PRA evaluations in support of regulatory decisions should be as
realistic as practicable and appropriate supporting data should
be publicly available for review.
The Commission's safety goals for nuclear power plants and subsidiary numerical objectives are to be used with appropriate consideration of uncertainties in making regulatory judgments on need for proposing and backfitting new generic requirements on nuclear power plant licensees.
NRC - REGULATORY GUIDE 1.177
An Approach for Plant-Apecific, Risk-Informed Decisionmaking: Technical Specifications