ENS 41413
ENS Event | |
|---|---|
18:31 Feb 16, 2005 | |
| Title | Degraded Condition - Reactor Building Normal Sump Level Increasing |
| Event Description | The licensee provided the following information via facsimile:
Event: On February 16, 2005 at 1331 hours0.0154 days <br />0.37 hours <br />0.0022 weeks <br />5.064455e-4 months <br /> 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 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. 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 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. 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.
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.
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. |
| Where | |
|---|---|
Oconee  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
| Time - Person (Reporting Time:+2.82 h0.118 days <br />0.0168 weeks <br />0.00386 months <br />) | |
| Opened: | Philip North 21:20 Feb 16, 2005 |
| NRC Officer: | John Knoke |
| Last Updated: | Feb 17, 2005 |
| 41413 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (18 %) |
WEEKMONTHYEARENS 562212022-11-14T11:30:00014 November 2022 11:30:00
[Table view]10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Reactor Coolant System (RCS) Pressure Boundary Degraded ENS 561972022-11-01T18:33:0001 November 2022 18:33:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Reactor Coolant System (RCS) Pressure Boundary Degraded ENS 495272013-11-11T10:20:00011 November 2013 10:20:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Unit 1 Commenced a Technical Specification Required Shutdown Due to Rcs Leakage ENS 426412006-06-14T18:00:00014 June 2006 18:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Leaking Decay Heat Removal Isolation Valve Bypass Line ENS 414132005-02-16T18:31:00016 February 2005 18:31:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Condition - Reactor Building Normal Sump Level Increasing 2022-11-14T11:30:00 | |