High temperature creep properties of ODS steel cladding for evaluating severe accident

Kato, Shoichi ; Furukawa, Tomohiro  ; Yano, Yasuhide  ; Tanno, Takashi  ; Otsuka, Satoshi   ; Oka, Hiroshi   ; Inoue, Toshihiko ; Kaito, Takeji ; Ukai, Shigeharu*; Kimura, Akihiko*; Hayashi, Shigenari*; Torimaru, Tadahiko*

Oxide dispersion strengthened (ODS) steel is a prime candidate for cladding tubes of Japan Sodium-cooled Fast Reactor (JSFR) due to the high temperature and radiation resistances. One of the safety design of JSFR for Design Extension Condition (DEC) is the control of severe plant conditions, including prevention of severe accidents and mitigation of severe-accident consequences. Therefore, it is necessary to acquire the mechanical properties at ultra-high temperature conditions for core materials to evaluate safety design. There are, however, no data for ODS claddings at ultra-high temperature condition for the reflecting to the design criteria. In this study, creep rupture tests of 9Cr-ODS, 12Cr-ODS and FeCrAl-ODS steel claddings have been done at elevated temperatures, and the effect of minor elements such as Al, Zr and O on the mechanical strength and the creep rupture curve for the safety design were evaluated. The effect of minor elements was estimated based on the data at 700C and 1000C. As the results, it was confirmed that the addition of Zr had an effect on the improvement of creep strength at elevated temperature for the FeCrAl-ODS steel claddings.