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:
a permanent or a temporary power source as a substitute for the EDG in an extended AOT to maintain the same level of defense-in-depth for safe shutdown of the plant. The staff believes that relying on a single AAC power source for an SBO in one unit and an inoperable EDG in the adjacent unit erodes the defense-in-depth aspects of the plant's design and operation and thereby reduces the safety margins due to a planned extended AOT. For some boiling water reactors, the Division III diesel generator (High Pressure Core Spray Pump (HPCS) diesel generator) may be used as a supplemental AC source. The staff has determined that the HPCS diesel generator can be considered a supplemental AC source provided cross-connect capability exists so that the HPCS diesel generator can be cross-connected to either Division I or Division II AC buses to power safe-shutdown loads. All support systems for HPCS diesel generator should be verified to be available during the extended AOT. The HPCS diesel generator should have the capacity to power LOOP loads to bring the unit to cold shutdown without any load shedding. For plants using AAC or supplemental power sources discussed above, the time to make the AAC or supplemental power source available, including accomplishing the cross-connection, should be approximately one hour to enable restoration of battery chargers and control reactor 8-8-5 Initial - February 2012 coolant system inventory. The availability of AAC or supplemental power source should be verified within the last 30 days before entering extended AOT by operating or bringing the power source to its rated voltage and frequency for 5 minutes and ensuring all its auxiliary support systems are available or operational. To support the one-hour time for making this power source available, 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