Application of on-line crack growth monitoring to evaluate nuclear power plant component performance

Pressure boundary components in nuclear power plant components are subjected to water chemistry conditions that could cause environmentally assisted cracking. Monitoring of environmental degradation is important in evaluating component performance and verifying fitness for continued service. This requires in-situ crack growth data since predictions based on bounding laboratory data can be overly conservative. This paper describes the use of a crack monitoring system (CMS) to determine stress corrosion crack growth rates in actively loaded, precracked austenitic stainless steel specimens exposed to a Boiling Water Reactor (BWR) environment. Crack growth is continuously measured in real time utilizing a reversing DC potential technology. The resultant crack growth data, and all pertinent water chemistry data, are combined in a master data base. Information from the CMS has been used to predict the progress of a crack in a BWR safe end and thereby monitor structural integrity. The case study described in this paper illustrates how the CMS results were used to eliminate an expensive mid-cycle ultrasonic examination while maintaining assurance of structural integrity