Recovery of Plutonium Traces from Nitric Acid-Fluorhydric Acid

Chemical Engineering Center, Energetic and Nuclear Research Center,. Cx Postal 11049 ... previously proposed for the recovery of plutonium traces from...
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2 Recovery of Plutonium Traces from Nitric A c i d -Fluorhydric A c i d Solutions by Sorption onto Alumina J. A D R O A L D O D E A R A Ú J O and A L C Í D I O A B R Ã O Chemical Engineering Center, Energetic and Nuclear Research Center, Cx Postal 11049, Pinheiros, S.P., Brazil

Sorption of plutonium traces onto alumina from uranyl nitrate solutions has been investigated. Several methods have been previously proposed for the recovery of plutonium traces from reprocessing solutions. Those methods include ion exchange (1,2), solvent extraction (3,4) and, extraction chromatography (5,6). Several hydrous oxides, such as those of aluminum, silicon and, iron have been used to extract traces ions. Nevertheless, the sorption mechanism is not definitively established. Those oxides probably exhibit some ion exchange capacity among their properties and they can act as anionic or cationic exchangers and sometimes both. The separation of plutonium traces in the presence of HF by sorption onto an alumina column is based on its chemical similarities with thorium and lantanide elements reported by Abrão (7). In this case only thorium and rare earths are sorbed onto alumina from nitric acid-fluoride solutions while uranium remains in the effluent. The redox methods are well known for the purification and concentration of plutonium from the Purex process solutions. This paper deals with three different oxidation states of plutonium Pu(III), Pu(IV), and Pu(VI) in HNO -HF systems. The c h r o m a 3

t o g r a p h i c c o l u m n method u s i n g a l u m i n a h a s b e e n a p p l i e d s u c c e s s f u l y t o t h e s e p a r a t i o n o f p l u t o n i u m when u r a n y l n i t r a t e s o l u t i o n c o n t a i n i n g 0 . 1 - 0 . 3 M HF was p e r c o l a t e d t h r o u g h t h e c o l u m n . EXPERIMENTAL A l l 239pu s o l u t i o n s u s e d d u r i n g t h e r u n s w e r e p r e p a r e d f r o m a s t a n d a r d s o l u t i o n ( A m e r s h a m / S e a r l e ) , o f 1 u C i / m l (160 y g / m l ) s p e c i f i c a c t i v i t y . The u r a n i u m s o l u t i o n s were o b t a i n e d by d i s s o l u t i o n o f n u c l e a r g r a d e u r a n i u m o x i d e s . One m l o f AI2O3 c h r o m a t o g r a p h i c g r a d e was c o n d i t i o n e d a c c o r d i n g BROCKMANN (8) w i t h 0 . 8 M HNO3 i n g l a s s c o l u m n s 0 . 6 c m i n d i a m e t e r and 20cm l o n g . The e x p e r i m e n t s were f o l l o w e d b y a l p h a s p e c t r o m e t r y a f t e r t h e p l u t o nium was e x t r a c t e d w i t h 0 . 5 M T T A / X Y L O L . The s a m p l e s 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 were p r e p a r e d b y e l e t r o p l a t i n g a c c o r d i n g t o WENZEL and HERZ (90 . The a l p h a e n e r g y m e a s u f e m e n t was made b y a

0-8412-0527-2/80/47-117-009$05.00/0 © 1980 A m e r i c a n C h e m i c a l Society

10

ACTINIDE SEPARATIONS

s u r f a c e b a r r i e r d e t e c t o r a s s o c i a t e d w i t h a ORTFC m u l t i c h a n n e l a n a l y s e r . The p l u t o n i u m o x i d a t i o n s t a t e s were d e t e r m i n e d b y a p h o t o m e t r i c method u s i n g ARSFNAZO I I I . The d e t e r m i n a t i o n s were carried o u t w i t h a d o u b l e beam PFPFIN-FLMF ? s p e c t r o p h o t o m e t e r vising q u a r t z 11

microcells. The f i r s t e x p e r i m e n t s were c a r r i e d o u t t o u n d e r s t a n d t h e p e r f o r m a n c e o f p l u t o n i u m in^an. A 1 0 - TîNO^ m e d i u m . T h i s was done by 0

p e r c o l a t i o n o f 25 m l o f 23 ^ p s o l u t i o n i n 0 . 8 M HNO^ w i t h a l p h a a c t i v i t y o f 55,000 -f 235 (counts/2000 s e c / m l ) , through a glass c h r o m a t o g r a p h i c c o l u m n ( i . d . 6mm) c o n t a i n i n g 1 ml o f A 1 0 ^ . n

