t a n e o u s s a m p l i n g i s r e -q u i r e d . R e c i r c u l a t i o n of a b o u t f i v e to t e n v o l u m e s of t h e t a n k c a p a c i t y , d e p e n d i n g u p o n t h e n a t u r e of w a s t e h a n d l e d , w i l l b e n e c e s s a r y t o e n s u r e h o m o g e n e i t y of t h e w a s t e . T h e p u m p w h i c h i s u s e d f o r t r a n s f e r r i n g t h e w a s t e f r o m t h e t a n k c a n a l s o b e u t i l i z e d f o r e f f e c t i n g r e c i r c u l a t i o n . T h e c a p a c i t y of s u c h a p u m p s h o u l d p r o v i d e f o r t h e d e s i r e d m i x i n g i n a r e a s o n -a b l y s h o r t t i m e .

5. 4. 2. M e c h a n i c a l a g i t a t o r s

V a r i o u s t y p e s of m e c h a n i c a l a g i t a t o r s a r e u s e d f o r m i x i n g c a t e g o r y - 2 a n d - 3 w a s t e s . T h e m o s t c o m m o n a g i t a t o r s u s e d a r e t h e p r o p e l l e r a n d t h e t u r b i n e t y p e s .

P r o p e l l e r m i x e r s a r e i n e x p e n s i v e , s i m p l e a n d c o m p a c t . T h e m i x i n g i s e f f e c t e d by r e v o l v i n g h e l i c a l b l a d e s p r o d u c i n g a x i a l c u r r e n t s i n t h e l i q u i d . T h e e f f i c i e n c y of a p r o p e l l e r m i x e r i s m u c h d e p e n d e n t on i t s l o c a t i o n and

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t h e s h a p e of t h e t a n k . T h e a r r a n g e m e n t s h o u l d p r o v i d e s u f f i c i e n t t u r b u l e n c e . In c i r c u l a r t a n k s , t h e u s e of b a f f l e s o r e c c e n t r i c m o u n t i n g of t h e i m p e l l e r a s s e m b l y i s p r e f e r a b l e . If t h e i m p e l l e r i s m o u n t e d v e r t i c a l l y , t h e u s e of a d r a f t t u b e w i l l p r o v i d e e f f i c i e n t m i x i n g . P r o p e l l e r m i x e r s c a n b e m o u n t e d d i r e c t l y on t o t h e t a n k e i t h e r f r o m the top o r f r o m t h e s i d e . S i d e - e n t e r i n g s t i r r e r s c a n b e u s e d f o r long h o r i z o n t a l t a n k s , bu t s u c h a t e c h n i q u e g i v e s r i s e to a p o s s i b l e l e a k - p a t h f o r t h e c o n t a i n e d l i q u o r t h r o u g h t h e s t i r r e r s h a f t g l a n d . P r o p e l l e r m i x e r s a r e q u i t e e f f i c i e n t f o r s u s p e n d i n g f i n e s o l i d s of low s p e c i f i c g r a v i t y w a s t e s . T u r b i n e - t y p e a g i t a t o r s g e n e r a t e s t r o n g r a d i a l c u r r e n t s a n d a r e s i m i l a r i n c o n s t r u c t i o n t o t h e i m p e l l e r s in c e n t r i -f u g a l p u m p s . T h e y p r o v i d e e f f i c i e n t m i x i n g of w a s t e s c o n t a i n i n g s u s p e n d e d s o l i d s of h igh s p e c i f i c g r a v i t y . T h e i n i t i a l o u t l a y o n t u r b i n e m i x e r s i s h i g h e r t h a n f o r p r o p e l l e r m i x e r s . S o m e of t h e c o m m o n t y p e s of a g i t a t o r s and t h e i r m o u n t i n g d e t a i l s a r e s h o w n in F i g . 8.

r n b*y

P R O P E L L E R MIXER WITH D R A U G H T T U B E

ECCENTRICALLY M O U N T E D P R O P E L L E R M I X E R

T U R B I N E M I X E R W I T H S I D E - E N T E R I N G P R O P E L L E R MIXER T A N K B A F F L E S

FIG. 8. Common types of agitators and their mountings.

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T h e u s e of a good s t u f f i n g b o x o r m e c h a n i c a l s e a l and s t r o n g b e a r i n g s i s i m p o r t a n t . A l s o , t h e v i b r a t i o n t r a n s m i t t e d t o t h e t a n k s f r o m a g i t a t o r s m o u n t e d d i r e c t l y on t o t h e t a n k s h a s t o b e k e p t t o a m i n i m u m to av o i d s t r e s s c o r r o s i o n in t a n k s .

T h e l a c k of a c c u r a t e q u a n t i t a t i v e t e r m s to d e s c r i b e a g i t a t i o n and of t r u l y b a s i c d a t a h a s c o m p l i c a t e d t h e s e l e c t i o n of a g i t a t o r s . T h e d e s i g n of a g i t a t o r s i s g e n e r a l l y b a s e d o n e x p e r i e n c e . A good g u i d e f o r t h e s e l e c t i o n of a g i t a t o r s a n d t h e e s t i m a t i o n of p o w e r r e q u i r e m e n t s c a n b e found in s t a n d a r d l i t e r a t u r e ( s e e R e f . [ 1 1 ] , p . 1218 a n d 1 2 2 6 - 2 7 ) .

5. 4. 3. A i r - l i f t c i r c u l a t o r s and s p a r g e r s

A i r - l i f t c i r c u l a t o r s a r e i d e a l f o r u s e i n l a r g e t a n k s ho ld ing c a t e g o r y - 4 w a s t e s f o r w h i c h m e c h a n i c a l a g i t a t o r s c a n n o t b e u s e d b e c a u s e of t h e a s s o -c i a t e d p r o b l e m s . T h e y p r o v i d e a s l o w and t h o r o u g h t u r n - o v e r of m a t e r i a l a t r e a s o n a b l e g a s f low r a t e s . A n o n - c o n d e n s a b l e g a s , u s u a l l y a i r , i s u s e d a s t h e m o t i v e f l u i d . .

T h e a i r - l i f t c i r c u l a t o r ( F i g . 9) c o n s i s t s of a s i m p l e v e r t i c a l p i p e wi th a n a i r d i s t r i b u t o r a t t h e b o t t o m . C i r c u l a t i o n of l i q u i d i s e f f e c t e d by f o r -m a t i o n of a n a e r a t e d m i x t u r e of l o w e r s p e c i f i c g r a v i t y . T h e m o t i v e f o r c e s h o u l d b e s u f f i c i e n t t o o v e r c o m e t h e f r i c t i o n a l and a c c e l e r a t i o n r e s i s t a n c e s . T o e n a b l e t h e e f f i c i e n t o p e r a t i o n of c i r c u l a t o r s a t v a r y i n g l i qu id d e p t h s , two o r t h r e e s e t s of c i r c u l a t o r s wi th d i f f e r e n t l e n g t h s h a v e t o b e i n s t a l l e d

FLOW MEASUREMENT LINES TO dp INSTRUMENT PURGE METER

AIR SUPPLY LINE

CIRCULATORS ON 20 ft RADIUS

MAX. L IQUID L E V E L 30 ft 8 in

WATER TANK 75 ft DIAM.

— 24in. DIAM.

dp LINES TO AIR PURGE & dp INSTRUMENT

60 l /8 - in . -D I AM. HOLES

10 in. O.D.

c 2in. I.D. OPEN END

TYPICAL FOR EACH CIRCULATOR

1-in. SCH 40 AIR SUPPLY

9 in. O.D.

FIG.9. Air-l ift circulator [ 2 0 ] .

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i n t h e t a n k . E x c e l l e n t w o r k h a s b e e n c a r r i e d out by C o o k and W a t e r s [ 20] on t h e e v a l u a t i o n of t h e p e r f o r m a n c e of s u b m e r g e d a i r - l i f t c i r c u l a t o r s .

J e t - s p a r g e r s a r e l ong v e r t i c a l t u b e s w i t h n o z z l e s a t t h e b o t t o m . C o n -n e c t i o n s a r e p r o v i d e d a t t h e top f o r c o m p r e s s e d a i r and v a c u u m a p p l i c a t i o n . W h e n in o p e r a t i o n , t h e l i qu id i n t h e c y l i n d e r i s e x p e l l e d t h r o u g h t h e n o z z l e by t h e a i r p r e s s u r e a n d t h e j e t s w e e p s t h e b o t t o m of t h e t a n k . T h e c y l i n d e r i s t h e n a l l o w e d t o r e f i l l w i t h l i qu id by a p p l y i n g v a c u u m f o r a s e c o n d p u r g e a n d t h e o p e r a t i o n i s r e p e a t e d i n c y c l e s .

C o m p r e s s o r s f o r u n i n t e r r u p t e d supp ly of a i r t o t h e c i r c u l a t o r s a n d s p a r g e r s a r e g e n e r a l l y d u p l i c a t e d .

5. 5. S a m p l e r s

S a m p l e s t a k e n f r o m t a n k s a r e t r a n s f e r r e d t o t h e s a m p l e s t a t i o n . S a m p l e s of c a t e g o r y - 2 a n d - 3 w a s t e s s t o r e d in t a n k s c a n b e o b t a i n e d by l o w e r i n g a b o t t l e of s u i t a b l e s h a p e a n d c a p a c i t y in to t h e t a n k and d r a w i n g i t out a t a c o n s t a n t s p e e d s o t h a t t h e b o t t l e i s j u s t f i l l e d a t t h e e n d of t h e o p e r a t i o n . T h i s p r o v i d e s a s a m p l e r e p r e s e n t i n g a l l t h e l e v e l s i n t h e t a n k . S a m p l e s c a n a l s o b e o b t a i n e d by l o w e r i n g a s t o p p e r e d b o t t l e t o v a r i o u s l e v e l s of l i q u i d i n t h e t a n k a n d r e l e a s i n g t h e s t o p p e r by r e m o t e o p e r a t i o n t o o b t a i n ' l i q u i d s a m p l e s a t d i f f e r e n t l e v e l s . I t i s i m p o r t a n t t o c o n t r o l c o n t a m i n a t i o n d u r i n g t h e s e p r o c e s s e s .

N o r m a l l y , a i r l i f t s a n d a i r j e t s a r e u s e d to m o v e t h e l i q u i d s a m p l e s f r o m t a n k s h o l d i n g c a t e g o r y - 4 w a s t e s t o t h e s a m p l i n g s t a t i o n . T h e o p e r a t i n g c o m p o n e n t s of a t y p i c a l h i g h - a c t i v e w a s t e s a m p l e r ( F i g . 10) i n c l u d e t h e f o l l o w i n g :

(a) O n e o r t w o a i r - o p e r a t e d j e t a s s e m b l i e s (b) S u c t i o n and d i s c h a r g e p ip ing to r e c i r c u l a t e t h e l i q u i d (c) S a m p l e pot (d) R e m o t e p i p e t t i n g d e v i c e (e) C a r r i e r s f o r t r a n s p o r t i n g s a m p l e s .

F o r h i g h e r - l e v e l r a d i o a c t i v e w a s t e s t h e s a m p l e s t a t i o n , t h e o p e r a t i n g c o m p o n e n t s and t h e c o n t r o l s s h o u l d b e i s o l a t e d b y s u i t a b l e s h i e l d i n g , w h i c h m a y b e c o n c r e t e o r l e a d , o r a c o m b i n a t i o n of b o t h . S a m p l e j e t s , f l ow c o n t r o l v a l v e s a n d p i p i n g a r e h o u s e d in a c o n c r e t e v a l v e p i t w i t h r e m o v a b l e c o v e r s . L e a d g l a s s w i n d o w s o r r e f l e c t i n g m i r r o r s s h o u l d be p r o v i d e d f o r v i e w i n g . T h e s t a t i o n s h o u l d h a v e a n e x h a u s t hood f o r p r e v e n t i n g a i r c o n -t a m i n a t i o n . T h e s a m p l e pot i s p l a c e d i n t h e s u c t i o n l i n e f o r m i x i n g . S a m p l e j e t a n d pot a s s e m b l i e s a r e c o n n e c t e d w i t h t h e p i p i n g f o r t h e c o n t i n u o u s f l ow of t h e l i q u i d f r o m t h e s a m p l i n g po in t t h r o u g h t h e s a m p l e po t t o t h e s u c t i o n s i d e of t h e j e t . A n a i r l i f t i s u s e d t o a s s i s t i n a t t a i n i n g r e a s o n a b l e r e c i r -c u l a t i o n r a t e s if h i g h l i f t s a r e r e q u i r e d . A r e m o t e p i p e t t e i s u s e d f o r c o l -l e c t i n g a f i x e d a m o u n t of s a m p l e f r o m t h e s a m p l e po t i n to t h e s a m p l i n g b o t t l e . T h e s a m p l e b o t t l e s c a n b e t r a n s p o r t e d to t h e l a b o r a t o r y by a s y s t e m of c o n v e y e r s .

S t e a m a s a m o t i v e f l u i d f o r t h e j e t s d i l u t e s t h e s a m p l e t h r o u g h c o n -d e n s a t i o n , T h e u s e of a i r l i f t s and a i r - o p e r a t e d j e t s i s t h e r e f o r e m o r e a d v a n t a g e o u s . T h e s a m p l i n g l i n e s shou ld b e s u i t a b l y a r r a n g e d a n d s l o p e d t o e n a b l e c o m p l e t e d r a i n a g e of t h e s y s t e m . T h e y s h o u l d b e p r o v i d e d w i t h

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FIG. 10. Operating components of a typical h igh- l eve l radioactive waste sampler.

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a f l u s h i n g a r r a n g e m e n t f o r a v o i d i n g c r o s s - c o n t a m i n a t i o n of s a m p l e s a n d f o r k e e p i n g t h e l i n e s c l e a r , p a r t i c u l a r l y w h e n s l u r r i e s a r e h a n d l e d .

T h e s a m p l i n g s y s t e m d e s c r i b e d a b o v e c a n a l s o b e u s e d f o r l o w - a c t i v e w a s t e s a m p l i n g . F o r t h i s , t h e s h i e l d i n g , s a m p l e po t a n d r e m o t e p i p e t t i n g m a y not b e n e c e s s a r y .

5. 6. L e a k d e t e c t o r s

L e a k d e t e c t o r s a r e u s e d t o d e t e c t t h e a c c i d e n t a l l e a k a g e s of r a d i o a c t i v e w a s t e s f r o m h o l d - u p t a n k s . T h e y a r e g e n e r a l l y e i t h e r e l e c t r i c a l c o n d u c t i v i t y p r o b e s o r r a d i a t i o n d e t e c t o r s .

T h e e l e c t r i c a l c o n d u c t i v i t y t y p e of d e t e c t o r s c o n s i s t s of two c o n d u c t o r s l o c a t e d v e r y c l o s e t o e a c h o t h e r . T h e y a r e m o u n t e d i n a f r a m e r e a s o n a b l y c l o s e t o t h e f l o o r . A p o t e n t i a l d i f f e r e n c e i s m a i n t a i n e d b e t w e e n t h e two p r o b e s . S u i t a b l e c u r r e n t m e a s u r i n g d e v i c e s and a l a r m s a r e i n c l u d e d i n t h e c i r c u i t . U n d e r n o r m a l c o n d i t i o n s , t h e p r o b e s a r e i n s u l a t e d f r o m e a c h o t h e r a n d t h e r e i s no f l ow of c u r r e n t . In t h e e v e n t of a l e a k a g e , t h e p r o b e s a r e s h o r t - c i r c u i t e d by t h e l i q u i d , wh ich r e s u l t s i n a f low of c u r r e n t . T h i s i s d e t e c t e d a n d u s e d to a c t u a t e a n a l a r m . F o r t h e s e d e t e c t o r s i t i s n e c e s -s a r y t o e n s u r e good i n s u l a t i o n b e t w e e n t h e e l e c t r i c a l c o n d u c t o r s , t h e s u p -p o r t s a n d t h e g r o u n d .

R a d i a t i o n c o u n t e r s u s e d f o r l e a k d e t e c t i o n s h o u l d b e v e r y s e n s i t i v e and a d e q u a t e l y s h i e l d e d to r e d u c e t h e b a c k g r o u n d to a m i n i m u m . T h e a s -s e m b l y i s p l a c e d n e a r t h e f l o o r w i t h t he window f a c i n g t h e f l o o r of t h e s e c o n d a r y c o n t a i n e r o r t h e c o l l e c t i o n s u m p . In t h e e v e n t of a l e a k a g e of r a d i o a c t i v e l i q u i d , t h e c o u n t s r e g i s t e r e d by t h e c o u n t e r w i l l i n c r e a s e , t h u s g i v i n g a n i n d i c a t i o n of t h e l e a k . P a r t i c u l a r c a r e s h o u l d b e t a k e n i n s e l e c t i n g t h e i n t e r - c o n n e c t i n g w i r e s in v i e w of the h igh v o l t a g e s i n v o l v e d and t h e l i k e l y a d v e r s e c o n d i t i o n of h igh h u m i d i t y .

