Irradiation of Minor Actinide–Bearing Uranium-Plutonium-Zirconium Alloys up to ~2.5 at. %, ~7 at. %, and ~10 at. % Burnups

An irradiation experiment on minor actinide (MA)-bearing uranium-plutonium-zirconium (U-Pu-Zr) alloys, in which contamination by rare earth (RE) elements was considered, was performed up to ~2.5 at. %, ~7 at. %, and ~10 at. % burnups in the Phenix fast reactor. All the irradiated metal fuel pins were subjected to nondestructive tests such as cladding profilometry and gamma spectroscopy. Then, cross-sectional metallography of the low-burnup and medium-burnup fuel alloys was performed, and the redistribution of the fuel matrix constituents—U, Pu, and Zr—in the low-burnup fuels was analyzed by energy dispersive X-ray spectroscopy. As a result, the irradiation growth of MA-rich and RE-rich precipitates was observed by comparing the low-burnup and medium-burnup fuels. From the postirradiation examinations carried out so far, it was confirmed that the irradiation swelling, the cross-sectional structures, and the migration of matrix constituent in metal fuels containing 5 wt% or less MAs and REs are almost the same as those in conventional U-Pu-Zr fuels.