In order to understand the fatigue behavior in PWR primary water environment, the influence of non-isothermal transient condition was investigated for austenitic stainless steel 316SS. In our previous study (PVP2016-63798), isothermal and non-isothermal environmentally assisted fatigue tests were performed. The fatigue life of the non-isothermal fatigue test consisted of a high temperature and tensile strain rate transient, a portion of which occurred in the compressive strain region of the strain cycle. The result of this test showed longer life than the predicted fatigue life estimated by the modified rate approach and Fen factor as presented in NUREG/CR-6909 Rev.1. In this paper, the reason why the fatigue test showed longer fatigue life is studied. Crack growth analysis was performed to understand the effect of the environment on fatigue life. Additionally, application of the Weighted K Rate (WKR) method described in reference (PVP2016-63497) was applied to a series of tests. This approach showed good agreement on fatigue life for a number of different waveforms for isothermal tests. The methodology was applied to some of this investigation’s non-isothermal fatigue tests and shown to be an improvement that justifies further investigation.

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