Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
hen a diverse means of performing the same or a different function may not be needed. When a diverse means is provided, Point 3 allows for the diverse means to be comprised of safety-related equipment or equipment that is not safety related, together with a documented basis that this equipment is of sufficient quality and is unlikely to be subject to the same CCF. The diverse means may already exist in the facility or may be installed in connection with the DI&C modification. For example, an anticipated transient without scram (ATWS) system may be credited as a diverse means of tripping the reactor, provided it is not vulnerable to the same CCF that could disable the safety function. The displays and controls credited for Point 4 provide for effective manual control of critical safety functions. The same assessment performed to address the first three points may identify whether the main control room (MCR) displays and controls for manual actuation of critical safety functions are independent and diverse from the proposed DI&C system. If so, these displays and controls may be used to credit manual operator actions in Point 3 (see BTP 7-19-13 Revision 9 — May 2024 section B.3.2.2). These independent and diverse displays and manual controls do not have to be safety grade or hardwired. Alternatively, the applicant may propose a different approach to Point 4 of SRM-SECY-22-0076 if the plant design provides a commensurate level of safety (see section B.4). 1.2 Critical Safety Functions Critical safety functions are those most important safety functions to be accomplished or maintained to prevent a direct and immediate threat to public health and safety.6 The critical safety functions listed in SECY-22-0076 (i.e., reactivity control, core heat removal, reactor coolant inventory, containment isolation, and containment integrity) are examples representative of operating light-water reactors. Other types of reactors may have different critical safety functions. The