Regulatory Guide: Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities

The U.S. Nuclear Regulatory Commission (NRC) is issuing for trial use, Revision 1 to Trial Regulatory Guide (RG) 1.247, "Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities." This 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 (NLWRs) and risk-informed activities. Trial RG 1.247 was originally issued in March 2022 with a 2-year trial period that ended in May 2024. The staff is issuing Revision 1 to RG 1.247 (with minimal changes) as a trial RG so that it can continue to be used by potential applicants while the staff addresses the remaining technical issues that are best resolved by continuing to test the guide against actual applications. As a trial RG, this issuance does not provide final staff positions and the guidance within may be revised based on experience obtained by the NRC with its use after its publication.