Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
tion of a specific risk metric). The characteristics and attributes of the PRA elements define specific criteria for successfully performing those technical analyses and achieving a defined objective. • Plant representation and PRA configuration control: Plant representation is defined in terms of how closely the PRA represents the plant as it is designed, built, and operated. In general, PRA results used to support applications after a certificate, approval, permit, or license has been issued should be derived from a PRA model that represents the as-designed, as-to-be-built, or as-to-be-operated plant or as-built, as-operated plant. Consequently, the PRA should be maintained and upgraded, where necessary, to ensure it represents the as-built and as-operated 5 The NLWR PRA standard uses the term “as-intended-to-operate” which is analogous to “as-to-be-operated.” “As-to-be- built” refers to the PRA used to model the plant configuration in the preoperational stages of the plant life cycle when the plant is not yet built or operated and therefore, this PRA reflects the plant as it is intended to be built (i.e., as-to-be-built) and as it is intended to be operated (i.e., as-to-be-operated). RG 1.247, Page 15 plant through an acceptable configuration control process. Regulatory Position C.1.4 provides guidance on plant representation in the PRA. C.1.1 Scope of a Probabilistic Risk Assessment The scope of a PRA used to support an application is defined by the set of initiating events included in the analysis; the set of computed risk metrics; and its intended use for representing the as-built and as-operated plant or the as-designed, as-to-be-built, and as-to-be-operated plant. The process of developing a PRA and its results used to support an application should be complete and comprehensive through consideration of the following: • All radiological sources at the plant (e.g., reactor cores, spent fuel, fuel reprocessing facilities for molten salt