Abstract

Oxygen to metal ratio has been measured by wet and dry chemical analysis to study the properties of sintered <TEX>$UO_2$</TEX> pellets and <TEX>$U_3O_8$</TEX> in the lithium reduction process of spent pressurized water reactor fuels. Uranium dioxide pellets simulated for the spent PWR fuels with burnup values of 20,000~60,000 MWd/MtU were prepared by mixing <TEX>$UO_2$</TEX> powder and oxides of fission product elements, pelleting the powder mixture and sintering it at <TEX>$1,700^{\circ}C$</TEX> under a hydrogen atmosphere. For wet chemical analysis, the simulated spent fuels were dissolved with mixed acid (10 M HCl : 8 M <TEX>$HNO_3$</TEX>, 2.5 : 1, v/v) using acid digestion bomb technique. The total amount of uranium and fission products added in the simulated spent fuels were measured using inductively coupled plasma atomic emission spectrometry. Weight change of the simulated fuel during its oxydation was measured by thermogravimetry and then the O/M ratio result was compared to that obtained by wet chemical analysis. Influence of <TEX>$Mo_{0.4}-Ru_{0.4}-Rh_{0.1}-Pd_{0.1}$</TEX>, quaternary alloy, on the determination of O/M ratio was investigated.