Risk Informing PRA Success Criteria; Application to the AP1000
- Westinghouse Electric Company, LLC, P.O. Box 355, Pittsburgh, PA, 15230 (United States)
The Westinghouse AP1000 Program is aimed at making available a nuclear power plant that is economical in the U.S deregulated electrical power industry in the near-term. The AP1000 is an advanced 1000 MWe PWR that uses passive safety systems to provide significant and measurable improvements in plant simplification, safety, reliability, investment protection and plant costs. The AP1000 is based on the AP600 which received Design Certification in 1999. The AP1000 retains a maximum amount of the AP600 design so as to maintain the licensing basis, detailed design information / analysis, module designs, construction plan, cost estimate developed in the $400 million dollar AP600 FOKE program. Westinghouse and the US NRC are well along on a program to complete Design Certification for the AP1000 in 2004. The AP1000 has used PRA in both design and licensing. The AP1000 PRA is a detailed level 3 PRA that models both at power and shutdown events. The success criteria used in the PRA is based on plant thermal hydraulic (T/H) analysis. In some cases, the T/H analysis from the safety analysis report (SAR) is applicable. Where the AP1000 can tolerate more than the single failure assumed in the deterministic safety analysis, additional T/H analysis are performed. The uncertainty in the success criteria T/H analysis was a licensing question. The T/H uncertainty in the PRA success criteria analysis has been bounded by identifying low margin, risk important sequences and then performing conservative T/H analysis with the detailed computer codes and methods used for the SAR analysis. The PRA event trees were expanded to contain more branches with fewer failures than is necessary to quantify the core damage frequency. This approach allowed differentiation between the limiting success criteria sequence (with multiple failures) and design basis sequences (with 1 failure). The probabilities of the low margin sequences were quantified. SAR computer codes were used to analyze the low margin sequences that were significant relative to the total core damage frequency and large release frequency. The level of detail and conservatisms in SAR computer codes and methods demonstrated that T/H uncertainty in the success criteria analysis is not risk important. The NRC has reviewed and accepted this approach. (authors)
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 21160721
- Resource Relation:
- Conference: ICAPP'04: 2004 international congress on advances in nuclear power plants, Pittsburgh, PA (United States), 13-17 Jun 2004; Other Information: Country of input: France; 7 refs; Related Information: In: Proceedings of the 2004 international congress on advances in nuclear power plants - ICAPP'04, 2338 pages.
- Country of Publication:
- United States
- Language:
- English
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