AECL-7686

ATOMIC ENERGY ^ ^ R E S L'ENERGIE ATOMIQUEOF CANADA UMITED W J ^ M F DU CANADA LIMITEE

MASS SPECTROMETRIC DETERMINATION OF THEISOTOPIC COMPOSITION OF URANIUM IN URANIUM FUELS

USED IN THE CHALK RIVER RESEARCH REACTORSAND CANDU POWER REACTORS

Determination par spectrometrie de masse de lacomposition isotopique de ('uranium dans les combustibles a based'uranium utilises dans les reacte *rs de recherche de Chalk River

et dans les reacteurs de puissance CANDU

L.W. GREEN, CM. KNIGHT, T.H. LONGHURST, I.H. CROCKER

Chalk River Nuclear Laboratories Laboratoires nucle'aires do Chalk River

Chalk River, Ontario

April 1982 avril

ATOMIC ENERGY OF CANADA LIMITED

MASS SPECTROMETRIC DETERMINATION OF THE ISOTOPIC COMPOSITIONOF URANIUM IN URANIUM FUELS USED IN THE CHALK RIVER RESEARCH

REACTORS AND CANDU POWER REACTORS

by

L.W. Green, C.H. Knight, T.H. Longhurst, I.H. Crocker

Chalk R i v e r Nuc lea r L a b o r a t o r i e sChalk R i v e r , O n t a r i o KOJ 1JO

1982 A p r i l

AECL-7fi36

L'ENERGIE ATOMIQUE DU CANADA, LIMITEE

Determination par spec^rometrie de masse de la composition lsotopique

de 1'uranium dans les combustibles a base d'uranium utilises dans

les reacteurs de recherche de Chalk River et dans les reacteurs

de puissance CANDU

par

L.W. Green, C.H. Knight, T.H. Longhurst et I.H. Crocker

Resume

On a developpe une methode pour determiner les taux isotopiques de1'uranium dans les combustibles a base d'uranium utilises dans les reacteursde recherche de Chalk River et dans les reacteurs de puissance CANDU. On aemploye la chromatographle liquide-liquide et a echange d'ions pour separer1*uranium de la gangue de combustible dissoute. Les taux isotopiques ontete mesures au moyt.* de la spectrometrie de masse par ionisation thermique.Les resultats obtenus pour une serie d'etalons isotopiques traites par leprocede complet ont demontre une polarisation relative moyenne de <0.1% etune deviation standard relative de 0.3% pour des taux de 235/238 dans l'in-tervalle allant de 5x10"3 § 2x10 . La methode a ete employee pour determinerla fission en pourcentage de l'atome dans un echantillon de combustiblefortement enrichi d'U 235 et le rSsultat a montre une bonne entente avec lavaleur obtenue par la methode 148 Nd.

Laboratoires nucleaires de Chalk RiverChalk River, Ontario KOJ 1J0

Avril 1982

AECL-7686

A T O M I C E N E R G Y OF C A N A D A L I M I T E D

M A S S S P E C T R O M E T R I C D E T E R M I N A T I O N OF THE ISOTOPIC C O M P O S I T I O NOF U R A N I U M IN URANIUM F U E L S U S E D IN THE CHALK RIVER R E S E A R C H

R E A C T O R S AND CANDU POWER R E A C T O R S

by

L.W. G r e e n , C . H . K n i g h t , T.H. L o n g h u r s t , I.H. C r o c k e r

ABSTRACT

A m e t h o d w a s d e v e l o p e d f o r t h e d e t e r m i n a t i o n o f t h e i s o t o p i cr a t i o s o f u r a n i u m in t h e u r a n i u m f u e l s u s e d in t h e C h a l k R i v e r a n dC a n d u r e a c t o r s . I o n - e x c h a n g e a n d l i q u i d - l i q u i d c h r o m a t o g r a p h yw e r e u s e d t o s e p a r a t e u r a n i u m f r o m t h e d i s s o l v e d f u e l m a t r i x .I s o t o p i c r a t i o s w e r e m e a s u r e d by t h e r m a l i o n i z a t i o n m a s s s p e c t r o -m e t r y . R e s u l t s f o r a s e r i e s o f i s o t o p i c s t a n d a r d s t r e a t e d by t h ee n t i r e p r o c e d u r e s h o w e d an a v e r a g e r e l a t i v e b i a s o f < 0 . 1 % a n d ar e l a t i v e s t a n d a r d d e v i a t i o n o f 0 . 3 % f o r 2 3 5 / 2 3 8 r a t i o s in t h er a n g e 5 x l O " 3 t o 2 x l 0 l . T h e m e t h o d w a s u s e d to d e t e r m i n et h e a t o m p e r c e n t f i s s i o n in a f u e l s a m p l e h i g h l y e n r i c h e d w i t h2 3 5 u a n d t h e r e s u l t s h o w e d g o o d a g r e e m e n t w i t h t h e v a l u eo b t a i n e d by t h e 1 4 8 N d m e t h o d .

