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FLUORESCENT X-RAY-ANALYSIS OF URANIUM USING INTERNAL STANDARD AND FILTER
METHODS
P. Arikan, A. Özmen
To cite this version:
P. Arikan, A. Özmen. FLUORESCENT X-RAY-ANALYSIS OF URANIUM USING INTERNAL
STANDARD AND FILTER METHODS. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-103-
C9-106. �10.1051/jphyscol:1987916�. �jpa-00227273�
JOURNAL DE PHYSIQUE
Colloque C9, supplbment au n 0 1 2 , Tome 48, dbcembre 1987
FLUORESCENT X-RAY-ANALYSIS OF URANIUM USING INTERNAL STANDARD AND FILTER METHODS
P. ARIKAN and A. OZMEN*
Ankara Nuclear Research and Training Center-Be~evler, Ankara, Turkey
"physics Department, Gazi University-Begevler. Ankara, Turkey
A b s t r a c t
I n t e r n a l s t a n d a r d and f i l t e r methods f o r f l u o r e s c e n t X-ray a n a l y s i s o f uranium i n o r e s a r e i n v e s t i g a t e d . I n t h e f i r s t method, s u c c e s s f u l a p p l i c a t i o n o f s t r o n t i u m K-X i n t e r n a l s t a n d a r d l i n e f o r uranium L-X a n a l y t e l i n e i s c a r r i e d o u t . S t a n d a r d i z a t i o n w i t h s t r o n t i u m e l i m i n a t e d t h e absorption-enhancement e f f e c t i n a n a l y s i s .
I n t h e second m e t h o d , s t r o n t i u m and thorium a r e chosen a s f i l t e r s f o r uranium L-X and K-X f l u o r e s c e n t r a y s r e s p e c t i v e l y - A t t e n u a t i o n ( H u l l ) f i l t e r s a r e u s e d t o remove UL6,UKs and primary beam l i n e s from s p e c t r a i n o r d e r t o p r e v e n t i n t e r f e r e n c e w i t h t h e a n a l y t e l i n e - w i t h h i g h e r i n t r i n s i c X-ray p r o d u c t i o n y i e l d s K and L l i n e s a n a l y s i s c a n b e performed on t h i c k and t h i n t a r g e t s .
The c o n c e n t r a t i o n o f uranium i n o r e s o b t a i n e d by two methods a g r e e s w e l l w i t h t h e r e f e r e n c e v a l u e .
I n t r o d u c t i o n
X-ray f l u o r e s c e n c e s p e c t r o m e t r y i s o f t e n u s e d a s powerful t e c h n i q u e f o r uranium a n a l y s g s d u r i n g r e c e r n y e a r s ( 1 - 3 ) . A l l t h e methods have been b a s e d upon t h e u s e o f e m i s s i o n l i n e g e n e r a t e d by t h e sample i t s e l f - T h e f l u o r e s c e n t i n t e n s i t y from a g i v e n c o n c e n t r a t i o n o f uranium may b e a f f e c t e d by t h e m a t r i x and t h e p a r t i c u l a t e n a t u r e of a sample- The d i f f i c u l t i e s r e l a t e d t o t h e c o m p o s i t i o n and p h y s i c a l s t a t e of t h e sample were g e n e r a l l y overcome by compensation methods s u c h a s i n t e r n a l s t a n d a r d .
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987916
C9-104 J O U R N A L D E PHYSIQUE
The u s e o f y t t r i u m a s a n i n t e r n a l s t a n d a r d f o r u r a n i u m a n a l y s i s h a s b e e n r e p o r t e d by Cope a n d L i n g a r d , who w e r e i n t e r e s t e d i n 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 n m i n e r a l b e a r i n g r o c k s ( 4)
.
