DEMONSTRATION OF THE ZIRFLEX AND SULFEX DECLADDING PROCESSES AND A MODIFIED PUREX SOLVENT EXTRACTION PROCESS, USING IRRADIATED ZIRCALOY-2 AND STAINLESS-STEEL-CLAD URANIA SPECIMENS

The Zirflex and Sulfex processes for chemical decladding Zircaloy or stainless-steel-clad UO/sub 2/ power reactor fuels were successfully demonstrated at irradiation levels as high as 28,200 Mwd/t. The Zircaloy jackets were dissolved in boiling 6 M NH/sub 4/F-- 1 M NH/sub 4/NO/sub 3/, and the stainless steel jackets were dissolved in refluxing 4 M H/sub 2/SO/sub 4/. Both processes gave average soluble losses of uranium and plutonium to the decladding reagents of about 0.05%. Centrifugation or filtration of the highly radioactive decladding waste solutions was required to recover UO/sub 2/ fines produced by fracture of the UO/sub 2/. The fines were recycled and dissolved with the UO/sub 2/ cores in boiling 4 M HNO/sub 3/ solution. About 5 to 6 hr were required for complete dissolution of the UO/sub 2/ core to produce terminal concentrations of 100 g of uranium per liter and 3 M HNO/sub 3/. The core solution was a suitable solvent extraction feed after clarification and adjustment of plutonium valence with sodium nitrite. One cycle of the modified Purex process, in Mini mixersettlers, using 100-g-uranium-per-liter feed solutions, gave losses of uranium and plutonium to the raffinate of less than 0.1%, and gross gamma decontamination factors of about 1.5 x 10/sup 4/ for the uranium product and about 5 x 10/sup 3/ for the plutonium product. High purity n-dodecane diluent for the 30% TBP solvent retarded the formation of nonremovable uranium-retaining degradation products in the solvent by factors of up to 20, compared to Amsco- diluted TBP as measured by the uranium content of the washed solvent after six simulated cycles through the modified Purex process. The feed solutions were prepared from fuel specimens irradiated to 13,000 Mwd/t and cooled about 1 year. (auth