C h a l k R i v e r N u c l e a r L a b o r a t o r i e sC h a l k R i v e r , O n t a r i o K O J 1 J 0

1 9 8 2 A p r i l

A E C L - 7 6 8 6

- 1 -

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

T h e p e r f o r m a n c e o f u r a n i u m f u e l s u s e d in t h e C h a l k R i v e rr e s e a r c h r e a c t o r s a n d C a n d u p o w e r r e a c t o r s h a s b e e n s t u d i e d form a n y y e a r s . T h e s e s t u d i e s h a v e i n v o l v e d f u e l s of w i d e l y v a r y i n gi r r a d i a t i o n h i s t o r i e s and c h e m i c a l ( U O 2 , UA1 ) and i s o t o p i c( n a t u r a l t o 9 3 % 2 3 5 u ) c o m p o s i t i o n s . T h e e n e r g y r e l e a s e d p e ru n i t m a s s of u r a n i u m ( b u r n u p ) is f u n d a m e n t a l to t h e s e fuel s t u d i e sa n d c a n b e d e t e r m i n e d f r o m m e a s u r e m e n t o f t h e p e r c e n t of h e a v ya t o m s t h a t h a v e f i s s i o n e d ( a t o m p e r c e n t f i s s i o n ) d u r i n g i r r a d i a -t i o n . T h e p r e f e r r e d m e t h o d for t h e d e t e r m i n a t i o n of a t o n p e r c e n tf i s s i o n in m o s t f u e l s is t h e 1 4 8 N d m e t h o d ( 1 ) w h e r e i n t h ef i s s i o n p r o d u c t 148|\|d is u s e d a s a m e a s u r e o f t h e n u m b e r off i s s i o n s . H o w e v e r , f o r t h e r m a l r e a c t o r f u e l s in w h i c h t h e o n l yh e a v y e l e m e n t in t h e s t a r t i n g m a t e r i a l is u r a n i u n t h e Z 3 5 ud e p l e t i o n m e t h o d is s u f f i c i e n t l y a c c u r a t e ( 2 , 3 ) . T h e l a t t e rm e t h o d is l e s s t i m e c o n s u m i n g t h a n t h e f o r m e r a n d is c u r r e n t l yu s e d at Chal'c R i v e r N u c l e a r L a b o r a t o r i e s ( C R N L ) f o r u r a n i u m f u e l s .

T h e d e t e r m i n a t i o n o f a t o m p e r c e n t f i s s i o n by t h ed e p l e t i o n m e t h o d r e q u i r e s d e t e r m i n a t i o n o f t h e u r a n i u m i s o t o p i cr a t i o s o f t h e i r r a d i a t e d a n d u n i r r a d i a t e d f u e l . T h e u r a n i u m i s o -t o p i c r a t i o s c a n be d e t e r m i n e d by t h e r m a l i o n i z a t i o n m a s s s p e c -t r o m e t r y ( 4 - 6 ) f o l l o w i n g s e p a r a t i o n o f t h e u r a n i u m f r o m t h e f u e lm a t r i x .

V a r i o u s p r o c e d u r e s f o r t h i s s e p a r a t i o n h a v e b e e n r e p o r t e d .M a e c k et al . ( 7 ) a n d J o n e s ( 8 ) u s e d s o l v e n t e x t r a c t i o n of u r a n y ln i t r a t e i n t o m e t h y l i s o b u t y l k e t o n e . H a r t e t a l . ( 9 ) u s e d a n i o n -e x c h a n g e c h r o m a t o g r a p h y w i t h a n i t r i c a c i d e l u e n t to r e m o v e p l u t o -n i u m , t h e n s o l v e n t e x t r a c t i o n o f u r a n y l n i t r a t e i n t o t r i b u t y lp h o s p h a t e d i l u t e d w i t h S o l t r o l to c o m p l e t e t h e s e p a r a t i o n . D u r h a ma n d C o r r i v e a u ( 1 0 ) a n d V a n d e r g r a a f et a l . ( 1 1 ) e x t r a c t e d u r a n y ln i t r a t e i n t o t r i b u t y l p h o s p h a t e in x y l e n e or c a r b o n t e t r a c h l o r i d e( 1 1 ) , w a s h e d t h e o r g a n i c p h a s e w i t h 5M H N O 3 a n d h y d r o x y l a m i n en i t r a t e s o l u t i o n s , a n d b a c k - e x t r a c t e d t h e u r a n i u m i n t o d i s t i l l e dw a t e r . T h e A m e r i c a n S o c i e t y for T e s t i n g M a t e r i a l s m e t h o d ( 1 ) u s e sa n i o n - e x c h a n g e c h r o i n a t o g r a p h y w i t h c o n s e c u t i v e n i t r i c a c i d andh y d r o c h l o r i c a c i d e l u e n t s . K r t i l et a l . ( 1 2 ) u s e d a s i n g l e a n i o n -e x c h a n g e c h r o m a t o g r a p h i c s e p a r a t i o n w i t h a m i x e d n i t r i c - h y d r o -c h l o r i c a c i d e l u e n t . W a l k e r a n d c o w o r k e r s ( 1 3 - 1 5 ) a n d F a s s e t eta l . ( 1 6 ) a d s o r b e d n a n o g r a m q u a n t i t i e s o f u r a n i u m o n t o a s i n g l ea n i o n - e x c h a n g e r e s i n b e a d a n d t r a n s f e r r e d t h e b e a d d i r e c t l y to t h em a s s s p e c t r o m e t e r f i l a m e n t . H a m l i n et a l . ( 1 7 ) u s e d l i q u i d -l i q u i d c h r o m a t o g r a p h y w i t h a t r i b u t y l p h o s p h a t e s t a t i o n a r y p h a s ea n d n i t r i c a c i d e l u e n t . T h e u n d e r l y i n g c o n c e p t s f o r t h e s e s e p a r a -t i o n m e t h o d s a r e d o c u m e n t e d in t h e l i t e r a t u r e ( 1 8 - 2 1 ) .

