Document: NRC Regulatory Guide
Document ID: 2559e7e3-22aa-4dda-8fee-ac029c2a69e4
Document Type: regulatory_guide
Title: Guidance for Residual Heat Removal
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0407/ML040750334.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.139
CFR Part: 
CFR Title: 

Content:
the containment. If interlocks are provided to automatically close the isolation valves when the RCS pres- sure exceeds the RHR design pressure, adequate relief capacity should be provided during the time that the valves are closing. 4. RHR SYSTEM PUMP PROTECTION The design and operating procedures of the RHR system should include provisions to prevent damage to the RHR system pumps due to overheating, cavitation, or loss of adequate pump suction head. S. RHR SYSTEM TESTING For the RHR system, the isolation valve operability and interlock circuits should be designed to permit on-line testing when operating in the RHR mode. System testing should meet the requirements of IEEE Standard 338 and the recommendations of Regulatory Guide 1.22. The preoperational and initial startup test program should be in conformance with Regula- tory Guide 1.68. The programs for pressurized water reactors should include tests with sup- porting analysis to confirm (a) that adequate mixing of borated water added prior to or during cooldown can be achieved under natural circulation conditions and permit estimation of the times required to achieve such mixing and (b) that the cooldown under natural circulation conditions can be achieved within the limits specified in the emergency operating procedures. Comparison with the performance of previously tested plants of similar design may be sub- stituted for these tests. 1.139-5 6. AUXILIARY FEEDWATER SUPPLY The seismic Category I water supply for the auxiliary feedwater system for a PWR should have sufficient inventory to permit operation at hot-standby conditions for at least 4 hours followed by cooldown to the conditions permitting operation of the RHR system. The inventory needed for cooldown should be based on the longest cooldown time needed with either only onsite or only offsite power available with an assumed single failure. 7. OPERATIONAL PROCEDURES The operational procedures for bringing the plant from normal operating power to cold