At 1914 EST on 12/12/12,
TVA determined that Sequoyah Unit 1 and 2 were at risk of flooding into the
ERCW [Emergency Raw Cooling Water] Station Building during a design basis flood due to conduit penetrations not being filled with material required to make the building water tight. The lack of a barrier would allow flood waters to enter the
ERCW building at a rate greater than the
sump pumps can remove creating a condition that could result in the
ERCW pumps being unavailable to perform their design function during a flood event above plant grade.
This condition places both units in an unanalyzed condition that significantly degrades plant safety [10 CFR 50.72 (b)(3)(ii)(B)], and could prevent the fulfillment of the safety related function of ERCW needed to shutdown the reactor and maintain it in a safe shutdown condition [10CFR 50.72 (b)(3)(v)(A)].
Compensatory actions are being established to be capable of removing or limiting water that could leak into the building during the event. The required safety related equipment is currently operable. There are no indications of conditions that might result in a flood in the near term.
The NRC Resident Inspector has been notified of this condition.
