ENS 46713
ENS Event | |
|---|---|
20:42 Mar 30, 2011 | |
| Title | Technical Specification Required Shutdown Initiated |
| Event Description | On March 30, 2011 at 1443 CDT, during a refueling outage, Browns Ferry Unit 2 received an invalid Common Accident Signal (CAS) as a result of maintenance activities. All four Unit 1/2 diesel [generators] auto started and all four Unit 3 diesel [generators] auto started. Unit 2 received a full Reactor SCRAM and Core Spray pumps A, B, C, and D auto started and injected into the reactor. Unit 2 Division I RHR [Residual Heat Removal] system was in Shutdown Cooling with only the C pump in service. The A RHR pump auto started and Shutdown Cooling flow increased, as expected. Unit 2 Division II RHR system was tagged out for maintenance. HPCI [High Pressure Coolant Injection] and RCIC [Reactor Core Isolation Cooling] received auto initiation signals, however the steam isolation valves were tagged closed and the systems did not start. MSIVs [Main Steam Isolation Valves] isolated as a result of the CAS signal.
Unit 1 was at 100% power when the CAS on Unit 2 occurred. This caused initiation of the Preferred Pump Logic which designates Division I CS [Core Spray] and LPCI [Low Pressure Coolant Injection] pumps on Unit 1 (1A and 1C) and the Division II pumps on Unit 2 (2B and 2D) and prevents Unit 1 Division II pumps from auto starting. This resulted in the Division II RHR and CS pumps [being] inoperable for Unit 1. Unit 1 subsequently entered Technical Specification 3.5.1, Condition H (two or more low pressure ECCS [Emergency Core Cooling System] injection/spray subsystems inoperable) which requires entering LCO 3.0.3 immediately. Unit 1 entered LCO 3.0.3 at 1443, which requires that actions shall be initiated within one hour to place the unit in Mode 2 within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />; Mode 3 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />; and Mode 4 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. At 1542 Unit 1 began lowering power in order to comply with LCO 3.0.3. CAS logic was reset at 1812 and Unit 1 exited LCOs 3.5.1.H and 3.0.3. This condition requires a four hour report in accordance with 50.72(b)(2)(i) - 'The initiation of any nuclear plant shutdown required by the plant's Technical Specifications.' The NRC Resident Inspector was notified. Service Request #346544 was initiated in the Corrective Action Program. |
| Where | |
|---|---|
Browns Ferry  Alabama (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-0.75 h-0.0313 days <br />-0.00446 weeks <br />-0.00103 months <br />) | |
| Opened: | Ray Swafford 19:57 Mar 30, 2011 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Mar 30, 2011 |
| 46713 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 536782018-10-21T05:00:00021 October 2018 05:00:00
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