9

A l l r u n s were made w i t h 0 . 8 M * N0~ s o l u t i o n s w i t h a Pu a l p h a a c t i v i t y of 10,000 316 ( c o u n t s / 2 0 0 0 s e c / m l ) a n d , F F c o n c e n t r a t i o n r a n g i n g from 0.1 to . 3 M . T

n

The f e e d s o l u t i o n f o r t h e A 1 0 ~ c o l u m n h a s t h e f o l l o w i n g comp o s i t i o n : 1,5 χ 1 0 " M P u ; a l p h a a c t i v i t y = 2 3 0 , 0 0 0 + 480 (coun0

S

2

3

9

ts/2000/sec/20ml); 0 . 8 M F.N0 ; 6.1 - n . 3 M F F ; u r a n y l n i t r a t e 47.6 g U / l ; 0 . 0 0 5 M FeSO^ and 0 . 0 4 M N a N 0 . P u ( I V ) was o b t a i n e d i n t h i s solution by p r e v i o u s r e d u c t i o n o f ^ t o t a l p l u t o n i u m to P u ( I I I ) w i t h F e ( I I ) f o l l o w e d b y o x i d a t i o n w i t h n i t r i t e . No i n t e r f e r e n c e o f u r a n i u m was o b s e r v e d i n t h e p r o c e s s . To a v o i d t h e interference 3

9

of 234j^ ( u r a n i u m d a u g h t e r ) on t h e measurements o f p l u t o n i u m , i t was p r e v i o u s l y removed b y p e r c o l a t i n g t h e s o l u t i o n i n t o a n o t h e r a l u m i n a column b e f o r e the a d d i t i o n o f 2 3 9 p a

u #

RESULTS AND_PISCUSSI0N The retained

results by t h e

t o n i u m must typical Table

I.

(Table

I)

show t h a t

alumina from 0 . 8

likely

be

complexed

plutonium breakthrough Plutonium Retention

Fxp.

M

o n l y 17

nitric

to

be

curve

of

acid

sorbed.

the

plutonium

is

and t h e r e f o r e

plu­

Figure

a

.1 shows

from 0.8H n i t r i c

f r o m 0 . 0 8 M ΤΙΝ0- o n t o

acid.

A1 0« 9

23° Pu.retained

1 2

(%) 1.8 1.0

3

0.8

4

0.9

5

1.1

T a b l e I I shows t h a t t h e p l u t o n i u m s o r p t i o n o n t o Alo^3 * 87% and i t was d e m o n s t r a t e d t h a t w i t h t h e a i d o f f l u o r i d e t h e r e c o v e r y o f p l u t o n i u m t r a c e s f r o m w a s t e s o l u t i o n s was possible. s

a

r

^ ions

o

u

n

ADROALDO D E ARAUJO A N D ABRAO

Sorption

Al O

ΟΠ

2

s

Figure 1. Breakthrough curve of Pu onto Al 0 column; feed: 25 ml Pu-O.8M HN0 ; ^Pu activity = 55,000 ± 235 counts/2000 sec/ml; column = 1 ml Al 0 ; flow rate = 0.8 ml/min/cm . 2

239

3

3

2

2

3

12

ACTINIDE SEPARATIONS

Table

II.

