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:
e fully submerged. Some plant designs have open or vented sumps downstream of the strainers. Table A-1 also applies in these cases. If the PWR pump suction inlet design deviates significantly from the bounding values of design parameters in the table, licensees should use plant-specific data to verify adequate hydraulic performance. e. For boiling-water reactors (BWRs), full-scale tests of pump suction inlet designs have shown that air ingestion is zero for Froude numbers less than 0.8, with a minimum submergence of 1.83 meters (6 feet). Operation up to a Froude number of 1.0 with the same minimum submergence DG-1385, Appendix A, Page A-5 may be possible before air ingestion levels of 2 percent occur. The reader should refer to NUREG-0897, Revision 1, “Containment Emergency Sump Performance: Technical Findings Related to Unresolved Safety Issue A-43,” issued October 1985 (Ref. A-3), and NUREG/CR-2772, “Hydraulic Performance of Pump Suction Inlets for Emergency Core Cooling Systems in Boiling Water Reactors,” issued June 1982 (Ref. A-4).1 1 See also NEI 09-10, Revision 1a-A, “Guidelines for Effective Prevention and Management of System Gas Accumulation,” issued April 2013, and the NRC staff SE (Ref. A-6). DG-1385, Appendix A, Page A-6 Table A-1 PWR Hydraulic Design Guidelines for Air Ingestion (Tables 5.1 and 5.2 in NUREG-0897, Revision 1) Zero Air Ingestion Item Horizontal Outlets Vertical Outlets Minimum submergence, s (ft) 9 9 (m) 2.7 2.7 Maximum Froude number, Fr 0.25 0.25 Maximum pipe velocity, U (ft/s) 4 4 (m/s) 1.2 1.2 NOTE: These guidelines were established using experimental results from NUREG/CR-2758 and other sources, and are based on sumps having a right rectangular shape. Air Ingestion Less than 2 Percent HORIZONTAL OUTLETS VERTICAL OUTLETS ITEM 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,