Document: NRC Regulatory Guide
Document ID: 96ecfd93-e64a-4f35-93fe-d3b95daac61d
Document Type: regulatory_guide
Title: Monitoring the Effectiveness of Maintenance at Nuclear Power Plants + HISTORY –HISTORY 06/2018 – DG-1336 , Proposed Revision 4 09/2011 – DG-1278 , Proposed Revision 3 08/1996 – DG-1051 , Proposed Revision 2 06/1994 – DG-1031, Proposed Revision 1 11/1992 – DG-1020, Proposed Revision 0 (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1812/ML18129A080.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.160
CFR Part: 
CFR Title: 

Content:
robability of occurring during the planned out-of-service duration. The NRC staff considers NUMARC 91-06 acceptable for use with the following clarification. The acceptable application of NUMARC 91-06 is limited in applicability to where it is applied in NUMARC 93-01 only. Examples of risk significant shutdown voluntary initiatives that are specified in NUMARC 91-06 include: 4.1.1 Loss of Decay Heat Removal Containment hatches (equipment and personnel) and other penetrations that communicate with the containment atmosphere (primary or secondary, as appropriate) should either be closed or capable of being closed prior to core boiling following a loss of decay heat removal (DHR) and should be addressed in procedures. 4.2.3 Inventory Loss to Suppression Pool (boiling water reactor) The automatic isolation function of the DHR system (on low water level) should be maintained functional during shutdown cooling periods. DG-1336, Page 16 Fire Scenario Success Path(s) The last paragraph of Section 11.3.3.1 "Scope of Assessment for Fire Risk” of NUMARC 93-01 states that some fire scenarios have no success paths available. The NRC does not agree with this statement, and the associated recommendation in NUMARC 93-01 (stating “It is recommended that these scenarios be screened from further consideration."). Each plant is required by 10 CFR 50.48, “Fire Protection,” to identify one train of safe-shutdown capability free of fire damage, such that the plant can be safely shut down in the event of a fire. When maintenance activities are conducted on the protected train, the staff’s position is that licensees should follow the guidance in Section 11.3.4.3 “Fire Risk Assessment Consideration” of NUMARC 93-01. Establishing Action Thresholds Based on Quantitative Considerations Section 11.3.7.2 “Establishing Action Thresholds Based on Quantitative Considerations” states: The configuration-specific CDF should be considered in evaluating the risk impact of the planned