The draft ASME Code Case N-809 provides a Fatigue Crack Growth (FCG) law for austenitic stainless steel in a Pressurised Water Reactor (PWR) environment. This growth law explicitly considers the effect of the environment through the additional parameters of temperature and rise time applied in conjunction with a standard Paris equation. FCG calculations using this growth law have been shown to have the potential to produce significantly faster growth rates than those predicted using the current ASME XI FCG law for an air environment.

The testing on which this new FCG law is based is predominantly sawtooth loading in isothermal conditions; interpretation of the rise time and temperature variables is not straightforward when applied to PWR thermal transients which exhibit temperature and stress variations simultaneously, and the stress rate is not constant. This paper discusses temperature and rise time assumptions which may be applied with the PWR environment FCG law, and the practical implications of carrying out calculations with these additional parameters.

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