Document: NUREG-0800
Document ID: 7916b088-fb90-4163-84fe-027bd315bcc5
Document Type: srp
Title: REVIEW OF RISK INFORMATION USED TO SUPPORT PERMANENT PLANT-
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0717/ML071700658.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.2
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Content:
(e.g., conditions generated during an accident sequence that influence the operability of more than one system), including generation of harsh environments that result in protective trips of systems, loss of pump net positive suction head (NPSH) when containment heat removal is lost, clogging of pump strainers from debris generated during a LOCA, failure of components outside the containment following containment failure attributable to harsh environment inside the containment, closure of safety relief valves in BWRs on high containment pressure, and coolant pipe breaks or equipment failures following (or resulting from) containment failure, • Operational dependencies (e.g., unavailability of the suppression pool cooling mode for a train of the residual heat removal system when the system is in the low pressure coolant injection mode). Reviewers should look for evidence that the licensee properly considered the above types of dependencies in the evaluation of the change. In most cases, these dependencies should be explicitly included in the fault tree or event tree logic models; however, in some cases, a qualitative evaluation process may be sufficient. Human Interaction Dependencies: These dependencies could become important contributors to risk if operator error can result in multiple component failures. Past PRAs show that the following plant conditions could lead to human interaction dependencies that can become important: • Tests or maintenance that require multiple components to be reconfigured, • Multiple calibrations performed by the same personnel, • Post-accident manual initiation (or backup initiation) of components that require the operator to interact with multiple components. Reviewers should verify that the licensee's evaluation of risk from proposed changes to plant procedures or changes to operator training included a process to identify these (or similar) activities, and that the licensee evaluated the activities that could be risk