ENS 45124
ENS Event | |
|---|---|
20:55 Jun 11, 2009 | |
| Title | Unit 2 Initiated a Tech Spec Required Shutdown Due to a Rise in Unidentified Drywell Leakage |
| Event Description | At noon on 06/11/2009 Browns Ferry Unit 2 experienced a rise in drywell leakage during reactor startup. The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> unidentified leak rate from 0800 to 1200 on 6/10/2009 was 0 GPM, while the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> unidentified leak rate from 0800 to 1200 on 6/11/2009 was 3.88 GPM. This increase in leak rate exceeded the allowable limit of a 2 GPM increase in unidentified leakage in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period per Technical Specification 3.4.4. At 1555 [CDT] on 06/11/2009, Unit 2 inserted a manual reactor SCRAM to comply with Technical Specification 3.4.4 Condition C to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
All systems responded as required except that when reset of the SCRAM was attempted after all control rods had inserted, a portion of the 'B' RPS channel (B2/B3) failed to reset. The 'A' RPS channel was then actuated by a spike on the Intermediate Range Monitors while they were being driven into the core resulting in a full RPS SCRAM actuation. The licensee notified the NRC Resident Inspector." Unit 2 is currently removing decay heat using normal feedwater with bypass steam to the main condenser. The electrical system is in a normal shutdown configuration. The licensee has not identified the source of the unidentified leakage and anticipates taking Unit 2 to Cold Shutdown (Mode 4).
Plant personnel entered the drywell after the reactor was shutdown. The resulting investigation revealed two sources of increased drywell leakage. One source of leakage was from 2-CKV-10-511 and 2-CKV-10-526, SRV Tailpipe Vacuum Breakers, which were apparently damaged by leakage past the pilot valve for 2-PCV-001-0023, Main Steam Safety Relief Valve. The combination of damaged vacuum breakers and a leaking pilot valve resulted in steam leakage into the drywell atmosphere. The other source of leakage was noted through the packing for 2-DRV-10-505, RPV Drain to RWCU. The vacuum breakers, pilot valve, and drain valve have been repaired. The 'B' RPS contactors were repaired and the scram reset. The NRC Resident Inspector has been notified." R2DO (McCoy) notified. |
| Where | |
|---|---|
Browns Ferry  Alabama (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-2.52 h-0.105 days <br />-0.015 weeks <br />-0.00345 months <br />) | |
| Opened: | Tim Taylor 18:24 Jun 11, 2009 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Jun 15, 2009 |
| 45124 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | Yes, Manual Scram |
| Before | Power Operation (12 %) |
| After | Hot Shutdown (0 %) |
WEEKMONTHYEARENS 536782018-10-21T05:00:00021 October 2018 05:00:00
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