Endorsement of ASME/ANS RA-S-1.4 Probabilistic Risk Assessment Standard for Advanced Non-Light Water Reactor Nuclear Power Plants

The advanced non-light water reactor PRA standard, ASME/ANS RA-S-1.4-2021, “Probabilistic Risk Assessment Standard for Advanced Non-Light Water Reactor Nuclear Power Plants,” was issued in February 2021 by the American Society of Mechanical Engineers and the American Nuclear Society.

On March 21, 2022, the NRC staff issued its endorsement of the standard as Trial Regulatory Guide (RG) 1.247  “Acceptability of Probabilistic Risk Assessment Results for Advanced Non-Light Water Reactor Risk-Informed Activities”.  This new guidance describes one acceptable approach for determining whether the acceptability of the probabilistic risk assessment (PRA) used to support a PRA application is sufficient to provide confidence in the results for non-light water reactors (non-LWRs) and risk-informed activities. This RG endorses ASME/ANS RA-S-1.4-2021 and industry guidance on non-LWR PRA peer reviews in, NEI 20-09, "Performance of PRA Peer Reviews Using the ASME/ANS Advanced Non-Light Water Reactor Standard."  As a trial RG, this issuance does not provide final staff positions and the guidance may be revised based on experience obtained by the NRC with its use after its publication. A public comment period was held following the publication of the trial comments received were considered and responded to. Following the conclusion of the public comment period, a 2-year trial use period started on May 24, 2022. On October 17, 2022, the NRC addressed the public comments that had been received on the trial use Regulatory Guide (87 FR 62894). At any time during the trial use period, suggestions for improvement can be submitted on the NRC’s public website.