The SPAR-H Human Reliability Analysis Method (NUREG/CR-6883, INL/EXT-05-00509)

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Publication Information

Manuscript Completed: September 2004
August 2005

Prepared by:
D.I. Gertman, H.S. Blackman, J.L. Marble, J.C. Byers, C.L. Smith

Idaho National Laboratory
P.O. Box 1625
Idaho Falls, Idaho 83415
Operated by Battelle Energy Alliance
for the U.S. Department of Energy

P. O’Reilly, NRC Project Officer

Prepared for:
Division of Risk Analysis and Applications
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code W6355

Availability Notice


In support of the Accident Sequence Precursor Program (ASP), the U.S. Nuclear Regulatory Commission (NRC), in conjunction with the Idaho National Laboratory (INL), in 1994 developed the Accident Sequence Precursor Standardized Plant Analysis Risk Model (ASP/SPAR) human reliability analysis (HRA) method, which was used in the development of nuclear power plant (NPP) models. Based on experience gained in field-testing, this method was updated in 1999 and renamed SPAR-H, for Standardized Plant Analysis Risk-Human Reliability Analysis method. Since that time, NRC staff analysts have been using this method to perform their risk-informed regulatory activities, such as determining the risk significance of inspection findings in Phase 3 of the Significance Determination Process, developing an integrated risk-informed performance measure in support of the reactor oversight process, and systematically screening and analyzing operating experience data in order to identify events/conditions that are precursors to severe accident sequences. As a result of implementation by staff analysts, and from other experience gained at the INL in applying the method in human reliability analysis (HRA), a number of needed improvements to definitions, terms, and concepts were identified. In 2003, to enhance the general utility of the SPAR-H method and to make it more widely available, the method was updated and reviewed for its applicability to low-power and shutdown applications. During this review, an approach to uncertainty representation was outlined, based on the beta distribution. Additional detail regarding human error probability (HEP) dependency assignment was also made available.

This document presents the current version of the SPAR-H method, along with guidance, definitions, improvements in representing uncertainty, and increased detail regarding dependency assignment for HEP calculations. This report also contains comparisons between this and other contemporary HRA approaches and findings specific to application of the method to low power and shutdown events.

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