Interaction of Cesium Hydroxide with Oxide Layers Under Simulated Light Water Reactor Severe Accident

A large amount of cesium hydroxide (CsOH) is generated during a light water reactor severe accident (SA) and transported through leaky parts to the environment. During that process, some CsOH may interact with oxidized structural materials and change their physicochemical properties. Accurate examination of this interaction is required by source term analysis to derive consistent and appropriate source term transport models, i.e., for SA, decommissioning, and dismantling work of a nuclear reactor. To obtain detailed interaction characteristics, in this study CsOH was exposed to Fe₃O₄/Fe₂O₃ and Cr₂O₃ under a simulated SA environment over a wide temperature range, from 300°C up to 1050°C. As a result, Cs₂FeO₄, CsFeO₂, and Cs₂CrO₄ were observed at respective temperatures. Cs₂FeO₄ is stable only at low temperatures and decomposes to form CsFeO₂ at about 591°C. However, both Cs₂FeO₄ and CsFeO₂ could react with Cr₂O₃ to form more stable Cs₂CrO₄, which melts at 957°C and then completely evaporates at higher temperatures.