5. 7. I n s t r u m e n t a t i o n

I n s t r u m e n t s f o r m e a s u r e m e n t and c o n t r o l of v a r i a b l e s l i k e l e v e l , d e n s i -t y , t e m p e r a t u r e , h y d r o g e n - i o n c o n c e n t r a t i o n , e t c . m a y b e r e q u i r e d f o r r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s . A b r i e f d e s c r i p t i o n of s o m e of t h e m o r e i m p o r t a n t i n s t r u m e n t s u s e d i s g i v e n b e l o w .

5. 7. 1. L e v e l m e a s u r e m e n t

A p u r g e d i p - t u b e s y s t e m i s m o s t c o m m o n l y u s e d f o r l e v e l m e a s u r e m e n t i n w a s t e s t o r a g e t a n k s ( F i g . 11) . A i r a t a p r e s s u r e w h i c h i s s l i g h t l y h i g h e r t h a n t h a t r e q u i r e d t o o v e r c o m e b o t h t h e h y d r o s t a t i c h e a d of t h e l i q u i d a n d t h e s t a t i c p r e s s u r e in t h e v a p o u r p h a s e of t h e t a n k i s p a s s e d a t a c o n t r o l l e d r a t e t h r o u g h a p u r g e t u b e s u b m e r g e d in t h e l i q u i d , and a s e c o n d a i r l i n e i s t e r m i n a t e d a t t h e t o p of t h e t a n k . T h e d i f f e r e n c e b e t w e e n t h e b a c k -p r e s s u r e s e x p e r i e n c e d by t h e a i r l i n e s i s p r o p o r t i o n a l t o t h e d e p t h of t h e l i qu id a b o v e t h e p u r g e t u b e . T h i s d i f f e r e n t i a l p r e s s u r e i s e i t h e r d i r e c t l y m e a s u r e d by a g a u g e n e a r t h e t a n k o r t r a n s m i t t e d f o r r e m o t e m e a s u r e m e n t by u s i n g d i f f e r e n t i a l p r e s s u r e t r a n s m i t t e r s .

T h e t i p of t h e p u r g e t u b e i n t h e t ank i s t a p e r e d a t a n a n g l e t o p r e v e n t c l o g g i n g a n d i s l o c a t e d a t a s u f f i c i e n t d i s t a n c e f r o m t h e t a n k b o t t o m to e n s u r e a l a y e r of h o m o g e n e o u s l i q u i d f r e e f r o m s l u d g e s a b o v e i t . T h e p u r g e

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TO L E V E L I N D I C A T O R O R D I F F E R E N T I A L P R E S S U R E T O P R E S S U R E G A U G E

F I G . 1 1 . L e v e l m e a s u r e m e n t b y a i r p u r g i n g .

t u b e s a r e s o i n s t a l l e d . a s t o e n a b l e t h e i r e a s y r e m o v a l f o r p e r i o d i c i n s p e c t i o n a n d c l e a n i n g .

T h e e l e c t r i c a l c o n d u c t i v i t y t y p e of l e v e l m e a s u r e m e n t c a n a l s o b e u s e d i n t a n k s w h e r e a q u a l i t a t i v e i n d i c a t i o n of t h e l i q u i d l e v e l i s s u f f i c i e n t , i . e . w h e t h e r t h e l i q u i d l e v e l i s a b o v e o r b e l o w a s e t po in t o r p o i n t s . T h i s m e t h o d i s v e r y c o m m o n l y u s e d f o r a u t o m a t i c c o n t r o l and a l a r m s y s t e m s . O n e o r m o r e e l e c t r i c a l c o n d u c t i v i t y p r o b e s a r e i n s t a l l e d a t t h e d e s i r e d d e p t h s i n t h e t a n k a n d t h e i n d i c a t i o n of t h e l i q u i d d e p t h i s o b t a i n e d by m a k i n g o r b r e a k -ing c o n t a c t b e t w e e n t h e p r o b e s c o r r e s p o n d i n g to t h e c o n d u c t i v i t y of t h e l i q u i d .

Good i n s u l a t i o n b e t w e e n t h e p r o b e s and p r o b e s u p p o r t s s h o u l d b e e n s u r e d . A n a c c u m u l a t i o n of s l u d g e s on t h e s u p p o r t s s h o u l d be p r e v e n t e d , a s i t t e n d s t o i n c r e a s e t h e p o s s i b i l i t y of a c u r r e n t f l ow b e t w e e n t h e p r o b e s , e v e n if t h e l i q u i d l e v e l i s b e l o w t h e p r o b e s , w h i c h r e s u l t s i n e r r o n e o u s i n d i c a t i o n s .

5. 7. 2. D e n s i t y m e a s u r e m e n t

T h e p r i n c i p l e a p p l i e d i n d e n s i t y m e a s u r e m e n t i s s i m i l a r t o t h a t d e s -c r i b e d a b o v e f o r l e v e l m e a s u r e m e n t . F o r e a c h d e n s i t y m e a s u r e m e n t t w o p u r g e t u b e s a r e u s e d . T h e t u b e s a r e i m m e r s e d i n t h e l i q u i d and a r e t e r -m i n a t e d a t a known , f i x e d , v e r t i c a l d i s t a n c e f r o m e a c h o t h e r . T h e d i f -f e r e n c e i n h y d r o s t a t i c h e a d a t t h e t u b e o p e n i n g s d e p e n d s on t h e d e n s i t y of t h e l i q u i d a n d t h e v e r t i c a l d i s t a n c e b e t w e e n t h e t u b e s . T h e l a t t e r b e i n g c o n s t a n t , t h e d i f f e r e n c e i n p r e s s u r e i s p r o p o r t i o n a l t o t h e d e n s i t y . T h e p r e s s u r e s f r o m t h e p u r g e t u b e s a r e f e d t o a r e c e i v e r g a u g e to i n d i c a t e t h e d e n s i t y .

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5. 7. 3. T e m p e r a t u r e m e a s u r e m e n t

F o r t e m p e r a t u r e m e a s u r e m e n t in t h e t a n k s t h e s e n s i n g e l e m e n t i s n o r m a l l y a t h e r m o c o u p l e . A s u i t a b l e ' w e l l ' m a d e of m a t e r i a l no t l i k e l y t o b e a f f e c t e d by t h e t a n k l i q u i d i s u s e d a s a s e c o n d a r y c o n t a i n m e n t f o r p r o t e c t i n g t h e s e n s i n g e l e m e n t . T h e m a t e r i a l s e l e c t e d s h o u l d h a v e h igh t h e r m a l c o n d u c t i v i t y . T h e s i g n a l f r o m t h e s e n s i n g e l e m e n t i s f e d t o a s t a n d a r d i n d i c a t o r o r r e c o r d e r . By l o c a t i n g m e a s u r i n g e l e m e n t s a t v a r i o u s p o i n t s t h e t e m p e r a t u r e a t d i f f e r e n t l e v e l s i n t h e t a n k c a n b e d e t e r m i n e d . F o r e a s e of i n s t a l l a t i o n a n d s e r v i c i n g t h e ' w e l l ' s h o u l d b e s t r a i g h t and of u n i f o r m b o r e w i t h t h e o p e n end s i t u a t e d a t a n a c c e s s i b l e p l a c e w h e r e t h e r a d i a t i o n l e v e l i s w i t h i n p e r m i s s i b l e l i m i t s .

5. 7. 4 . pH m e a s u r e m e n t

T h e p H of t h e l i q u i d i n t h e t a n k s c a n b e d e t e r m i n e d u s i n g c o m -m e r c i a l l y a v a i l a b l e i m m e r s i o n - t y p e p H - e l e c t r o d e a s s e m b l i e s r a t e d f o r t h e t e m p e r a t u r e s e x p e c t e d i n t h e t a n k s . T h e a s s e m b l y c o n s i s t s of a m e a s u r i n g e l e c t r o d e , a r e f e r e n c e e l e c t r o d e a n d a t e m p e r a t u r e c o m p e n s a t o r m o u n t e d a t t h e end of a l ong s t a i n l e s s - s t e e l p i p e . T h e e l e c t r o d e s a r e p r o t e c t e d f r o m m e c h a n i c a l d a m a g e by m e a n s of a w i r e c a g e . T h e p i p e e x t e n d s t o t h e t o p of t h e t a n k f r o m w h e r e l e a d s a r e t a k e n t h r o u g h a t e r m i n a l b o x a n d c o n n e c t e d t o m e a s u r i n g i n s t r u m e n t s . T h e pH v a l u e i s o b t a i n e d a f t e r a m p l i f i c a t i o n of t h e e l e c t r i c a l s i g n a l on a s u i t a b l e m e t e r .

M o s t of t h e c o m m e r c i a l l y a v a i l a b l e e l e c t r o d e s h a v e t o b e kep t w e t f o r r e l i a b l e o p e r a t i o n . A r r a n g e m e n t s s h o u l d b e m a d e to e n s u r e t h a t t h e p r o b e i s k e p t w e t i n t h e e v e n t of t h e t a n k l i q u i d f a l l i n g b e l o w t h e l e v e l of t h e e l e c t r o d e s . T h e s o l i d p a r t i c l e s i n t h e l i q u i d t e n d to a d h e r e t o t h e e l e c -t r o d e s t h u s g i v i n g r i s e t o e r r o n e o u s r e a d i n g s . R e g u l a r and f r e q u e n t c l e a n -ing of t h e e l e c t r o d e s i s t h e r e f o r e e s s e n t i a l . In t h e c a s e of h i g h e r - l e v e l r a d i o a c t i v e w a s t e s i t m a y b e p r e f e r a b l e t o m e a s u r e t h e pH by s a m p l i n g .

5. 7. 5. P r e s s u r e m e a s u r e m e n t

P r e s s u r e g a u g e s c a n b e u s e d i n c o n j u n c t i o n w i t h p i p e s c o n n e c t e d w i t h t a p p i n g s on t h e t o p of t h e t a n k s f o r m e a s u r i n g t h e p r e s s u r e i n t h e t a n k s . A i r m a y b e p u r g e d t h r o u g h t h e p i p e to p r e v e n t i n f i l t r a t i o n of r a d i o a c t i v e v a p o u r s f r o m t h e t a n k . If a i r p u r g e i s not u s e d a n d t h e i n d i c a t o r i s r e m o t e f r o m t h e t a n k i t s h o u l d b e e n s u r e d t h a t t h e a i r t e m p e r a t u r e i n t h e l i n e a t t h e g a u g e i s t h e s a m e a s t h a t i n t h e t a n k . C o n d e n s a t i o n of v a p o u r i n t h e l i n e s h o u l d b e p r e v e n t e d by l a g g i n g a n d / o r h e a t i n g .

5. 7. 6. F l o w m e a s u r e m e n t

T h e f l o w of t h e l i q u i d t h r o u g h p i p e - l i n e s w h e n e n t e r i n g o r l e a v i n g a t a n k c a n b e m e a s u r e d u s i n g h e a d - f l o w m e t e r s . T h e v e n t u r i t u b e i s t h e m o s t s u i t a b l e f l o w m e t e r f o r w a s t e c o n t a i n i n g s u s p e n d e d s o l i d s . T h e s t r e a m - l i n e d c o n s t r u c t i o n of t h i s d e v i c e p r e v e n t s t h e s o l i d s f r o m s t i c k i n g to t h e s i d e s of t h e b o d y . T h e d i f f e r e n t i a l p r e s s u r e d e v e l o p e d by t h e v e n t u r i t u b e i s p i p e d t o a f l o w t r a n s m i t t e r , t h e ou tpu t of t h e t r a n s m i t t e r be ing f e d t o a r e c e i v e r g a u g e . A s v e n t u r i t u b e s a r e e x p e n s i v e , i n marry c a s e s o r i f i c e p l a t e s m a y s e r v e t h e s a m e p u r p o s e . T h e o r i f i c e p l a t e s c r e a t e a

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p r e s s u r e d i f f e r e n c e and a m e a s u r e m e n t of t h i s g i v e s a n i n d i c a t i o n of t h e f l o w . A n o r i f i c e p l a t e u s e d i n t h e s l u r r y - c a r r y i n g p i p e - l i n e s h o u l d b e e c c e n t r i c t o t h e b o r e a t t h e b o t t o m of t h e p i p e i n o r d e r t o p r e v e n t b u i l d -u p of s l u d g e s on t h e u p s t r e a m s i d e of t h e o r i f i c e . T h e t a p p i n g s t o t h e t r a n s m i t t e r a r e t a k e n f r o m t h e s i d e s of t h e p i p e .

6. O P E R A T I N G T E C H N I Q U E S

6. 1. G e n e r a l

A l l t h e o p e r a t i o n s c o n n e c t e d w i t h a r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s h o u l d b e c a r e f u l l y p l a n n e d a n d c o n t r o l l e d . T h o u g h t h e d e s i g n of t h e s y s t e m e n s u r e s r e a s o n a b l e s a f e t y , p o o r o p e r a t i o n a l p r a c t i c e w i l l l e a d t o i t s f a i l u r e . I t i s t h e r e f o r e n e c e s s a r y t o e n s u r e t h e i n t e g r i t y of t h e t a n k s a t a l l t i m e s a n d to p r o m p t l y d e t e c t s p r e a d of c o n t a m i n a t i o n . A n y u n f o r e s e e n o c c u r r e n c e s d u r i n g o p e r a t i o n h a v e t o b e p r o p e r l y e v a l u a t e d and t h e f i n d i n g s r e c o r d e d f o r f u t u r e g u i d a n c e . B a s e d on t h e a c t u a l e x p e r i e n c e g a i n e d i n t h e o p e r a t i o n of t h e s t o r a g e s y s t e m , t h e o p e r a t i n g p r o c e d u r e s s h o u l d b e r e v i e w e d p e r i o d i -c a l l y a n d i m p r o v e d u p o n . If e v e r y i t e m of e x p e n d i t u r e i n c u r r e d i n t h e o p e r a -t i o n i s c a r e f u l l y r e c o r d e d i n a c c o r d a n c e w i t h t h e a c c e p t e d c o s t i n g p r o c e d u r e s , u s e f u l d a t a w i l l b e a v a i l a b l e f o r f u t u r e e c o n o m i c e v a l u a t i o n .

A s t h e d e t a i l s of o p e r a t i n g t e c h n i q u e s a r e s p e c i f i c t o a p a r t i c u l a r i n -s t a l l a t i o n a n d g e n e r a l i z a t i o n i s not p r a c t i c a l , on ly a f e w i m p o r t a n t a s p e c t s a r e s u m m a r i z e d i n t h e f o l l o w i n g .

6. 2. T r a n s f e r o p e r a t i o n s

C a t e g o r y - 2 and - 3 w a s t e s a r e n o r m a l l y s t o r e d i n t a n k s f o r s h o r t p e r i o d s a n d f r e q u e n t t r a n s f e r o p e r a t i o n s a r e r e q u i r e d f o r t r e a t m e n t and d i s p o s a l of t h e s e w a s t e s . W a s t e s c o l l e c t e d i n s i t e s t o r a g e t a n k s a r e t r a n s p o r t e d t o t r e a t m e n t p l a n t s e i t h e r by u s i n g t a n k t r u c k s o r t h r o u g h p i p e - l i n e s . S m a l l v o l u m e s of w a s t e s m a y b e t r a n s p o r t e d by t a n k t r u c k s . W a s t e s a r e g e n e r a l l y t r a n s f e r r e d in to t h e t a n k t r u c k by a p p l y i n g s u c t i o n t o t h e t r u c k c o n t a i n e r . T h e p i p e s and h o s e s c o n n e c t i n g t h e t a n k a n d t h e t a n k t r u c k h a v e t o b e l e a k -t i g h t a n d p r e f e r a b l y k e p t a t a n i n c l i n a t i o n s o a s t o e n a b l e c o m p l e t e d r a i n a g e of t h e l i q u i d b a c k t o t h e t a n k a t t h e end of t h e t r a n s f e r o p e r a t i o n . T a n k t r u c k s a r e e m p t i e d e i t h e r by a l l o w i n g t h e w a s t e t o f l ow by g r a v i t y o r by p u m p i n g . If t h e w a s t e i s t r a n s p o r t e d by p i p e - l i n e s i t i s a d v i s a b l e t o r e m o v e t h e s u s p e n d e d m a t t e r n e a r t h e p o i n t of o r i g i n t o a v o i d s l u d g e a c c u m u l a t i o n a t low p o i n t s ; W h e n e v e r p i p e s , v a l v e s , e t c . a r e b l o c k e d , t h e y h a v e t o b e c l e a r e d by p a s s i n g a i r , w a t e r o r s t e a m a t a n a p p r o p r i a t e p r e s s u r e t h r o u g h t h e p i p e s . T h e m e t h o d d e p e n d s on t h e c h a r a c t e r i s t i c s of t h e p ip ing m a t e r i a l a n d t h e s y s t e m . B e f o r e a n y t r a n s f e r o p e r a t i o n i s c a r r i e d ou t it i s d e s i r a b l e t o m i x t h e t a n k c o n t e n t s .

