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:
arge Early Release Frequency a. Areas of Review The purpose of this section is to provide guidance for use in reviewing the licensee’s evaluation of changes in LERF stemming from proposed changes to the plant’s design or operations. In general, only a subset of CDF sequences will be affected by a change. Whether or not this subset contributes significantly to LERF depends on several plant-specific characteristics. This section focuses on the characteristics that strongly affect LERF and identifies review approaches based on these characteristics. It also provides guidance to help reviewers identify the major items related to functional plant capability that directly affect the potential for large early release, to direct reviewers in establishing whether the proposed changes can affect this capability, and to determine whether the licensee has appropriately addressed these items in estimating changes in LERF. b. Review Guidance and Procedures There are several ways in which a change to the plant’s design or operation can significantly alter LERF, including those that: • Change the frequency of containment bypass sequences (e.g., steam generator tube ruptures and interfacing system LOCAs). • Change the frequency of core damage sequences that pose severe challenges to containment (e.g., sequences resulting in elevated reactor coolant system (RCS) pressure during core damage and at vessel failure). • Change the performance of systems involved in containment safety functions (e.g., containment isolation, containment heat removal, containment sprays, hydrogen control). • Change the performance of systems or operator actions that affect accident management strategies (e.g., depressurization, venting). • Change the frequency of core damage sequences occurring at shutdown with containment functionality reduced. The guidance provided below focuses, for each plant type, on particular examples of these general categories. Based on previous PRAs, draft