PROBABILISTIC RISK ASSESSMENT OF SPENT FUEL POOL FIRE

摘要

The risk of spent fuel pool (SFP) fire that may result from SFP leaks or other loss of inventory events is evaluated. The frequency of uncovery of spent fuel is estimated as a surrogate for the risk of spent fuel fire. The analysis includes both internal and external initiating events that may occur during power operation and during outage. The four categories of initiating events considered are: loss of SFP cooling, loss of SFP inventory, loss of offsite power, events that may cause catastrophic failure of the SFP structure, including earthquakes, tornado-generated missiles, aircraft crashes, and heavy load drops. The possible evolutions involved in the process from shutdown, reactor disassembly, fuel movement, to reactor reassembly are grouped into three general configurations: SFP to transfer canal gate installed, SFP to transfer canal gate removed and fuel transfer tube (FTT) isolation valve closed, and SFP to transfer canal gate removed and FTT isolation valve open. The dominant contributor to the frequency of uncovery of spent fuel stored in the SFP is seismic events. Power operation has the highest frequency of spent fuel uncovery among the different plant configurations because it has the longest duration compared to the outage configurations. Among the three outage configurations, the two configurations with the SFP gate installed or FTT isolated have greater contributions to the frequency of spent fuel uncovery, also because of the longer duration compared to the outage configuration in which the FTT is open.