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
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Content:
onditions and for prevention or mitigation of the consequences of accidents. The VWS 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 VWS 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. For the passive designs, the VWS may be classified as either RTNSS Criterion B (RTNSS B) or RTNSS Criterion C (RTNSS C), which are defined below: 1. Criterion B – Required to address SSC functions relied upon to resolve long-term (post-72 hour) safety and to address seismic events. This criterion pertains to SSCs required after 72 hours of a design-basis accident (DBA) initiation that are key to maintaining core cooling, containment integrity, control room habitability, and post- accident monitoring that would require a RTNSS evaluation. Note: Long-term safety is defined as the period beginning 72 hours after a design basis event and lasting the following 4 days (168 hours) hereafter referred to as the “post-72 hour period.1” 2. Criterion C – Required to meet safety goals of core damage frequency (CDF) less than 1.0E-4 and large release frequency (LRF) less than 1.0E-6, each reactor year. This criterion pertains to active nonsafety-related-components relied upon to reduce initiating event frequencies, CDF and LRF 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