New fabrication process of large grain pellet for LWR

摘要

"Oxidation-sintering pellets" and "Al_2O_3/SiO_2 additive pellets" were developed. Both pellets will be used for high burnup due to their good FGR and PCI properties. In the "oxidation-reduction sintering process", U_3O_8 powder is added to UO_2 powder as a source of oxygen to produce U_4O_9 and to get large grain pellets. Atmosphere of the oxidation sintering process is O_2+N_2 and the sintering temperatures for both the oxidation and the reduction processes are relatively low compared with that for the standard sintering process. In Al_2O_3/SiO_2 addition , Al_2O_3/SiO_2 covers UO_2 grain and enhances its grain growth. Contents of Al_2O_3 and SiO_2 are very low (～50,50 PPM), therefore there is little impact on a reprocessing process.rnBoth type of pellets are under irradiation in test reactors and a commercial reactor as demonstration fuels. We will choose one type of pellet after PIE, and will use it for high burnup (55 GWd/t) as commercial fuels.