Experimental Determination of Burn-up of Mixed-Oxide Fuels Irradiated in PWL, CIRUS using Thermal Ionisation Mass Spectrometry

摘要

Experimental determination of burn-up was carried out for four samples from mixed oxide (UO_2+4% PuO_2) clusters irradiated in Pressurized Water Loop (PWL) of CIRUS research reactor. This involved dissolution of the irradiated fuel sample, separation and purification and determination of heavy elements (U and Pu) and the stable fission product (~(148)Nd) used as a burn-up monitor. Isotope Dilution-Thermal Ionisation Mass Spectrometry (ID-TIMS) was employed for the quantification of the heavy elements (U and Pu) and burn-up monitor (Nd). A triple spike consisting of Nd, U and Pu was used to determine the concentrations of Nd, U and Pu, respectively, in the irradiated fuel dissolver solution". Fractional fission contributions from the major fissile nuclides were calculated based on the Nd isotopic composition data, which showed that Pu accounted for majority of fissions in all the samples. The burn-up values ranged from 0.3 to 1.5 atom% fissions.