Evaluation of severe accident risk during mid-loop operation at Surry Unit-1
- Brookhaven National Lab., Upton, NY (United States). Dept. of Advanced Technology
This paper describes an analysis of accident progression and offsite consequences (level 3 probabilistic risk assessment (PRA)) carried out for the Surry plant. The focus of the level 3 PRA was on mid-loop operation, which is a plant operational state (POS) that can occur while the plant is shutdown for maintenance or refueling. Mid-loop refers to a configuration when the reactor coolant system is lowered to the mid-plane of the hot leg to allow essential maintenance to be performed. This operational state was selected after an initial coarse screening study indicated that reduced inventory during mid-loop operation could pose higher risk than other POSs. The methodology used to perform the level 3 PRA was based on the methods developed for the NUREG-1150 full power study of Surry. However, the interfaces between the core damage frequency analysis and the plant damage states (PDSs) and the accident progression event tree (APET) had to be modified to reflect the plant configuration during mid-loop operation. In addition, due to the long time over which an accident can occur during shutdown, appropriate modifications were made to incorporate the effects of reduced decay heat levels and correspondingly reduce radionuclide inventories. Specifically, modifications were made to the accident progression event tree (APET) analyses, the source term, and consequence analyses.
- OSTI ID:
- 251008
- Report Number(s):
- CONF-960306--; ISBN 0-7918-1226-X
- Country of Publication:
- United States
- Language:
- English
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