M o d i f i c a t i o n o f a f l u o r o m e t r i c method was a d o p t e d f o r a n a l y s i s o f uranium i n w a t e r and b r i n e employing i n t e r n a l s t a n d a r d by Kehl a n d R u s s e l l (5). I n p r e s e n t work, a c c o r d i n g t o t h e r e p r e s e n t e d i d e a l c o n d i t i o n , s t r o n t i u m K l i n e was s e r v e d a s a n i n t e r n a l s t a n d a r d f o r uranium L l i n e . The method i s c a p a b l e o f g r e a t a c c u r a c y a n d h a s s i g n i f i c a n t a d v a n t a g e t o overcome t h e a b s o r p t i o n - e n h a n c e m e n t e f f e c t s .The s p e c t r a o b t a i n e d f r o m s a m p l e may i n c l u d e h i g h l e v e l unwanted background w i t h t h e i n t e r f e r e n c e s o f a n a l y t e a n d X-rays e m i t t e d by t h e e l e m e n t s a n d p r i m a r y r a d i a t i o n . A p p l i c a t i o n s o f f i l t e r s a r e u s e f u l t e c h n i q u e t o r e d u c e i n t e r f e r e n c e s by e l e m e n t s e x h i b i t i n g l i n e s a t c l o s e l y a d j a c e n t e n e r g i e s . ' A s u r v e y o f t h e l i t e r a t u r e i n d i c a t e s t h a t some a u t h o r s h a v e u s e d t h e f i l t e r s t o remove p r i m a r y p h o t o n s o r t o r e d u c e t h e background i n t e n s i t y i n t h e r e g i o n o f a s p e c i f i c a n a l y t e l i n e ( 6 ) - I n t h i s work, s t r o n t i u m a n d t h o r i u m t h i n l a y e r a r e s e l e c t e d a s H u l l f i l t e r s f o r u r a n i u m L-X and K-X f l u o r e s c e n t a n a l y s i s r e s p e c t i v e l y .
I n t e r n a l S t a n d a r d Method
I n t e r n a l s t a n d a r d i z a t i o n i s t h e most well-known method f o r m a t r i x e f f e c t c o r r e c t i o n . A p r o p e r l y c h o s e n s p e c t r a l l i n e a n d p r o p e r l y s e l e c t e d i n t e r n a l s t a n d a r d e l e m e n t w i l l be a b s o r b e d t o t h e same e x t e n t f r o m m a t r i x e l e m e n t . I n p r a c t i c e , t h e c r i t e r i o n i s t h a t t h e i n t e r n a l s t a n d a r d ( s t r o n t i u m ) a n d a n a l y t e l i n e ( u r a n i u m ) a n d a b s o r p t i o n e d g e s s h o u l d h a v e e n e r g i e s a s c l o s e a s p o s s i b l e .
The method, a s a d a p t e d f o r t h e a n a l y s i s o f u r a n i u m was b a s e d o n t h e r a t i o o f t h e i n t e n s i t y o f t h e UL, l i n e t o t h a t o f t h e K, l i n e from t h e known amount o f added s t r o n t i u m . I n t h a t c a s e , UL, a n d SrK, l i n e s a r e a b s o r b e d a n d e n h a n c e d t o s u b s t a n t i a l l y t h e same e x t e n t by t h e a d j a c e n t e l e m e n t s .
E x p e r i m e n t a l s e t u p was d e s i g n e d f o r q u a n t i t a t i v e d e t e r m i n a t i o n o f uranium i n u r a n i u m b e a r i n g o r e s . A m o n o e n e r g e t i c e x c i t a t i o n s o u r c e 1°9cd was u s e d a n d t h e s a m p l e was c o n s i d e r e d t o b e t h i n . S i ( L i ) d e t e c t o r d u e t o h i g h e f f i c i e n c y i n uranium L-X r a y s r e g i o n was employed f o r t h e d e t e c t i o n a n d c o n n e c t e d t o N I M modules, 4096 c h a n n e l a n a l y z e r .
