Journal of Nuclear Fuel Cycle and Waste Technology

Quantitative analysis on release behavior of the 85Kr and 14C fission gases from the spent fuel material during the voloxidation and OREOX process has been performed. This thermal treatment step in a remote fabrication process to fabricate the dry-processed fuel from spent fuel has been used to obtain a fine powder The fractional release percent of fission gases from spent fuel materials with burn-up ranges from 27,000 MWd/tU to 65,000 MWd/tU have been evaluated by comparing the measured data with these initial inventories calculated by ORIGEN code. The release characteristics of 85Kr and 14C fission gases during the voloxidation process at 500 ℃ seem to be closely linked to the degree of conversion efficiency of UO2 to U3O8 powder, and it is thus interpreted that the release from grain-boundary would be dominated during this step. The high release fraction of the fission gas from an oxidized powder during the OREOX process would be due to increase both in the gas diffusion at a temperature of 700 ℃ in a reduction step and in U atom mobility by the reduction. Therefore, it is believed that the fission gases release inventories in the OREOX step come from the inter-grain and intra-grain on UO2 matrix. It is shown that the release fraction of 85Kr and 14C fission gases during the voloxidation step would be increased as fuel burn-up increases, ranging from 6 to 12%, and a residual fission gas would completely be removed during the OREOX step. It seems that more effective treatment conditions for a removal of volatile fission gas are of powder formation by the oxidation in advance than the reduction of spent fuel at the higher temperature.

Keywords

DUPIC,Spent fuel. Voloxidation,OREOX,Oxidized powder,Fractional release percent,85Kr,14C