Publications

EPRI/NRC-RES fire human reliability analysis guidelines

Cooper, Susan E.; Hill, Kendra; Julius, Jeff; Grobbelaar, Jan; Kohlhepp, Kaydee; Forester, John; Hendrickson, Stacey M.; Hannaman, Bill; Collins, Erin; Najafi, Bijan

Over the past 2 decades, the U.S. nuclear power plant (NPP) fire protection community and overseas has been transitioning toward risk-informed and performance-based (RI/PB) practice in design, operation and regulation. To make more realistic decisions for risk-informed regulation, fire probabilistic risk analysis (PRA) methods needed further development. To address this need, in 2001, the U.S. Nuclear Regulatory Commission's (NRCs) Office of Nuclear Regulatory Research (RES) and the Electric Power Research Institute (EPRI) collaborated under a joint Memorandum of Understanding (MOU) to develop NUREG/CR-6850 (EPRI 101989), "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities," a state-of-art fire PRA methodology. The fire human reliability analysis (HRA) guidance provided in NUREG/CR-6850 included: (1) a process for identification and inclusion of the human failure events (HFEs), (2) a methodology for assigning quantitative screening values to these HFEs, and (3) initial considerations of performance shaping factors (PSFs) and related fire effects that might need to be addressed in developing best-estimate human error probabilities (HEPs). However, NUREG/CR-6850 did not identify or produce a methodology to develop these best-estimate HEPs given the PSFs and the fire-related effects. In 2007, EPRI and RES embarked upon another cooperative project - building on existing HRA methods - to develop explicit guidance for estimating HEPs for human error events under fire-generated conditions. This collaborative project produced draft NUREG-1921, "EPRI/NRC-RES Fire Human Reliability Analysis Guidelines." The guidance presented in this report is intended to be both an improvement upon and an expansion of the initial guidance provided in NUREG/CR-6850. This paper will summarize the fire HRA guidance developed through this collaborative project, which addresses the range of fire procedures used in existing plants, the range of strategies for main control room (MCR) abandonment, and the potential impact of fire-induced electrical spurious actuation effects on crew performance. This guidance presents a three tiered, progressive approach for fire HRA quantification. The quantification approaches include: a screening approach per NUREG/CR-6850 guidance, a scoping approach, and detailed quantification using either EPRI's Cause-Based Decision Tree (CBDT) and Human cognitive Reliability/Operator Reliability Experiment (HCR/ORE) or NRC's A Technique for Human Event ANAlysis (ATHEANA) approach with modifications to account for fire effects. The newly developed scoping approach is intended to be less resource intensive than a detailed HRA, while providing less conservative HEPs than rough screening. The expectation is that the majority of the actions can be quantified using the scoping approach, thus detailed HRA will only be used for the more complex actions that do not meet the criteria for the scoping approach. It is anticipated that this guidance will be used by the industry as part of transition to the risk-informed, performance-based fire protection rule, 10 CFR 50.48c, that endorsed National Fire Protection Association (NFPA) 805, "Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants" and possibly in response to other regulatory issues such as multiple spurious operation (MSO) and operator manual actions (OMAs). As the methodology is applied at a wide variety of NPPs, the guidance may benefit from future improvements to better support industry wide issues being addressed by fire PRAs.