Study on the mechanism of stress generation of straight pipe and elbow pipe which has thermal stratification
栗林 大 Hiroshi KURIBAYASHI 久永 晃司 Koji HISANAGA 鈴木 正昭 Masaaki SUZUKI 佐藤 拓哉 Takuya SATO 笠原 直人 Naoto KASAHARA
High cycle thermal fatigue Pipe Thermal stratification oscillation Thermal stress
In nuclear power plants, a lot of failure cases by high cycle thermal fatigue have been reported, which is induced by temperature fluctuation of the coolant. To ensure the safety of the nuclear power plants, the thermal fatigue failure should be prevented adequately. Thus The Japan Society of Mechanical Engineers (JSME) published the high cycle thermal fatigue evaluation guideline. In the guideline, it is proposed that the structural integrity can be judged by the location of thermal stratification, which is typical thermal fatigue phenomenon in nuclear power plants. However, this evaluation method is not rational enough because the method is not based on stress. Thus stress evaluation method is needed. To develop stress evaluation method, it is necessary to clarify the mechanism of stress generation caused by thermal stratification. In this paper, the mechanism of stress generation of elbow pipe is studied by comparing with the mechanism of stress of straight pipe.