Study of the radiolytic decomposition of CsI and CdI2 aerosols deposited on stainless steel, quartz and Epoxy painted surfaces

Abstract

CsI and Cdl2 aérosol décomposition rate under irradiation has been quantified at 80°C and 120°C in presence of humidity and on different substrate (stainless steel, quartz and Epoxy paint). A model has been developed for the ASTEC-SOPHAEROS code to reproduce the data and help the identification of the gaps remaining in the understanding of iodine volatility in a severe accident of a Nuclear Power Plant (NPP). The current model applied to model the gaseous iodine behaviour in the containment of PHEBUS-FP tests does not fit with the experimental data probably because the nuclear aerosol reaching the containment are much more complex than pure CsI aerosols. It has been clearly shown than the radiolytic oxidation of metallic iodide aerosol into molecular iodine can significantly impact the source term evaluation even if additional experimental data area required to cover the variety and complexity of nuclear iodide aerosols.