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
CFR Part: 
CFR Title: 

Content:
sequences of functional failure of the affected elements. Therefore, the results derived from risk evaluations and the associated analysis of uncertainties (especially in the analysis areas and models affected by the application) will provide useful information to help in the reviewers’ decisionmaking. As an example, in evaluating available safety margins, reviewers should consider the risk profile of the plant. If a proposed LB change creates or exacerbates a situation where risk is dominated by a few elements (SSCs or human actions) or a few accident sequences, the reviewers should carefully evaluate the modeling of these elements or sequences including the modeling of uncertainties. Reviewers should consider the results from the analysis of uncertainty when determining the acceptability of the reduction in margin from the proposed change. In demonstrating available safety margins, licensees will in some cases support their proposal by citing new data from plant tests or research projects, or they will conduct analyses using models that are predicated on new data. The following examples illustrate situations in which data and analyses can be used effectively to support the LB change request. • It is shown that a phenomenon of concern cannot occur or is less likely to occur than originally thought. • It is shown that the amount of safety margin in the design is significantly greater than that which was assumed when the requirement or position was imposed. • It is shown that time available for operator actions is greater than originally assumed. The reviewers' primary objective is to verify the relevance and acceptability of the new information with respect to the requested LB change. Data that directly apply to the original technical concern should be considered in the decision process. Depending on the circumstances, the cognizant review branch may have additional specific guidance available for use in reviewing the quality and acceptability of the data.