Analysis of fatigue crack growth rate data for A508 and A533B steels in LWR environments

The effect of light water reactor (LWR) environments on fatigue crack propagation in pressure vessel steels has been studied extensively in recent years. In this project, data from about 800 well-documented A508 Class 2 and Class 3 and A533B pressure vessel steel fatigue tests in LWR environments, at temperatures up to 290 degree C (550 degree F), were collected and analyzed. The data were from a variety of laboratories worldwide, in most cases contributed to the EPRI Database on Environmentally Accelerated Cracking (EDEAC). The data were analyzed using an advanced computer code, FATDAC, which reduces the original (a,N) data to (da/dN,ΔK) form by an optimization technique that minimizes the scatter arising from numerical differentiation.The influence of high-temperature water on crack growth was found to be relatively small in low-sulfur materials, nominal reactor water chemistry, and high flow rate conditions. Other conditions can produce bimodal crack growth rates (slightly enhanced or highly enhanced relative to air data). This report presents criteria based on material sulfur content, water chemistry, R-ratio, load rise time, and flow rate for identifying combinations of variables with a high probability of observing the highly enhanced mode of crack growth rates. A model of the expected crack propagation rate, given that the enhanced mode is observed, is also presented