Containment performance observations and insights of LWRs based on the IPEs

Generic Letter 88-20, open-quotes Individual Plant Examination for Severe Accident Vulnerabilities - 10CFR 50.54(f),close quotes requesting the IPEs, was issued by the NRC on November 23, 1988. U.S. licensee were requested to conduct an Individual Plant Examination (IPE) in order to identify potential severe accident vulnerabilities at their plant and to implement cost-effective plant improvements to reduce or eliminate these vulnerabilities. Supplements to the Generic Letter forwarded technical insights obtained by the NRC staff through its Containment Performance Improvement (CPI) program. These insights were deemed important enough by the staff to bring to the attention of the licensees for use, as they deemed appropriate, in the IPEs which they were preparing. Coupled to their Level 1 results, licensees were requested to report the results of their analyses regarding containment performance. These results included those related to the general methodology used, plant data, plant features, plant damage states, models and methods used in the accident progression analysis, containment failure characterization, containment event trees and their end states, and radionuclide release characterization. At this time, most of the IPEs have been submitted by the licensees. In a follow-up effort to support regulatory activities, the NRC staff with assistance from Brookhaven National Laboratory, has initiated a program involving a global examination of the containment performance results documented in the IPEs. The objective is to identify insights of potential generic safety significance relative to plant design, operation and maintenance, as well as to assess response to the previously forwarded CPI insights