Document: NUREG-0800
Document ID: eb117be6-f688-40f6-97a8-c91b8e9f8e74
Document Type: srp
Title: CONTAINMENT HEAT REMOVAL SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070457.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.2
CFR Part: 
CFR Title: 

Content:
1 (Ref. 5) describes methods acceptable to the staff for evaluating the 34 NPSH margin. In the recirculation phase; i.e., in the long term (after about 1 hour) following a LOCA, the containment spray system is required to circulate the water in the containment. The NPSH analysis will be acceptable if (1) it is done in accordance to the guidance in Regulatory Guide 1.82, Rev. 1 (Ref. 5) and (2) it is done in accordance with the 35 guidelines of Regulatory Guide 1.1 (Ref. 4), i.e., is based on maximum expected 36 temperature of the pumped fluid and with atmospheric pressure in the containment. For clarification, the analysis should be based on the assumption that the containment pressure equals the vapor pressure of the sump water. This ensures that credit is not taken for containment pressurization during the transient. The recirculation spray system for a subatmospheric containment is designed to start about 5 minutes after a loss-of-coolant accident, i.e., during the injection phase of spray system operation. For subatmospheric containments, the guidelines of Regulatory Guide 1.1 as defined above will apply after the injection phase has terminated, which occurs about 1 hour after the accident. Prior to termination of the injection phase the NPSH analyses should include conservative predictions of the containment atmosphere pressure and sump water temperature transients. 3. In evaluating the performance capability of the containment spray system, to satisfy GDC 38, 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. c. The type of spray nozzles used and the nozzle atomizing capability, i.e., the spray drop size spectrum and mean drop size emitted from each type of nozzle as a function of differential pressure across the nozzle. 6.2.2-5 DRAFT Rev. 5 - April 1996 d.