ENS 50573
ENS Event | |
|---|---|
11:11 Oct 29, 2014 | |
| Title | Loss of Control Room Emergency Air Conditioning System Operability |
| Event Description | At 0711 EDT, Salem Unit 2 entered TSAS [Technical Specification Action Statement] 3.0.3 due to the Salem Unit 1 - 1B Vital instrument bus inverter failing which resulted in a loss of the Unit 1 - 1B Vital instrument bus. The loss of power to the 1B Vital instrument bus resulted in Salem Unit 2 initiating the accident pressurized mode of control room ventilation. All dampers and fans repositioned correctly with the exception of the Unit 1 Control Room Emergency Air Conditioning System (CREACS) intake dampers, 1CAA48, 50, and 51. The 1CAA48 was pinned closed to support Unit 1 - 1A125VDC scheduled maintenance. The 1CAA50 and 51 failed to move to the open position (required for Unit 2 accident pressurized mode) due to the loss of power to the 1B Vital Instrument Bus. With the 1CAA48, 50 and 51 dampers closed, this isolated the Unit 1 CREACS intake in the closed position. For an accident in Unit 2, the CREACS intake for Unit 1 is required to open.
Salem Unit 2 exited TSAS 3.0.3 at 0822 EDT when the 1CAA50 and 51 were pinned in the open position to implement accident pressurized mode for Salem Unit 2 in accordance with S1/S2.OP-SO.CAV-0001, Control Area Ventilation Operation. Salem Unit One is Defueled. This event is being reported under the requirements of 10 CFR 50.72(b)(3)(v)(D) as 'Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of systems that are needed to perform mitigation of the consequences of an accident.' The licensee has notified the NRC Resident Inspector. No one was injured as a result of the failure of 1B Vital instrument inverter. The licensee notified Lower Alloways Township.
A subsequent review of the condition reported on 10/29/2014 in EN 50573 determined that the Control Room Emergency Air Conditioning System (CREACS) was operable and capable of performing its safety function. Therefore, there was no reportable condition. Circuit analysis identified that the Unit 2 Control Room Intake Isolation (CRIX) Train B circuit remained fully functional and able to respond to a Unit 2 Safety Injection (SI) signal or actuation from radiation monitor 2R1B Channel 1 (radiation levels in the Unit 2 normal Control Area Ventilation intake). The loss of the 1B vital instrument bus did not affect the normal actuation circuitry. The appropriate Unit 1 dampers would have received an open signal and the appropriate Unit 2 dampers would have received a closed signal, thereby isolating the Unit 2 CREACS intake and opening the Unit 1 CREACS intake. Thus, the CREACS would have been capable of mitigating the consequences of an accident. The NRC Resident Inspector has been notified. Notified R1DO (Ferdas). |
| Where | |
|---|---|
Salem  New Jersey (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.72 h0.113 days <br />0.0162 weeks <br />0.00373 months <br />) | |
| Opened: | William Muffley 13:54 Oct 29, 2014 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Dec 22, 2014 |
| 50573 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (98 %) |
| After | Power Operation (98 %) |