Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown
- Avaplan Oy, Espoo (Finland)
- Brookhaven National Lab., Upton, NY (United States)
When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested.
- Research Organization:
- Brookhaven National Lab., Upton, NY (United States)
- Sponsoring Organization:
- USNRC; Nuclear Regulatory Commission, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6682750
- Report Number(s):
- BNL-NUREG-48150; CONF-9209300-1; ON: DE93005589
- Resource Relation:
- Conference: Advances in reliability analysis and probabilistic safety assessment, Budapest (Hungary), 7-11 Sep 1992
- Country of Publication:
- United States
- Language:
- English
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BWR TYPE REACTORS
ENGINEERED SAFETY SYSTEMS
OUTAGES
REPAIR
HEAT TRANSFER
HYDRAULICS
MAINTENANCE
MATHEMATICAL MODELS
REACTOR COOLING SYSTEMS
REACTOR SAFETY
REACTOR SHUTDOWN
RISK ASSESSMENT
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FLUID MECHANICS
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REACTOR COMPONENTS
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