Document: NUREG-0800
Document ID: 5cdeed4a-6cd5-4840-90c0-5159fbf2c9f0
Document Type: srp
Title: CHILLED WATER
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1409/ML14093A350.pdf
Revision Date: 2023-06
Chapter: 9
Section ID: 9.2.7
CFR Part: 
CFR Title: 

Content:
in the focused probabilistic risk assessment (PRA) sensitivity study, the baseline PRA, or in the assessment of uncertainties that would require a RTNSS evaluation. 1 The “Post 72-hour period” as stated in SRP 19.3 is defined as the period beginning 72 hours after a design basis event and lasting the following 4 days. This period is important from a safety perspective because passive plants are designed such that safety-related SSCs can satisfy all safety functions for a period up to 72 hours following a design basis event, but additional equipment and procedural action will be needed to either extend the ability of safety-related SSCs to accomplish the safety functions or perform the safety functions themselves until systems designed to bring the plant to a long-term cold shutdown condition can be put in service. 9.2.7-3 Draft Revision 0 – July 2014 The reliable nonsafety-related system SSCs are evaluated under SRP 17.6, “Maintenance Rule,” (Ref. 29). These nonsafety-related system components shall be monitored for performance against licensee-established goals, in a manner sufficient to provide reasonable assurance that these SSCs are capable of fulfilling their intended functions. Depending on the design and RTNSS analysis, the VWS may be classified as: • Safety-related risk-significant • Safety-related nonrisk-significant • Nonsafety-related risk-significant, which may include RTNSS Criterion B and RTNSS Criterion C SSCs • Nonsafety-related nonrisk-significant, which may include functions to support cold shutdown (CSD) conditions The application will include the classification of SSCs, a list of risk-significant SSCs, and a list of RTNSS equipment. Based on this information, the staff will review according to SRP Sections 3.2, 17.4 and 19.3 to confirm the determination of the safety-related and risk-significant SSCs. RTNSS Criterion B function pertains to SSCs required during the post-72 hour period that are key to maintaining long term safety