During an extent of condition review of
DC control circuits, it was identified there are additional unprotected
DC control circuits which are routed between separate Appendix R fire areas. A postulated fire in one area can cause a short circuit and potentially result in secondary fires or cable fires in other fire areas where the cables are routed. The secondary fires or cable failures degrade the degree of separation for redundant
safe shutdown trains and are outside the assumptions of the
10 CFR 50 Appendix R Safe Shutdown Analysis. This condition is reportable in accordance with
10 CFR 50.72(b)(3)(ii)(B).
Compensatory actions for affected fire areas have been implemented. Design modifications in the affected control circuits are being developed and will be scheduled to correct this condition.
