United States Nuclear Regulatory Commission - Protecting People and the Environment

Pressurizer Issues

Operating experience, both domestic and foreign, has demonstrated that Alloy 82/182/600 materials connected to a pressurized water reactor (PWR) pressurizer are susceptible to primary water stress corrosion cracking (PWSCC). Most recent leakage events were the result of axially-oriented PWSCC of the pressure boundary portion of pressurizer heater sleeves. Recent non-destructive examination results on heater sleeves have demonstrated that circumferentially-oriented PWSCC can occur in the non-pressure boundary portion of these components.

Extensive operational experience with PWSCC in Alloy 82/182/600 materials used in the fabrication of pressurizer penetrations and steam space piping connections is not surprising. The initiation and growth of PWSCC flaws is known to be strongly dependent on the temperature of the primary system water to which the Alloy 82/182/600 materials are exposed. Given the fact that at the pressurizer, the reactor coolant system environment attains a temperature of about 650°F (343°C), PWSCC should be expected to occur in these materials and an effective degradation management program is warranted. The following links include information on the NRC and nuclear industries activities on reactor coolant pressure boundary integrity of the pressurizer.

Page Last Reviewed/Updated Tuesday, May 07, 2013