Industry Average Parameter Estimates
NUREG/CR-6928 characterizes industry-average performance for components and initiating events at U.S. commercial nuclear power plants using data available through the end of 2002. Trending studies on this web site indicate that industry performance has generally improved since the 1980s and early 1990s, so the characterization of current industry-average performance is an important step in maintaining up-to-date risk models. Four types of events are covered here: component unreliability (e.g., pump fail to start or fail to run), component or train unavailability resulting from test or maintenance outages, special event probabilities covering operational issues (e.g., pump restarts and injection valve re-openings during unplanned demands), and initiating event frequencies. Typically data starting from 1998 were used in previous studies to characterize current industry-average performance, although many initiating events required longer periods to adequately characterize frequencies. However, with the continued improved industry performance, the 2020 Update responsed to the industry comments and used the most recent 15-year period data in the analysis so that the results could reflect the most recent industry performance yet still provide sufficient data. Results (beta distributions for failure probabilities upon demand and gamma distributions for rates) are used as inputs to the U.S. Nuclear Regulatory Commission's Standardized Plant Analysis Risk (SPAR) models covering U.S. commercial nuclear power plants.
The 2020 Update also puts the data, parameter estimates, and detailed data sheets together in one report to facilitate easier usage by analysts.
Note that the System Special Events have not been updated with new data. These estimates are based on system studies that are not regularly updated, and that are largely superseded by the component and system studies that are regularly updated.
2020 Results:
2015 Results:
Summary
- Component Reliability 2015
- Component/Train Unavailability 2015
- Initiating Events 2015
- Parameter Estimates Spreadsheet 2015
Detailed Data Sheets
2010 Results:
Summary
- Component Reliability 2010
- Component/Train Unavailability 2010
- System Special Events 2010
- Initiating Events 2010
- Parameter Estimates Spreadsheet 2010
Detailed Data Sheets
- Component Reliability 2010
- Component/Train Unavailability 2010
- System Special Events 2010
- Initiating Events 2010
Historical Results:
Summary
- Component Reliability
- Component/Train Unavailability
- System Special Events
- Initiating Events
- Parameter Estimates Spreadsheet
Detailed Data Sheets
Page Last Reviewed/Updated Monday, September 30, 2024