If a c o m m o n t r a n s f e r s y s t e m s e r v e s a g r o u p of t a n k s i n a s y s t e m h a n d -l i n g a v a r i e t y of c a t e g o r y - 4 w a s t e s , t h e t r a n s f e r l i n e s s h o u l d b e f l u s h e d b e f o r e e v e r y c h a n g e of t h e t y p e of w a s t e h a n d l e d ( s e e R e f . [ 4 ] , p . 20). B e f o r e f l u s h i n g , a v o l u m e of w a t e r e q u i v a l e n t t o t h a t of t h e r e m a i n i n g w a s t e i n t h e t r a n s f e r l i n e i s f i r s t p u m p e d i n , s o t h a t t h e w a s t e i s c o m p l e t e l y r e p l a c e d b y w a t e r . T h e w a s h - w a t e r i s c o l l e c t e d s e p a r a t e l y and t h e p i p e -l i n e i s t h e n t h o r o u g h l y f l u s h e d . A f t e r c o m p l e t i n g t h e f l u s h i n g o p e r a t i o n ,

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t h e w a t e r i n t h e p i p e - l i n e i s r e p l a c e d b y t h e n e w s t r e a m of w a s t e and t h e r o u t i n g i s c h a n g e d t o f i l l t h e w a s t e s t o r a g e t a n k . T h e u s e of a c t i v i t y m o n i t o r s i n t h e t r a n s f e r l i n e a n d t h e r e t u r n f l u s h l i n e w i l l h e l p in c o n t r o l l i n g t h e s e o p e r a t i o n s . S u c h a p r a c t i c e w i l l avo id c r o s s - c o n t a m i n a t i o n of w a s t e s t r e a m s a n d d i l u t i o n of w a s t e s d u r i n g f l u s h i n g .

Hot c o n c e n t r a t e s c o m i n g f r o m w a s t e e v a p o r a t o r s a r e c o o l e d by u s i n g c o o l i n g a r r a n g e m e n t s p r o v i d e d f o r t h i s p u r p o s e , s o a s to av o i d v a p o r i z a t i o n i n t h e p i p e - l i n e s . D u r i n g e v a p o r a t i o n i t i s i m p o r t a n t to c o n t r o l t h e w a s t e c o n c e n t r a t i o n i n s u c h a w a y t h a t s o l i d f o r m a t i o n by c r y s t a l l i z a t i o n i s avoided^ a n d t h u s b l o c k a g e of p i p e - l i n e s and e n h a n c e d e r o s i o n a r e p r e v e n t e d .

6. 3. A n a l y t i c a l c o n t r o l

A n a l y t i c a l c o n t r o l i s r e q u i r e d f o r e f f e c t i n g a c h e c k on h a n d l i n g , d i s p o s a l o r s t o r a g e of c a t e g o r y - 2 , - 3 a n d - 4 w a s t e s . T h e a n a l y s i s of t h e s e e f f l u e n t s w i l l h e l p i n d e c i d i n g t h e t r e a t m e n t m e t h o d to b e a d o p t e d a n d t h e d e g r e e of d e c o n t a m i n a t i o n t o b e a c h i e v e d b e f o r e t h e y a r e d i s c h a r g e d . Such a c o n t r o l w i l l i n v o l v e r a d i o c h e m i c a l a n d c h e m i c a l a n a l y s e s of a v a r i e t y of l i q u i d s and s l u d g e s s t o r e d i n t a n k s .

R a d i o c h e m i c a l . a n a l y s i s g e n e r a l l y i n c l u d e s t h e d e t e r m i n a t i o n of g r o s s a c t i v i t i e s a n d h a z a r d o u s r a d i o n u c l i d e s l i k e 9 0 S r , 1 3 7 C s , 2 2 6 R a , e t c . C h e m i c a l a n a l y s i s i n v o l v e s t h e d e t e r m i n a t i o n of p H , s o l i d s c o n t e n t and a m o u n t s of v a r i o u s c o n s t i t u e n t s l i k e s o d i u m , p o t a s s i u m , c a l c i u m , m a g n e s i u m , p h o s -p h a t e s , b i c a r b o n a t e s , e t c . , w h i c h h a v e s i g n i f i c a n t e f f e c t on t h e t r e a t m e n t m e t h o d s t o b e a d o p t e d . A n e s t i m a t i o n of c h l o r i d e s and p o l y v a l e n t i o n s ( s u c h a s f e r r i c a n d c h r o m i c ) p r e s e n t i n t h e w a s t e i s of i m p o r t a n c e a s t h e y i n d u c e c o r r o s i o n i n t h e t a n k s . T h e c h e m i c a l c o n s t i t u e n t s m a y e x i s t in s e v e r a l v a l e n c y s t a t e s i n t h e f o r m of c o m p l e x e s a n d c o l l o i d s . It i s n e c e s s a r y t o d e t e r m i n e t h e b i o l o g i c a l o x i d a t i o n d e m a n d f o r w a s t e s c o n t a i n i n g b i o d e g r a d -a b l e m a t e r i a l s t h a t a r e r e l e a s e d to s e w a g e s y s t e m s . W h e r e v e r a p p l i c a b l e , i t i s a l s o d e s i r a b l e t o d e t e r m i n e c h e m i c a l l y t o x i c m a t e r i a l s s u c h a s c y a n i d e s , c h r o m i u m , b e r y l l i u m , e t c . in e f f l u e n t s b e f o r e d i s c h a r g e .

T h e a n a l y t i c a l m e t h o d s t o b e f o l l o w e d a r e c o n v e n t i o n a l a n d c a n b e found in R e f s [ 21, 2 2 ] . T h e i r c h o i c e d e p e n d s u p o n t h e p u r p o s e of t h e a n a l y s i s , t h e r e q u i r e d a c c u r a c y , t h e c o n c e n t r a t i o n s of a c t i v e a n d i n a c t i v e c o n s t i t u e n t s and t h e a v a i l a b l e i n s t r u m e n t s .

I n v i e w of t h e h igh r a d i a t i o n l e v e l s i n v o l v e d i n t h e a n a l y s i s of h i g h e r -l e v e l r a d i o a c t i v e w a s t e s , t h e u s e of s o p h i s t i c a t e d a n a l y t i c a l e q u i p m e n t w i t h a h igh d e g r e e of a u t o m a t i o n m a y b e n e c e s s a r y . C o n v e n t i o n a l s a m p l i n g and l a b o r a t o r y a n a l y s i s a r e t i m e - c o n s u m i n g and a t t i m e s m a y l i m i t t h e w a s t e - h a n d l i n g o p e r a t i o n s . T h e d e v e l o p m e n t of m o d e r n i n s t r u m e n t s h a s m a d e i t p o s s i b l e t o o b t a i n q u a n t i t a t i v e a n a l y t i c a l d a t a d i r e c t l y and v i r t u a l l y i n s t a n t a n e o u s l y . H o w e v e r , i t i s i m p o r t a n t t o no t e t h a t a c c u r a c y and p r e -c i s i o n d e p e n d on r e a l i s t i c e s t i m a t e s of t h e r e q u i r e m e n t s .

6 . 4 . D e c o n t a m i n a t i o n

W h e r e v e r n e c e s s a r y , t h e d e c o n t a m i n a t i o n of w a s t e s t o r a g e t a n k s c a n b e c a r r i e d o u t by - f lush ing t h e t a n k s wi th s u i t a b l e d e c o n t a m i n a t i n g r e a g e n t s . T h e c o m p o s i t i o n and t h e c o n c e n t r a t i o n of the. r e a g e n t s e m p l o y e d d e p e n d

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u p o n t h e t a n k m a t e r i a l and t h e n a t u r e of c o n t a m i n a t i o n . D e c o n t a m i n a t i o n p r o c e d u r e s and r e a g e n t s u s e d f o r v a r i o u s m a t e r i a l s c a n be found in E e f . [ 2 3 ] .

F o r m o s t s u r f a c e s t h e i n i t i a l d e c o n t a m i n a t i o n s t e p i s u s u a l l y a t h o r o u g h w a s h wi th hot w a t e r . T h e d e c o n t a m i n a t i o n s o l u t i o n i s g e n e r a l l y p r e p a r e d i n a s e p a r a t e v e s s e l and p u m p e d t h r o u g h s p r a y n o z z l e s l o c a t e d i n t h e t a n k . D e c o n t a m i n a t i o n i s m a d e m o r e e i f fec t ive by s t e a m - h e a t i n g a n d a i r - a g i t a t i o n . W h e n l a r g e q u a n t i t i e s of d e c o n t a m i n a t i n g s o l u t i o n s h a v e t o b e u s e d i t i s n e c e s s a r y to r e c i r c u l a t e t h e s o l u t i o n t o s a v e c o s t s on d e c o n t a m i n a t i n g a g e n t s . T h e s p e n t r e a g e n t s o l u t i o n i s d r a i n e d to a c o l l e c t i o n v e s s e l and t h e t a n k • i s f l u s h e d wi th hot w a t e r t o r e m o v e t h e r e m a i n i n g c h e m i c a l s . A s m a l l -c a p a c i t y t a n k r e q u i r i n g a h igh d e g r e e of d e c o n t a m i n a t i o n c a n be f i l l e d t o i t s c a p a c i t y wi th t h e d e c o n t a m i n a t i n g s o l u t i o n , h e a t e d f o r a f ew h o u r s and f i n a l l y f l u s h e d t h o r o u g h l y w i t h ho t w a t e r . T h e u s e d r e a g e n t s o l u t i o n a n d t h e w a s h - w a t e r h a v e t o b e t r e a t e d a s r a d i o a c t i v e w a s t e .

6. 5. O p e r a t i o n a l s a f e t y

P l a c e s w h e r e r a d i o a c t i v e l i q u i d w a s t e s a r e s t o r e d s h o u l d b e t r e a t e d a s c o n t r o l l e d a r e a s a n d d u e a t t e n t i o n i s n e c e s s a r y t o p r o v i d e s a f e w o r k i n g c o n d i t i o n s f o r t h e o p e r a t i n g p e r s o n n e l b o t h d u r i n g n o r m a l o p e r a t i o n and m a i n t e n a n c e .

A p r o p e r r e c o r d of t h e q u a n t i t y and t h e a c t i v i t y l e v e l of t h e w a s t e h a n d l e d s h o u l d b e m a i n t a i n e d s o a s t o e n s u r e a d e q u a t e o p e r a t i o n a l c o n t r o l . S u f f i c i e n t s p a r e c a p a c i t y s h o u l d a l w a y s b e p r o v i d e d i n a t a n k i n s t a l l a t i o n t o m e e t a n y p e a k d e m a n d d u r i n g o f f - s t a n d a r d o p e r a t i n g c o n d i t i o n s . It i s a d v i s a b l e t o a l w a y s k e e p t h e q u a n t i t y of s t o r e d w a s t e a s low a s i s p r a c t i c a b l e . S p e c i a l c a r e s h o u l d be t a k e n w h i l e o p e n i n g s t o r a g e t a n k s ho ld ing w a s t e s w h i c h m a y c o n t a i n f l a m m a b l e s o l v e n t s .

If c o n t a m i n a t i o n of t h e o p e r a t i n g a r e a s o c c u r s due to a c c i d e n t a l s p i l l a g e of w a s t e s f r o m t h e t a n k o r i t s a c c e s s o r i e s , i m m e d i a t e m e a s u r e s s h o u l d b e t a k e n to p r e v e n t s p r e a d of c o n t a m i n a t i o n and e x p o s u r e of t h e o p e r a t i n g s t a f f . T h e c o n t a m i n a t e d a r e a s s h o u l d b e i s o l a t e d and a f t e r p r o p e r l y a s s e s -s i n g t h e n a t u r e a n d e x t e n t of c o n t a m i n a t i o n , c l e a n - u p o p e r a t i o n s s h o u l d b e c a r r i e d ou t . T h e a r e a m a y b e d e c l a r e d s a f e on ly a f t e r t h e r e s i d u a l c o n -t a m i n a t i o n i s found t o b e w i t h i n s a f e l i m i t s . A s u r v e y of e x t e r n a l r a d i a t i o n a n d p e r s o n n e l c o n t a m i n a t i o n s h o u l d b e c a r r i e d out r e g u l a r l y and s u i t a b l e p e r s o n a l p r o t e c t i v e e q u i p m e n t s h o u l d b e m a d e r e a d i l y a v a i l a b l e t o t h e p e r s o n s e n g a g e d i n o p e r a t i o n a n d m a i n t e n a n c e .

7. S H I E L D I N G O F W A S T E S T O R A G E TANKS

7 . 1 . G e n e r a l

F o r t a n k s h o l d i n g h i g h e r - l e v e l r a d i o a c t i v e w a s t e s , s h i e l d i n g i s r e q u i r e d f o r r e d u c i n g t h e r a d i a t i o n f i e l d to a n a c c e p t a b l e l e v e l . T h e d e s i g n of t a n k s h i e l d i n g i s u s u a l l y b a s e d on s t a n d a r d m e t h o d s d e s c r i b e d in l i t e r a t u r e .

7 . 2 . F a c t o r s i n f l u e n c i n g s h i e l d i n g d e s i g n

T h e s t o r a g e t a n k s b e l o w g r o u n d a r e g e n e r a l l y s h i e l d e d wi th e a r t h , w h e r e a s f o r t he a b o v e - g r o u n d t a n k s c o n c r e t e i s u s e d a s t h e s h i e l d i n g

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m a t e r i a l . T h e c a l c u l a t i o n of t h e s h i e l d i n g r e q u i r e m e n t s f o r s t o r a g e t a n k s i s c o m p l i c a t e d b e c a u s e of t h e l a r g e n u m b e r of i s o t o p e s p r e s e n t in t h e w a s t e and t h e e x t e n d e d s o u r c e g e o m e t r y i n v o l v e d .

T h e g a m m a f lux d i s t r i b u t i o n a r o u n d t h e s o u r c e h a s to b e c a l c u l a t e d in o r d e r t o a r r i v e at the d e s i r e d t h i c k n e s s of t h e s h i e l d i n g m a t e r i a l f o r r e d u c i n g t h e g a m m a r a d i a t i o n to t h e a c c e p t a b l e l i m i t s . T h i s r e q u i r e s a b a s i c k n o w l e d g e of t h e n u m b e r of pho tons of a p a r t i c u l a r e n e r g y o r of t h e e f f e c t i v e e n e r g y of t h e g a m m a r a d i a t i o n e m i t t e d by t h e n u c l i d e s p r e s e n t in a un i t v o l u m e of t h e w a s t e . F o r t h e s h i e l d i n g d e s i g n of w a s t e s t o r a g e t a n k s a c a l c u l a t i o n of t he f lux d i s t r i b u t i o n a r o u n d t h e t ank a l o n g t h e l i ne of m a x i m u m f l u x h a s to b e c a r r i e d out i n d i v i d u a l l y f o r e a c h of t he e n e r g i e s o r t h e e f f e c t i v e e n e r g i e s c o n c e r n e d .

