ToF-SIMS and XPS characterizations of model fission products (I, Cs) deposits after thermal treatment simulating late phase conditions of a nuclear power plant severe accident

During a Severe Accident (SA) occurring in nuclear power plant, many Fission Products (FP) are released from the degraded fuel and transported Reactor Coolant System (RCS). Depending on their volatility, FP can be either deposited surface of (RCS) or into containment building where they may environment case early failure. This was for Fukushima Daiichi (FD) accident with important releases which were observed following vessel failure lasted up to several weeks after accident. If phase well predicted by SA simulation codes, delayed not correctly [1]. Such discrepancies attributed revaporization deposits inside RCS yet modeled tools. Previous experiments over past 20 years evidenced possible formation CsI [2]. However, now, no clear mechanism has been determined. In order propose mechanism, this study (scheduled within OECD/NEA/ESTER project) aims at determining speciation each species remaining substrate tests under different conditions using XPS ToF-SIMS (X-ray Photoelectron Spectroscopy Time Flight Secondary Ion Mass Spectrometry. These two combined techniques allow identification main residue leading proposition reactions.