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:
containment pressure above that which is necessary to preclude pump cavitation. In the determination of NPSHa for this situation, the calculation of available containment pressure and sump/pool water temperature as a function of time should underestimate the expected containment pressures and overestimate the sump/pool water temperatures. 1.3.1.3 If credit is taken for operation of an ECCS or containment heat removal pump in cavitation, licensees should conduct prototypical pump tests, along with a posttest examination of the pump, to demonstrate that pump performance will not be degraded and that the pump will continue to meet all of the performance criteria assumed in the safety analyses. The time period in the safety analyses during which the pump may be assumed to operate while cavitating should not be longer than the time period for which the performance tests demonstrate that the pump meets the performance criteria. 1.3.1.4 Because high water temperatures reduce NPSHa and can affect the potential for flashing and impact fluid properties, such as density and viscosity, the determination of the water temperature should include the decay and residual heat produced following accident initiation. This calculation should include uncertainty in the determination of the decay heat (uncertainty in decay heat is typically included at the 2-sigma level). The licensee should calculate the residual heat with margin. 1.3.1.5 Licensees should not use the correction factor for pumping high-temperature fluid discussed in ANSI/HI 14.3-2019 to determine the margin between the available and required NPSH for the ECCS and the containment heat removal systems. 1.3.1.6 The calculation of NPSHa should consider the minimum calculated height of water above the pump suction and strainer surfaces. The calculated height of water should not consider quantities of water that do not contribute to the sump or suppression pool (e.g., atmospheric steam, pooled water on floors and in refueling