NUREG/CR-6753
(PDF - 366 KB)
Publication Information
Manuscript Completed: August 2001
Date Published:
Prepared by David I. Gertman, Principal Investigator, Bruce P. Hallbert,
Program Manager, Mark W. Parrish, Martin B Sattision, Doug Brownson,
James P. Tortorelli
Idaho National Engineering and Environmental
Bechtel BWXT Idaho, LLC
Idaho Falls, ID 83415
Eugene A. Trager, J. J. Persensky NRC Program Managers
Prepared for
Office of Nuclear Regulatory Research
Division of Systems Analysis and Regulatory Effectiveness
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
Availability
Notice
Abstract
This report presents the findings of a study of the contributions
of human performance to risk in operating events at commercial nuclear
power plants. The Nuclear Regulatory Commission (NRC) Accident Sequence
Precursor (ASP) Program and the Human Performance Events Database
(HPED) were used to identify safety significant events in which human
performance was a major contributor to risk. Conditional core damage
probabilities (CCDPs) were calculated for these events using Systems
Analysis Programs for Hands-on Integrated Reliability Evaluation (SAPHIRE)
software and Standardized Plant Analysis Risk (SPAR) models.
Forty-eight events described in licensee event reports and augmented
inspection team reports were reviewed. Human performance did not play
a role in 11 of the events, so they were excluded from the sample.
The remaining 37 events were qualitatively analyzed. Twenty-three
of these 37 events were also analyzed using SPAR models and methods.
Fourteen events were excluded from the SPAR analyses because they
involved operating modes or conditions outside the scope of the SPAR
models.
The results showed that human performance contributed significantly
to analyzed events. Two hundred and seventy human errors were identified
in the events reviewed and multiple human errors were involved in
every event. Latent errors (i.e., errors committed prior to the event
whose effects are not discovered until an event occurs) were present
four times more often than were active errors (i.e., those occurring
during event response). The latent errors included failures to correct
known problems and errors committed during design, maintenance, and
operations activities. The results of this study indicate that multiple
errors in events contribute to the probabilistic risk assessment (PRA)
basic events present in SPAR models and that the underlying models
of dependency in HRA may warrant further attention.
