A review of industry Operating Experience identified that there were unprotected
DC control circuits for non safety-related
DC motors which are routed from the turbine building to other separate fire areas. Fuses used to protect the motor power conductors appear to be inadequate to protect the control conductors. The concern is that under fire
safe shutdown conditions, it is postulated that a fire in one area can cause short circuits potentially resulting in secondary fires or cable failures in other fire areas where the cables are routed. The secondary fires or cable failures are outside the assumptions of the
10 CFR 50 Appendix R Safe Shutdown Analysis.
This condition is reportable as an 8-hour ENS report in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. Compensatory measures (fire watches) have been implemented for affected areas of the plant.
The NRC Resident Inspector has been notified.
