Event Notification Report for November 23, 2012

INADVERTENT LOSS OF INSTRUMENT AIR

"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."

PRIMARY CONTAINMENT ISOLATION ACTUATION SIGNAL DURING SURVEILLANCE

"This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting multiple Main Steam Isolation Valves (MSIVs).

"On November 23, 2012 at 0435 Central Standard Time, during performance of Surveillance Instruction 1-SI-3.3.1.A, ASME Section XI System Leakage Test of the Reactor Pressure Vessel and Associated Piping, as the Residual Heat Removal Loop II Shutdown Cooling was being placed in service, Group 1, Division II Primary Containment Isolation System (PCIS) logic groups A2 and B2 actuated resulting in an unanticipated Division II, Group 1 Complete Isolation and subsequent Inboard MSIV closure. The Outboard MSIVs had been previously tagged closed.

"Plant conditions which initiate Group 1 actuations are Reactor Vessel Low-Low-Low Water Level, Main Steamline Break, and Low Main Steamline Pressure at the Inlet to the Turbine. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid.

"The affected equipment responded as designed.

"This condition was the result of the reactor vessel water level being within two inches of the reactor head vent when Shutdown Cooling was placed into service, causing pressure perturbations. When these perturbations occurred, they gave an indication of low water level, causing the isolation and MSIV closure.

"There were no safety consequences or impact to the health and safety of the public as a result of this event.

"This event was entered into the [Browns Ferry Nuclear Plant] Corrective Action Program as Problem Evaluation Report 646607.

"The NRC Resident Inspector has been notified."