ISLOCA evaluation guidelines. Final report, September 1991

Generally, ISLOCA accounts for a small percentage of total plant risk. Nevertheless, there may be situations where it becomes desirable to calculate the ISLOCA risk for a specific nuclear power plant. In such situations it is helpful to have available a methodology and a set of evaluation guidelines that can familiarize the analyst with the most important risks and guide him step-by-step through the analysis. The ISLOCA evaluation guidelines presented in this report can be used in determining the potential ISLOCA pathways, low pressure system overpressurization frequency, ISLOCA core damage frequency, and the associated radionuclide release frequency and magnitude. The guidelines yield 'best estimate' results and are applicable to all PWRs and BWRs. The report includes a library of typical event frequencies and equipment reliability data. Because human interactions can lead to a number of the postulated and observed isolation valve failure modes, human reliability analysis is explicitly addressed by the guidelines. These guidelines will be of greatest interest to analysts who must quantify ISLOCA risk. (author)