Fission products chemisorption mechanism following severe accidents; A Separate effect study on CsOH reaction with stainless steel

Di Lemma, F. G.; Yamashita, Shinichiro   ; Nakajima, Kunihisa  ; Takada, Juntaro; Osaka, Masahiko  ; Nagase, Fumihisa 

Fission products chemisorption on reactor structural materials is an important phenomenon to be considered following an accident, as it can lead to retention of fission products in the containment, affecting the radioactive release to the environment and reactor decommissioning. The knowledge acquired from this study could help improve the models for cesium(Cs) chemisorption and could be applied to evaluate the distribution and properties of Cs deposits in the Fukushima-Daiichi Nuclear Power Plant, providing guidance for its decommissioning. Our studies were performed vaporizing CsOH over stainless steel samples, varying experimental parameters, such as temperature (800-1000C) and atmosphere (H/Ar, H/HO/Ar). Sample surfaces were analyzed by SEM/EDX, XRD to evaluate the deposit microstructure and chemical composition. The EDX characterization results demonstrate a congruent distribution between Cs and Si, and the XRD patterns indicate the formed Cs compound as CsFeSiO. These results show the importance of the presence of impurities in stainless steel, affecting the formation of stable Cs deposits.