Effect

o f HF o n Pu R e t e n t i o n

23Q

FF

'Pu

(M)

0.1 0.1 0.1 0.2 0.2 0.3 0.3

As

was

D.F.

ret. (%)

C 'Pu) J

7.0 6.9 7.2 6.4 6.5 9.5 9.5

85.7 85.5 86.1 84.4 84.8 89.6 89.4

observed

i n the

on A1„0,

first

experiments,

p l u t o n i u m was

not

c o m p l e t e l y s o r b e d o n t o a l u m i n a f r o m 0 . 1 t o 0.3>f F F . So t h e n e x t s t e p was t o examine t h e p o s s i b i l i t i e s o f a d d i n g r e d o x a g e n t s t o m a i n t a i n a s i n g l e o x i d a t i o n s t a t e . A c o n c e n t r a t i o n o f 0 . 1 M HF was c h o s e n b e c a u s e t h i s i s enough F F t o c o m p l e x a l l t h e p l u t o n i u m (Pu - 10~^M) £ h f e e d s o l u t i o n and w i l l n o t c a u s e s i g n i f i c a n t c o r ­ n

t

G

r o s i o n e f f e c t s o n t h e g l a s s c o l u m n . Some o f t h e r e d o x a g e n t s u s e d and t h e a v e r a g e y i e l d s o f p l u t o n i u m r e c o v e r y a r e g i v e n i n T a b l e I I I . T e t r a v a l e n t p l u t o n i u m i s b e t t e r s o r b e d t h a n Pu ( I I I ) o r Pu ( V I ) . The t h r e e o x i d a t i o n s t a t e s o f p l u t o n i u m were d e t e r m i n e d s p e c t r o p h o t o m e t r i c a l l y by c o m p l e x i n g Pu w i t h ARSFNAZO I I I ( 1 ° ) i n n i t r i c a c i d medium b y a d a p t i n g b o r a t o r s (11,12) . Table

III.

Fffect tion:

the

o f Pu o x i d a t i o n 2

3

9

Pu

method

states

~ 1 0 0 , 0 0 0 + 316

0 . 8 M HN0- ~ 0 . 1 M HF c o l u m n :

Pu Valence III VI

Redox

agent

i n the

load

cone.

-0.2M

NH .0H.HC1 9

0.01M N a N 0

IV

0 . 0 3 M NaNCC

IV

0.1M ΝΗ .ΝΠ 9

i.d.

65.0 87.2 89.0 90.9

9

-O.01M NaN0

(NO )

0.002M Fe

IV

N H H . F C l - 0.02M N a N 0 0.ΠΟ5Μ F e S O , - 0 . 0 4 M N a N 0 4 I n

-

?

IV

9

on s o r p t i o n ,

counts/2000

69.7

PC10*

IV

NEMODRUCK and

6mn;

Pu ret. (?) CO

solution 0 . 2 M NF .NH

of

Feed

sec/10

vol.

colla­

solu­ ml;

1 ml

A1 0 ?

D.F. (

Pu)

2.8 3.6

7.8

9.0 11.0

0.W 0

o

°2.3

13.0

07.8

47.2

A s e t o f l a b o r a t o r y e x p e r i m e n t s n r o v e d t h a t t h e most e f f e c t i ­ v e and c o n s i s t e n t method t o e l u t e p l u t o n i u m f r o m t h e a l u m i n a was by r e d u c i n g p l u t o n i u m t o t r i v a l e n t s t a t e i n n i t r i c a c i d . The c o l ­ l e c t e d d a t a ( T a b l e IV) p r e s e n t good r e s u l t s when 3M HNO - 0 , 0 0 5 ! ' F e S 0 , s o l u t i o n was u s e d as « l u t r i e n t . ApA

2.

ADROALDO D E ARAUJO AND ABRAO

proximately re

Sorption

on

2

95% o f t h e p l u t o n i u m was r e c o v e r e d

( 2 5 ° C ) . To d e t e r m i n e

Table

a s h a r p e r peak w h i l e

I V . Plutonium e l u t i o n

from A l 0 o

Elutrient (M)

HN0

s

a t room

i f the temperature could

t o n i u m d e s o r p t i o n , t h e e l u t i o n was done w i t h a t 25 and 5 0 ° C . F i g u r e 2 , shows t h e s e c u r v e s elution presents some t a i l .

temperatu­

improve

the

plu­

t h e same e l u t r i e n t a n d , a t 500C, t h e

the curve

o

13

Al O

column

Pu e l u t e d

at

at

25°C

exibits

25°C.

