Ultra-high temperature tensile properties of ODS steel claddings under severe accident conditions

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

Ultra-high temperature ring tensile tests were carried out to investigate the tensile behavior of oxide dispersion strengthened (ODS) steel claddings and wrapper materials under severe accident conditions; temperatures ranged from room temperature to 1400C which is near the melting point of core materials. The experimental results showed that tensile strength of 9Cr-ODS steel claddings was highest in the core materials at the ultra-high temperatures between 900 and 1200C, but that there was significant degradation in tensile strength of 9Cr-ODS steel claddings above 1200C. This degradation was attributed to grain boundary sliding deformation with / transformation, which was associated with reduced ductility. On the other hand, tensile strength of recrystallized 12Cr-ODS and FeCrAl-ODS steel claddings retained its high value above 1200 C unlike the other tested materials. Present study includes the result of "R&D of ODS ferritic steel fuel cladding for maintaining fuel integrity at the high temperature accident condition" entrusted to Hokkaido University by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).