CHARACTERISATION OF VOLATILE FISSION PRODUCTS, INCLUDING IODINE, AFTER A POWER RAMP

摘要

The behaviour of iodine during a power ramp is an important topic in the framework of studies on pellet-to-clad mechanical interaction (PCMI). Up to now, little experimental data have been available on iodine characterisation in the nuclear ceramic because its concentration is too low to be measured with Electron Probe Micro Analysis (EPMA). However, in our laboratory, a shielded SIMS was recently installed, which enables the detection of low abundant species, and a research programme was built up to use these new possibilities in order to better characterise the volatile fission products (FPs) during a power ramp, with a special care given to iodine. This programme was aimed at studying how the volatile FPs can leave the UO_2 ceramic and how they behave once they have left the ceramic. For that purpose a power ramp was designed to have a high thermal level during a short time in order to enhance the release mechanisms and at the same time to limit solid-state diffusion and to avoid failure.