Document: NUREG-0800
Document ID: b1bccb14-17b6-422b-93ee-6d4f00b6512b
Document Type: srp
Title: CHILLED WATER SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1510/ML15103A559.pdf
Revision Date: 2023-06
Chapter: 9
Section ID: 9.2.7
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CFR Title: 

Content:
nces, and accident conditions and for prevention or mitigation of the consequences of accidents. The CWS may perform cooling water functions to nonsafety-related risk-significant and nonsafety-related nonrisk-significant equipment as part of a “passive plant” design. For these designs, the CWS may be subject to special regulatory treatment of nonsafety-related system (RTNSS) considerations. NUREG-0800 Standard Review Plan (SRP) Section 19.3, “Regulatory Treatment of Non-Safety Systems (RTNSS) for Passive Advanced Light Water Reactors,” provides the process used to identify the structures, systems, and components (SSCs) that are to be treated as RTNSS. As indicated in SRP Section 19.3, the RTNSS process uses Criteria A through E to determine the SSC functions. The CWS may be classified as either RTNSS Criterion B (RTNSS B) or RTNSS Criterion C (RTNSS C). RTNSS Criterion B functions pertain to SSCs required during the post-72 hour period1 after a design basis event and are key to maintaining long term safety which includes the functions to maintain core cooling and containment integrity. RTNSS B SSCs are considered nonsafety-related backups to safety-related SSCs. RTNSS Criterion C functions address safety goals of core damage frequency and large release frequency. RTNSS C SSCs are considered nonsafety-related defense-in-depth backups. The reliable nonsafety-related SSCs are evaluated in accordance with 10 CFR 50.65, and SRP 17.6, “Maintenance Rule.” 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 CWS may be classified as: • Safety-related risk-significant 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