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The licensee provided the following information via facsimile: Event: On February 16, 2005 at 1331 hours EST, Operations discovered that the Oconee Unit 3 Reactor Building Normal Sump (RBNS) level was increasing. Chemistry sampled the containment normal sump to determine the water source and could not conclusively rule out Low Pressure Service Water (LPSW). The leak rate into the sump is approximately 1.9 gpm. LPSW is the cooling medium used for the Reactor Cooling Pump (RCP) motor coolers, the Reactor Building Cooling Units (RBCU), and the Reactor Building Auxiliary Cooling Units (RBACU). Unit 3 entered Technical Specification 3.6.1.A at 1331. This requires restoring containment to Operable status within 1 hour. The approximately 1.9 gpm leakage is above the leakage allowed in calculation OSC-7005 "LPSW Allowable Leakage Inside Containment". At 1431 Unit 3 entered Technical Specification 3.6.1 B which requires being in mode 3 in 12 hours. Initial Safety Significance: By limiting the amount of LPSW leakage inside containment then containment operability is ensured. Above the calculated LPSW leakage as stated in OSC-7005, containment operability is in question. The LPSW system pressure could be less than containment LOCA peak pressure. Therefore containment atmosphere has the potential to leak through the LPSW system, during a LOCA, and out the return line resulting in a containment leak path. Collective Action(s): Additional sampling and process indications suggest that the cause of the Reactor Building Normal Sump rate increase is feedwater or main steam. A power reduction to 18% has been completed and a reactor building entry is in progress to confirm the source of the leakage. If the source is confirmed to be feedwater or main steam, Technical Specification 3.6.1 will be exited. The turbine is still loaded and the electrical grid was not affected by the power decrease to 18%. All systems functioned as required and other units at Oconee were not affected by this event. NRC Resident Inspector was notified.

• * * UPDATE ON 2/17/05 @ 0018 BY JOHN COLLINS TO CHAUNCEY GOULD * * * UPDATE

They entered the containment and verified a steam leak off the impulse line for the "3B" steam generator main steam pressure transmitters. They are currently at 18% power and making a decisions on repair options. The NRC Resident Inspector will be informed. The Reg 2 RDO(Bernhard) was notified.

• * * UPDATE ON 2/17/05 @ 0139 BY JOHN COLLINS TO CHAUNCEY GOULD * * * RETRACTION

At 0012 on February 17, 2005 entry into the Unit 3 reactor building confirmed that the source of leakage into the reactor building normal sump was the Main Steam system. Specifically, the location of the leak appears to be a fitting downstream of an instrument root valve off the 3B Main Steam line. Based on this information, Technical Specification 3.6.1 was exited and this event is not reportable per 10CFR50.72. and therefore being retracted. A shutdown to MODE 3 will be conducted to facilitate repairing the leak. The NRC Resident Inspector will be informed. Reg 2 RDO(Bernhard) was notified.