T h e r e q u i r e m e n t s o f a s e p a r a t i o n p r o c e d u r e f o r u r a n i u m f u e l sa t C R N L i n c l u d e t h e f o l l o w i n g : ( a ) it m u s t b e a p p l i c a b l e t o t h ew i d e v a r i e t y o f f u e l s u s e d in t h e r e s e a r c h a n d p o w e r r e a c t o r s , ( b )it i.i u s t b e p r a c t i c a l f o r h o t c e l l w o r k , a n d ( c ) it m u s t p r o v i d em i c r o g r a m q u a n t i t i e s o f u r a n i u m s u f f i c i e n t l y d e c o n t a m i n a t e d f o rn o r m a l m a s s s p e c t r o m e t e r f i l a m e n t n a n i p u l a t i o n w i t h o u t r e c o u r s e t oa q l o v e b o x . E x p e r i e n c e in o u r l a b o r a t o r i e s h a s s h o w n t h a t t h ea b o v e - m e n t i o n e d i o n - e x c h a n g e p r o c e d u r e s d o n o t m e e t r e q u i r e m e n t s( a ) a n d ( c ) a n d t h e s o l v e n t e x t r a c t i o n p r o c e d u r e s d o n o t r e a d i l ym e e t r e q u i r e m e n t ( b ) .

T h e l i q u i d - l i q u i d c h r o m a t o g r a p h i c p r o c e d u r e o f H a m l i n et al .( 1 7 ) a p p e a r e d p r o m i s i n g b u t r e q u i r e d m o d i f i c a t i o n s t o a c h i e v e s e p -a r a t i o n f r o m p l u t o n i u n a n d z i r c o n i u m . U e h a v e d e v e l o p e d a p r o c e -d u r e t h a t u s e s a n i o n - e x c h a n g e c h r o m a t o g r a p h y ( I E C ) t o r e m o v e m o s to f t h e P l u t o n i u m a n d l i q u i d - l i q u i d c h r o m a t o g r a p h y ( L L C ) t o r e m o v et h e r e m a i n i n g i m p u r i t i e s . T h e u p t a k e o f z i r c o n i u m a n d r e s i d u a lP l u t o n i u m b y t h e L L C c o l u m n w a s p r e v e n t e d by u s i n g o x a l i c a c i d a n dh y d r o x y l a m i n e n i t r a t e , r e s p e c t i v e l y . T h i s p r o c e d u r e h a s b e e n u s e df o r t h e p a s t s i x y e a r s in o u r l a b o r a t o r i e s a n d h a s m e t a l l o f t h ea b o v e - m e n t i o n e d r e q u i r e m e n t s .

T h e p u r p o s e o f t h i s r e p o r t is t o d e s c r i b e t h e s e p a r a t i o n a n dm a s s s p e c t r o m e t r y p r o c e d u r e s u s e d at C R N L a n d t o d e m o n s t r a t e t h ea c c u r a c y a n d p r e c i s i o n o f t h e o v e r a l l m e t h o d f o r i s o t o p e r a t i od e t e r m i n a t i o n . F o r t h e l a t t e r p u r p o s e a s e r i e s o f N a t i o n a l B u r e a uo f S t a n d a r d s ( N B S ) i s o t o p i c s t a n d a r d s , r a n g i n g in 2 3 5 u c o n t e n tf r o m 0 . 5 % t o 9 3 % , w e r e a n a l y z e d b o t h d i r e c t l y a n d a f t e r t r e a t m e n tb y t h e s e p a r a t i o n p r o c e d u r e . T h e r e s u l t s f o r t h e 2 3 5 / 2 3 8 r a t i o sw e r e e x a m i n e d t o d e t e r m i n e : t h e i n f l u e n c e o f i s o t o p i c c o m p o s i t i o no n a c c u r a c y a n d p r e c i s i o n , t h e a v e r a g e b i a s a n d s t a n d a r d d e v i a t i o no f t h e m a s s s p e c t r o m e t r y p o r t i o n o f t h e p r o c e d u r e , a n d t h e a v e r a g eb i a s a n d s t a n d a r d d e v i a t i o n o f t h e e n t i r e p r o c e d u r e . F o r t h e s ep u r p o s e s t h e i s o t o p e r a t i o d a t a w e r e c o n v e r t e d t o K v a l u e s ( 2 2 )w h e r e

RcK = IT. Rm - enK c = r a t i o c e r t i f i e d b y t h e N B S

^ m = m e a s u r e d r a t i o

T o f u r t h e r d e m o n s t r a t e t h e a c c u r a c y o f i s o t o p e r a t i o d e t e r -m i n a t i o n t h e a t o m p e r c e n t f i s s i o n o f a f u e l s a m p l e w a s d e t e r m i n e dan r) t h e r e s u l t w a s c o m p a r e d t o t h a t o b t a i n e d b y t h em e t h o d . A f u e l s a m p l e h i g h l y e n r i c h e d w i t h 2 3 5 u W d s c h o s e n f o rt h e c o m p a r i s o n s o t h a t t h e o n l y s i g n i f i c a n t f i s s i l e i s o t o p e w o u l db e 2 3 5 I J a n d t h u s t h e p r i m a r y s o u r c e o f e r r o r w o u l d b e t h e i s o -t o p e r a t i o d e t e r n i n a t i o n .

- 3 -

EXPERIMENTAL

A p p a r a t u s

(a ) P u r i f i c a t i o n

A 5 0 0 inL r o u n d b o t t o m f l a s k e q u i p p e d w i t h a F r i e d r i c h sc o n d e n s e r w a s u s e d f o r f u e l d i s s o l u t i o n . D i s p o s a b l e p o l y p r o -p y l e n e c o l u m n s 0 . 7 c m x 4 c m w e r e u s e d f o r s e p a r a t i o n s . T h ec o l u m n s w e r e m o u n t e d in f o u r - c o l t m n r a c k s d e s i g n e d s p e c i f i -c a l l y f o r h o t c e l l u s e . T h e p u r i f i c a t i o n s w e r e p e r f o r m e d ina h o t c e l l e x c e p t f o r t h e f i n a l w h i c h w a s p e r f o r m e d in aC l a s s C ( 4 x l 0 5 B q ) f u m e h o o d .

