Component Repair Times Obtained from MSPI Data
- Curtiss-Wright/Scietech, Ketchum, ID (United States)
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
Information concerning times to repair or restore equipment to service given a failure is valuable to probabilistic risk assessments (PRAs). Examples of such uses in modern PRAs include estimation of the probability of failing to restore a failed component within a specified time period (typically tied to recovering a mitigating system before core damage occurs at nuclear power plants) and the determination of mission times for support system initiating event (SSIE) fault tree models. Information on equipment repair or restoration times applicable to PRA modeling is limited and dated for U.S. commercial nuclear power plants. However, the Mitigating Systems Performance Index (MSPI) program covering all U.S. commercial nuclear power plants provides up-to-date information on restoration times for a limited set of component types. This paper describes the MSPI program data available and analyzes the data to obtain median and mean component restoration times as well as non-restoration cumulative probability curves. The MSPI program provides guidance for monitoring both planned and unplanned outages of trains of selected mitigating systems deemed important to safety. For systems included within the MSPI program, plants monitor both train UA and component unreliability (UR) against baseline values. If the combined system UA and UR increases sufficiently above established baseline results (converted to an estimated change in core damage frequency or CDF), a “white” (or worse) indicator is generated for that system. That in turn results in increased oversight by the US Nuclear Regulatory Commission (NRC) and can impact a plant’s insurance rating. Therefore, there is pressure to return MSPI program components to service as soon as possible after a failure occurs. Three sets of unplanned outages might be used to determine the component repair durations desired in this article: all unplanned outages for the train type that includes the component of interest, only unplanned outages associated with failures of the component of interest, and only unplanned outages associated with PRA failures of the component of interest. The paper will describe how component repair times can be generated from each set and which approach is most applicable. Repair time information will be summarized for MSPI pumps and diesel generators using data over 2003 – 2007. Also, trend information over 2003 – 2012 will be presented to indicate whether the 2003 – 2007 repair time information is still considered applicable. For certain types of pumps, mean repair times are significantly higher than the typically assumed 24 h duration.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1194022
- Report Number(s):
- INL/CON-14-32831; TRN: US1500177
- Resource Relation:
- Conference: International Topical Meeting on Probabilistic Safety Assessment and Analysis (PSA 2015), Sun Valley, ID (United States), 26-30 Apr 2015
- Country of Publication:
- United States
- Language:
- English
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