Event Notification Report for August 27, 2011

UNUSUAL EVENT DECLARED DUE TO ENTRY INTO EAL HU 4-1

The licensee declared a Notice of Unusual Event per emergency plan condition HU 4-1 due to a security event. Contact the Headquarters Operations Officer for details.

The licensee notified the NRC Resident Inspector.

* * * UPDATE FROM DANNY BRADFORD TO PETE SNYDER AT 0410 EDT ON 8/27/11 * * *

The Notice of Unusual Event has been terminated. Contact the Headquarters Operations Officer for details.

Notified: R4DO (Haire), NRR (Bahadur), DHS (Knox), FEMA (Blankenship).

EMERGENCY SIRENS OUT-OF-SERVICE

"Sirens in St. Mary's and Calvert counties are out of service exceeding the minimum required of 19. Currently 44 sirens are out of service due to local power outages caused by the storm. Compensatory measures are in place for the affected counties. Route alerting will be used if necessary."

The licensee notified the NRC Resident Inspector.

* * * UPDATE AT 1730 EDT ON 09/02/11 FROM TOM JONES TO S. SANDIN * * *

As of 1655 EDT on 9/2/11, all 72 emergency sirens have been returned to service.

The licensee informed the NRC Resident Inspector. Notified R1DO (DiPaolo).

UNUSUAL EVENT - TRANSFORMER EXPLOSION NEAR TURBINE BUILDING

"At 2248 on 8/27/2011, the Unit 1 Reactor experienced an automatic trip due to loss of load. This trip occurred due to a phase to phase short on the main generator output step-up transformer that resulted from a large section of turbine building siding breaking loose in high winds from Hurricane Irene and impacting the transformer. This impact resulted in an explosion (briefly until the trip removed power from the impact area) which met emergency action level declaration criteria A.U.6.2.2, 'Unanticipated explosion within Protected Area resulting in visible damage to permanent structures or equipment.' The Unusual Event was declared at 2302, 8/27/2011. Follow-up investigation determined no fire resulted from the explosion.

"Following the trip, Emergency Procedure, EOP-0, 'Post Trip Immediate Actions' was implemented. All safety functions were met during EOP-0 indicating an uncomplicated reactor trip response, allowing transition to EOP-1, 'Reactor Trip,' at 2300, 8/27/2011. During implementation of EOP-1, it was noted that #14 Containment Air Cooler had stopped running, as had #21 and #24 Containment Air Coolers on Unit 2. This was investigated and it was determined they had stopped running due to an instantaneous voltage drop that had occurred on the site distribution system during the phase to phase short event. This short duration voltage drop caused the Containment Air Coolers' controller to drop out and secure them. They were restarted without issue.

"At 2400, 8/27/2011, numerous alarms on the 1A DG started to be received. These were investigated and it was found that water was intruding down the DG exhaust piping resulting in a DC ground. Based on these indications the 1A DG was declared inoperable and appropriate technical specifications implemented.

"Besides the above issues plant response was as expected and EOP-1 was exited at 0130, 8/28/2011. [Procedure] OP-4, 'Shutdown from Power Operation to Hot Standby,' was implemented at that time.

All control rods fully inserted on the reactor trip. The plant is in a normal post-trip electrical lineup.

The licensee notified the NRC Resident Inspector.


* * * UPDATE FROM GREGG BUCKMASTER TO PETE SNYDER AT 0811 EDT ON 8/28/11 * * *

At 0755 EDT the licensee exited the Unusual Event condition based on the fact that they were able to inspect the area in the daylight and were satisfied that they knew the extent and nature of the damage.

The licensee will notify the NRC Resident Inspector. Notified R1 IRC (Dentel), DHS (Hill), FEMA (Via).

SHUTDOWN COOLING TEMPORARILY ISOLATED

"In accordance with 10 CFR 50.72 (b)(3)(v)(B) this event notification is being made to report an event that could have prevented the fulfillment of the safety function to remove residual heat. On August 27, 2011, following refueling, the plant was shutdown in Mode 4 with reactor coolant temperature being maintained 100-120 degrees F. Reactor coolant temperature was being controlled with RHR B operating in the Shutdown Cooling mode. At 2021 [EDT], an equipment failure caused a loss of Reactor Protection System (RPS) B resulting in a closure of RHR-V-9 (RHR Shutdown Cooling Inboard Isolation Valve), interrupting shutdown cooling flow. Operators transferred RPS B to the alternate power supply and restored RHR B to shutdown cooling. Shutdown cooling was out of service for 34 minutes.

