Abstract
We performed environmental fatigue testing in simulated primary water reactor (PWR) primary water and reference fatigue testing in air in the framework of an international, collaborative project (INCEFA-PLUS), where the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied. Our fatigue lives obtained on machined specimens in air at 300 °C lie close to the NUREG/CR6909 mean air fatigue curve and are in line with INCEFA-PLUS air fatigue lives. Our environmental fatigue lives obtained in simulated PWR primary water at 300 °C lie relatively close to the NUREG/CR6909 mean fatigue curve; derived from the NUREG/CR6909 mean air fatigue curve and the applicable environmental correction factor (Fen). The PWR results show that (1) a polished surface finish has a slightly higher and a ground surface finish a slightly lower fatigue life than the NUREG/CR6909 prediction; (2) the ratio of polished to ground specimen life is ~1.37 at 300 °C and ~1.47 at 230 °C; (3) holds—at zero strain after a positive strain-rate—have a slightly detrimental effect on fatigue life. These results are in line with the INCEFA-PLUS PWR fatigue lives. A novel gauge-strain extensometer was deployed in order to perform a true gauge-strain-controlled fatigue test in simulated PWR primary water.
Highlights
Environmentally-assisted fatigue (EAF) is worldwide a hot topic since the introduction of the requirement in USNRC Regulatory Guide 1.207 to address it [1]
We report on further fatigue tests, performed in air and in simulated primary water of a pressurized water reactor (PWR), and on our analysis of (1) our fatigue data and (2) of fatigue data downloaded from the INCEFA-PLUS database as per September 2019
There, the mean fatigue life in air and up to 400 ◦ C for austenitic stainless steel is given by Equation (1)
Summary
Current regulation is based on a state-of-the-art review of light water reactor fatigue data and effects [2]. Sparked by EPRI roadmap and gap analysis reports on EAF [3,4,5] and industry needs, a consortium of 16 organizations from across Europe participated in the five-year EAF project INCEFA-PLUS [6,7,8,9,10]. The effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments have been studied; these being issues of common interest to all participants and mentioned as gaps to be addressed in [3,4,5].
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