(%)

3

1

62.9

2

65.3

3

78.9

4

70.6

5

22.6

6

15.7

(M) HNO

-

(M) F e S 0

A

1

0.005

2

0.005

30.8 81.3

3

0.005

94.7

To d e m o n s t r a t e t h e v a l i d i t y o f t h i s p r o c e d u r e f o r t h e r e c o v e ­ r y o f t r a c e amount o f p l u t o n i u m f r o m d i l u t e s o l u t i o n s , 30 l i t e r s o f s o l u t i o n w i t h a s p e c i f i c a c t i v i t y o f 2 3 9 p 135 + 12 ( c o u n t s / 2 0 0 0 / s e c / m l ) was p e r c o l a t e d t h r o u g h a s m a l l c o l u m n c o n t a i n i n g 10 u

ml

of A l ^ O ^ .

About

97% o f p l u t o n i u m were s o r b e d

The e x p e r i m e n t s

have

shown t h a t

trace

onto

sorption

the

alumina.

of Pu(IV)

onto

A1 0 i s a l m o s t c o m p l e t e f r o m 0 . 8 M HNO^ - O . i y H F . T h e s t a b i l i z a ­ t i o n o f £ u ( I V ) s t a t e was o b t a i n e d b y p r i o r r e d u c t i o n t o P u ( I T I ) and r e o x i d a t i o n t o P u ( I V ) u s i n g F e ( I I ) and n i t r i t e . 2

3

The ^lo^3 c o l u m n

loaded

with

p l u t o n i u m was s a t i s f a c t o r i l y

washed w i t h an 0 . 1 M HNO^ - 0 . 0 5 M TIF s o l u t i o n f o r t h e r e m o v a l of t h e l a s t t r a c e s o f u r a n i u m and o t h e r e l e m e n t s n o t s o r b e d . T h e e f ­ f l u e n t s c o n t a i n e d l e s s t h a n 0.01% o f p l u t o n i u m . W a s h i n g t h e c o l u m n w i t h a n 0.8M HN0 - 0.05M HF s o l u t i o n r e s u l t e d i n 0.1% o f p l u t o ­ n i u m a c t i v i t y i n t h e e f f l u e n t . T h i s i n d i c a t e s t h a t the. column 3

should b e washed w i t h more d i l u t e n i t r i c a c i d . The e f f e c t i v i n e s s o f ^ e l u t i o n w i t h FNO^ p l u s a r e d u c i n g a g e n t a t room t e m p e r a t u r e and 50 C was c o n f i r m e d i n b o t h c a s e s . As P u ( I ) i s more s o r b e d o n t o a l u m i n a t h a n t h e o t h e r p l u t o n i u m o x i d a t i o n s t a t e s , i t was r e d u c e d t o P u ( I I I ) t o i m p r o v e t h e e l u t i o n . On t h e o t h e r hand HNO^ i s t h e most c o n v e n i e n t medium f o r f u r t h e r u s e s o f n l u t o n i u m , so f o r t h a t r e a s o n n i t r i c a c i d (1-6M) was s e l e c t e d as e l u t r i e n t . P u r e 3M IWO^ at room t e m p e r a t u r e e l u t e d 79% o f p l u t o n i u m . A 3M ΗΝ0~ - 0f005M F e S O . s o l u t i o n was c h o s e n as e l u t i n g a g e n t a n d , t h e e l u t i o n y i e l d u

Figure 2. Elution curve of Pu from Al 0 column; Al 0 = 1 ml; flow rate = 1.4 ml/minicm , surface barrier detector: (Ο) 3 M HNO -0.005M Fe \ tempera­ ture ~ 25°C (A)3M HNO -0.005M Fe \ temperature ~ 50°C. 239

2

3

2

2

3

3

;

