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:
firm 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 which includes the functions to maintain core cooling and containment integrity. RTNSS B SSCs are considered nonsafety-related backups to safety-related SSCs (Ref. 25, 32 and SRP 19.3). RTNSS Criterion C functions address safety goals of core damage frequency. RTNSS C SSCs are considered nonsafety-related defense-in-depth backups (Ref. 25 and 32). Defense-in-depth principles consist of a number of elements as described in Regulatory Guide (RG) 1.174 (Ref. 28). The specific areas of review for the safety-related VWS are as listed below. Additionally, the nonsafety-related areas of review, including RTNSS B and C functions, are shown below each area of review for the safety-related VWS in bold-italics. Therefore, when the description after an item states that “RTNSS B: applies”, for example, this means that for SSCs classified as RTNSS B, the area of review is applicable. 1. Review safety/risk-significant classification as discussed above. Safety-related: Safety/risk-significant classifications are to be verified. RTNSS B and C and nonsafety-related nonrisk-significant: Safety/risk-significant classifications are to be verified. 2. Compliance with the requirements of General Design Criteria (GDCs) 1, 2, 4, 5, 44, 45, and 46. 9.2.7-4 Draft Revision 0 – July 2014 Note: RTNSS B SSCs are designed to withstand the effects of natural phenomena without loss of function. RTNSS C SSCs are evaluated, utilizing the “graded approach philosophy,” against the effects of the most probable hazards (e.g., floods, winds, missiles, seismic events). As a result of this evaluation, RTNSS C SSCs may be designed against the effects of natural phenomena. SRP Section 19.3 provides further guidance related to the reliability and availability missions of RTNSS B and C SSCs. Note: RTNSS B