Process Optimization of DUPIC Fuel Pellet Fabrication

Abstract

DUPIC pellets are remotely fabricated by using DUPIC powder prepared by the OREOX treatment of spent fuel pellets. DUPIC pellets were successfully fabricated using spent PWR fuel material with an average discharge bum-up of 27,300 MWd/tU. Sintered density, grain size and surface roughness of the DUPIC pellets were investigated on the basis of CANDU fuel criteria. In order to optimize the DUPIC pellet manufacturing processes, 3 series of experiments for the pre-qualification and 3 series for the qualification were performed. In these experiments, the sintered densities of the pellets ranged from 10.35 g/cm3(95.7 % of T.D.) to 10.43 g/cm3(96.4 % of T.D.) and the average grain size ranged from 14.6 to 14.9 um. Based on these results, the optimum manufacturing processes of DUPIC pellets have been established. Then, under the control of the QA program developed with the assistance of AECL, 8 series of production runs have been performed to make DUPIC pellets in a batch size of 1 kg. The sintered densities of the fabricated pellets ranged from 10.26 g/cm3 to 10.43 g/cm3. The surface roughness of the ground pellets was less than Ra 0.8 um by the dry grinding process. As the results of the production runs, DUPIC fuel pellets meeting the standard CANDU fuel specifications were successfully fabricated by the established processes.