Effects of heavy-ion irradiation on Gd2Zr2O7 bearing simulated TRPO waste

Considering the urgent demand of nuclear waste disposal, a comprehensive study on the irradiation performance of nuclear waste forms is extremely necessary, especially on those containing multiple-nuclides with multiple-valence. The irradiation effects of Gd2Zr2O7 pyrochlore bearing simulated trialkyl phosphine oxides (TRPO) waste (consisting of ZrO2, MoO3, RuO2 and PdO) were studied in this work. Gd10.685Mo4.734Zr28.924Ru1.000Pd1.745O91.825 and Gd8.883Mo9.901Zr33.760Ru2.089Pd3.644O118.368 were irradiated by 1.5 MeV Xe20+ to fluences from 1 × 1012 to 1 × 1015 ions/cm2 at room temperature. The results showed an irradiation induced disordering with slight micro-swelling. In addition, the ion irradiation tolerance of the solid solutions decreased as the TRPO waste content increased. The decrease and shift of Raman peaks indicated the structural disordering and inner stress after irradiation. The micromorphology and element distribution of the irradiated surface remained almost unchanged. The structural evolution from pyrochlore to fluorite and even amorphous structure were disclosed in this study.