Document: NRC Regulatory Guide
Document ID: 08964ae0-0fa8-4e51-af44-0c6a1ee6e94c
Document Type: regulatory_guide
Title: Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1221/ML12216A011.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.108
CFR Part: 
CFR Title: 

Content:
ld be accomplished by synchronizing the generator with the offsite power and assuming a load at the max- imum practical rate. d. After completion of the diesel generator unit reliability demonstration under Regulatory Postition 2 Valid test as defined in Regulatory Position C.2.e. C.2.a.(9), the interval for periodic testing under Regulatory Position C.2.c (on a per diesel generator unit basis) should be no more than 31 days and should depend on demonstrated performance. If more than one failure has occurred in the last 100 tests (on a per nuclear unit basis), the test interval should be shortened in accordance with the following schedule.: (I) If the number of failures in the last 100 valid tests is one or zero, the test interval should be not more than 31 days. (2) If the number of failures in the last 100 valid tests is two, the test interval should be not more than 14 days. (3) If the number of failures in the last 100 valid tests is three, the test interval should be not more than 7 days. (4) If the number of failures in the last 100 valid tests is four or more, the test interval should be not more than 3 days. e. Valid tests and failures (under Regulatory Positions C.2.a.(9) and C.2.d) should be based on the following criteria: (1) All start attempts (automatic, including those from bona tide signals, or manual) that result in a failure to start, except as noted in (2) below, should be considered valid tests and failures. (2) Unsuccessful start and load attempts that can definitely be attributed to operating error, to spurious operation of a trip that is bypassed in the emergency operating mode, to malfunction of equip- ment that is not operative in the emergency operating mode (e.g., synchronizing circuitry) or is not part of the defined diesel generator unit design should not be considered valid tests or failures. (3) Successful starts, including those initiated by bona fide signals, followed by successful loading (se- quential or manual) to at least 50% of