( b ) M a s s S p e c t r o m e t r y

S a m p l e s w e r e d e p o s i t e d on t h e s i d e f i l a m e n t s o fC a t h o d e o n ( C a t h o d e o n L t d . , C a m b r i d g e , E n g . ) t r i p l e f i l a m e n tt y p e 5 5 3 a s s e m b l i e s e q u i p p e d w i t h t u n g s t e n o r t a n t a l u m s i d ef i l a m e n t s a n d r h e n i u m c e n t r e f i l a m e n t s . I s o t o p e r a t i o d e t e r -m i n a t i o n s w e r e p e r f o r m e d w i t h a 3 8 c m r a d i u s , 9 0 ° s e c t o r ,N u c l i d e ( N u c l i d e C o r p . , S t a t e C o l l e g e , P e n n . ) S . U . 2 . 2 n a s ss p e c t r o m e t e r e q u i p p e d w i t h a 1 6 - s t a g e e l e c t r o n m u l t i p l i e rd e t e c t o r ( 2 3 ) . D a t a w e r e a c q u i r e d a n d p r o c e s s e d w i t h aG e n e r a l A u t o m a t i o n ( G e n e r a l A u t o m a t i o n I n c . , A n a h e i m , C A )S P C - 1 6 / 4 5 c o m p u t e r p r o g r a m m e d w i t h N u c l i d e D A / C S - I I I s o f t -w a r e .

R e a g e n t s

A l l n i t r i c a c i d u s e d w a s d o u b l e - d i s t i l l e d . R e a g e n t g r a d ec h e m i c a l s a n d d e i o n i z e d w a t e r w e r e u s e d f o r p r e p a r a t i o n o f a l lo t h e r s o l u t i o n s . B i o - R a d ( B i o - R a d L a b o r a t o r i e s , M i s s i s s a u g a ,O n t a r i o ) A 6 M P - 1 2 0 0 - 4 0 0 m e s h a n i o n - e x c h a n g e r e s i n w a s u s e d f o ri o n - e x c h a n g e c h r o m a t o g r a p h y . C h r o m o s o r b - W ( A n a l a b s I n c . , N o r t hH a v e n , C o n n . ) 8 0 - 1 0 0 m a s h p a r t i c l e s , a c i d w a s h e d a n d d i m e t h y l d i -c h l o r o s i l a n e t r e a t e d , w e r e u s e d f o r l i q u i d - l i q u i d c h r o m a t o g r a p h y .

P r o c e d u r e

( a ) C o l u m n P r e p a r a t i o n

T h e I E C c o l u n n s w e r e p r e p a r e d b y t r a n s f e r r i n g a w a t e rs l u r r y o f t h e r e s i n in t h e n i t r a t e f o r m i n t o t h e c o l u m n s t of o r m 1 c m h i g h b e d s . T o c o n d i t i o n t h e c o l u m n s f o r f u e l s e p a -r a t i o n t h e b e d s w e r e w a s h e d w i t h 8 m L o f 8 M H N O 3 .

- 4 -

T h e C h r o m o s o r b - U p a r t i c l e s w e r e i m p r e g n a t e d w i t h 2 0 %tri'Dutyl p h o s p h a t e in x y l e n e s o l u t i o n . T h e x y l e n e w a s s u b -s e q u e n t l y e v a p o r a t e d in a i r . To p r e p a r e t h e L L C c o l u m n s t h ei m p r e g n a t e d p a r t i c l e s w e r e p a c k e d t o a h e i g h t of 3 . 5 c m ,w a s h e d w i t h 5 m L o f 1M N a O H (to r e m o v e t r i b u t y l p h o s p h a t e d e -g r a d a t i o n p r o d u c t s ) , w a s h e d w i t h d e i o n i z e d w a t e r a n d 5M H N O 3 ,t h e n s t o r e d in 5M H U O 3 . T h e f l o w r a t e w a s t y p i c a l l y b e t w e e n1 a n d 2 m L * m i n - l .

(b ) S e p a r a t i on

S u f f i c i e n t e q u i p m e n t w a s a s s e m b l e d t o p e r m i t s i m u l t a n -e o u s d i s s o l u t i o n of 2 s a m p l e s a n d s i m u l t a n e o u s s e p a r a t i o n o f4 s a m p l e s . To a v o i d c r o s s c o n t a m i n a t i o n , c o m p o n e n t s t h a tw e r e in c o n t a c t w i t h t h e s a m p l e w e r e u s e d o n c e o n l y , e x c e p tf o r t h e c o n d e n s e r s w h i c h w e r e r i n s e d w i t h d e i o n i z e d w a t e rb e t w e e n s a m p l e s .

