Recent Japanese research activities on probabilistic fracture mechanics for pressure vessel and piping of nuclear power plant

Kanto, Yasuhiro*; Onizawa, Kunio ; Machida, Hideo*; Isobe, Yoshihiro*; Yoshimura, Shinobu*

JAEA had sponsored research committees on probabilistic fracture mechanics (PFM) organized by the Japan Welding Engineering Society (JWES) for more than a decade. This work still continues with the same members in JWES. The purpose of the continuous activity is to provide probabilistic approaches in several fields of integrity problems of nuclear power plant. This paper shows some of the newest results of the JWES research committee. First topic is evaluation of the new JSME code case with rules of fitness-for-service from the view of PFM, including reactor pressure vessel subject to pressurized thermal shock loading, piping with a crack of the allowable size and effect of sizing accuracy for piping integrity. Another is development of new PFM techniques including reliability assessment of piping with domestic SCC data and maintenance optimization of LWRs based on risk and economic models. The last topic is the international round robin program just starting from 2008.