Ultra-high temperature creep and transient burst strength of ODS steel cladding tube

Yano, Yasuhide  ; Sekio, Yoshihiro  ; Kato, Shoichi ; Tanno, Takashi  ; Inoue, Toshihiko ; Oka, Hiroshi   ; Otsuka, Satoshi   ; Furukawa, Tomohiro  ; Uwaba, Tomoyuki ; Kaito, Takeji ; Ukai, Shigeharu*

ODS steels have been noticed as a prospective candidate for long-life fuel claddings of FR due to their high temperature strength and radiation resistance. It is necessary to acquire data on tensile strength and creep rupture resistance of core materials at ultra-high temperature for use in safety design. The authors reported some data of tensile properties of ODS steel cladding at ultra-high temperatures, however, there are few data on creep rupture strength. In this study, ultra-high temperature creep rupture strength and transient burst properties with wide range of heating rates have been investigated for ODS claddings. Internal creep rupture tests for 9Cr-ODS claddings were carried out at temperatures between 650 and 1000C, and ring creep tests were performed at 1000C. The temperature-transient-to-burst tests were performed on both steel cladding tubes. Creep-rupture curves for 9Cr-ODS claddings were linear shape as a function of long rupture time, although it is well known that those curves for conventional martensitic steels have a sigmoidal shape to long rupture times. The failure temperatures for 9Cr-ODS steels decreased with decreasing the heating rate in a manner to similar to PNC-FMS claddins. However, transient burst strengths for 9Cr-ODS were much higher than those for PNC-FMS at all conditions. Using these data, discussions were carried out on a technique for evaluating rupture life of ODS steel cladding after various load-time-temperature histories.