7 . 3 . S h i e l d i n g d e s i g n

T h e s t e p s n o r m a l l y f o l l o w e d in the s h i e l d i n g d e s i g n a r e : (a) E s t i m a t i o n of c o n c e n t r a t i o n s of n u c l i d e s p r e s e n t in t h e w a s t e (b) D e t e r m i n a t i o n of t h e s h i e l d i n g c o n s t a n t s (c) E s t i m a t i o n of f l ux d i s t r i b u t i o n a l o n g t h e l i ne of m a x i m u m f lux a n d

s e l e c t i o n of p r o p e r s h i e l d t h i c k n e s s . T h e c o n c e n t r a t i o n s of g a m m a - e m i t t i n g n u c l i d e s p r e s e n t in f i s s i o n -

p r o d u c t w a s t e s d e p e n d upon t h e n a t u r e and t y p e of t h e p a r e n t f u e l , i t s b u r n -up, c o o l i n g h i s t o r y a n d the v o l u m e of t h e w a s t e g e n e r a t e d p e r uni t w e i g h t of t h e f u e l . It i s d i f f i c u l t t o e s t i m a t e t h e e x a c t d i s t r i b u t i o n of t he g a m m a r a d i a t i o n of v a r i o u s e n e r g y l e v e l s p r e s e n t in t h e w a s t e b e c a u s e of t h e l a r g e n u m b e r of i s o t o p e s p r e s e n t . In s h i e l d i n g c a l c u l a t i o n s it h a s b e c o m e c o m m o n p r a c t i c e to d iv ide t h e m in to d i s c r e t e e n e r g y g r o u p s a n d e s t i m a t e t h e c o n c e n t r a t i o n s of e a c h g r o u p h a v i n g a p a r t i c u l a r e f f e c t i v e e n e r g y . F r o m the e n e r g y r e l e a s e d b y e a c h of t he e n e r g y g r o u p s t h e c o n c e n t r a t i o n s of v a r i o u s n u c l i d e s in a uni t we igh t of t h e f u e l f o r e a c h of t h e e n e r g y g r o u p s c a n b e e s t i m a t e d [ 24] .

F o r t h e s p e c i f i c t y p e of s h i e l d i n g m a t e r i a l t he c a l c u l a t i o n of t h e f lux d i s t r i b u t i o n r e q u i r e s t h e k n o w l e d g e of s h i e l d i n g c o n s t a n t s s u c h a s a t t e n u -a t i o n c o e f f i c i e n t a n d b u i l d - u p f a c t o r . B e c a u s e of t h e e x t e n d e d s o u r c e g e o m e t r y t h e s h i e l d i n g c a l c u l a t i o n s f o r the s t o r a g e t a n k s h o u l d t a k e in to a c c o u n t t h e s e l f - s h i e l d i n g p r o v i d e d by t h e s o u r c e i t s e l f . T h i s i n t u r n wi l l d e p e n d o n t h e v a r i o u s c o n s t i t u e n t s p r e s e n t in t h e s t o r e d w a s t e . T h e s h i e l d i n g p r o p e r t i e s of e a r t h and c o n c r e t e v a r y wi th t h e i r c o m p o s i t i o n . T h e t o t a l l i n e a r a t t e n u a t i o n c o e f f i c i e n t of a m i x t u r e i s o b t a i n e d by t h e s u m -m a t i o n of t h e l i n e a r a t t e n u a t i o n c o e f f i c i e n t s of t h e v a r i o u s e l e m e n t s p r e s e n t i n t h e m i x t u r e , a n d t h e e s t i m a t i o n of the b u i l d - u p f a c t o r i s b a s e d on t h e e f f e c t i v e a t o m i c n u m b e r [ 2 5 ] . A t t e n u a t i o n c o e f f i c i e n t s of t h e e l e m e n t s g e n e r a l l y p r e s e n t in e a r t h and c o n c r e t e a r e g i v e n in R e f . [ 2 6 ] . W a l k e r a n d G r o t e n h u i s [ 2 5 ] h a v e c o m p i l e d d a t a on t h e s h i e l d i n g c o n s t a n t s f o r c o n c r e t e . B e c a u s e of t h e v a r i a t i o n s i n t h e c o m p o s i t i o n of w a s t e s a n d t h e l i m i t e d p u b l i s h e d d a t a on t h e s h i e l d i n g c o n s t a n t s t he d e s i g n e r i s o f t e n c o m p e l l e d t o m a k e a p p r o x i m a t i o n s b a s e d on t h e a v a i l a b l e d a t a .

T y p e s of t a n k s t h a t a r e o f t e n m e t in s h i e l d i n g c a l c u l a t i o n s a r e t h o s e f o r h o l d i n g h i g h e r - l e v e l w a s t e s , w h i c h a r e g e n e r a l l y c y l i n d r i c a l i n s h a p e . T h e f l u x d i s t r i b u t i o n a l o n g t h e l i n e of m a x i m u m f l u x a long t h e r a d i a l s i d e of a c y l i n d r i c a l t a n k i s of i n t e r e s t i n o r d e r t o a r r i v e a t t he s h i e l d i n g r e q u i r e -m e n t s f o r t h e a b o v e - g r o u n d t a n k s , wh i l e t h e f lux d i s t r i b u t i o n a l o n g t h e l i ne

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of m a x i m u m f lux a l o n g the a x i a l s i d e w i l l e n a b l e t h e e s t i m a t i o n of t h e s a m e f o r t h e u n d e r g r o u n d t a n k s . M e t h o d s b a s e d on a p p r o x i m a t i o n s t o s i m p l e s o u r c e g e o m e t r i e s w i t h due c o n s i d e r a t i o n of t h e s e l f - s h i e l d i n g of t h e s o u r c e p r o v i d e t h e r e q u i r e d a c c u r a c y f o r t h e s h i e l d i n g c a l c u l a t i o n s . T h e m e t h o d i n d i c a t e d by R o c k w e l l (Re f . [ 2 4 ] , p . 360) can b e u s e d t o o b t a i n t he g a m m a f lux d i s t r i b u t i o n a l o n g t h e r a d i a l s i d e of a c y l i n d e r . T h e f l u x a l o n g t h e a x i a l s i d e of a c y l i n d e r can b e a r r i v e d at by a p p r o x i m a t i n g i t t o a l a r g e o r s m a l l c o n e ( R e f . [ 2 4 ] , p . 4 0 1 ) to o b t a i n t he m a x i m u m and m i n i m u m v a l u e s of t he f lux e x p e c t e d a t t h e po in t of i n t e r e s t . T h e s t a c k e d d i s k s o l u t i o n i s a n o t h e r m e t h o d f o r a m o r e a c c u r a t e e s t i m a t i o n of f l ux a l o n g t h e a x i a l s i d e . T h i s m e t h o d a s s u m e s t h e c y l i n d e r t o b e m a d e up of a s e r i e s of t h i n s t a c k e d d i s k s [ 2 7 ] ,

T o o b t a i n t he p r o p e r s h i e l d i n g t h i c k n e s s , t h e f lux d i s t r i b u t i o n a l o n g t h e l i n e of m a x i m u m f lux h a s t o b e c a l c u l a t e d f o r d i f f e r e n t s h i e l d i n g t h i c k n e s s e s . T h e d o s e r a t e s due t o e a c h of t he e n e r g i e s o r t h e e f f e c t i v e e n e r g i e s h a v e to b e c a l c u l a t e d a n d s u m m e d up t o ob t a in a r e l a t i o n s h i p b e t w e e n d o s e r a t e s a n d s h i e l d i n g t h i c k n e s s . T h e r e q u i r e d s h i e l d i n g t h i c k n e s s c a n b e r e a d i l y s e l e c t e d f r o m t h e a b o v e r e l a t i o n s h i p a f t e r f i x i n g t h e a l l o w a b l e d o s e on t h e s u r f a c e of t h e s h i e l d i n g , b a s e d on t h e o c c u p a n c y f a c t o r .

8 . E N V I R O N M E N T A L S A F E G U A R D S

8 . 1 . G e n e r a l

E n v i r o n m e n t a l c o n t a m i n a t i o n d u e t o r e l e a s e of t a n k c o n t e n t s can l e a d t o s e r i o u s c o n s e q u e n c e s . T h e c r i t e r i a f o r s e l e c t i n g s i t e s f o r t he l o c a t i o n of t a n k s , p a r t i c u l a r l y t h o s e h o l d i n g h i g h e r - l e v e l r a d i o a c t i v e w a s t e s , s h o u l d b e c a r e f u l l y e v a l u a t e d t o e n s u r e e n v i r o n m e n t a l s a f e t y and to d e v i s e s u i t a b l e m e a s u r e s f o r c o n t r o l of c o n t a m i n a t i o n f r o m a p o t e n t i a l r e l e a s e of r a d i o a c t i v e w a s t e s f r o m t a n k s .

8 . 2 . L o c a t i o n of t a n k s and t a n k f a r m s

T h e s i t e s e l e c t i o n c r i t e r i a f o r l o c a t i n g n u c l e a r f a c i l i t i e s s h o u l d t a k e in to a c c o u n t t he a s s o c i a t e d 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 a s p e c t s . T h i s i s p a r t i c u l a r l y i m p o r t a n t w h e n h i g h e r - l e v e l r a d i o a c t i v e w a s t e s t o r a g e f a c i l i t i e s w i l l b e l o c a t e d at t h e s i t e . F o r t h e s e l e c t i o n of a s u i t a b l e l o c a t i o n of t h e t a n k s t h e m o v e m e n t of r a d i o a c t i v i t y t h r o u g h t h e g r o u n d in t h e c a s e of i t s r e l e a s e n e e d s p r o p e r e v a l u a t i o n .

8 . 2 . 1 . G e o l o g i c a l c o n d i t i o n s

F o r l o c a t i n g t a n k s and t a n k f a r m s f o r h i g h e r - l e v e l r a d i o a c t i v e w a s t e s , a r e g i o n a l g e o l o g i c a l s u r v e y of t h e a r e a h a s t o b e m a d e . A l s o , c o m p r e h e n -s i v e m i c r o g e o l o g i c a l s t u d i e s , wh ich s h o u l d i n c l u d e s u b s u r f a c e e x p l o r a t i o n by d r i l l i n g a n d i n v e s t i g a t i o n s r e g a r d i n g h y d r o g e o l o g y of t h e s i t e , a r e u s e f u l . I t i s d e s i r a b l e t o s e l e c t an a r e a w h i c h h a s a c o m p a c t b e d r o c k , p r e f e r a b l y w i t h o u t j o i n t s , f a u l t s and f o l d e d s t r u c t u r e s . G r a n i t e s , q u a r t z i t e s and b a s a l t s a r e s u i t a b l e a s good b a s e m e n t r o c k s f o r t he f o u n d a t i o n of t a n k s . W h i l e s o m e of t h e s o f t and f r i a b l e f o r m a t i o n s l i k e s h a l e s , s l a t e s , s a n d

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s t o n e s , e t c . a r e c h e a p e r f o r e x c a v a t i o n , t he r e q u i r e m e n t f o r g r o u t i n g of t h e b a s e m e n t and s p e c i a l w a t e r - p r o o f i n g m a y i n c r e a s e t h e t o t a l c o s t .

8 . 2 . 2 . H y d r o l o g i c a l c o n d i t i o n s

T h e h y d r o l o g i c a l c o n d i t i o n s in t he a r e a d e p e n d upon t h e a m o u n t of r a i n -f a l l it r e c e i v e s , t h e r e c h a r g e a r e a of t h e g r o u n d - w a t e r , t h e r u n - o f f and the t h i c k n e s s of t he a q u i f e r z o n e . H y d r o l o g i c a l s t u d i e s of t h e a r e a w i l l r e v e a l t h e p a t t e r n of t h e m o v e m e n t of r a d i o a c t i v i t y in t he g r o u n d . T h e c o m p l e x i t y of m i c r o h y d r o l o g i c a l s t u d i e s i s m a i n l y due t o t h e h e t e r o g e n e o u s n a t u r e of s o i l s and w e a t h e r e d r o c k . E x t r e m e c a r e h a s t o be t a k e n in m a k i n g p r e d i c -t i o n s r e g a r d i n g t h e r a t e and d i r e c t i o n of g r o u n d - w a t e r m o v e m e n t . T r a c e r t e c h n i q u e s a r e o f t e n u s e f u l f o r t h i s p u r p o s e . E v e n t h o u g h s o m e of t h e s e t e c h n i q u e s a r e h e l p f u l f o r p r e d i c t i n g t he r a d i o a c t i v i t y m o v e m e n t p a t t e r n in t he c a s e of a t a n k f a i l u r e a n d f o r t a k i n g p r e v e n t i v e m e a s u r e s , i t i s a s a f e r p r a c t i c e t o l o c a t e t h e s t o r a g e t a n k s h o l d i n g h i g h e r - l e v e l r a d i o a c t i v e w a s t e s a b o v e t h e w a t e r t a b l e .

8 . 2 . 3 . M o v e m e n t of r a d i o a c t i v i t y in t h e g r o u n d

T h e m o v e m e n t of r a d i o a c t i v i t y and t h e e x t e n t of c o n t a m i n a t i o n of t h e s u r r o u n d i n g s of a t a n k due t o l e a k a g e w i l l d e p e n d upon t h e f o l l o w i n g f a c t o r s :

(a) N a t u r e of w a s t e (b) T y p e and c o m p o s i t i o n of t he s o i l (c) E f f e c t i v e r e t e n t i o n c a p a c i t y of t h e s o i l f o r t h e r a d i o n u c l i d e s p r e s e n t

i n t h e w a s t e (d) R a t e a n d d i r e c t i o n of m o v e m e n t of g r o u n d - w a t e r (e) A d d i t i o n a l r e t e n t i o n in t h e a q u i f e r zone (f) Di lu t ion , if a n y , of t h e c o n t a m i n a t e d g r o u n d - w a t e r at t he point of

e m e r g e n c e .

W h e n w a s t e e s c a p e s f r o m the t ank it p e r c o l a t e s t h r o u g h t h e s u r r o u n d i n g s o i l , u n d e r g o e s c o m p l e x p h y s i c o - c h e m i c a l c h a n g e s a n d j o i n s t h e g r o u n d -w a t e r . D u r i n g p e r c o l a t i o n , s o m e of t h e r a d i o n u c l i d e s s u c h a s s t r o n t i u m , c a e s i u m , e t c . a r e r e t a i n e d by t h e s o i l . T h e e x t e n t of s u c h r e t e n t i o n d e p e n d s on t h e n a t u r e of w a s t e a n d the t y p e of t h e s o i l . R a d i o n u c l i d e s l i k e r u t h e n i u m , which a r e n o t r e a d i l y r e t a i n e d by t h e s o i l , w i l l c o n t a m i n a t e t he a q u i f e r z o n e . S o m e of t h e r a d i o n u c l i d e s i n i t i a l l y r e t a i n e d b y t h e s o i l m a y , i n c o u r s e of t i m e , be r e l e a s e d d u e t o l e a c h i n g , wh ich w i l l a l s o r e s u l t in t h e c o n t a m i n a t i o n of t h e a q u i f e r z o n e .

8 . 3 . E n v i r o n m e n t a l m o n i t o r i n g

L e a k a g e s f r o m s t o r a g e t a n k s a r e u s u a l l y d e t e c t e d a n d c o n t a i n e d at t h e s o u r c e i t s e l f by p r o v i d i n g s u i t a b l e d e v i c e s . O n c e t h e w a s t e r e a c h e s t he g r o u n d , t h e d e t e c t i o n of r a d i o a c t i v i t y i n t h e s o i l and in t h e g r o u n d - w a t e r i s l i k e l y t o b e d e l a y e d and t h e r e c o v e r y of t h e l i q u i d w a s t e i s n o l o n g e r p o s -s i b l e . C o n t i n u o u s p u m p i n g and a n a l y s i s of t h e g r o u n d - w a t e r f r o m s u i t a b l y p l a c e d m o n i t o r i n g w e l l s w i l l e n s u r e the d e t e c t i o n of p o s s i b l e c o n t a m i n a t i o n of t h e e n v i r o n m e n t . A c o s t l y but m o r e r e l i a b l e a l t e r n a t i v e t o t h i s wou ld b e c l o s e p l a c e m e n t of w e l l s a n d a n a l y s i s of t h e g r o u n d - w a t e r .

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A n a l y s i s of s o i l and g r o u n d - w a t e r s a m p l e s and d e t e r m i n a t i o n of t he r a t e a n d d i r e c t i o n of g r o u n d - w a t e r f low p r o v i d e s a t i s f a c t o r y d a t a t o d e t e c t t h e m o v e m e n t of s u b - s u r f a c e r a d i o a c t i v i t y . T h e s e d a t a a r e a l s o u s e f u l f o r p r e d i c t i n g t h e t i m e i t t a k e s t h e r a d i o n u c l i d e s p r e s e n t in t h e w a s t e to r e a c h t h e b o u n d a r i e s of t h e c o n t r o l l e d a r e a .

8 . 4 . C o n t r o l m e a s u r e s

S o m e of t h e c o n t r o l m e a s u r e s tha t m a y b e c o n s i d e r e d f o r d e c r e a s i n g the e x t e n t of e n v i r o n m e n t a l c o n t a m i n a t i o n a r e :

(a) M a k i n g t h e s u r r o u n d i n g s o i l i m p e r m e a b l e (b) I n s t a l l i n g ' l i l e - d r a i n a g e s y s t e m s ' (c) P r o v i d i n g p r o t e c t i v e b a r r i e r s .

