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On February 27, 2011, at 2159 CST, during the testing of the A train safety injection (SI) system (BQ), it was discovered that the oiler for the Unit 2, B train SI pump, had rotated and the oil had drained out. The B train SI pump was declared inoperable. At the time of the event, the A train of SI was out of service for performance of a routine inservice test. Because both trains of SI were inoperable, LCO 3.0.3 was entered. Upon completion of the A train inservice test, Unit 2 exited LCO 3.0.3 at 2211 CST.

Immediate corrective actions taken included restoring the oiler to the vertical position, refilling it and performing a 5-minute pump run. The root cause of the event was determined to be a 1995 modification to the SI pump oiler which introduced a latent design/configuration flaw. Additional corrective actions will include a design change to the SI pumps and oiler assemblies for both units to reduce the possibility of accidental misalignments. The actions are being tracked to completion in the corrective action program.

An 8-hour ENS report was made in accordance with 10 CFR 50.72(b)(3)(v)(D) on February 28, 2011 at 0345 CST.