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| Entered date | Event description | |
|---|---|---|
| ENS 47493 | 1 December 2011 16:05:00 | At 1344 hours (EST) on December 1, 2011, the Control Building Instrument Air Dryer failed resulting in loss of control air. As a result, the three Control Room Air Conditioning subsystems required by Technical Specification (TS) 3.7.4, 'Control Room Air Conditioning (AC) System,' and the two Control Room Emergency Ventilation (CREV) subsystems required by TS 3.7.3, 'Control Room Emergency Ventilation (CREV) System,' became inoperable. As a result, this condition could have prevented the fulfillment of the safety function for these systems. Because Brunswick has a shared control room, Unit 1 and Unit 2 entered TS 3.7.3 Required Action C.1, for two CREV subsystems inoperable (i.e., be in Mode 3 within 12 hours) and TS 3.7.4, Required Action E.1, for three Control Room AC subsystems inoperable (i.e., enter LCO 3.0.3 immediately). Operability of two Control Room AC subsystems and one CREV subsystem was restored and LCO 3.0.3 was exited, at 1410 hours, when the Instrument Air Dryer was bypassed. No power reduction took place as a result of the LCO 3.0.3 entry. This report applies to both Units 1 and 2 and is being made in accordance with 10 CFR 50.72(b)(3)(v)(D), as a condition that at the time of discovery could have prevented fulfillment of the safety function of systems that are needed to mitigate the consequences of an accident. The safety significance of this event is considered minimal. The condition existed for approximately 26 minutes. Plant staff took immediate actions to return the equipment to service. For the brief time the Control Room AC and CREV systems were inoperable, performance of plant personnel and equipment in the Control Room was not adversely affected. The maximum Control Room back panel temperature during this event was approximately 68 degrees F. Troubleshooting activities are under way to determine the cause of the Instrument Air Dryer failure. The licensee notified the NRC Resident Inspector. |