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Katsuyama, Jinya; Yamaguchi, Yoshihito; Li, Y.*; Onizawa, Kunio
no journal, ,
Weld residual stress is one of the most important factors for stress corrosion cracking growth in nuclear reactor piping weld joints. Recently very large earthquakes which exceed the design base seismic load, such as the Niigata-ken Chuetsu-Oki Earthquake and the Great East Japan Earthquake, have occurred in Japan. In order to assess the structural integrity of piping welds under such a large earthquake, the effect of cyclic loading subjected to piping due to the large earthquake on the residual stress has been analyzed with finite element method. After conducting welding simulation, effects of crack existence, cyclic loading patterns and maximum load to piping welds on variation of weld residual stress have been evaluated. The analyses showed that higher cyclic load caused larger relaxation of weld residual stress near piping welds.
Yamaguchi, Yoshihito; Li, Y.*; Katsuyama, Jinya; Onizawa, Kunio
no journal, ,
In recent years, Japanese nuclear power plants experienced multiple large earthquakes, such as Niigata-ken Chuetsu-Oki Earthquake in 2007 and the Great East Japan Earthquake in 2011. The magnitude of these earthquakes exceeded the design-base condition for some nuclear power plants. Therefore it is an important issue to establish the evaluation method of excessive loading on the structural integrity of reactor components. In this study, the crack growth behaviors were investigated based on an elastic-plastic fracture mechanics parameter, J-integral. It was indicated that the crack growth due to the cyclic excesive loading could be the sum of fatigue and ductile crack growth. The retardation effect on the crack growth due to excessive loading was observed from experiments. An evaluation method for the amount of crack growth under cyclic excessive loading is suggested based on J-integral. The effect of excessive loading on the failure probability of piping is also evaluated by probabilistic fracture mechanics analysis.
Shobu, Takahisa; Yada, Hiroki; Muramatsu, Toshiharu; Takase, Kazuyuki
no journal, ,
Yamashita, Susumu; Yamada, Tomonori; Kunugi, Tomoaki*; Muramatsu, Toshiharu
no journal, ,
Yamada, Tomonori; Shobu, Takahisa; Yamashita, Susumu; Nishimura, Akihiko; Muramatsu, Toshiharu
no journal, ,
no abstracts in English
Kanto, Yasuhiro*; Onizawa, Kunio; Yoshimura, Shinobu*
no journal, ,
In this paper, Japanese research activities on probabilistic fracture mechanics (PFM) are introduced; which purpose is to provide probabilistic approaches in several fields of integrity problems for the reactor components in nuclear power plants. The research activities include the 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, so on. The international round robin analysis on probabilistic fracture mechanics conducted with a nuclear power advanced nations in Asia, Korea, Taiwan and China, is also presented as well as future research plan.