Release of volatile fission products during thermal annealing of irraidated LWR UO2 fuels

Volatile fission products release during thermal annealing of UO2 fuels irradiated at different burnup and temperature has been measured with a Knudsen cell mass spectrometer system. The release kinetics and the semi quantitative analysis of the fission products have been performed for burnup ranging from 27 to 240 GWd/Ty, and for irradiation temperatures ranging from 500 to 1200 aC. The microstructure of the samples at end of irradiation and after the laboratoiy annealing tests has been studied by scanning and by transmission electron microscopy. The thermal release profiles have been interpreted based on the original microstructure as well as on the evolution of this microstructure during heating.JRC.E.3-Materials researc