"During the 34 minute interruption of shutdown cooling, reactor coolant temperature rose from 107 degrees F to 111 degrees F. Following restoration of shutdown cooling, reactor coolant temperature was restored. All containment isolations resulting from the loss of RPS B occurred as expected. Further investigation is ongoing to determine the cause of the equipment failure that caused the loss of RPS B."

The licensee notified the NRC Resident Inspector.

INVALID AUTOMATIC ACTUATION OF AN EMERGENCY DIESEL GENERATOR

"At 2130 [EDT] on August 27, 2011, an automatic actuation of the Unit 1 Train A emergency diesel generator occurred due to an actuation signal from the load sequencer. The Train A 4160 kV emergency bus transferred to the emergency diesel generator and all Train A emergency loads required for Mode 2 started and sequenced onto the Train A 4160 KV emergency bus except the 480 volt center breaker to the bus E1A2 that did not close. The load sequencer is designed upon the receipt of a safety injection actuation and/or loss of offsite power to provide a signal to strip loads from the 4160 kV emergency bus and then, in sequence, to re-energize the associated 480 volt buses and to load engineering safety feature components onto the 4160 kV and associated 480 volt emergency buses in a predetermined sequence. Per 10 CFR 50.72(b)(3)(iv)(B), additional emergency safety features loads that actuated were the Train A reactor containment fan coolers and auxiliary feedwater system.

"Unit 1 remains critical at 100 percent power. No emergency core cooling system injection occurred into the reactor coolant system.

"The event occurred during surveillance testing when the Train A sequencer was taken from the AUTO Test position to the local position. It is not understood why the actuation occurred. In addition, it is not understood why the 480 volt load center breaker to the bus E1A2 did not close.

"The 480 volt bus E1A2 was re-energized at 2308 [EDT] on August 27, 2011. The Train A 4160 kV bus was restored to the offsite power source at 0150 [EDT] on August 28, 2011 and the Train A emergency diesel generator and engineering safety features loads were restored to their normal condition at 0201 [EDT] on August 28, 2011.

"With the Train A sequencer non-functional, the following Train A components are inoperable: 1) High Head Safety Injection Pump 1A; 2) Low Head Safety Injection Pump 1A; 3) Containment Spray Pump 1A; 4) RCFC [Reactor Containment Fan Cooler] Fan 11A; 5) RCFC Fan 12A; 6) Component Cooling Water Pump 1A; 7) Essential Cooling Water Pump 1A; 8) Aux Feedwater Pump 11; 9) Control Room/Elect. Aux Bldg HVAC; 10) Ess [Essential] Chiller 12A; and 11) ESF Diesel Generator 11.

"Although these components will not automatically start on a safety injection signal or loss of offsite power, these loads can be manually actuated. Engineered Safety Features Trains B and C remain operable."

The licensee notified the NRC Resident Inspector.

* * * UPDATE ON 10/13/11 AT 1221 EDT FROM MORRIS TO HUFFMAN * * *

The licensee is updating this event report to retract the originally reported valid specified system actuation and report it instead as a 60-day invalid specified system actuation report made by telephone:

"This update is a 60-day telephone notification in lieu of a written licensee event report being made under 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1).

"This event was originally reported per 50.72(b)(3)(iv)(A) as a valid actuation of the Unit 1 Train A emergency diesel generator and sequencing of Mode II (Loss of Offsite Power) emergency loads. The actuation occurred during surveillance testing when the Train A load sequencer was taken from the AUTO test position to the local position. Subsequent investigation has determined that the actuation occurred due to a faulty integrated chip within the sequencer's load sequence auto test module, and was not due to sensed or simulated plant conditions that would require a Mode II actuation. Unit 1 was at 100% power and no loss of offsite power occurred.

"The Train A equipment response to this invalid actuation is described in the original notification information provided on 08/28/2011.

"Additionally, the 10CFR50.72 Notification originally reported under Event Number 47210 is being retracted, since the actuation has been determined to be not valid."

The licensee will notify the NRC Resident Inspector. R4DO (Whitten) notified.