T h e i r r a d i a t e d f u e l s w e r e s t o r e d a m i n i m u m o f 6 m o n t h sb e f o r e d i s s o l u t i o n t o a l l o w s h o r t - l i v e d f i s s i o n p r o d u c t s tod e c a y . A s a m p l e w a s c u t f r o m an e l e m e n t a n d d i s s o l v e d byr e f l u x i n g in c o n c e n t r a t e d H N O 3 (or 6M H N O 3 , 0 . 0 5 M Hg( N 0 3 ) 2 f o r UA1 f u e l ) f o r 6 h in a h o t c e l l . An a l i q u o tc o n t a i n i n g 1 0 t o 2 0 m g o f U w a s d i l u t e d w i t h s u f f i c i e n t 1MH N O 3 ( 1 M H N O 3 w a s u s e d t o a v o i d t h e f o r m a t i o n o f i n s o l -u b l e P u ( I V ) p o l y m e r ) t o a d j u s t t h e a c i d i t y t o 8 M H N O 3 a n dt h e n w a s t r a n s f e r r e d t o t h e IEC c o l u n n . U r a n i u m w a s e l u t e dw i t h 3 iiL of 8 M H N O 3 a n d c o l l e c t e d in t h e l a s t 2 m L ( P u ( I V )w a s r e t a i n e d by t h e c o l u m n ) . T h e U f r a c t i o n w a s n i x e d w i t h 1m L o f 0 . 1 5 M o x a l i c a c i d (to c o m p l e x Z r ( I V ) ) a n d t r a n s f e r r e dt o t h e L L C c o l u m n . F i s s i o n p r o d u c t s , Pu a n d Al w e r e e l u t e dby p a s s i n g t h e f o l l o w i n q s o l u t i o n s t h r o u g h t h e c o l u n n in s u c -c e s s i o n : 7.5 ml o f 5M H N O 3 , 1.5 m L o f 3M H N O 3 , 1.5 m L o f1 0 % ( v / v ) h y d r o x y 1 a m i n e n i t r a t e , a n d 5 m L o f 3M H N O 3 .U r a n i u m w a s e l u t e d w i t h 5 m L of d e i o n i z e d w a t e r , r e m o v e d f r o mt h e h o t c e l l , and t a k e n t o a C l a s s C f u m e h o o d if t h e g a m m aa c t i v i t y w a s l e s s t h a n 5 m R / h . T h e U w a s p r e c i p i t a t e d w i t ha f e w d r o p s o f c o n c e n t r a t e d N H 3 s o l u t i o n , c e n t r i f u g e d , s e p -a r a t e d f r o m t h e s u p e r n a t a n t l i q u i d , d i s s o l v e d in 1 m L o f 5MH N O 3 , r e p u r i f i e d by t h e L L C p r o c e d u r e , r e p r e c i p i t a t e d a n dr e c e n t r i f u g e d , a n d r e d i s s o l v e d in 1 m L o f 5M H N O 3 . T h eg a m m a a c t i v i t y on c o n t a c t w i t h t h e f i n a l s o l u t i o n w a s u s u a l l yl e s s t h a n 1 0 c o u n t s p e r s e c o n d as m e a s u r e d w i t h an e n d - w i n d o wg e i g e r c o u n t e r .

T h e N B S i s o t o p i c s t a n d a r d s w e r e t r e a t e d in an i d e n t i c a lf a s h i o n . H o w e v e r , b e c a u s e of l i m i t e d q u a n t i t y o n l y 1 0 0 m gw a s i n i t i a l l y d i s s o l v e d a n d o n l y 2 m g w a s p u r i f i e d .

- 5 -

( c ) M a s s S p e c t r o n e t r y

A 2 JJ L a l i q u o t ( c o n t a i n i n g 1 0 t o 2 0 ^ g o f U ) o f t h ep u r i f i e d U s o l u t i o n w a s p i p e t t e d o n t o t h e c e n t r a l p o r t i o n o fe a c h s i d e f i l a m e n t o f t h e t r i p l e f i l a m e n t a s s e m b l y , s l o w l yd r i e d b y p a s s i n g a s m a l l e l e c t r i c c u r r e n t (1 t o 2 A ) , a n dh e a t e d t o f o r m a y e l l o w - o r a n g e u r a n i u m o x i d e d e p o s i t b yb r i e f l y p a s s i n g a l a r g e r e l e c t r i c c u r r e n t ( 2 t o 4 A f o r ^ 2 s ) .D e p o s i t i o n o f u r a n i u n o n t h e c e n t r e f i l a m e n t w a s p r e v e n t e d b yp o s i t i o n i n g t h e s i d e f i l a m e n t s a w a y f r o m t h e c e n t r e f i l a n e n t .T h e t r i p l e f i l a n e n t a s s e m b l y w a s l o a d e d i n t o t h e m a s s s p e c -t r o m e t e r a n d d e g a s s e d b y p a s s i n g c u r r e n t s o f 4 . 5 A t h r o u g ht h e c e n t r e f i l a m e n t a n d 2 A t h r o u q h t h e s i d e f i l a m e n t s u n t i lt h e p r e s s u r e f e l l t o < 8 x 1 0 - 4 P a .

