Surface analyses of cesium hydroxide chemisorbed onto type 304 stainless steel

Di Lemma, F. G.; Nakajima, Kunihisa  ; Yamashita, Shinichiro   ; Osaka, Masahiko  

Chemisorption is of main importance during a Severe Accident (SA) at a light water reactor, as it can influence fission products retention in the reactor vessel. Information on the distribution, composition and properties of such deposits can influence the decommissioning practice after a SA. Moreover such information can enhance the description of the chemisorption models applied in SA codes, consequently improving the source term assessment. This paper will present the results obtained from CsOH chemisorption experiments onto type 304 stainless steel samples, used as simulants of reactor structural materials. The samples post-analyses showed that CsOH will absorb onto the surface, reacting preferentially with Si impurities and forming a newly detected compound, CsFeSiO. From our results, it can be inferred that Si content in structural materials can determine the amount of radioactive Cs deposited onto the reactor vessel after a SA.