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:
emonstrate 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 NPSHa, since testing at a lower NPSHa can actually reduce, rather than increase, the cavitation erosion rate in some cases. • The test duration is for the time during which NPSHa is predicted to be less than NPSHreff (LOCA) or NPSHr3% (special event). • The flow rate and discharge head remain above the values necessary to provide adequate core and containment cooling. B-9.6 To reduce the likelihood of a preexisting containment leak, licensees proposing to use CAP in determining NPSH margin as illustrated in the flowchart in Figure B-7 should do the following: a. Determine the minimum containment leakage rate sufficient to lose the CAP needed for adequate NPSH margin. b. Propose a method to determine whether the actual containment leakage rate exceeds the leakage rate found in (a) above. For inerted containments, this method could consist of a periodic, appropriately frequent quantitative measurement of the nitrogen makeup. For subatmospheric containments, a similar procedure could be used. c. Propose a limit on the time the plant can operate while the actual containment leakage rate exceeds the leakage rate determined in (a) above. B-9.7 The zone of maximum erosion rate should be between NPSH margin ratios of 1.2 and 1.6. For pumps of very high suction energy, the permissible time in this range should be limited unless operating experience, testing, or analysis