T h e a c c e l e r a t i n g v o l t a g e w a s s e t t o 1 0 . 4 k V a n d t h ed y n o d e s t r i n g c u r r e n t t o 0 . 1 5 m A t o y i e l d a n e l e c t r o n m u l t i -p l i e r g a i n o f 4 x 1 0 ^ . T h e s o u r c e a n d c o l l e c t o r s l i t s w e r ea d j u s t e d t o g i v e a r e s o l u t i o n ( R = m / A m w h e r e A m w a s m e a s u r e da t 5 % o f p e a k h e i g h t ) o f ^ 3 0 0 . T h e c o r r e s p o n d i n g a b u n d a n c es e n s i t i v i t y w a s ^ 3 p p m . T h e c u r r e n t t h r o u g h t h e c e n t r e f i l -a m e n t w a s a d j u s t e d t o b r i n g t h e f i l a m e n t t e m p e r a t u r e t o1 9 5 0 ° C ( u n c o r r e c t e d f o r w i n d o w e f f e c t s ) a s d e t e r m i n e d b y aP y r o ( P y r o m e t e r I n s t r u m e n t C o . , N o r t h v a l e , N . J . ) o p t i c a lp y r o m e t e r . T h e c u r r e n t s t h r o u g h t h e s i d e f i l a m e n t s w e r ea d j u s t e d t o y i e l d an i o n b e a m c u r r e n t o f ^ 3 x 1 0 - 1 3 Af o r t h e m a j o r U i s o t o p e . T h e s o u r c e p l a t e v o l t a g e s w e r ea d j u s t e d t o o p t i m i z e p e a k s h a p e a n d i o n b e a m i n t e n s i t y a n dt h e d a t a a c q u i s i t i o n r o u t i n e w a s i n i t i a t e d . In t h e d a t aa c q u i s i t i o n m o d e t h e m a g n e t i c f i e l d w a s a u t o m a t i c a l l y s t e p p e dt o s e q u e n t i a l l y f o c u s t h e i o n b e a m s c o r r e s p o n d i n g t o e a c hp r e s e l e c t e d i s o t o p e p l u s a b a s e l i n e m a s s n u m b e r o n t o t h ef i r s t d y n o d e o f t h e e l e c t r o n m u l t i p l i e r . T h e i o n b e a m c u r -r e n t a t e a c h m a s s n u m b e r w a s s a m p l e d 1 6 t i m e s . A f t e r a l l t h ep r e s e l e c t e d i o n b e a m c u r r e n t s h a d b e e n s a m p l e d t n e d a t a w e r ea u t o m a t i c a l l y p r o c e s s e d a n d p r i n t e d o u t . T h e a c q u i s i t i o np r o c e s s t o o k ^ 5 0 s a n d w a s r e p e a t e d 3 0 t o 4 0 t i m e s in a nA B B A p a t t e r n t o c o m p l e t e a n a n a l y s i s . T h e o v e r a l l a v e r a g e sa n d s t a n d a r d d e v i a t i o n s w e r e c a l c u l a t e d a f t e r r e j e c t i o n o fv a l u e s w h i c h w e r e q r e a t e r t h a n 3 s t a n d a r d , d e v i a t i o n s f r o m t h em e a n v a l u e o r w h i c h w e r e s u s p e c t d u e t o o b s e r v e d n o n o p t i m a li n s t r u m e n t p e r f o r m a n c e .

T h e m a s s s p e c t r o m e t e r w a s p e r i o d i c a l l y c a l i b r a t e d b yc o m p a r i n g t h e r e s u l t s o b t a i n e d f o r an N B S s t a n d a r d w i t h t h ec o r r e s p o n d i n g c e r t i f i e d v a l u e s . T h e o b s e r v e d b i a s w a s t y p i c -a l l y 0 . 3 5 % p e r m a s s u n i t a n d w a s a t t r i b u t e d t o m a s s d i s c r i m -i n a t i o n e f f e c t s . T h e . m e a s u r e d b i a s f a c t o r w a s p l a c e d in t h ed a t a p r o c e s s i n g r o u t i n e t o e f f e c t t h e a p p r o p r i a t e c o r r e c t i o n .

- 6 -

RESULTS AND DISCUSSION

Separati ons

The q u a l i t y of the se p a r a t i o n s was found to be dependent onthe poro s i t y of the stationary phase used in the LLC c o l u m n . Anex a m i n a t i o n of a variety of support m a t e r i a l s ( K e l - F , T e e - S i x ,F l u o r o p a k - 8 0 , C h r o m o s o r b - T , C h r o n o s o r b - W ) showed that the re t e n -tion of u r a n i u m , and hence the quali t y of the s e p a r a t i o n , wasgreater for the par t i c l e s of higher p o r o s i t y . The greater reten-tion of ur a n i u n observed for the par t i c l e s of higher porosity wasatt r i b u t e d to the greater retention of tributyl p h o s p h a t e by thesep a r t i c l e s . The retention of uraniun on C h r o m o s o r b - W support wasgrea t e r than that observed for the other p a r t i c l e s , henceC h r o n o s o r b - W was used in the sep a r a t i o n p r o c e d u r e .

Mass Spectrotnetry

The Mass spectra of uraniun samples usually showed w e l l -d e f i n e d peaks for the isotopes 2 3 4 , 2 3 5 , 2 3 6 , and 238 (Figure 1)and t h e i r o x i d e s . During the initial filament h e a t i n g period themo n o x i d e ion was the dominant species but it decayed to less than1 0 % after 10-15 m i n , d u r i n g which time the U + ion became d o m i n -a n t . The dio x i d e ion decayed from an initial a b u n d a n c e of ̂ 6%to < 1% in 15 m i n u t e s ; higher oxides were not d e t e c t e d . Thesec h a n g e s were likely due to depletion of oxygen in the filamentsand c h a n g e s in chemical form of the U deposit during the initialh e a t i n g p e r i o d . During this period the re p r o d u c i b i 1 i t y ofisotop i c ratio m e a s u r e m e n t s using the U + ion was p o o r , thus dataa c q u i s i t i o n was delayed until the U + ion became d o m i n a n t .D o n i n a n c e of the U + ion was recognized by a steady or slightlyd e c r e a s i n g U + ion beam c u r r e n t .

A c c u r a c y and Precision

The results for the de t e r m i n a t i o n of K for four NBS stand a r d sanalyzed d i r e c t l y by the mass s p e c t r o n e t r y p r o c e d u r e are listed inTable I and plotted in Figure 2. The data show that there was nota s i g n i f i c a n t d e p e n d e n c e of K on 235 / 2 3 8 ratio in the range 5 x10-3 to 3. The t r i p l i c a t e a n a l y s i s of UbOO shows the scatterthat is s o m e t i m e s o b t a i n e d . The mean K value is l . O O O j , and in-dic a t e s that the bias of the mass s p e c t r o m e t e r was ap p r o p r i a t e l yc o r r e c t e d . The standard d e v i a t i o n is 0.004 and i s ^ 8 timesg r e a t e r than the best values obtained by others ( 1 6 , 2 2 , 2 4 ) ; how-e v e r , the an a l y s e s in this study were performed to sim u l a t eroutine fuel a n a l y s e s as close as p o s s i b l e and not to op t i m i z e thep r e c i s i o n . Thus the higher standard deviation was expected and isco m p a r a b l e to the values obtained &y others under suchci r c u m s t a n c e s ( 2 2 ) .

