Document: NUREG-0800
Document ID: a78c6fc8-c253-4d08-bf41-f8120025f067
Document Type: srp
Title: CONTAINMENT HEAT REMOVAL SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0701/ML070160661.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.2
CFR Part: 
CFR Title: 

Content:
. This analysis should also demonstrate that the available NPSH is greater than or equal to the required NPSH. Regulatory Guide 1.82, Revision 3 (Ref. 1), describes methods acceptable to the staff for evaluating the NPSH margin. If containment accident pressure is credited in determining available NPSH, an evaluation of the contribution to plant risk from inadequate containment pressure should be made. One acceptable way of making this evaluation is to address the five key principles of risk-informed decisionmaking stated in Section 2 of Regulatory Guide 1.174 (Ref. 2). 3. In evaluating the performance capability of the CSS to satisfy GDC 38, the analyses of its heat removal capability should be based on the following considerations: A. The locations of the spray headers relative to the internal structures. B. The arrangement of the spray nozzles on the spray headers and the expected spray pattern. The spray systems should be designed to ensure that the spray header and nozzle arrangements produce spray patterns which maximize the containment volume covered and minimize the overlapping of the sprays. C. The spray drop size spectrum and mean drop size emitted from each type of nozzle as a function of differential pressure across the nozzle. D. The effect of drop residence time and drop size on the heat removal effectiveness of the spray droplets. 4. In evaluating the performance capability of the fan cooler system to satisfy GDC 38, the design heat removal capability (i.e., heat removal rate versus containment temperature) of the fan coolers should be established on the basis of qualification tests on production units or acceptable analyses that take into account the expected postaccident environmental conditions and variations in major operating parameters, such as the containment atmosphere steam-air ratio, condensation on finned surfaces, and cooling water temperature and flow rate. The equipment housing and ducting associated with the fan cooler system should be