Document: NUREG-0800
Document ID: 9cfc38bf-7808-446e-a43d-4ca9ff55df2a
Document Type: srp
Title: AC POWER SYSTEMS (ONSITE)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1007/ML100740289.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8.3.1
CFR Part: 
CFR Title: 

Content:
e probability of their coincident loss (GDC 17), nor can the design be made immune to common failure modes (Section 5.2.1(5) of IEEE Std. 308). Further details amplifying the basis for this conclusion are included in BTP 8-2, which sets forth 8.3.1-27 Revision 4 - May 2010 the basis for not using the diesel generator sets for purposes other than emergency standby power supplies. Operating experience has provided insights into aging-, operation-, and design-related problems associated with medium-and low-voltage switchgear equipment, electrical buses, and circuit breakers used in the onsite ac power system. These include, but are not limited to: - bus failures, involving the integrity of bus bar splice joints, torque relaxation, cyclical bus loading, and incipient damage resulting from a high fault current transient/arcing fault explosion, that can lead to a LOOP (Reference 8); - failures of safety-related circuit breakers due to problems with preventive maintenance programs, circuit breaker lubrication, licensee/vendor interface, control voltage criteria, and review of circuit breaker operating experience (References 5 and 6); - metal-clad switchgear circuit breaker failure involving an energetic arcing fault fire/explosion that propagated damage to adjacent circuit breaker cubicles and resulted in a LOOP (Reference 9); and - potential for degradation of switchgear control and protection wiring at the circuit breaker cubicle door hinges that could affect safety equipment function (Reference 10). The review should verify that medium and low-voltage switchgear, metal-enclosed bus preventive maintenance and performance and condition monitoring activities are evaluated periodically in accordance with the Maintenance Rule and that they incorporate, where practical, the insights of internal and industry-wide operating experience. 4. Standby Power Supplies The reviewer should ensure that the requirements of GDC 17 and the recommendations of IEEE Std. 308 have been met with