- 7 -

T h e r e s u l t s f o r t h e d e t e r m i n a t i o n o f K f o r e i g h t N B S s t a n d -a r d s t r e a t e d b y t h e s e p a r a t i o n p r o c e d u r e are l i s t e d in T a b l e IIa n d p l o t t e d i n F i g u r e 3 . A g a i n , a d e p e n d e n c e o f K o n 2 3 b / 2 3 8r a t i o w a s n o t o b s e r v e d . T h e m e a n K v a l u e i s l . u U U g a n d t h es t a n d a r d d e v i a t i o n i s 0 . 0 0 3 . T h e s e v a l u e s are c o n s i d e r e d t o b er e p r e s e n t a t i v e o f t h e a c c u r a c y a n d p r e c i s i o n o f t h e e n t i r e p r o c e -d u r e f o r t h e d e t e r m i n a t i o n o f u r a n i u m i s o t o p i c r a t i o s , i n t h er a n g e o f b x 1 0 - 3 t o 2 x 1 0 * , i n u r a n i u m f u e l s . T h e y aren o t s i g n i f i c a n t l y d i f f e r e n t f r o m t h e v a l u e s f o r t h e m a s s s p e c t r o -m e t r y p o r t i o n o f t h e p r o c e d u r e a n d t h u s t h e s e p a r a t i o n p r o c e d u r ed o e s n o t a p p e a r t o i n t r o d u c e s i g n i f i c a n t b i a s o r u n c e r t a i n t y i n t ot h e r e s u l t s .

A p p l i c a t i o n

A n e x a m p l e o f m a s s s p e c t r o n i e t r y d a t a f o r a f u e l s a m p l e i sg i v e n i n T a b l e I I I . T h e t a b l e s h o w s r e s u l t s f o r 1 0 s e q u e n t i a ld e t e r m i n a t i o n s ; a t o t a l o f 3 0 d e t e r m i n a t i o n s w e r e p e r f o r m e d a sd e s c r i b e d i n t h e p r o c e d u r e . T h e a v e r a g e v a l u e s f o r t h e 3 0 d e t e r -m i n a t i o n s w e r e t h e s a m e a s t h o s e f o r t h e 1 0 d e t e r m i n a t i o n s . T h ed a t a s h o w t h a t t h e r e l a t i v e s t a n d a r d d e v i a t i o n s f o r s e q u e n t i a lm a s s s p e c t r o m e t r i c rteterninations c a n b e m u c h s m a l l e r t h a n t h o s eo b s e r v e d f o r t h e o v e r a l l p r o c e d u r e ; h o w e v e r , s u c h h i g h p r e c i s i o nw a s n o t a l w a y s o b s e r v e d a n d c o u l d o n l y b e a t t a i n e d c o n s i s t e n t l y i fg r e a t c a r e w a s t a k e n d u r i n g s a m p l e p r e p a r a t i o n a n d p e a k s h a p eo p t i m i z a t i o n .

T h e f u e l s a m p l e w a s a U A 1 f u e l w i t h t h e f o l l o w i n g i n i t i a li s o t o p i c c o m p o s i t i o n : 2 3 4 / 2 3 8 ; . 1 8 3 , 2 3 5 / 2 3 8 ; 1 6 . 9 9 , a n d 2 3 6 / 2 3 8 ;0 . 0 b 6 3 . T h e a t o n p e r c e n t f i s s i o n i n 2 3 b u ( F 5 ) w a s c a l c u l a t e da c c o r d i n g t o :

F5 = HIIMZIL^JLS/ILI C2]

w h e r e ; MS, = a t o n p e r c e n t Z38u" in u n i r r a d i a t e d fuel

R 5 / B > R s / a = a t o m i c r a t i o of 2 3 ! ) U t o 2 3 8 U inu n i r r a d i a t e d and i r r a d i a t e d f u e l ,r e s p e c t i v e l y ( c o r r e c t i o n for 2 3 8 Ud e s t r u c t i o n w a s i n s i g n i f i c a n t )

- 8 -

as = effective ratio of 23bu (n,Y ) capture-to-fission cross sections (appropriate value wasU.18 (2b))

A value of 74% ± 1% (1 standard deviation) was obtained andrepresents the total fission in the fuel since 23bu was theonly significant fissioninq nuclide. The value is in good agree-ment with the value of 7 4 % ± 2% obtained by the 148Nd methodin our l a b o r a t o r i e s . This agreement further demonstrates theaccuracy of the overall procedure for uraniurc isotope ratio deter-mination described in this paper.

- 9 -

REFERENCES

1. ASTM E321 , Annual Book of ASTM Standards, Part 45,Nuclear Standards, American Society for Testing andMaterials , Philadelphia, PA. 1980

2. ASTM E244, Annua\ Book of ASTM Standards, Part 45,Nuclear Standards, American Society for Testing andMaterials, Philadelphia, PA. 1980

3. R.fi. HART, M. LOUNSBURY, C D . MCKAY, Report AECL-1176,1961

4. E.L. GARNER, L.A. MACHLAN, W.R. SHIELDS, Nat. Bur.Stand. Spec. Publ . 260-27, 1971

5. J.E. DELMORE, The Ionization of Selected Elements ofInterest in the Nuclear Fuel Cycle, Proc. Syrup. Nucl .Mass S p e c , J.G. VAN RAAPHORSF (ed.), Neth. Energy Res.Found., Petten, 1978

