Document: NUREG-0800
Document ID: 743c65f7-fe56-43cc-8658-f69bb64672dc
Document Type: srp
Title: Final Revision 0 – April 2014
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1311/ML13115A156.pdf
Revision Date: 2023-06
Chapter: 18
Section ID: 18
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Content:
t: A Practical Guide, Cambridge University Press,” 1991). Prior experience with tasks or subtasks similar to the actions proposed to be credited in the defense-in-depth analysis may provide valuable insights for the analysis/estimates of operator response times. Operating Experience Review (OER) data used to provide input to the analysis/estimates of operator response times should be supplemented with information about the similarities and differences between the credited actions and the actions identified in the OER. A time margin should exist between the analyzed time(s) as the difference between time available and time required for operator action is a measure of the safety margin and as it decreases, uncertainty in the estimate of the difference between these times should be appropriately considered. This uncertainty could reduce the level of assurance and potentially invalidate a conclusion that operators can perform the action reliably within the time available. One acceptable method is for the time margin to equal the maximum recovery time for any single credible3 operator error. The basis for the specific time margin used in the analysis 1 For an example of an expert panel elicitation, see NUREG-1852, “Demonstrating the Feasibility and Reliability of Operator Manual Actions in Response to Fire.” 2 ANSI/ANS 58.8, “Time Response Design Criteria for Safety-Related Operator Actions,” provides an acceptable task decomposition methodology for this purpose. However, the time intervals described in ANSI/ANS 58.8 were validated using analog controls and; therefore, may not be accurate for this application. 3 As used here, credible operator errors are any errors of omission or commission that are plausible considering applicable operating experience and a human reliability analysis for the task. 18-A-5 Final Revision 0 – April 2014 should be justified and documented. Insights from the HFE program, especially the OER and Human Reliability Analysis, should