Document: NUREG-0800
Document ID: cd35e91a-3d44-430c-9102-2c8a74c133ab
Document Type: srp
Title: SAFE SHUTDOWN SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1602/ML16020A086.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.4
CFR Part: 
CFR Title: 

Content:
ngineered safety feature (ESF) systems are used to achieve and maintain safe shutdown, the review of these systems in this section is limited to those features that are unique to safe shutdown and not directly related to accident mitigation. The features within the scope of SRP Section 7.4 may involve individual component control for safe shutdown versus system-level actuation for accident mitigation, or system-level controls used to achieve and maintain safe shutdown but not used for accident mitigation. System-level controls used for accident mitigation may also need to be reviewed using SRP Section 7.4 if the safe shutdown functions of these controls involve features or operating modes that are unique to their safe shutdown functions. This SRP section also addresses the review of those systems required for safe shutdown that are not classified as ESF systems. The specific arrangement of these systems depends on (1) the type of plant: pressurized-water reactor (PWR) or boiling-water reactor (BWR), (2) individual plant design features, and (3) the conditions under which the safe shutdown has to be achieved and maintained. The functional performance requirements of safe shutdown systems and auxiliary supporting features and other auxiliary features are reviewed by other branches in accordance with the SRP sections that address these systems. During safe shutdown, reactivity control systems must maintain a subcritical condition of the core, and residual heat removal systems must operate to maintain adequate cooling of the core. For definitions of plant-specific shutdown conditions, see Chapter 16 in the applicant’s or licensee’s safety analysis report (SAR). Section 7.5, “Information Systems Important to Safety,” of the SRP addresses the information systems important to safety that provide information to the operator for the manual control of systems required for safe shutdown. Section 9.5.1.1, “Fire Protection Program,” of the SRP includes the I&C