O/U ratio of uo_2 pellets sintered at low temperature and reduced in different atmospheres

摘要

In this work it was aimed to investigate the O/U ratio and density and usabilituy of the low level hydrogen concentration used in reducing atmosphere. By using ex-ADU UO_2 powder UO_2 fuel pellets were produced by low temperature sintering. The sintering temperature was determined as 1150 deg C in order to obtain 95percent theoretical density. Different ratios of H_2/Ar atmosphere were used as reducing atmosphere. The sintered pellets were reduced in 0.1 percent H_2 + 99.9 percentAr, 0.5percentH_2 + 99.5percentAr, 1percentH_2 + 99percentAR and 100percentH_2 atmospheres for 1, 2, 3 and 6 hours. The relationships of O/U ratio and hydrogen concentration, O/U ratio and density of tehse pellets were determined. It was determined that with increasing hydrogen concentrationin reducing atmosphere the O/U ratio and the density of the UO_2 pellets were decreased. It was determined that by using 1percentH_2 + 99percentAr atmosphere it is possible to obtain the desired O/U ratio in shorter time compared to 0.1percentH_2 + 99.9percentAr and 0.5percentH_2 + 99.5percentAr atmosphere.