I n t e r n a l s t a n d a r d s t r o n t i u m i n s o l u t i o n was added t o s a m p l e a t
5 0 0 5 5 0 6 0 0 6 5 0 >
7 0 0 Channel number
Fig.1. The spectrum of uranium aample added strontium
0 1 3 5 7
U r a n i u m c o n c e n t r a t i o n ( % ) F i g . 2, Cali b r a t i o n curve f o r uranium
c o n c e n t r a t i o n l e v e l e q u i v a l e n t t o a b o u t t h e m i d d l e o f t h e e x p e c t e d uranium c o n c e n t r a t i o n . The s l u r r y mixed, d r i e d , g r o u n d and c o m p r e s s e d a t 25 t o n s i n 3 c m d i a m e t e r p e l l e t s . The s p e c t r u m of u r a n i u m o r e s a m p l e added s t r o n t i u m i s shown i n Fig.1. The b a c k g r o u n d s o f uranium L
,
and s t r o n t i u m K , were measured s i m u l t a n e o u s l y . C a l i b r a t i o n c o n s t a n t w a s d e r i v e d f r o m o r e s t a n d a r d s h a v i n g known c o n c e n t r a t i o n s o f uranium a n d s t r o n t i u m a s i n t e r n a l s t a n d a r d . The c a l i b r a t i o n c u r v e f o r uranium i s g i v e n i n F i g . 2.F i l t e r Method
An a t t e n u a t i o n f i l t e r i s a t h i n f o i l o r l a y e r p l a c e d i n an X-ray beam t o p r e f e r e n t i a l l y abso? a c e r t a i n e n e r g y o r band o f e n e r g i e s . H u l l f i l t e r h a s a n a b s o r p t i o n e d g e e i t h e r between t h e u r a n i u m K, a n d K g o r L a a n d L B l i n e . F i l t e r i n g a d j a c e n t e n e r g i e s i n s p e c t r u m c a u s e d r e d u c t i o n o f t h e o b s e r v e d uranium X-ray i n t e n s i t i e s i n o r e s a m p l e i n g a i n i n g t h e a d v a n t a g e o f l o w e r background l e v e l s o f sample.
The f i l t e r was p r e p a r e d a t h i n l a y e r o f p u r e compound o f s t r o n t i u m h a v i n g K a b s o r p t i o n e d g e a t 16.106 keV j u s t g r e a t e r t h a n a n a l y t e l i n e UL, a t 1 3 . 6 1 3 keV. T h i n l a y e r was mounted on mylar f i l m a n d p l a c e d o v e r t h e window o f S i ( L i ) d e t e c t o r . S i m i l a r c o u n t i n g s y s t e m d e s c r i b e d i n p r e v i o u s work was u s e d f o r a n a l y s i s o f u r a n i u m c o n s i d e r i n g La l i n e - F i g u r e 3 shows a c o m p a r i s o n o f t h e s p e c t r a of t h e uranium L-X r a y s w i t h o u t f i l t e r and w i t h s t r o n t i u m f i l t e r o v e r t h e window o f S i ( L i ) . U s e o f t h i s f i l t e r d e m o n s t r a t e d a b s o r p t i o n o f t h e unwanted background i n t e n s i t y e m i t t e d by s a m p l e a n d p r i m a r y r a d i a t i o n f r o m s o u r c e however r e d u c t i o n o f t h e UL, i n t e n s i t y t o a b o u t 30 $ t h e i n t e n s i t y w i t h no f i l t e r u s e d ,
The s e c o n d f i l t e r s e l e c t e d was t h e m i x t u r e o f t h o r i u m o x i d e p r e p a r e d i n t h i n l a y e r w i t h c e l l u l o s e a s a b i n d e r . An a n n u l a r s o u r c e of 5 7 ~ 0 was c h o s e d t o u t i l i z e t h e p r i m a r y r a d i a t i o n a t 1 2 2 . 1 keV f o r e x c i t i n g t h e u r a n i u m K s h e l l . Thorium f i l t e r was s e t t l e d o v e r t h e G e ( L i ) d e t e c t o r a n d a b s o r b e d t h e UKB l i n e a n d o t h e r p r i m a r y beam l i n e s v e r y s t r o n g l y . The measurement s y s t e m c o n s i s t e d o f s p e c t r o s c o p y a m p l i f i e r w i t h a PUR a n d 4096 m u l t i c h a n n e l a n a l y z e r .
