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:
n line losses from pool to pump (ft) Hloss Included in the NPSHa term CAP available in NPSH analysis Available wetwell pressure (assumed absolute initial wetwell pressure above pool surface) (hatm − hmin) (Note 2) DG-1385, Appendix B, Page B-18 Notes for Table B-1 1. NEDC-33347P-A/NEDO-33347-A, Sections 3.1 and 3.1.2 for DBA LOCA, has short-term and long-term groups in which representative state points were selected as shown in Appendices A and B to NEDC-33347P-A/NEDO-33347-A. 2. The head is converted to pressure using the liquid density. 3. Suppression pool temperature as a function of time can be calculated from a deterministic (conservative) analysis, or from a statistical analysis resulting in a minimum value of Hww (combination of the suppression pool temperature and Pww) for LOCA, or a mean Hww value for special events. NEDC-33347P-A/NEDO-33347-A, Section 2.2, defines Hww as (Pww – Pv) x 144/ρw. Pressurized-Water Reactor Plants For PWRs, the following options are acceptable when calculating NPSHa using CAP greater than the containment pressure before the postulated accident: (1) use the vapor pressure corresponding to the sump water temperature, or (2) use a Monte Carlo procedure. It is possible that the NPSHa may be less than NPSHreff (LOCA) or NPSHr3% (special event). In this case, operation in this mode is acceptable if appropriate tests are done to demonstrate that the pump will continue to perform its safety function(s). The following conditions should apply: • Predicted operation during the postulated accident below NPSHreff (LOCA) or NPSHr3% (special event) is of limited duration (less than 100 hours). • The tests are conducted on the actual pump, with the same mechanical shaft seal (including flush system), or at least on a pump of the same model, size, impeller diameter, materials of construction, and pump seal/flush system. • The test is conducted at the same speed as at the plant site. • The test is conducted at the actual predicted