Document: NRC Regulatory Guide
Document ID: 6f0a99f2-d25a-44e3-b7f2-3286449a9752
Document Type: regulatory_guide
Title: Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident (Rev. 5)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2126/ML21266A185.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.82
CFR Part: 
CFR Title: 

Content:
s desirable to use ECCS suction strainers to protect the pump inlets from debris that may block restrictions in the systems served by the ECCS pumps or damage components. Suction strainers are passive devices that limit the amount of debris entering the ECCS pump suction line by capturing it on a surface with small openings that reduce the amount of debris that can pass through. ECCS and CSS pumps are normally centrifugal pumps. For a centrifugal pump to perform its safety function, an adequate margin must exist between the available and the required NPSH2 (NPSHr). Failure to provide and maintain adequate NPSH for the ECCS pumps could cause cavitation and subsequent failure to deliver the amount of water assumed in design-basis LOCA safety analyses. Because the safety of a nuclear power plant depends on the performance of the pumps in the ECCS and the containment heat removal system, it is important to maintain adequate margin between the available and required NPSH under all potential conditions. The available NPSH (NPSHa) is the total suction head of liquid absolute, determined at the first-stage impeller datum, less the absolute vapor pressure of the liquid. The required NPSH, as defined 1 Throughout this RG, the NRC uses the term “licensee” in a generic sense. The user of this document may be a nuclear power plant licensee, an applicant for a license, or a vendor performing evaluations on behalf of a licensee or applicant. 2 The term “required NPSH” does not refer to an NRC regulatory requirement. American National Standards Institute/Hydraulic Institute (ANSI/HI) 14.3-2019, “American National Standard for Rotodynamic Pumps for Design and Application” (Ref. 10), defines NPSH parameters, including required NPSH. DG-1385, Page 7 in ANSI/HI 14.3-2019, is the amount of suction head, over vapor pressure, required to prevent more than a 3-percent loss in total head of the first stage of the pump at a specific capacity. The predicted performance of the ECCS