3

2

2

ADROALDO ED ARAUJO AND ABRAO

Sorption

on

Al O 2

s

WASTE SOLUTION Pu traces U-W g/l

FEED

ADJUSTMENT

0./-0.8M HN0 Q/-0.3M HF _ O0O5M F e S 0 PuUW Q.04M NaNOzt 3

J

M

4

WASHING

ELUTRIENT

O./M HN0 0.05M HF

3

3M HN0 0Ό05Μ FeS0 | 20-50°C 3

4

AI2O3

QQLUm

PuilV) PRODUCT 3M HN0 PuilV) HF traces I FeS04 traces I

EFFLUENT

3

waste

EFFLUENT waste Recycle PROCESS

CONTROL

Influent, effluent, product : A) Pu extraction: 0,5M TTA/xylol B) Pu

eletroplating

C) Pu alpha counting

Figure 3.

Proposed flowsheet for recovery of Pu traces from reprocessing solu­ tions

ACTINIDE SEPARATIONS

16

being ence

improved to in

the

The of

about

95%.

descontamination

uranyl nitrate

easily

(N0 )

0. 8 .

U0

with

plutonium-239,

through

3

the

2

of

the

t e m p e r a t u r e has

plutonium traces

by s o r p t i o n

and s u c e s s f u l l y 2

Also

some

influ-

elution. of Pu(IV)

accomplished.

solution, the

from

3

macroquantities

an A l 0 ^

column

o

Percolation

0.8M i n HN0

Pu was

onto

of

vas

a

and 0 . 3 M i n HF t r a c e d

sorbed"while

uranium

passed

A ^ O ^ column.

CONCLUSION The alumina the

sucessful

p r o p o s e d method

solutions urse, are

experiments

for

f r o m HNO^-HF s o l u t i o n i n the

to

separate

presence

o n l y macroamounts

serious

interfering

thorium,

ions,

since

they

p l u t o n i u m , t h o r i u m and r a r e

for

Pu was

neptunium i n the HF s o l u t i o n s

around

95%.

Figure

the

of

uranium (IV)

of

from r e p r o c e s s i n g

waste

to

recomend

precipitate

earths.

(VI).

and r a r e

same s y s t e m

flowsheet

Of

co-

earths

iv'ith H F . The

s h o u l d be

The r e t e n t i o n

i n progress.

proposed

p l u t o n i u m onto

p l u t o n i u m from waste

The s o r p t i o n m e c h a n i s m

established. Pu t r a c e s

3 shows

is

of

confidence

uranium

milar yield

of

o f macroamounts

of

expected

n e p t u n i u m f r o m HNO^ -

retention

traces

behavior to

for

the

gave enough

The is for

si-

of

sorption not

well

recovery

solutions.

LITERATURE CITED 1. Aikin, A.M. Chem. Engng. Progr. 1957 53, 82. 2. Billiau, R., Lafontaine, I., Mostin, N., Zamorani, E. Proc. Symp. chimie des traitments des combustibles irradies par voie aqueuse, Bruxelles, 1963. 3. Howells, G.R., Hughes, T.G., Mekey, D.R., Saddington, K. ETR report 222, March, 1968. 4. Merril, E.T., Stevenson, R.L. HW report 38684, 1955. 5. Eschrich, H. Hundere, I. ETR report 222, March, 1968. 6. Siekiersk, S., Fidelis, I. J. Chromatog. 1960, 4, 60. 7. Abrão, A. IEA report 217, June, 1970. 8. " The Merck index ", 8 ed. Rahway, N.J. Merck & Co., 1968, 46. 9. Wenzel, V., Herz, D. KFA-Jülich, ICT Jahresbericht für den Zeitraum von 1 Juli 1972 bis 30 Juni 1973, 1973, 115. 10. Milynkova, M.S., Sawin, S.B. Russ J. Anal. Chem. 1967, 22,308 11. Nemodruck, Α.Α., Gluklova, L.P. Russ J . Anal. Chem. 1963, 18, 85. 12. Nemodruck, Α.Α., Kochetkova, N.F. Russ. J. Anal. Chem. 1962, 17, 333. RECEIVED May 25, 1979.