Fission product release and microstructure changes of irradiated MOX fuel at high temperatures

Samples of irradiated MOX of 44 GWd/tHM mean burn-up were prepared by core drilling at three different radial positions of a fuel pellet. They were subsequently heated in a Knudsen effusion mass spectrometry system up to complete vaporization of the sample (~2600 K) and the release of fission gas (krypton and xenon) and helium was measured. Scanning electron microscopy was used in parallel to investigate the evolution of the microstructure of a sample heated in the same condition up to given key temperatures as determined from the gas release profiles. A clear difference for fission gas release and microstructure was observed as a function of the radial position of the samples and therefore of irradiation temperature. A good correlation between the microstructure evolution and the gas release could be established as a function of the temperature of irradiation and (laboratory) heating.JRC.E.3-Materials researc