Publications Details
Observations and insights from the Grand Gulf Low Power and Shutdown Study of POS 5 during a refueling outage
With the completion of the documentation of the results from the Grand Gulf Nuclear Power Plant Low Power and Shutdown (LP and S) Project funded by the US Nuclear Regulatory Commission, detailed probabilistic risk assessment (PRA) information from a boiling water reactor for a specific time period in LP and S conditions became available for examination. This paper summarizes why LP and S conditions should be examined and how the particular operational state was selected. It also summarizes observations and insights extracted from an examination of: (1) results in the LP and S documentation, (2) the specific models and assumptions used in the LP and S analyses, (3) selected results from the full power analysis, (4) the experience of the analysts who performed the original LP and S study, and (5) results from sensitivity calculations to help determine the impact that model assumptions and data values had on the results from the original LP and S analysis. Observations and insights on core damage frequency and aggregate risk (early fatalities and total latent cancer fatalities) associated with operations during plant operational state 5 (i.e., basically cold shutdown as defined by Technical Specifications) during a refueling outage for traditional internal events are provided. In addition, a discussion of similarities and differences between full power accidents and accidents during LP and S conditions is provided. As part of this discussion, core damage frequency and risks results are presented on a per hour and per calendar year basis, allowing alternative perspectives on both the core damage frequency and risk associated with these two operational states.