Validation of SolventExtraction Scheme for the Reprocessingof Advanced Heavy Water Reactor Spent Fuel Using N,N-Dihexyl Octanamide as Extractant.

Even though tri-n-butyl phosphate (TBP)has beenthe work horse for spent fuel reprocessing, some of its drawbacksare of major concern. Based on batch extraction studies, our groupat Radiochemistry Division, BARC has proposed N,N-dihexyl octanamide (DHOA) as an alternative extractant to TBP forthe reprocessing of three component Advanced Heavy Water Reactor (AHWR)spent fuels. To validate the batch data, twelve stage counter-currentmixer settler runs were carried out on a simulated AHWR feed [∼2g/L U + ∼2 g/L Pu + 100 g/L Th + 0.03 M HF + 0.1 M Al(NO3)3at ∼3.5 M HNO3] (with a Putracer instead of 2 g/L; due to marginal variation in its extractionbehavior) with 0.18 M TBP and 0.36 M DHOA/n-dodecaneas extractants. Quantitative extraction of Pu and U was achieved in∼5 stages (maintaining volume ratio (O/A) as 1.1) leaving thebulk of thorium in the raffinate. Co-extracted thorium (∼4.5%)from the organic phase was scrubbed using 4 M HNO3. Partitioningof Pu from a loaded organic phase was carried out employing 0.5 Mhydroxyl ammonium nitrate (HAN) at 2 M HNO3as the strippant.Finally, uranium was stripped quantitatively using 0.01 M HNO3. The results clearly established the cocurrent studies using0.36 M DHOA/n-dodecane as the extractant. The proposedflow sheet using 0.36 M DHOA/n-dodecane appears attractivewith respect to the volume of the organic waste generated as comparedto that of 0.18 M TBP/n-dodecane. Radiolytic degradationand hydrodynamic parameters of 0.36 M DHOA were also evaluated vis-à-vis0.18 M TBP in n-dodecane. [ABSTRACT FROM AUTHOR]