14 Recovery of Americium-Curium From High -Activity Waste Concentrate by In-Canyon-Tank Precipitation as Oxalates L. W. GRAY, G. A. BURNEY, T. W. WILSON, and J. M. McKIBBEN
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Ε. I. du Pont de Nemours & Company, Savannah River Laboratory, Aiken, SC 29808 The Savannah River Laboratory (SRL) and Savannah River Plant (SRP) have been separating actinides for more than 25 years. Work continues to upgrade processes and to initiate new processes. This report summarizes work on a precipitation process developed to separate kg amounts of Am and Cm from hundreds of kilograms of NaNO and Al(NO ) . The new process includes formic acid denitration of the Am-Cm bearing streams for acid adjustment; oxalate precipitation of the Am-Cm; and Mn -catalyzed HNO oxidation of oxalate in both the decanted supernate and the precipitated acti nides. The new process generates one-fourth as much radioactive waste as the solvent extraction process which it replaced and produces a cleaner feed solution for downstream processing to separate the Am and Cm before conversion to their respective oxides. 3
3
3
2+
3
Origin of Am-Cm Solutions 243
244
252
Large-scale purification of Am, Cm, and Cf by pres surized cation exchange has been planned at SRP for many years (1,2). Initial small-scale work involved isolation of a crude actinide-lanthanide fraction by batch extraction in the large (>10,000 L) SRP canyon tanks followed by solvent extraction and ion exchange in the SRL high level caves. Processing r a t e s i n the caves, however, were inadequate f o r l a r g e - s c a l e p u r i f i c a t i o n of AmCm. 243
2l+1+
For l a r g e - s c a l e p u r i f i c a t i o n , the Purex P l a n t solvent e x t r a c t i o n bank was used f i r s t t o separate Am-Cm from the Pu i n the t a r g e t element and then to separate Am-Cm from the A l i n the t a r g e t element. I n each of the four campaigns that have been processed, the Pu i n the t a r g e t element has been p u r i f i e d by the normal Purex flowsheet. I n each case, the Am-Cm f r a c t i o n was i n i t i a l l y r e j e c t e d to the waste (1AW) stream.
0097-6156/81/0161-0223$05.00/0 ©
1981 A m e r i c a n Chemical Society
Navratil and Schulz; Transplutonium Elements—Production and Recovery ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
TRANSPLUTONIUM
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224
E L E M E N T S
1AF 1.5M
AI(N0 ) 3
0.6M
3
HNO3
0.01 g / L
ΡυΠΠ)
1 AS
3 0 % Τ BP
6Μ Ν α Ν 0
3
ΙΑ AI(NO) Να(Ν0 ) 3
30%
Figure 1.
Waste Solvent
ΤΒΡ
op
3
3>
IB
IBP
1BX
Am Cm HN0
0.1M H N 0
3
1C
3
1CU
1CX
Pu 0.3M H N 0
0.01M HAN 0.05M HN0
3
A ctinide separations flowsheet
Navratil and Schulz; Transplutonium Elements—Production and Recovery ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
3
14.
GRAY
Ιπ-Canyon-Tank
E T A L .
225
Then f o r the f i r s t three campaigns, the 1AW was evaporated and a c i d a d j u s t e d t o form feed f o r a second-pass through the s o l v e n t e x t r a c t i o n c y c l e to e x t r a c t the Am-Cm f r a c t i o n . T h i s flowsheet, shown i n F i g u r e 1, was used t o recover a t o t a l of ^6.1 kg Am and ^2.3 kg ^Cm. The o v e r a l l recovery of Am-Cm f o r these three campaigns was >99%. The p u r i f i e d product from these three campaigns was evaporated and combined i n a s i n g l e tank. U n f o r t u n a t e l y , the c o n t r i b u t i o n of both entrainment and s o l u b i l i t y of NaN03 from the scrub (IAS) stream was s u f f i c i e n t to y i e l d 8500 moles of NaN03 i n the p u r i f i e d Am-Cm s o l u t i o n . The high-pressure ion-exchange process i n the M u l t i - P u r p o s e P r o c e s s i n g F a c i l i t y (MPPF), however, demands that the monovalent c a t i o n contamination of the Am-Cm feed be reduced t o
