Document: NUREG-0800
Document ID: 3571c656-1693-466b-a77d-6c05b7eed41e
Document Type: srp
Title: REACTOR SYSTEMS - INSPECTIONS, TESTS, ANALYSES, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070660623.pdf
Revision Date: 2023-06
Chapter: 14
Section ID: 14.3.4
CFR Part: 
CFR Title: 

Content:
y of figures p. Active systems that provide defense-in-depth functions designated as non-safety systems 14.3.4-6 March 2007 Appendix C to SRP 14.3 provides “checklists” for the fluid systems as an aid for establishing consistency and comprehensiveness in the review of the system. 2. The source of information used to determine safety significance of SSCs for the design of reactor and core cooling systems include applicable rules and regulations, general design criteria, unresolved safety issues, and generic safety issues, NRC generic correspondence, PRA, insights from the standard design’s safety and severe accident analyses, and operating experience. Inputs from the PRA review, including shutdown safety evaluations, and severe accident analyses ensure important insights and design features from these analyses are incorporated into Tier 1. For both PRA and severe accident analyses, although large uncertainties and unknowns may be associated with the event phenomena, design features important for severe accident prevention and mitigation resulting from these analyses should be selected for treatment in Tier 1. 3. The passive-designed reactors use safety systems that employ passive means (natural forces), such as gravity, natural circulation, condensation and evaporation, and stored energy, for accident mitigation. These designs also include active systems that provide defense-in-depth capabilities for reactor-coolant makeup and decay heat removal. These active systems are the first line of defense to reduce challenges to the passive systems in the event of transients or plant upsets. SECY-95-132, “Policy and Technical Issues Associated with Regulatory Treatment of Non-Safety Systems (RTNSS) in Passive Plant Designs (SECY-94-084)” provides certain guidance and positions for ensuring consistent and complete treatment of those systems that might be classified as non-safety-related by the designer or applicant but are important to safety or otherwise provide