AQUEOUS PROCESSING OF THORIUM FUELS. PART II

The status of aqueous processing methods for Th fuels is reviewed. A specially designed 320 ton shear was successfully tested for chopping full size simulated Consolidated Edison type unirradiated assemblies into 0.25-1.5 in. lengths. Pieces about 0.5-in. long are preferred since the core pellets are more severely crushed during the chopping operation, and consequently, the rate of core dissolution is enhanced. The Darex (dtlute aqua regia) and Sulfex (4 to 6 M sulfuric acid) processes for dissolution of stainless steel claddings were developed on a small engineering scale with unirradiated fuel. In hot cell tests on stainless steel clad ThO/sub 2/-UO/sub 2/ fuel pins irradiated up to 22,000 Mwd/ton of fuel, the core pellets were severely fractured and losses of U and Th to the Sulfex and Darex solutions were approximates 0.3% and 3 to 5%, respectively. The latter losses are easily recovered in the extraction system. U and Th can be recovered from graphite base fuels by burning and dissoiution of the ash in HNO/sub 3/ or by grinding to approximates 200 mesh followed by HNO/sub 3/ leaching. The Acid Thorex extraction process was developed to recover both U and Th using tributyl phosphate (TBP) as the solvent and the Acid Interim 23 process to recover only the U using either TBP or disecbutyl phenyl phosphate as the solvent. The Acid'' processes use HNO/sub 3/ rather than Al as the salting agent. (auth