Investigation of effect by the late-phase release of boron containing atmosphere on CsI deposit formed on reactor structural material SUS304L

Rizaal, M.   ; 三輪 周平  ; 鈴木 恵理子   ; 井元 純平 ; 逢坂 正彦  ; Goullo, M.*

Rizaal, M.; Miwa, Shuhei; Suzuki, Eriko; Imoto, Jumpei; Osaka, Masahiko; Goullo, M.*

The gaseous species interaction with the early FP deposits (mostly Cs and I) on the surface of reactor coolant system (RCS) material is considered as one of the factors of gaseous iodine generation at late phase and could affect the containment atmosphere. In this study, we investigated the reaction of CsI deposit formed on stainless steel type 304 L with steam-boron flow. The experiments for reproducing the RCS temperature gradient in the range of 1000-400 K showed a significant depletion of CsI at 850 K, resulted in formation of low volatile cesium borates on the former surface and simultaneously released gaseous iodine that could reach a range below 400 K.