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:
M DUAL SINGLE DUAL SINGLE Coefficient α0 −2.47 −4.75 −4.75 −9.14 Coefficient α1 9.38 18.04 18.69 35.95 Minimum submergence, s (ft) 7.5 8.0 7.5 10.0 (m) 2.3 2.4 2.3 3.1 Maximum Froude number, Fr 0.5 0.4 0.4 0.3 Maximum pipe velocity, U (ft/s) 7.0 6.5 6.0 5.5 (m/s) 2.1 2.0 1.8 1.7 Maximum screen face velocity (blocked and minimum submergence) (ft/s) 3.0 3.0 3.0 3.0 (m/s) 0.9 0.9 0.9 0.9 Maximum approach flow velocity (ft/s) 0.36 0.36 0.3 0.36 (m/s) 0.11 0.11 0.11 0.11 Maximum sump outlet coefficient, CL 1.2 1.2 1.2 1.2 * Air ingestion (α) is empirically calculated as α = α0 + (α1 × Fr), where α0 and α1 are coefficients derived from test results as given in the table. This table applies to pump suction inlet geometry. The guidance developed to resolve Generic Letter 2008-01, “Managing Gas Accumulation in Emergency Core Cooling, Decay Heat Removal, and Containment Spray Systems,” dated January 11, 2008 (Ref. A-5), which appears in the Nuclear Energy Institute (NEI) document NEI 09-10, Revision 1a-A, “Guidelines for Effective Prevention and Management of System Gas Accumulation,” issued April 2013 (Ref. A-6), addresses gas accumulation downstream of the inlet. DG-1385, Appendix A, Page A-7 A-3 Effects of Ingested Air on Pump Performance Table A-2 presents the guidance limits for air or gas ingestion. Higher levels than those listed have been shown to degrade pumping capacity. Independently of pumping capacity, NPSH can be affected by air or gas void ingestion from vortex formation, deaeration, and entrainment from splashing. These gas sources are included in the limits and in the calculation to adjust the required NPSH described in the next paragraph. Further details can be found in NEI 09-10, Revision 1a-A, including the U.S. Nuclear Regulatory Commission staff safety evaluation. The limit on sump air or gas ingestion for pumping capacity and the NPSH criteria are applied independently. As stated in NUREG-0897, Revision 1, steady-state air or