Document: NUREG-0800
Document ID: 8e754440-b70e-4b8a-9816-b4a64b631220
Document Type: srp
Title: Initial – February 2012
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1136/ML113640138.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
able, plants must assess their ability to cope with loss of all AC power for one hour independent of an AAC power source. The plant should have formal engineering calculations for equipment sizing and protection and have approved procedures for connecting the AAC or supplemental power sources to the safety buses. The EDG or offsite power AOT should be limited to 14 days to perform maintenance activities. This time period is based on industry operating experience; for example, a maximum of 216 hours (13.5 days, consisting of two shifts, each shift working 8 hours) is considered to be sufficient for a major EDG overhaul or offsite power major maintenance. The licensee must provide justification for the duration of the requested AOT (actual hours plus margin based on plant-specific past operating experience). An EDG or offsite power AOT license amendment of more than 14 days should not be considered by the staff for review. The TS must contain Required Actions and Completion Times to verify that the supplemental AC source is available before entering extended AOT. The availability of AAC or supplemental power source shall be checked every 8-12 hours (once per shift). If the AAC or supplemental power source becomes unavailable any time during extended AOT, the unit shall enter the LCO and start shutting down within 24 hours. This 24-hour period will be allowed only once within any given extended EDG AOT. Additionally, the staff expects that the licensee will provide the following Regulatory Commitments: • The extended AOT will be used no more than once in a 24-month period (or refueling interval) on a per diesel basis to perform EDG maintenance activities, or any major maintenance on offsite power transformer and bus. • The preplanned maintenance will not be scheduled if severe weather conditions are anticipated. • The system load dispatcher will be contacted once per day to ensure no significant grid perturbations (high grid loading unable to withstand a single