Effects of environmental factors on fatigue crack growth behaviours of A533B steel in BWR water

Much progress has been made in a knowledge of corrosion fatigue behaviours of low alloy pressure vessel steels in LWR environments by collaborative works, for instance, ICCGR (International cooperative group on Cyclic Crack Growth Rate) and JCF(Japanese committee on Corrosion Fatigue). Quantitative evaluation of influential factors not only of mechanical ones such as stress ratio, frequency, wave form but also of environmental ones such as temperature, dissolved oxygen,flow rate and material ones such as sulfur content in steels has been disclosed( Cullen 1983a , 1986 ). Compared to the mechanical factors, however, the knowledge of the environmental factors seems to be insufficient and there still remain areas to be investigated. Among the environmental factors influencing the fatigue crack growth rate in low alloy steels in LWR water both temperature and dissolved oxygen(DO) are considered to be critical variables.