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.