T h e s u r r o u n d i n g e a r t h c a n b e m a d e i m p e r m e a b l e by p u m p i n g an a s p h a l t e m u l s i o n in to i t . It h a s b e e n r e p o r t e d t h a t a 10% a s p h a l t e m u l s i o n i n w a t e r s e a l s s a n d o r s a n d y c l ay t y p e s of s o i l [ 28] . As t h e g r o u n d - w a t e r i s t h e m a i n c a r r i e r of r a d i o n u c l i d e s p r e s e n t in t he w a s t e , t h e g r o u n d - w a t e r m o v e m e n t t h r o u g h t h e t a n k f a r m a r e a c a n be c o n t r o l l e d by p r o v i d i n g a s u i t a b l e ' t i l e - d r a i n a g e s y s t e m ' [ 2 9 ] , N a t u r a l l y - o c c u r r i n g c l ay m i n e r a l s l i k e b e n t o n i t e , c l i n o p t i l o l i t e o r e x p a n d e d v e r m i c u l i t e m a y b e p r o v i d e d a s b a r r i e r s in the t a n k f a r m a r e a f o r t h e e f f e c t i v e r e t e n t i o n of s o m e of the r a d i o n u c l i d e s . T h e a b s o r p t i o n c a p a c i t y of t h e s o i l c a n b e i n c r e a s e d by i n j e c t i n g s u i t a b l e c h e m i c a l r e a g e n t s which r e a c t wi th s i l i c a p r e s e n t in the s o i l . At Mol L a b o r a t o r i e s , B e l g i u m , t h e s y s t e m ' s i l i c a - h y d r o f l u o r i c a c i d - a n t i m o n i c a c i d ' h a s b e e n u s e d f o r t he e f f e c t i v e r e m o v a l of s t r o n t i u m [ 3 0 ] . It i s n e c e s s a r y t o e n s u r e l o n g - t e r m r e l i a b i l i t y and u s e f u l n e s s of t h e a b o v e - c i t e d p r e v e n t i v e m e a s u r e s f o r a p a r t i c u l a r s i t e .

8 . 5 . E m e r g e n c y p r o v i s i o n s

C o n d i t i o n s l e a d i n g to e m e r g e n c y in a t a n k i n s t a l l a t i o n m a y a r i s e due t o f a i l u r e of t h e t a n k i t s e l f o r of any of i t s a c c e s s o r i e s . It s h o u l d be p o s -s i b l e to d e t e c t t he f a i l u r e wi thou t any d e l a y s o t h a t r e m e d i a l a c t i o n can be t a k e n . T h e s e c o n d a r y c o n t a i n m e n t p r o v i d e d f o r a t ank s h o u l d h a v e s u f f i -c i e n t c a p a c i t y t o r e c e i v e t h e e n t i r e c o n t e n t s of t h e t a n k in t h e c a s e of t a n k f a i l u r e . F o r t a n k i n s t a l l a t i o n s ho ld ing h i g h e r - l e v e l r a d i o a c t i v e w a s t e s c r i t i c a l c o m p o n e n t s t h a t a r e l i k e l y t o f a i l shou ld b e d u p l i c a t e d by i n d e p e n -den t c o n t r o l s t o f a c i l i t a t e t h e i s o l a t i o n of t h e d e f e c t i v e u n i t s t h u s a s s u r i n g c o n t i n u e d o p e r a t i o n .

9. S U M M A R Y O F E X P E R I E N C E

9 . 1 . G e n e r a l

N u c l e a r i n s t a l l a t i o n s u s e a v a r i e t y of t ank d e s i g n s , d e p e n d i n g on the n a t u r e and q u a n t i t y of w a s t e p r o d u c e d , t he p u r p o s e of s t o r a g e and the p r e -v a i l i n g e n v i r o n m e n t a l c o n d i t i o n s . The d e s i g n d e t a i l s of t y p i c a l t a n k s tha t a r e b e i n g u s e d at v a r i o u s i n s t a l l a t i o n s , t o g e t h e r wi th the o p e r a t i o n a l e x p e r i e n c e ( w h e r e v e r r e p o r t e d ) , a r e s u m m a r i z e d b e l o w .

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W a s t e s r e s u l t i n g f r o m t h e o p e r a t i o n of n u c l e a r r e a c t o r s a r e b e i n g m a n a g e d s u c c e s s f u l l y b y u s i n g s u i t a b l e t a n k s f o r t r e a t m e n t o r c o n t r o l l e d d i s c h a r g e t o t h e e n v i r o n m e n t . T h e t a n k d e s i g n a t d i f f e r e n t i n s t a l l a t i o n s d o e s no t v a r y m u c h f o r s i m i l a r t y p e s of r e a c t o r s , a s the m e t h o d s a d o p t e d f o r t h e i r m a n a g e m e n t h a v e b e e n m o r e o r l e s s s t a n d a r d i z e d .

R a d i o a c t i v e w a s t e s a r i s i n g f r o m r e s e a r c h l a b o r a t o r i e s a r e c o l l e c t e d i n t a n k s u s u a l l y i n s t a l l e d a t t h e p r o d u c t i o n s i t e s of t h e w a s t e s . A s t h e n a t u r e , a c t i v i t y a n d v o l u m e of t h e s e w a s t e s v a r y c o n s i d e r a b l y f r o m s i t e t o s i t e , t a n k s of d i f f e r e n t t y p e s and c a p a c i t i e s a r e b e i n g u s e d .

9 . 2 . N u c l e a r p o w e r s t a t i o n s [ 31 ]

9 . 2 . 1 . Y a n k e e A t o m i c E l e c t r i c Co . (USA)

T h e l i qu id w a s t e s f r o m t h i s p r e s s u r i z e d - w a t e r r e a c t o r a r e s e g r e g a t e d i n t o h y d r o g e n - and a i r - b e a r i n g w a s t e s t r e a m s . T h e h y d r o g e n - b e a r i n g s t r e a m i s c o l l e c t e d i n a p r i m a r y d r a i n c o l l e c t i o n t a n k (28 .4 m 3 ) m a d e of s t a i n l e s s s t e e l . W a s t e f r o m t h i s t ank i s p u m p e d to a s t a i n l e s s - s t e e l - c l a d w a s t e h o l d - u p t a n k (284 m 3 ) . T h e w a s t e s p r o d u c e d d u r i n g s h u t - d o w n a r e p u m p e d f r o m a l o w - p r e s s u r e s u r g e t a n k t o a s t a i n l e s s - s t e e l - c l a d a c t i v i t y d i l u t i o n t ank (284 m 3 ) . T h e c h e m i c a l w a s t e s t r e a m c o n t a i n i n g a i r , r e s u l t i n g f r o m t h e d e c o n t a m i n a t i o n of e q u i p m e n t , i s s t o r e d in a s t a i n l e s s - s t e e l m o n i t o r i n g t a n k ( 1 7 . 7 9 m 3 ) .

D e p e n d i n g on t h e i r a c t i v i t y c o n t e n t , h y d r o g e n - b e a r i n g l i q u i d s a r e e i t h e r d i s c h a r g e d t h r o u g h a d i s p o s a b l e c a r t r i d g e f i l t e r t o t h e c o n d e n s e r c o o l i n g - w a t e r e f f l u e n t o r e v a p o r a t e d . T h e a i r - b e a r i n g w a s t e s a r e c o l l e c t e d in t w o s t a i n l e s s - s t e e l t a n k s ( 5 . 1 9 m 3 e a c h ) . D e p e n d i n g on the a c t i v i t y c o n t e n t , t h e s e w a s t e s a r e e i t h e r d i s c h a r g e d a t a c o n t r o l l e d r a t e t o t h e m a i n c o n d e n s e r c o o l i n g - w a t e r d i s c h a r g e l i n e o r t r a n s f e r r e d t o t h e g r a v i t y d r a i n t a n k s f o r f u r t h e r t r e a t m e n t by e v a p o r a t i o n . T h e w a s t e s a r e p r o c e s s e d i n a n e v a p o r a t o r i n s e p a r a t e b a t c h e s t o p r e v e n t a p o s s i b l e a i r - h y d r o g e n e x p l o s i v e m i x t u r e . T h e c o n d e n s a t e i s p u m p e d t o e i t h e r of t h e two a l u m i n i u m t e s t t a n k s ( 3 0 . 4 3 m 3 e a c h ) h a v i n g d i a p h r a g m s e a l s . B a s e d on t h e a n a l y s i s of s a m p l e s , t he w a s t e i s t r a n s f e r r e d t o p r i m a r y - w a t e r m a k e - u p o r d i s c h a r g e d a f t e r d i l u t i o n . T a b l e HI g i v e s t he d e s i g n d a t a of t he t a n k s u s e d i n t h i s i n s t a l l a t i o n [ 3 2 ] .

9 . 2 . 2 . C e n t r a l E l e c t r i c i t y G e n e r a t i n g B o a r d (UK)

R a d i o a c t i v e l i q u i d w a s t e s a r i s i n g f r o m M a r k I (Magnox) G a s - C o o l e d R e a c t o r (GCR) p o w e r s t a t i o n s a r e n o r m a l l y of l o w s p e c i f i c a c t i v i t y , r a n g i n g f r o m a b o u t 10"5 t o 10"2 C i / m 3 . T h e p H - v a l u e s of w a s t e s m a y v a r y f r o m abou t 3 t o 12 .

T h e n o r m a l p r a c t i c e a t M a r k I GCR p o w e r s t a t i o n s i s t o p r o v i d e an e f f l u e n t t r e a t m e n t p l an t i n wh ich a c t i v e e f f l u e n t i s c o l l e c t e d in p r i m a r y m o n i t o r i n g a n d d e l a y t a n k s . T h e e f f l u e n t i s n e u t r a l i z e d a n d , a f t e r p a s s i n g t h r o u g h f i l t e r s , h e l d in f i n a l m o n i t o r i n g a n d d e l a y t a n k s f o r s a m p l i n g , a n a l y s i s and f i n a l d i s c h a r g e f r o m t h e s t a t i o n in t h e c o o l a n t w a t e r o u t l e t , i n w h i c h i t i s w e l l m i x e d a n d d i l u t e d n o r m a l l y by a f a c t o r g r e a t e r t h a n 10 4 . T h e a c t i v e e f f l u e n t d i s c h a r g e d f r o m a t y p i c a l M a r k I GCR p o w e r s t a t i o n i s of t h e o r d e r of 36 m 3 / d a y .

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P a r t i c u l a t e m a t t e r i s e x t r a c t e d by f i l t e r s a t a l l s t a t i o n s a n d c o l l e c t e d by b a c k w a s h i n g and s e t t l e m e n t f o r a c c u m u l a t i o n a t t he s i t e . In s p e c i a l c a s e s , f o r e x a m p l e at T r a w s f y n y d d , w h e r e t he l i q u i d e f f l u e n t i s d i s c h a r g e d in to a l a k e , an a d d i t i o n a l p l a n t i s p r o v i d e d to r e m o v e the s o l u b l e a c t i v i t y .

T h e e f f l u e n t t r e a t m e n t p lan t t a n k s in M a r k I G C R s t a t i o n s a r e n o r m a l l y l i n e d t o r e s i s t c o r r o s i o n a n d h a v e p r o v i s i o n f o r c o n t a i n m e n t and d e t e c t i o n of l e a k s , u s u a l l y b y s t a n d i n g on a n a s p h a l t t r a y wi th t e l l - t a l e d r a i n s and s u m p s . T h e t a n k s a r e s i z e d f o r e s t i m a t e d m a x i m u m d a i l y a r i s i n g s and a r e n o r m a l l y d u p l i c a t e d f o r u s e on a l t e r n a t e d a y s . F a c i l i t i e s a r e p r o v i d e d f o r s t i r r i n g o r r e c i r c u l a t i o n t o m i n i m i z e s e t t l e m e n t , f o r n e u t r a l i z i n g and f o r c o l l e c t i n g r e p r e s e n t a t i v e s a m p l e s . F i n a l d i s c h a r g e p u m p s a r e n o r m a l l y c a p a b l e of d i s c h a r g i n g t h e f i n a l m o n i t o r i n g a n d d e l a y t a n k s in abou t two h o u r s .

D e s i g n f e a t u r e s of s o m e of t h e e f f l u e n t t r e a t m e n t p l an t t a n k s u s e d a t M a r k I GCR p o w e r s t a t i o n a t S i z e w e l l 'A' a r e g i v e n in T a b l e III [ 3 3 ] .

9 . 2 . 3 . D o u g l a s P o i n t P o w e r S t a t i o n ( C a n a d a )

T h i s i s a 2 0 0 - M W ( e ) h e a v y - w a t e r n a t u r a l - u r a n i u m t y p e p o w e r r e a c t o r . T h e l i q u i d w a s t e s p r o d u c e d a r e s e g r e g a t e d in to p o t e n t i a l l y a c t i v e , a c t i v e / n o n - c h e m i c a l and a c t i v e / c h e m i c a l s t r e a m s .

T h e f i r s t two s t r e a m s a r e r e l e a s e d in a c o n t r o l l e d m a n n e r i n t o t h e e n v i r o n m e n t , t a k i n g a d v a n t a g e of t h e d i l u t i o n a v a i l a b l e a t t h e p l a n t s i t e . T h e t h i r d s t r e a m i s d i s c h a r g e d a f t e r t r e a t m e n t . A l s o , p r o v i s i o n i s m a d e to d i v e r t t h e l o w - a c t i v e s t r e a m f o r t r e a t m e n t w h e n e v e r t h e s p e c i f i c a c t i v i t y i s h i g h e r o r t he p l a n t e f f l u e n t f low r a t e i s not a d e q u a t e t o a f f e c t t h e d i s c h a r g e wi th in t h e p e r m i s s i b l e l i m i t s .

T h e p o t e n t i a l l y a c t i v e w a s t e i s d i r e c t l y s e n t to t he p l a n t coo l an t w a t e r t h r o u g h a n i n - l i n e a c t i v i t y m o n i t o r . If t he a c t i v i t y e x c e e d s t he m o n i t o r - s e t po in t , t he w a s t e i s a u t o m a t i c a l l y r e d i r e c t e d t o a h o l d - u p t a n k (31. 62 m 3 ) . T h e a c t i v e n o n - c h e m i c a l w a s t e s t r e a m s a r e r e c e i v e d in a h o l d - u p t ank f o r d e c a y and a n a l y s i s . If t h e a c t i v i t y i s low, t he w a s t e i s d i v e r t e d t o a d i s p o s a l t a n k (182 m 3 ) . T w o t a n k s a r e p r o v i d e d f o r t h i s p u r p o s e . R e m o t e l y o p e r a t e d m e c h a n i c a l a g i t a t o r s a r e u s e d f o r m i x i n g . T h e p u m p i n g r a t e f r o m t h i s t a n k to t he p lan t e f f l u e n t l i n e can b e a d j u s t e d d e p e n d i n g upon t h e d i l u t i o n a v a i l a b l e . A l s o , p r o v i s i o n i s m a d e f o r d i l u t i n g t h e w a s t e s t o t h e d e s i r e d l e v e l b e f o r e p u m p i n g t h e m in to t h e p l an t c o o l a n t w a t e r . T h e h i g h e r - a c t i v e s t r e a m s a r e d i v e r t e d f o r t r e a t m e n t .

T h e a c t i v e c h e m i c a l w a s t e s a r e c o l l e c t e d in a s t a i n l e s s - s t e e l t a n k (9. 09 m 3 ) and a r e t r e a t e d on a da i ly b a s i s . An a g i t a t o r i s p r o v i d e d in t h e t a n k f o r m i x i n g ; if t h e q u a n t i t y h a n d l e d i s s m a l l , m i x i n g i s e f f e c t e d by r e c i r c u l a t i o n . T h e a c i d i c w a s t e s a r e n e u t r a l i z e d in t h i s t a n k and t r e a t e d , if n e c e s s a r y .

S a l i e n t d e s i g n d e t a i l s of t h e t a n k s d e s c r i b e d a b o v e a r e g iven in T a b l e IH [ 34 ] .

9 . 3 . R e s e a r c h e s t a b l i s h m e n t s

9 . 3 . 1 . Oak R i d g e N a t i o n a l L a b o r a t o r y , T e n n e s s e e (USA) [ 3 5 ]

T h e r e s e a r c h and d e v e l o p m e n t w o r k and the o p e r a t i o n of n u c l e a r r e a c -t o r s g ive r i s e to l a r g e q u a n t i t i e s of w a s t e s v a r y i n g in n a t u r e and a c t i v i t y .

