Development of a new materials surveillance technology for fast reactors

Okajima, Satoshi ; Ando, Masanori ; Toyota, Kodai ; Ishigami, Katsuo*; Onuma, Terumitsu*; Takahashi, Ryoya*; Asayama, Tai ; Wakai, Takashi 

This paper describes current efforts within the JAEA to develop a new materials surveillance technology for SFRs that aims at raising the confidence levels in operating reactors' structural integrity to the ones which could otherwise be achieved only by a vast amount of long-term material test data that needs decades to accumulate. The technology would allow for monitoring on-going materials degradation processes in an actual reactor, namely fatigue and creep-fatigue, by inserting a newly developed specimen for this purpose into the reactor and establishing procedures to observe and evaluate the specimen to get desired information such as the extent of degradation and residual life. To establish the test procedure, a passive creep-fatigue test model was developed in the framework of CNWG, a collaboration agreement between the US and Japan, and a demonstration test was performed under cyclic thermal loads using an electric furnace. As a result, the test specimen failed by several hundred thermal cycles. Macroscopic inspection of the specimen after the test showed the test had been performed successfully without buckling. Fracture surface observations suggested that the failure caused probably by fatigue or creep-fatigue.