6. O.H. SMITH, H.S. MCKOWN, W.H. CHRISTIE, R.L. WALKER,J.A. CARTER, Report ORNL/TM-5485 , 1976

7. W.J. MAECK, G.L. BOOMAN, M.C. ELLIOTT, Anal. Chem. 30(1958) 1902

8. R.J. JONES, Report TID-7029, USAEC, 1973

9. R.G. HART, M. LOUNSBURY, C.B. BIGHAM, L.P.V. CORRIVEAU,F. GIRARDI, Report AECL-813, 1959

10. R.W. DURHAM, L.P.V. CORRIVEAU, Report AECL-4313, 1973

11. T.T. VANDERGRAAF, L.M. CAREFOOT, D.G. BOASE, ReportAECL-5964, 1978

12. J. KRTIL, F. SUS, J. MENCL, J. Radioanal. Chen. 28(1975) 109

13. R.L. WALKER, R.E. CBY, C.A. PRITCHARD, J.A. CARTER,Anal. Lett. 7 (8 & 9) (1974) 563

14. O.H. SMITH, R.L. WALKER, L.K. BERTRAM, J.A. CARTER,Anal. Lett. 12 (A7), (1979) 831

15. D.H. SMITH, W.H. CHRISTIE, R.E. E6Y, Int. Jo Mass Spec.Ion Phys. 36 (1980) 301

>• 10 -

16. J.ü. FASSET, U.R. KELLY, L.A. MACHLAN, L.J. MOORE, MassSpectronetric Isotope Metrology of Uranium on ResinBeads, in Radioelement Progress and Problems, Proc. 23rdConf. on Anal. Chem. in Energy Tech., Catlinburg, Tenn,1979

17. A.G. HAMLIN, B.J. ROBERTS. W. LOUGHLIN, S.G. WALKER,Anal. Chem., 33 (1961) 1547

18. F.R. BRUCE, J.H. FLETCHFR, H.H. HYMAN, J.J. KATZ,(eds.), Progress in Nuclear Energy, Series III, ProcessChemistry, Vol.1, Pergainon Press, London, 1956

19. F.R. BRUCE, O.M. FLETCHER, .H.H. HYMAN, (eds.), Progressin Nuclear Energy, Series III, Process Chemistry, Vol.2,Perganon Press, London, 1958

20. F.R. BRUCE, J.M. FLETCHER, H.H. HYMAN, (eds.), Progressin Nuclear Energy, Series III, Process Chemistry, Vol.3,Pergamon Press, London, 1961

21. C.E. STEVENSON, E.A. MASON, A.T. GRESKY, (eds.) Progressin Nuclear Energy, Series III, Process Chemistry, Vol.4,Pergamon Press, London, 1970

22. P. deBIEVRE, Seminar of Standards, Standardization,Quality Control, and Interlaboratory Test Programmes,Nuclear Mass Spectronetry, J.G. VAN RAAPHORSF (ed.),Neth. Energy Res. Found., Petten, 1978, 211-227

23. I.H. CROCKER, AECL unpublished report CRNL-Î443, 1975

24. P. DE REGGE, R. BODEN, Advances in Mass Spectrometry,7A, (1978) 528

25. W. HEEDS, Reactor Physics Branch, Chalk River NuclearLaboratories, Chalk River, Ontario, private communica-tion

- 11 -

T A B L E I . K V a l u e s f o r D i r e c t l y A n a l y z e d S t a n d a r d s

Standard

U005

U200

U5 00

U500

U500

U750

R ?35/238

0.004919

0.25126

0.9997

0.9997

0.9997

3.1661

0.

0.

0.

1.

0.

1.

K

9998

999e

9945

0070

999-

000,

K = l . O O O i

s = 0 . 0 0 4

- 12 -

TABLE II. K Values for Standards Treated by the PurificationProcedure

Standard

0005

U0?n

U020

U050

U35O

U500

U750

U930

R 235/238

0.004919

0.01014

0.02081

0,05278

0.54648

0.9997

3.1661

17.349

K

1.0022

0.995a

1.0000

0.997s

1.0043

1.005o

1.0033

0.998e

K = l.OOOg

S = 0.003

- 13 -

T A B L E I I I . I s o t o p i C C o m p o s i t i o n o f a H i g h B u r n u p , H i g h l yE n r i c h e d , UA1 F u e l

U e t e r t n i n a t i o n A t o n i c R a t i o t o 2 3 8

1

2

3

4

5

6

7

8

9

10

234

0.0789161'

0.0791650

0.0797891

0.0794949

0.0791489

0.0789367

0.0791037

0.0794121

0.0793216

0,0792954

235

0.961635

0.960921

0.964680

0.963931

0.962523

0.962490

0.962225

0.961538

0.962126

0.963249

236

2.29259

2.30039

2.30570

2.30272

2.30271

2.29859

2.29557

2.29955

2.30285

2.30165

R

s

rsd

0.0793

0.0003

0.3%

0 .963

0 .001

0.1%

2.300

0 .004

0.2%

- 14 -

10 3 100 3 fA

238 236 235 234

FIGURE 1 : MASS SPECTRUM OF U930. SWEEP RATE: 0 .625 AMU/HIN.

"235/238

FIGURE 2: K vs 2 3 5U TO 2 3 8U RATIO FOR STANDARDS ANALYZED DIRECTLY BY MASS SPECTROMETRY.

K

1.010

1.005

1000

0.995

0.990

o

oo

o

1 1

o oo

o

1 1

0.01 0.1 10

235/238

FIGURE 3: K vs 2 3 5 u TO 238y R A T i o FOR STANDARDS TREATED BY THE PURIFICATION PROCEDURE.

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