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T A B L E III. DESIGN DATA O F T Y P I C A L TANKS U S E D F O R T H E S T O R A G E O F R A D I O A C T I V E W A S T E S F R O M N U C L E A R P O W E R R E A C T O R S [ 3 1 - 3 4 ]

Name of installation

Average activity level

( C i / m 3 ) Purpose of storage

Capacity of tank -(m 3 )

Material of construction

General details Important accessories Salient safety

features

Yankee Atomic i o - 2 Gravity drain tank 17.79 Stainless steel Underground cyl indrical Level indicator, high- 61-mm-thick Electric Co. (USA)

-

tank'with dished head; shell and end-plates of 4.76 and 7.93 mm respectively

level alarm, auto-pump start, etc.

concrete provides shielding

10~Z Primary drain collection tank

28.4 Stainless steel Underground cyl indrical - tank with dished head;

shell and-end-plates of 6.35 and 7.93 mm respectively

Level and temperature indicator, auto-pump start, etc.

Same

io " 3 Waste hold-up and activity dilution decay tank

284 Concrete Above-ground cyl indrical tank clad with stainless steel; shell top and bottom plates of 9.52. 7.93 and 12.48 mm respectively

Sample valve, level and temperature indicator, etc.

Same

10"7 Test tank 30.43 Aluminium Above-ground cyl indrical tanks; shell top and bottom plates of 4. 76 and 6.35 mm respectively

Sample valve,, level and temperature indicator, high-level alarm, etc.

' - Monitored waste 5.1!) Stainless steel Above-ground cyl indrical Agitator -

tank tank with dished bottom; shell and end-plates of 4.76 mm

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Central Electr ic i ty ' Generating Board,

Sizewell ' A * (UK)

Act ive drain reception tank

20.45 Concrete Above-ground tank on . asphalt tray wi th sump

Sampler, leve l indicator and alarm, leak detector, e tc .

Concrete shielding, internal coating of Adcora Pervon (isocyanate bitumen, epoxy, e tc . )

- Neutral izat ion tank 104.55 • Concrete Same Same - Same

- Backwash col lect ion tank

19.32 - Concrete Same Same Same

Setting tank 31.82 Carbon steel Same Same - Concrete shielding, internal coating of neopcene, e tc .

Other than t r i t i um 6 x 10"4

Tr i t i um ' 2 X 10~2

Final monitor ing and delay tank

105.45 Concrete - Above-ground concrete tank on asphalt tray wi th t e l l - t a l e drains and sumps

Sampler, leve l indicator and alarm, leak detector, etc.

Same

Douglas Point Power Station (Canada)

2 X 10"2 Hold-up tank 31.82 Carbon steel - Above-ground cy l indr ica l tank w i th shell and head-plates of 7.93 m m

Agitator, sample valve, monitor, recorder, leve l indicator, etc.

Concrete shielding, internal v i n y l coating, basement pi t , e tc .

1 Evaporator tank 9 .00 Stainless steel Above-ground cy l indr ica l tank with shell and head-plates of 7.93 m m

Agitator, sampler, leve l indicator, monitor, e tc .

Basement pi t

10"4 Dispersal tank 181.81 ' Carbon steel Above-ground cy l indr ica l .tank with shel l and end-plates of 6 .35 m m

Agitator, sampler, tank leve l alarm, i n - l i ne ac t iv i ty monitor, etc.

Internal v i n y l coating, •• basement p i t , e tc .

00

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L i q u i d w a s t e s l o c a l l y c a l l e d i n t e r m e d i a t e - l e v e l w a s t e s ( ILW), r a n g i n g i n a c t i v i t y l e v e l f r o m 3 X 1 0 " 3 to 3 X 1 0 s C i / m 3 , a r e p r o d u c e d at a n a v e r a g e r a t e of 20 X 40 m 3 / d o r about 1. 1 X 104 m 3 / y r . T h e s e w a s t e s a r e c o l l e c t e d b y g r a v i t y f low t h r o u g h s t a i n l e s s - s t e e l p i p e l i n e s to 21 m o n i t o r i n g t a n k s , e a c h l o c a t e d n e a r a m a j o r s o u r c e of w a s t e . T h e p u r p o s e of t he m o n i t o r i n g t a n k s i s to p r o v i d e a t e m p o r a r y h o l d - u p of t h e w a s t e f o r s a m p l i n g and v o l u m e m e a s u r e m e n t p r i o r to s e g r e g a t i o n and s u b s e q u e n t t r e a t m e n t o r d i s c h a r g e . T o p r o t e c t the t a n k s , t he t r a n s f e r p i p e s and l e s s c o r r o s i o n -r e s i s t a n t e q u i p m e n t in t h e w a s t e s y s t e m , t he w a s t e in t h e m o n i t o r i n g t a n k s i s m a d e a l k a l i n e b y a d d i n g c a u s t i c s o d a s o l u t i o n whi l e t he t a n k s a r e b e i n g f i l l e d .

T h e t a n k s v a r y in c a p a c i t y f r o m 2 t o 10 m 3 e a c h (to p r o v i d e a b o u t two d a y s ' f i l l i n g t i m e ) . A t y p i c a l m o n i t o r i n g t a n k i n s t a l l a t i o n i s s h o w n in F i g . 12 . T h i s i s a n u n d e r g r o u n d s t a i n l e s s - s t e e l t a n k ( A m e r i c a n I r o n & S t e e l I n s t i t u t e , t y p e 347) a n c h o r e d t o a c o n c r e t e s a u c e r t h a t s l o p e s t o w a r d s a s u m p . A f l o a t t y p e o r a p n e u m a t i c b u b b l e r t y p e l iqu id l e v e l gauge i s p r o v i d e d t o i n d i c a t e t h e q u a n t i t y of w a s t e in t h e t a n k . T h e t a n k i s a l s o p r o v i d e d wi th a r e c i r c u l a t i n g t y p e s a m p l e r , a m e a n s of a g i t a t i n g t h e t ank c o n t e n t s , and a ven t t h r o u g h a f i l t e r to t h e a t m o s p h e r e o r t o t h e v e s s e l o f f -g a s s y s t e m of t he f a c i l i t y . T h e s u m p u n d e r t h e t a n k c a n b e s a m p l e d t h r o u g h a ' d r y w e l l ' e x t e n d i n g to t h e s u r f a c e t o d e t e c t any l e a k a g e f r o m t h e t a n k . C r u s h e d s t o n e i s p a c k e d a r o u n d t h e tank a b o v e the c o n c r e t e s a u c e r t o t h e t a n k t o p . At l e a s t 1. 3 m of e a r t h i s p r o v i d e d a b o v e t h e t a n k t o p t o s e r v e a s s h i e l d i n g . T h e l i qu id l e v e l s in a l l t h e m o n i t o r i n g t a n k s a r e c o n t i n u o u s l y t e l e m e t e r e d to , a n d r e c o r d e d a t , t he w a s t e m o n i t o r i n g c e n t r e , w h e r e a n o p e r a t o r i s on du ty a t a l l t i m e s .

T h e ILW in t h e m o n i t o r i n g t a n k s i s t r a n s f e r r e d b y s e l f - p r i m i n g p u m p s o r s t e a m j e t s t h r o u g h 5 - c m - d i a m . s t a i n l e s s - s t e e l p i p e - l i n e s t o a n u n d e r -g r o u n d 645 m 3 c o n c r e t e t a n k , w h i c h s e r v e s f o r t e m p o r a r y s t o r a g e and p r o v i d e s s u r g e c a p a c i t y f o r a c c o m m o d a t i n g the l a r g e v o l u m e s of w a s t e t h a t m a y a r i s e f r o m e m e r g e n c y o p e r a t i o n s . T h e c h o i c e b e t w e e n p u m p s and j e t s i s d e t e r m i n e d by t h e e l e v a t i o n of t h e m o n i t o r i n g t a n k s and t h e l e n g t h of t h e t r a n s f e r l i n e s . F r o m t h e s u r g e t a n k t h e w a s t e i s p u m p e d in b a t c h e s t o t h e w a s t e e v a p o r a t o r f a c i l i t y , w h e r e it i s c o n c e n t r a t e d by a f a c t o r of 20 t o 1 in a s i n g l e - s t a g e p o t - t y p e e v a p o r a t o r . T h e c o n c e n t r a t e i s s e n t t o a n o t h e r 645 m 3 u n d e r g r o u n d c o n c r e t e t a n k i d e n t i c a l t o t h e s u r g e t a n k , w h e r e it i s s t o r e d t e m p o r a r i l y ( s e v e r a l m o n t h s ) b e f o r e b e i n g p u m p e d a b o u t 3 . 2 k m t h r o u g h a 5 - c m - d i a m . c a r b o n s t e e l p i p e - l i n e to t h e s h a l e - f r a c t u r i n g s i t e f o r u l t i m a t e d i s p o s a l in d e e p (300 m ) u n d e r g r o u n d f o r m a t i o n s .

T h e two 645 m 3 u n d e r g r o u n d c o n c r e t e t a n k s p r e v i o u s l y m e n t i o n e d a r e g r o u p e d wi th f o u r o t h e r s u c h t a n k s in two r o w s of t h r e e t a n k s s p a c e d wi th t h e i r c e n t r e s 20 m a p a r t . T h e t a n k s a r e i n t e r c o n n e c t e d by a s y s t e m of p i p e - l i n e s a l l o w i n g t h e c o n t e n t s of any of t he t a n k s to b e t r a n s f e r r e d to a n o t h e r . E a c h t a n k i s 1 5 . 4 m in d i a m e t e r by 3 . 7 m d e e p , s u r m o u n t e d by a d o m e d t o p h a v i n g a m a x i m u m d e p t h of 2 m . T h e t a n k b o t t o m s a r e 7. 6 c m t h i c k , and t h e s i d e s a r e 1 5 . 2 c m th ick at t h e b o t t o m and 12. 7 c m t h i c k a t t h e t o p . T h e t a n k b o t t o m s r e s t on c o n c r e t e s a u c e r s p l a c e d on b e d - r o c k a t a d e p t h of 5 . 5 m b e l o w the s u r f a c e , e a c h s a u c e r h a v i n g a s l i g h t l y l a r g e r d i a m e t e r t h a n t h e t a n k s a n d a c u r b a r o u n d t h e o u t e r r i m . C r u s h e d s t o n e i s p a c k e d a r o u n d the o u t s i d e s of t he t a n k s a b o v e t h e c o n c r e t e s a u c e r s to t h e po in t of m a x i m u m l i q u i d l e v e l in t h e t a n k s . E a c h t a n k b o t t o m and s a u c e r s l o p e s 2% t o w a r d s a low poin t f r o m which a 1 5 - c m - d i a m . t e r r a - c o t t a p ipe

44

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FIG. 12. Monitoring tank at Oak Ridge National Laboratory [ 3 5 ] .

c o n d u c t s any d r a i n a g e f r o m t h e . t a n k to a dry . w e l l t h a t e x t e n d s t o t he s u r f a c e . A l l s i x d r y w e l l s d r a i n t o a l e a k d e t e c t i o n s y s t e m t h a t i s c o n t i n u o u s l y m o n i t o r e d f o r r a d i o a c t i v i t y . T h e t o p s of t h e t a n k s a r e c o v e r e d u n i f o r m l y wi th 2 m of e a r t h t o p r o v i d e s h i e l d i n g . E a c h t a n k i s e q u i p p e d wi th a p n e u -m a t i c b u b b l e r t y p e l i q u i d l e v e l g a u g e a n d a s a m p l e r a n d i s v e n t e d t h r o u g h a f i l t e r t o t h e a t m o s p h e r e .

T h e t a n k s w e r e c o n s t r u c t e d in 1943 b y t h e G u n i t e p r o c e s s , by w h i c h a c e m e n t - s a n d m i x t u r e c o m b i n e d wi th w a t e r w a s d i s c h a r g e d in t h e f o r m of m o r t a r f r o m t h e n o z z l e of a c e m e n t gun . T h e m i n i m u m c o n c r e t e s t r e n g t h

45

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s p e c i f i e d w a s 175 k g / c m 2 . T h e t ank b o t t o m s , s i d e s and d o m e - s h a p e d t o p s a r e r e i n f o r c e d wi th w i r e m e s h a n d s t e e l r o d s , e a c h t ank c o n t a i n i n g a p p r o x i m a t e l y 743 m 2 of w i r e m e s h and o v e r 6 t o n n e s of r e i n f o r c i n g r o d w i th in t h e c o n c r e t e . T h e i n s i d e s u r f a c e s of t he t a n k s w e r e c o a t e d wi th a b i t u m a s t i c o r a s p h a l t i c p a i n t . T h e s e t a n k s w e r e o r i g i n a l l y i n t e n d e d t o s t o r e t h e ILW f o r an i n d e f i n i t e p e r i o d , but t h e q u a n t i t y of t h e w a s t e soon e x c e e d e d t h e c a p a c i t y of. t he t a n k s and t h e y h a v e s i n c e b e e n u s e d on ly f o r t e m p o r a r y s t o r a g e (a f ew m o n t h s ) .

9 . 3 . 2 . A t o m i c E n e r g y R e s e a r c h E s t a b l i s h m e n t , H a r w e l l (UK) [ 36 ]

T h e r e s e a r c h c a r r i e d out and the o p e r a t i o n of e x p e r i m e n t a l r e a c t o r s p r o d u c e a n a v e r a g e e s t i m a t e d v o l u m e of 240 m 3 / d of l iqu id w a s t e s . T h e a c t i v i t y l e v e l s of t h e s e w a s t e s v a r y f r o m d e t e c t i o n l e v e l t o 10 C i / m 3 and the pH v a r i e s f r o m 1 to 11.

C a t e g o r y - 4 w a s t e s (10" 1 t o 10 C i / m 3 ) a r e s t o r e d i n t a n k s of 10 m 3

c a p a c i t y m a d e of e i t h e r s t a i n l e s s s t e e l o r r e s i n - b o n d e d g l a s s - r e i n f o r c e d l a m i n a t e f o r r e t e n t i o n p r i o r t o t r e a t m e n t in t he h i g h - l e v e l p l a n t . F o u r s u c h t a n k s a r e c o n t a i n e d i n a l a r g e , h e a v i l y s h i e l d e d r e i n f o r c e d c o n c r e t e (40 c m ) o u t e r t a n k w h i c h i s l i n e d wi th a b r i c k o u t e r l i n i n g and a t i l e d b r i c k i n n e r l i n i n g . S ix s u c h t a n k s a r e c o n t a i n e d i n t h e i r i n d i v i d u a l s u m p s m a d e of r e i n f o r c e d c o n c r e t e wi th a n a s p h a l t l i n i n g , w h i c h a r e l a r g e enough to ho ld t h e e n t i r e c o n t e n t of t h e t a n k . T h e c a t e g o r y - 4 w a s t e t r e a t m e n t p l a n t s h o w i n g s t o r a g e t a n k s i s g i v e n . i n F i g . 13 .

C a t e g o r y - 3 w a s t e s ' ( 1 0 " s t o 10" 1 C i / m 3 ) r e c e i v e d f r o m h o l d - u p t a n k s a r e s t o r e d i n t e n a b o v e - g r o u n d c y l i n d r i c a l t a n k s . m a d e of c a r b o n s t e e l and h a v i n g a c a p a c i t y of 88 m 3 e a c h . T h e w a l l a n d t h e b o t t o m of t h e t a n k s a r e 0 . 6 5 and 1 . 3 c m t h i c k r e s p e c t i v e l y . S ix of t h e s e t a n k s a r e u s e d f o r l i q u i d s and f o u r f o r s t o r a g e of r a d i o a c t i v e s l u d g e s . T h e s e t a n k s a r e h o u s e d in s u m p s to p r e v e n t c o n t a m i n a t i o n of t h e g r o u n d . T h e w a s t e i s m i x e d e i t h e r by r e c i r c u l a t i o n o r by a i r s p a r g i n g .

