Document: NUREG-0800
Document ID: ac43f632-9db1-4857-9f56-bfba45965456
Document Type: srp
Title: * These are modifications to a plant’s design, operations, or other activities that require NRC approval. These modifica
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0232/ML023250195.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19
CFR Part: 
CFR Title: 

Content:
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. However, the data or analyses must be clearly applicable to the plant and specific circumstances in which they are being applied. III.2.1.3 Current Regulations Reviewers should ensure that the proposed change satisfies current regulations (including the General Design Criteria), unless the licensee explicitly includes a proposed exemption or rule change (i.e., a "specific exemption" as allowed by 10 CFR 50.12 or a "petition for rulemaking" in accordance with 10 CFR 2.802). The LB also applies until the staff approves modifications to the existing basis. It is expected that some applications will seek to modify the LB in risk-informed submittals. Applications that seek to make qualitative changes to the LB (such as