ENS 48533
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ENS Event | |
|---|---|
02:08 Nov 24, 2012 | |
| Title | Inadvertent Loss of Instrument Air |
| Event Description | On 11/23/2012 at approximately 1956 CST, it was reported that the Control Room (VC) B Chiller breaker was cycling open and closed. In order to stop the cycling, Control Building Unit Sub B was manually tripped causing the following isolations/actuations: loss of power to instrument air (IA) system containment isolation valves causing the Division 2 valves to isolate; loss of power to the low pressure switch that resulted in an automatic start of Division 2 Shutdown Service Water (SX) system; and loss of power to fuel building (VF) system ventilation Division 2 dampers resulting in a trip of the VF system. High Pressure Core Spray (HPCS) became inoperable based on inoperability of the room cooler for the associated Division 4 inverter and battery charger. Operations entered the Loss of AC Power and Automatic Isolation off-normal procedures. Following the loss of power to the VF system ventilation, at 2008, secondary containment differential pressure became positive. At 2009, power was restored to Control Building Unit Sub B and HPCS was restored to operable. At 2011, the standby gas treatment system (VG) was started and at 2013, secondary containment differential pressure was restored. Following re-energization of Unit Sub B, the IA containment isolation valves were re-opened, VG was secured, VF restarted and the Division 2 SX pump was secured.
The loss of secondary containment differential pressure is reportable under 10 CFR 50.72(b)(3)(v)(C) as an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material An unplanned inoperability of HPCS reportable under 10 CFR 50.72(b)(3)(v)(D) as HPCS is a single train safety system The cause of the breaker cycling is unknown at this time. The NRC Resident has been informed. |
| Where | |
|---|---|
Clinton  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.17 h0.0488 days <br />0.00696 weeks <br />0.0016 months <br />) | |
| Opened: | David Wells 03:18 Nov 24, 2012 |
| NRC Officer: | Charles Teal |
| Last Updated: | Nov 24, 2012 |
| 48533 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (97 %) |
| After | Power Operation (97 %) |
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