On 2/2/10, at 1615 [CST], the Unit 1
TDAFW [Turbine Driven Auxiliary Feed Water] Pump was declared
inoperable due to a high temperature identified on an electrical cable in the
TDAFW UPS [Uninterrupted Power Supply]. The 1B Diesel Generator had previously been removed from service for scheduled maintenance. As required by the Diesel Generator LCO Required Action Statement, the Unit 1 'B'
MDAFW [Motor Driven Auxiliary Feed Water] Pump was declared
inoperable at 2015 [CST], on 2/2/10, due to the combination of its
inoperable emergency power supply and
inoperable redundant equipment. This resulted in two of three trains of
Auxiliary Feed Water being
inoperable. Because two out of the three trains of
AFW [Auxiliary Feed Water] are required to meet flow requirements for limiting design basis accidents, this represents a condition that could have prevented the fulfillment of a safety function.
Repairs to the electrical cable were immediately initiated. At 2216 [CST], on 2/2/10, the Unit 1 TDAFW Pump was returned to operable status, allowing the 1B MDAFW Pump to be declared operable, and restoring the safety function.
The licensee determined that the high temperature in the electrical cable was caused by a high resistance between the lug and cable connection.
The licensee will notify the NRC Resident Inspector.
