Document: NRC Regulatory Guide
Document ID: 1731a882-b0c5-418d-b65e-55646c26be5c
Document Type: regulatory_guide
Title: 03/2007
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0703/ML070380553.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.9
CFR Part: 
CFR Title: 

Content:
nd preoperational test data are usually available. However, the design-basis event loads during the operating license or combined license stages should be within the continuous rating of the emergency diesel generators with sufficient margin (i.e., not less than 5 percent). The reliability of emergency diesel generators can be one of the main factors affecting the risk of core damage from a station blackout event. Thus, both attaining and maintaining the high reliability of emergency diesel generators at nuclear power plants contribute greatly to reducing the probability of station blackout. Regulatory Guide 1.155, “Station Blackout” (Ref. 4), calls for the use of the reliability of the diesel generator as one of the factors in determining the length of time a plant should be able to cope with a station blackout. If all other factors (i.e., redundancy of emergency diesel generators, frequency of LOOP, and probable time needed to restore offsite power) remain constant, a higher reliability of the diesel generators will result in a lower probability of a station blackout, with a corresponding decrease in coping duration for certain plants. The design of the emergency diesel generators should also incorporate high operational reliability, and this high reliability should be maintained throughout their lifetime by initiating a reliability program that is designed to monitor, improve, and maintain reliability. Increased operational reliability can be achieved through appropriate testing and maintenance, as well as an effective root cause analysis of all emergency diesel generator failures. Rev. 4 of RG 1.9, Page 4 This guide provides explicit guidance in the areas of preoperational testing, periodic testing, reporting and recordkeeping requirements, and valid demands and failures. The preoperational and periodic testing provisions set forth in this guide provide a basis for taking the corrective actions needed to maintain high inservice reliability of installed