ABSTRACT
The phenomena of initiation and subcritical propagation of cracks in structural materials due to the conjoint actions of stress, material microstructure, and environment have been recognized for many years, and the mechanisms have been extensively investigated. This is especially the case for stressed alloys in environments containing high anionic concentrations of e.g., chlorides, phosphates, and hydroxides, either in the bulk environment (e.g., in the paper, chemical, petrochemical, and marine industries) or in localized environments where boiling or gradients in electrochemical potential, temperature etc. can concentrate species. However, it has been recognized that environmentally assisted cracking under static or cyclic loading (i.e., stress corrosion or corrosion fatigue) can occur in ultrahigh-purity water even when the concentration of non-OH anions is <10 ppb. Although the cracking susceptibility is generally lower than in the concentrated environments, it is sufficient to cause concern when extended lives or high levels of plant availability are required, as in the power generation industry and especially for light water reactors (LWRs). The objective of this chapter is to discuss the development and use of mechanistically based models of environmentally assisted cracking of structural materials in highpurity water, with special emphasis on boiling water reactors (BWR) and occasional reference to pressurized water reactors (PWR).
