Model calculation of Cr dissolution from steel surface exposed to high-temperature flowing sodium

Otsuka, Satoshi   ; Tanno, Takashi  ; Oka, Hiroshi   ; Yano, Yasuhide  ; Hashidate, Ryuta ; Kato, Shoichi ; Furukawa, Tomohiro  ; Kaito, Takeji ; Ito, Chikara   

JAEA has been developing ODS steels for the high burnup fuel cladding tubes of sodium-cooled fast reactors (SFR). Evaluation of sodium environmental effects is important since the outer surface of SFR fuel cladding tubes are exposed to high temperature flowing sodium and the tube wall is very thin. In this study, the numerical calculations were conducted based on thermodynamics and rate theory for understanding and predicting Cr dissolution behaviors of Fe-Cr steel in flowing sodium. The calculation results indicated that Cr concentration of steel surface gradually deceased with time, and approached to a unique value no matter what Cr concentration the steel contains in initial stage. Increasing flow velocity shortened the time for surface Cr concentration approaching the converged value. In the presentation, the calculated results will be compared to experimentally measured data, and discussions will be conducted to improve the Cr dissolution model constructed in this study.