D e t e r m i n a t i o n o f uranium c o n c e n t r a t i o n was p e r f o r m e d by t h e c a l i b r a t i o n s t a n d a r d i z a t i o n .
JOURNAL DE PHYSIQUE
:'''\.
... ....
....
4 7 0 5 5 0 6 5 0 7 5 0 8 5 0 9 5 0
C h a n n e l number
strontium f i l t e r and vj-thout Fig.3. The s p e c t r a of t h e uranium with r f i l t e r R e s u l t s a n d D i s c u s s i o n
The r e s u l t s o f measured u r a n i u m c o n c e n t r a t i o n by u s i n g i n t e r n a l s t a n d a r d a n d f i l t e r methods w e r e summarized i n T a b l e 1,
Table 1. Analyses o f uranium , o r e sample
Method XRF, U(%) Recommended Value, U( %)
I n t e r n a l Standard 1-020
1
0.004 1.020%
0.010S r f i l t e r 1.019
+
0.007 1.0202
0.010 Th f i l t e r 1.022 ; 0.007 1.020 + 0.010A method u s i n g t h e uranium f l u o r e s c e n c e t o s t r o n t i u m a s a n i n t e r n a l s t a n d a r d r a t i o t o p r o v i d e a d e q u a t e c o m p e n s a t i o n f o r a b s o r p t i o n enhancement e f f e c t s was d e s c r i b e d - S r K , s e r v e d a s i n t e r n a l s t a n d a r d l i n e f o r U L , a n a l y t e l i n e . It was p r o v e d t h i s s t u d y i s
s u c c e s s f u l a p p l i c a t i o n o f K l i n e o f i n t e r n a l s t a n d a r d f o r L l i n e o f a n a l y t e .
The f i l t e r s was c h o s e n w i t h an a b s o r p t i o n e d g e between t h e two uranium p e a k s t o c a u s e p r e f e r e n t i a l a b s o r p t i o n o f t h e peak w i t h g r e a t e r e n e r g y . T h r e e i m p o r t a n t c o n s i d e r a t i o n s w e r e t a k e n i n t o a c c o u n t i n f i l t e r s p r e p a r a t i o n f r o m u s a b l e p u r e compounds. F i r s t was t h e d e g r e e o f a t t e n u a t i o n o f unwanted r a d i a t i o n , s e c o n d was t h e r e s i d u a l i n t e n s i t y of wanted r a d i a t i o n a n d t h i r d o n e was p o s s i b l e unwanted c o n t r i b u t i o n s t o background i n t e n s i t y d u e t o e x c i t a t i o n o f f i l t e r e l e m e n t s .
References
1. P-ARIKAN, 1-ALKAN, J-Radioanal-Chem.,67(2),(1981)403.
2. P-ARIKAN, A-BZMEN, J. Radioanal.Nucl.Chem.Letters,108( 61, (1986) 327.
3. P. ARIKAN, A. GZMEN, Communications, S e r i e A2( 19871, ( t o be published).
4. J-H-COPE, A-L-LINGARD, Fourth Annual X-ray Symposium,Denver(l955).
5. W-L-KEHL, R-G-RUSSEL, Anal-Chem, 28(1956)1350.
6. E-BERTIN, P r i n c i p l e s and p r a c t i c e of X-ray spectrometric a n a l y s i s , Plenum Press, Neu York, 1975.