C a t e g o r y - 2 w a s t e s (10~3 C i / m 3 ) a r e s t o r e d at p r o d u c t i o n s i t e s in g r a v i t y - f e d d e l a y t a n k s c o n s t r u c t e d of c a r b o n s t e e l ( 0 . 6 5 c m ) , e n g i n e e r i n g b r i c k s (15 c m ) o r r e i n f o r c e d c o n c r e t e (15 c m ) . T h e s e t a n k s a r e m o s t l y r e c t a n g u l a r i n s h a p e , on ly t h o s e of s m a l l v o l u m e s a r e c y l i n d r i c a l . T h e i r c a p a c i t y v a r i e s f r o m 2. 3 m 3 t o 4 5 . 4 m 3 d e p e n d i n g upon t h e q u a n t i t y of w a s t e s p r o d u c e d . A l l t h e s t e e l t a n k s a r e p a i n t e d on the o u t s i d e f o r c o r r o s i o n r e s i s t a n c e . A h a r d - r u b b e r l i n ing a t t he i n n e r s u r f a c e h a s b e e n found t o b e s a t i s f a c t o r y . A l l t a n k s a r e c o n t a i n e d in t h e i r own s u m p of a s p h a l t - l i n e d b r i c k o r c o n c r e t e t o p r e v e n t l e a k a g e t o t h e g r o u n d . At l e a s t two t a n k s a r e p r o v i d e d in a b u i l d i n g so t h a t w h i l e one t a n k i s b e i n g f i l l e d t h e o t h e r i s a v a i l a b l e f o r s a m p l i n g , m o n i t o r i n g and t r a n s f e r t o t he p r e -t r e a t m e n t t a n k s .

T h e two p r e t r e a t m e n t t a n k s (1820 m 3 c a p a c i t y each ) of r e i n f o r c e d c o n c r e t e (30 crri) a r e c o n s t r u c t e d u n d e r g r o u n d wi th an a c i d - r e s i s t i n g b r i c k l i n i n g . E a c h i s p r o v i d e d w i t h s i x s t i r r e r s . T h e t a n k s h a v e s l o p i n g b o t t o m s w i t h s u m p s f o r c o l l e c t i n g t h e s l u d g e . S a m p l e s a r e t a k e n f r o m s e v e r a l p o s i t i o n s and m i x e d to g ive a r e p r e s e n t a t i v e s a m p l e . L e a k a g e c a n b e d e t e c t e d b y l e v e l m e a s u r e m e n t .

T h e two p o s t - t r e a t m e n t t a n k s u s e d (1360 m 3 c a p a c i t y e a c h ) a r e s i m i l a r t o t h e p r e t r e a t m e n t ta:riks and a r e c o n s t r u c t e d of r e i n f o r c e d c o n c r e t e wi th a b i t u m e n l i n i n g .

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CATEGORY-4 TYPE WASTE STORAGE TANKS

FIG. 13. Model of c a t ego ry -4 waste t r ea tmen t plant showing storage tanks, Harwell [ 3 6 ] ,

9 . 3 . 3 . N u c l e a r C e n t r e , C a d a r a c h e ( F r a n c e ) [3 7]

The p r o c e s s i n g of f i s s i l e m a t e r i a l s , r e s e a r c h a c t i v i t i e s and the ope ra t ion of r e a c t o r s p roduce r ad ioac t ive liquid w a s t e s r ang ing in ac t iv i ty f r o m 10"1 to 10~a C i / m 3 and va ry ing in pH f r o m 2 to 9. The e s t i m a t e d quant i ty of w a s t e s p roduced i s about 50 m 3 / d .

T h r e e s t a i n l e s s - s t e e l t anks of 25 m 3 capac i ty each a r e used for i n t e r i m s t o r a g e of i ncoming e f f l u e n t s to f ac i l i t a t e ana ly s i s b e f o r e t r a n s f e r to the su i t ab le p r e t r e a t m e n t t a n k s . The p r e t r e a t m e n t s t o r a g e fac i l i ty c o n s i s t s of eight s t a i n l e s s - s t e e l and eight p r e s t r e s s e d c o n c r e t e t a n k s . The s t a i n l e s s -s t e e l t a n k s a r e used fo r s t o r i n g e f f l uen t s containing a lpha o r v e r y low b e t a -g a m m a ac t iv i ty . The p r e s t r e s s e d c o n c r e t e t anks coated i n t e rna l l y with Epiko te o r i s o m e r i c r u b b e r pa in t s a r e used for s to r ing e f f l uen t s of h i g h e r -l eve l r ad ioac t iv i t y and a l s o fo r e f f luen t s containing c o r r o s i v e e l e m e n t s l ike f l u o r i d e s .

The de ta i l s of s t a i n l e s s - s t e e l t a n k s a r e shown in F i g . 14. T h e s e t anks a r e of 250 m 3 capac i ty each , with an in s ide d i a m e t e r of 9 . 4 m and a height of 2. 98 m . F o u r of the p r e s t r e s s e d c o n c r e t e t a n k s u t i l ized a r e of 250 m 3

capac i ty each , having a d i a m e t e r of 8. 5 m and a height of 4. 5 m . The r e m a i n i n g four t anks , of 500 m 3 capac i ty each , have a d i a m e t e r of 12 m and a height of 4 . 5 m .

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FIG. 14. Sta inless-s teel tanks used at the t r ea tmen t plant , Cadarache [ 3 7 ] .

All p r e t r e a t m e n t tanks a r e ins ta l l ed on c o n c r e t e p l a t f o r m s which prov ide con ta inment for l e a k a g e . A t r a p e z o i d a l block m a d e of compac t so i l , 8 m wide at the b a s e and many m e t r e s high, p rov ide s sh ie ld ing . At one s ide , a 0 . 4 - m - t h i c k conc re t e sh ie ld ing wal l i s c o n s t r u c t e d be tween the s t o r a g e fac i l i ty and the t r e a t m e n t p lan t . The feed and t r a n s f e r a r e a s s u r e d by a g roup of c e n t r i f u g a l p u m p s which a r e ins ta l led in the o p e r a t i n g g a l l e r y . The mix ing i s e f f ec t ed by r e c i r c u l a t i o n with pumps having a flow r a t e of 25 to 30 m 3 / h . Samples a r e d r a w n by pumping and tapping the e f f luen t s in a glove box. Conductivi ty type e l e c t r i c a l p r o b e s a r e provided f o r leak de tec t ion with v i sua l a l a r m in the con t ro l r o o m . I n s t r u m e n t s for level , t e m p e r a t u r e and pH m e a s u r e m e n t a r e a l s o p rov ided .

The p o s t - t r e a t m e n t s t o r a g e fac i l i ty c o n s i s t s of p r e s t r e s s e d c o n c r e t e t a n k s of 500 and 1000 m 3 capac i ty . T h e s e tanks a r e c o n s t r u c t e d in a r e t en t ion pit m a d e of c o n c r e t e . The t r e a t e d e f f luen t s a r e s t o r e d in t h e s e t a n k s for a n a l y s i s and d i s c h a r g e .

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9 . 3 . 4 . B h a b h a A t o m i c R e s e a r c h C e n t r e , T r o m b a y ( India) [ 3 8 ]

T h e r e s e a r c h and d e v e l o p m e n t w o r k c a r r i e d out and t h e o p e r a t i o n of e x p e r i m e n t a l r e a c t o r s p r o d u c e l a r g e q u a n t i t i e s of w a s t e s of v a r y i n g c o m p o -s i t i o n and a c t i v i t y l e v e l s .

C a t e g o r y - 3 a n d - 4 w a s t e s (10" 4 to 10 C i / m 3 ) a r e s t o r e d a f t e r n e u t r a l i -z a t i o n in s i x u n d e r g r o u n d c y l i n d r i c a l t a n k s of 227 m 3 c a p a c i t y e a c h . T h e s e a r e c o n s t r u c t e d of r e i n f o r c e d c o n c r e t e a n d a r e l i n e d wi th a c a r b o n s t e e l l i n e r . T h e y h a v e a 1 - f t - t h i c k c o n c r e t e e l l i p s o i d a l r o o f and a f l a t b o t t o m . T h e n e u t r a l i z e d w a s t e s a r e fed b y g r a v i t y f low t h r o u g h c a r b o n s t e e l p i p e -l i n e s o r f r o m a t a n k c a r . T h e t a n k s a r e p r o v i d e d wi th f low i n d i c a t o r s , a g i t a t o r s and i n s t r u m e n t s f o r m e a s u r i n g pH, d e n s i t y , t e m p e r a t u r e s , l e v e l , e t c . T h e t a n k s a r e v e n t e d t h r o u g h f i l t e r s . A f t e r s u f f i c i e n t d e c a y , t h e s e w a s t e s a r e e i t h e r c o n c e n t r a t e d by e v a p o r a t i o n o r c h e m i c a l l y t r e a t e d .

C a t e g o r y - 2 w a s t e s (10~ 4 C i / m 3 ) a r e s t o r e d in s i t e s t o r a g e t a n k s . F i g u r e 15 s h o w s t h e a r r a n g e m e n t of t h r e e s u c h u n d e r g r o u n d t a n k s , s i m i l a r i n c o n s t r u c t i o n , u s e d at one of t h e l a b o r a t o r i e s e n g a g e d in r a d i o i s o t o p e s , r a d i o c h e m i s t r y and r a d i o m e t a l l u r g i c a l r e s e a r c h . One t y p i c a l t a n k u s e d i s m a d e of c a r b o n s t e e l w i t h 3 - m m - t h i c k l i n i n g of f u l l y b a n d e d p o l y v i n y l c h l o r i d e . T h e c a r b o n s t e e l p l a t e s u s e d a r e 6 . 3 5 m m t h i c k . T h e t a n k h a s a d i a m e t e r of 1 . 6 7 m and a he igh t of 1. 5 m w i t h an e f f e c t i v e c a p a c i t y of 2 . 2 7 m 3 . T h e t a n k i s p a i n t e d e x t e r n a l l y wi th an e p o x y - b a s e pa in t (poly-a m i n e - c u r e d ) and i s c o n t a i n e d in a s u m p pi t w i th a r e i n f o r c e d c o n c r e t e w a l l and a r e m o v a b l e c o n c r e t e b a t c h of 2 . 5 c m t h i c k n e s s . T h e l i q u i d w a s t e s a r e f ed by g r a v i t y and the t a n k c o n t e n t s a r e m i x e d b y u s i n g s u b m e r g e d p u m p s .

T h e w a s t e s f r o m t h e a b o v e t a n k s a r e t r a n s f e r r e d to a t r e a t m e n t p l a n t . T h e p r e t r e a t m e n t t a n k u s e d i s m a d e of r e i n f o r c e d c o n c r e t e (675 m 3 c a p a c i t y ) l i n e d wi th 6 . 35 m m c a r b o n s t e e l p l a t e s . T h e t a n k i s d iv ided in to t h r e e c o m p a r t m e n t s , e a c h h a v i n g a s l o p i n g b o t t o m l e a d i n g to a s u m p . S t i r r e r s a r e p r o v i d e d f o r m i x i n g t h e t a n k c o n t e n t s .

T h e p o s t - t r e a t m e n t t a n k i s s i m i l a r in c o n s t r u c t i o n t o t h e p r e t r e a t m e n t t ank e x c e p t t h a t s t i r r e r s a r e not p r o v i d e d . T h e t r e a t e d w a s t e s a r e d i s c h a r g e d in to t he s e a , t h r o u g h a c e n t r a l d i s c h a r g e f a c i l i t y a f t e r m e a s u r i n g r a d i o a c t i v i t y a n d f l o w .

10 . C O S T S

1 0 . 1 . G e n e r a l

T h e d e g r e e of s a f e t y e n v i s a g e d i s t h e p r i m e f a c t o r i n f l u e n c i n g t h e d e s i g n and c o n s e q u e n t l y t h e c o s t of a r a d i o a c t i v e w a s t e s t o r a g e s y s t e m . E a c h of t h e s a f e t y m e a s u r e s i n c o r p o r a t e d in t he d e s i g n h a s a d i r e c t b e a r i n g on t h e c o s t . H e n c e a b a l a n c e m u s t b e s t r u c k b e t w e e n c o s t and s a f e t y . O n c e s a f e t y in r e s p e c t of a p a r t i c u l a r i n s t a l l a t i o n i s c l e a r l y d e f i n e d , t h e d e s i g n c a n b e d e c i d e d a n d t h e c o s t t h e r e o f e s t i m a t e d . C o s t i n g i s e s s e n t i a l f o r c o m p a r i n g a l t e r n a t i v e s c h e m e s and s e l e c t i n g t h e m o s t e c o n o m i c a l and s a f e d e s i g n . A l a r g e n u m b e r of v a r i a b l e s i s i n v o l v e d in c o s t i n g ; c o s t s of m a t e r i a l and l a b o u r v a r y c o n s i d e r a b l y f r o m c o u n t r y t o c o u n t r y and m a y d i f f e r in t h e s a m e c o u n t r y f r o m one r e g i o n to a n o t h e r . Such f a c t o r s r e n d e r d i r e c t c o m p a r i s o n of c o s t s u n r e a l i s t i c .

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oi o

P L A N T A I R HEADERS

M I C H - L E V E L DRAIN HEADER L O W - L E V E L ORAIN HEADER

TO EXHAUST DUCT

T O E V A P O R A T I O N P L A N T

TO H O L D - U P TANKS FOR T R E A T M E N T

H I G H - L E V E L DRAIN T A N K H I G H - L E V E L TANK SUMP PIT

H I G H - L E V E L D R A I N T A N K L O W - L E V E L TANK SUMP P I T

L O W - L E V E L DRAIN T A N K

FIG.15. Arrangement of waste co l lect ion tanks for the radiological laboratory, Bhabha Atomic Research Centre [ 3 8 ] .

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T h i s s e c t i o n s u m m a r i z e s t he v a r i o u s f a c t o r s w h i c h i n f l u e n c e t he c o s t of r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s .

1 0 . 2 . C o s t i n g p r o c e d u r e s

T h e p u b l i s h e d c o s t d a t a on r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s a r e of l i m i t e d u s e f o r c o s t c o m p a r i s o n b e c a u s e of t h e d i f f e r e n c e s in t he p r o c e d u r e s a d o p t e d f o r c a l c u l a t i o n s and a l s o b e c a u s e c o s t e s t i m a t e s at d i f f e r e n t s i t e s m a y no t i n c l u d e e q u i v a l e n t c o m p o n e n t s . It i s of p r i m e i m p o r t a n c e t h a t a l l c o s t c o m p o n e n t s s h o u l d be t a k e n i n t o c o n s i d e r a t i o n . T h i s i s p a r t i c u l a r l y • t r u e f o r c o s t s s u c h a s o v e r h e a d s , t h e c o m p o n e n t s of w h i c h c a n b e c o m e a p p a r e n t on ly a f t e r a s y s t e m h a s b e e n i n u s e f o r a s u f f i c i e n t l y l ong p e r i o d . F o r s e t t i n g u p a w a s t e s t o r a g e s y s t e m t h e c a p i t a l c o s t a n d t h e o p e r a t i n g c o s t s h o u l d b e e s t i m a t e d wi th a f a i r d e g r e e of a c c u r a c y . T h e c a p i t a l c o s t i s t h e t o t a l a m o u n t r e q u i r e d f o r s e t t i n g up t h e s y s t e m . T h e o p e r a t i n g c o s t , w h i c h a l s o i n c l u d e s d e p r e c i a t i o n and c o s t of m a i n t e n a n c e , p r o v i d e s a good b a s i s f o r a r r i v i n g at t h e uni t c o s t of s t o r a g e a n d f o r c o m p a r i n g a l t e r n a t i v e s c h e m e s .

1 0 . 2 . 1 . C a p i t a l c o s t s

S o m e of t h e m a j o r i t e m s of e x p e n d i t u r e wh ich c o n s t i t u t e t h e c a p i t a l c o s t s a r e :

(a) L a n d and s i t e p r e p a r a t i o n (b) B u i l d i n g s a n d s t r u c t u r a l w o r k s (c) W a s t e t a n k s i n c l u d i n g s h i e l d i n g , s e c o n d a r y con ta inment : , e t c . (d) P r o c e s s p i p i n g , v a l v e s , v a l v e p i t s and a u x i l i a r y p r o c e s s e q u i p m e n t (e) A u x i l i a r y f a c i l i t i e s l i k e e l e c t r i c a l s u b - s t a t i o n , w a t e r s t o r a g e and

d i s t r i b u t i o n , s a n i t a r y and s t o r m w a t e r s y s t e m s , e m e r g e n c y p o w e r , r o a d s , f e n c i n g , e t c .

(f) I n s t r u m e n t a t i o n (g) E n g i n e e r i n g d e s i g n a n d i n s p e c t i o n (h) C o n s t r u c t i o n o v e r h e a d s (i) C o n t i n g e n c i e s .

C o s t d a t a in r e s p e c t of m o s t of t h e a b o v e i t e m s c a n b e r e a d i l y o b t a i n e d f o r a p a r t i c u l a r s i t e o r e s t i m a t e d wi th r e a s o n a b l e a c c u r a c y . It i s a d v i s a b l e t o o b t a i n t h e l a t e s t c o s t d a t a f r o m t h e m a n u f a c t u r e r f o r t h e m a t e r i a l s o r e q u i p m e n t . S o m e i d e a of t h e c o s t of v a r i o u s m a t e r i a l s and e q u i p m e n t c a n a l s o b e o b t a i n e d f r o m R e f s [ 3 9 - 4 1 ] ,

H o w e v e r , due to t h e c o n s t a n t c h a n g e in c o s t s of m a t e r i a l s , l a b o u r , t a x e s and p lan t o v e r h e a d s , t he c o s t d a t a m a y b e c o m e r a p i d l y o b s o l e t e . T h e r e f o r e i t i s n e c e s s a r y t o b r i n g t h e c o s t d a t a up to d a t e . T h e m e t h o d n o r m a l l y f o l l o w e d f o r u p d a t i n g s u c h d a t a i s b a s e d on 1 c o s t i n d i c e s ' w h i c h a r e c o s t s w i t h r e f e r e n c e t o a b a s e y e a r [ 4 2 , 43] .

T h e c o s t of a n e q u i p m e n t (CA) of c a p a c i t y (A) can b e a p p r o x i m a t e d f r o m t h e known c o s t (CB ) of a d i f f e r e n t c a p a c i t y f o r t h e s a m e e q u i p m e n t . ( B ) f r o m t h e f o l l o w i n g r e l a t i o n s h i p [ 44 ]

C a = C b 4 ° - 6

51

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T h i s r e l a t i o n s h i p c a n b e r e l i a b l y u s e d w h e r e t h e r a n g e of c a p a c i t i e s i s l e s s t h a n t e n f o l d .

T h e c o s t f a c t o r s b a s e d on' c o n v e n t i o n a l c h e m i c a l p l a n t c o s t s e v a l u a t e d by S t o c k d a l e (Ref . [ 4 1 ] , p . 304) can b e u s e d f o r e s t i m a t i n g r a d i o c h e m i c a l p l a n t c a p i t a l c o s t s .

1 0 . 2 . 2 . O p e r a t i n g c o s t s

T h e c o s t e l e m e n t s t o b e t a k e n in to a c c o u n t f o r c o m p u t i n g t h e t o t a l o p e r a t i n g cos t of a w a s t e s t o r a g e s y s t e m a r e :

(a) T r a n s p o r t (b) S t o r a g e (c) E n v i r o n m e n t a l m o n i t o r i n g (d) M a i n t e n a n c e (e) E m e r g e n c y o p e r a t i o n s r e q u i r e d , if any (f) D e p r e c i a t i o n (g) O v e r h e a d s (h) O t h e r c o s t s .

T o t h e c o s t of e a c h of t h e a b o v e i t e m s h a v e to be a d d e d the c o s t s of l a b o u r , m a t e r i a l , u t i l i t i e s and s e r v i c e s . T h o u g h t h e c o s t s of t h e s e i t e m s can be e s t i m a t e d by u s i n g c o s t i n g p r o c e d u r e s a n d t h e d a t a a v a i l a b l e f o r c o n v e n t i o n a l i n d u s t r i e s , t he v a l i d i t y of t he s a m e f o r r a d i o a c t i v e w a s t e s t o r a g e s y s t e m s h a s t o b e f u l l y e s t a b l i s h e d .

T r a n s p o r t . T h e c o s t of t r a n s p o r t a t i o n d e p e n d s m a i n l y on the c h e m i c a l n a t u r e , t h e a c t i v i t y l e v e l , t he quan t i t y of w a s t e s a n d t h e l o a d f a c t o r . It h a s b e e n r e p o r t e d t h a t f o r a v o l u m e of l e s s t h a n about 1200 m 3 / y r of l i qu id w a s t e t h e t r a n s p o r t by t a n k e r s i s m o r e e c o n o m i c a l [ 4 5 ] .

S t o r a g e . T h e c o s t of a r a d i o a c t i v e w a s t e s t o r a g e s y s t e m i s d e p e n d e n t on t h e n a t u r e a n d q u a n t i t y of w a s t e , t he p e r i o d of s t o r a g e , t h e m e t h o d of f i l l i n g t h e t a n k a n d t h e t y p e of e n v i r o n m e n t . T h o u g h t h e b a s i c d e s i g n f e a t u r e s m a y no t c o n s i d e r a b l y c h a n g e w i t h i n c r e a s i n g s p e c i f i c a c t i v i t y of t h e w a s t e , t h e c o s t of s h i e l d i n g t h a t m a y b e r e q u i r e d wi l l i n c r e a s e t h e t o t a l c o s t . .

E n v i r o n m e n t a l m o n i t o r i n g . E n v i r o n m e n t a l m o n i t o r i n g i n c l u d e s g r o u n d -w a t e r m o n i t o r i n g and a i r m o n i t o r i n g . T h e m o n i t o r i n g c o s t f o r l o n g - t e r m s t o r a g e of h i g h e r - l e v e l r a d i o a c t i v e l i qu id w a s t e s c a n b e a s i g n i f i c a n t c o m p o n e n t of t h e o p e r a t i n g c o s t , d e p e n d i n g upon t h e s i t e c o n d i t i o n s .

M a i n t e n a n c e . T h e m a i n t e n a n c e c o s t i n c l u d e s t h e c o s t of r e p a i r s , r e p l a c e m e n t , r o u t i n e i n s p e c t i o n , e t c . T h e c o s t of m a i n t e n a n c e v a r i e s w i d e l y wi th t h e s t a t u s of t h e i n s t a l l a t i o n and i t s d e s i g n f e a t u r e s . M a i n t e n a n c e c o s t s w i l l n o r m a l l y v a r y f r o m 5 to 10% of t h e c o s t of i n v e s t m e n t . F o r i n s t a l l a t i o n s h a n d l i n g h i g h e r - l e v e l w a s t e s t h e m a i n t e n a n c e c o s t s c a n e v e n b e h i g h e r if d i r e c t m a i n t e n a n c e i s i n v o l v e d .

E m e r g e n c y o p e r a t i o n s . T h e o p e r a t i n g c o s t s s h o u l d i n c l u d e e s t i m a t e s of t h e c o s t of e m e r g e n c y o p e r a t i o n s l i k e d e c o n t a m i n a t i o n of p lan t a r e a s , e m e r g e n c y t r a n s f e r of w a s t e s , e t c .

52

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D e p r e c i a t i o n . D e p r e c i a t i o n p r o v i d e s f o r t h e r e c o v e r y of t he c a p i t a l c o s t t o w a r d s t h e r e p l a c e m e n t of e q u i p m e n t , b u i l d i n g s , e t c . a f t e r t h e i r u s e f o r t h e e x p e c t e d l e n g t h of u s e f u l s e r v i c e . T h e e x p e c t e d l i f e v a r i e s f o r d i f f e r e n t i t e m s and i s v e r y m u c h d e p e n d e n t on t h e d e s i g n and c o n s t r u c t i o n . T h e b e s t a p p r o a c h f o r e s t i m a t i n g t h e l i f e of a n e q u i p m e n t i s to b a s e i t on t he a c t u a l e x p e r i e n c e g a i n e d wi th s u c h e q u i p m e n t in s i m i l a r p l a n t s .

O v e r h e a d s . O v e r h e a d s a r e c o s t s wh ich canno t b e a s s i g n e d to a n y s p e c i f i c o p e r a t i o n . T h e y i n c l u d e t h e c o s t s of o v e r a l l s u p e r v i s i o n , c l e r i c a l s t a f f , m e d i c a l f a c i l i t i e s , s t o r e s , s e c u r i t y , i n s u r a n c e , e t c .

O t h e r c o s t s . E x p e n d i t u r e i n c u r r e d f r o m a p p l i e d r e s e a r c h and i n t e r e s t on i n v e s t m e n t w i l l h a v e to b e i n c l u d e d in t he o p e r a t i n g c o s t s . T h e c o s t of a p p l i e d r e s e a r c h s h o u l d i n c l u d e t he c o s t of w o r k c a r r i e d out to d e v e l o p and i m p r o v e the e x i s t i n g e q u i p m e n t o r m e t h o d s t h a t a r e of d i r e c t u s e f o r t h e s i t e . T h e i n t e r e s t on c a p i t a l b o r r o w e d o r i n v e s t e d can a l s o be t a k e n a s an i n d i r e c t c o s t . Such c o s t s a r e w o r k e d out on a p e r c e n t a g e b a s i s f o r t he c a p i t a l i n v o l v e d .

A C K N O W L E D G E M E N T S

T h e a u t h o r w i s h e s to o f f e r h i s g r a t i t u d e t o s o m e of h i s c o l l e a g u e s in t he D e s a l i n a t i o n a n d E f f l u e n t E n g i n e e r i n g D i v i s i o n of B A R C , p a r t i c u l a r l y M e s s r s . H . N . S i r i a h , J . L . K h a r b a n d a and P . K . P a n i c k e r , f o r t h e i r a s s i s t a n c e in c o m p i l i n g u s e f u l i n f o r m a t i o n . T h a n k s a r e a l s o due t o D r . H . N . S e t h n a , D i r e c t o r , B A R C , and M r . K . T . T h o m a s , H e a d , • D e s a l i n a t i o n and E f f l u e n t E n g i n e e r i n g D i v i s i o n of B A R C , f o r t h e i r e n c o u r a g e m e n t and s u p p o r t in c o m p l e t i n g t h i s a s s i g n m e n t .

R E F E R E N C E S

[1] INTERNATIONAL ATOMIC ENERGY AGENCY, Management of Radioactive Wastes at Nuclear Power Plants, Safety Series No. 28, IAEA, Vienna (1968) 4 6 - 5 5 .

[2] INTERNATIONAL ATOMIC ENERGY AGENCY, Standardization of Radioactive Waste Categories, Technica l Reports Series No. 101, IAEA. Vienna (1970).

[3] BROWNELL, L.E., YOUNG. E .H. , "Design of shells for f lat-bottomed cylindrical vessels", Process Equipment Design - Vessel Design, John Wiley & Sons, New York (1959) 39 -43 .

[4] MARCUS, F. , OMAY, M., Basis of the Design for Medium Level Wastes Storage, ETR-102 ( 1961) 5 - 9 . [5] SMITH, E.F. , Structural Evaluation of Underground Waste Storage Tanks, Rep.HW-37519 (1955) 11. [6] DEN KINS, R.F. , NORTHUP, T . E . , Concrete containment structures, Nuc l .Sa f . 6 2 (1964/65) 195-96. [7] DANIEL, A . N . , Underground Storage of Low Level Radioactive Wastes at the Savannah River Plant -

Engineering Considerations, Du Pont de Nemours (E.I . ) and Co . , Rep. DP-478 (1960) 48 . [8] HOLT, N . D . , A Preliminary Review of the Design and Feasibility of Prestressed Concrete Pressure

Vessels for Nuclear Reactors, Rep. AARC/TM 198(1963) 3 . [9] KRISTAL, F . A . , ANNETT, F . A . , Pumps: Types, Selection, Installation, Operation and Maintenance,

McGraw-Hill, New York ( 1948). [10] WORTHINGT ON PUMP AND MACHINERY CORP., Worthington Engineers Pump Handbook, New York

(1927) . [11] PERRY, J.H. (Ed.) , Chemical Engineers' Handbook, 3rd Edn, McGraw-Hill, New York (1950) 1439,

1453. [12] SABIN CROCKER. M.E. , Piping Handbook, Rev.4th Edn, McGraw-Hill, New York (1945) 81 -118 .

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[13] CHILTOÑ, C . H . (Éd.) , Cost Engineering in the Process Industries, McGraw-Hill , New York (1960) 210.

[14] JASKE, R . T . , An Evaluation of Buried Waste Line Design Practice, Interim Rep. No .2 , Underground

•Pipeline and Structure Corrosion Study Programme. Rep. HW-35000 (Apr. 1955).

[15] JASKE, R . T . , Cathodic Protection of Stainless Steel Waste Lines, Rep. HW-33504 (Nov .1954) .

[16] UDINE, G . H . , Protection of Exterior Buried Waste Lines, Rep. HW-24500 (Oct . 1952).

[17] TERLINDEN, A . J . , VON DONGEN J.R.J. , Trans. Am. Soc. mech. Engrs. 80 (1958) 245.

[18] JONES, W.P . , Development of Venturi scrubbers, Ind.Engng Chem. 41 11 (1949) 2424.

[19] BLASEWITE, A . O . , in Hearings before the Special Subcommittee on Radiation, Joint Committee on

Atomic Energy Congress of the United States, on Industrial Radioactive Wastes Disposal, United States

Government Printing Office, Washington 2 (1959) 1660.

[20] COOK, M . W . , WATERS, E . D . , Operational Characteristics of Submerged Gas-lift Circulators, Rep.

HW-39432 ( D e c . 1955).

[21] WHITNEY, I.B. (Ed.) , Health and Safety Laboratory Manual of Standard Procedures, New York Operations

Office, Analytical'Division (Feb. 1960).

[22] VOGEL, A . I . , A Text-Book of Quantitative Inorganic Analysis Including Elementary Instrumental Analysis,

3rd Edn, Longmans, Green and Co. Ltd., London (1961) .

[23] ATOMIC ENERGY RESEARCH ESTABLISHMENT, Int .Symp.Decontamination of Nuclear Installations,

AERE, Harwell, England (May 1966).

[24] ROCKWELL, Th. III (Ed.) , Reactoi Shielding Design Manual, McGraw-Hill, New York (1956) 35.

[25] WALKER, R.L., GROTENHUIS, M., A Summary of Shielding Constants for Concrete, Rep. ANL-6443

(1961) .

[26] ARGONNE NATIONAL LABORATORY, Reactor Physics Constants, 2nd Edn, Rep. ANL-5800 (1963) 653.

[27] RASH, L . A . , Uncolloided flux from finite right-circular cylinder viewed endwise, Kansas State Univ.

Bulletin 45 12 (Dec . 1961).

[28] PATTERSON, C . M . , Waste Management Research Abstracts, No .4 , Div. of Health, Safety and Waste

Disposal, IAEA, Vienna (1968) 106-8 .

[29] PLEAT, G.B . , LENNEMANN, W.L. , "Considerations of long term waste storage and disposal at USAEC

sites", The Solidification and Long-term Storage of Highly Radioactive Wastes ( Proc. Symp.Richland,

Wash., 1966) 24.

[30] INTERNATIONAL ATOMIC ENERGY AGENCY, Disposal of Radioactive Wastes into the Ground (Proc.

Symp. Vienna, 1967), IAEA, Vienna (1967) 229-39.

[31] INTERNATIONAL ATOMIC ENERGY AGENCY, Management of Radioactive Wastes at Nuclear Power

Plants, Safety Series No. 28, IAEA, Vienna ( 1968).

[32] CONNELLY, J . M . , personal communication, 10 March 1969.

[33] BROWN, M . D . , personal communication, 25 June 1969.

[34] SIMMONS, R .B .V. , personal communication, 7 March 1969.

[35] BROWDER, F . N . , personal communication, 8 July 1969.

[36] BURNS, R.H. , personal communication, 21 May 1969.

[37] RENOU, J . , personal communication, 28 May 1969.

[38] GAD, V . M . , personal communication, 19 March 1969.

[39] PULVER, H . E . , Construction, Estimate and Costs, McGraw-Hill, New York(1940) .

[40] WEAVER, J .B. , More help in finding cost data, Chem. Engng 62 (1955) 247.

[41] CHILTON, C . H . (Ed.) , Cost Engineering in the Process Industries, McGraw-Hill, New York ( 1960).

[42] STEVENCE, R. W., Equipment cost index for process industries, Chem. Engng 54 11 ( 1947) 124.

[43] Engineering News Record 155 1 3 ( 1 9 5 5 ) .

[44] CHILTON, C . H . , Chem.Engng (June 1949) 9 7 - 1 0 6 .

[45] INTERNATIONAL ATOMIC ENERGY AGENCY, Economics in Managing Radioactive Wastes, Technical

Reports Series No. 83, IAEA, Vienna (1968) 20.

54

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APPENDIX

CONVERSION T A B L E

To convert from T o Multiply by

Centimetres Cubic metres Cubic metres

Inches Cubic feet ( US) Gallons (Brit.)

0.3937 35.3147 219.9694

Cubic metres Gallons (Brit.) Gallons (US, liq.)

Gallons (US, liq.) Gallons (US, liq.) Gallons (Brit.)

264.1721 1.20095 0.83267

Litres Litres Litres

Cubic feet Gallons (Brit.) Gallons (US, liq. )

0.03532 0.21998 0.26418

Metres Metres Microns Microns

Feet Inches Inches Metres

3.28084 39.37008 3.937008 X 10" 1 X 10"6

Milligram per litre Square centimetres

Parts per million Square feet

1.0 0.00108

55

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