Event Notification Report for April 07, 2011

UNUSUAL EVENT DECLARED DUE TO HYDROGEN BURN DURING MAINTENANCE

"[The licensee declared an Unusual Event at 1607 PDT due to a small hydrogen burn when opening the stator cooling water system for maintenance. There were no injuries or equipment damage."

The licensee entered EAL 93U3 'Toxic Gases inside the Protected Area Boundary.'

The licensee notified state/local agencies and will inform the NRC Resident Inspector. The licensee plans to issue a press release.

* * * UPDATE FROM MATT HUMMER TO DONG PARK AT 0003 EDT ON 04/08/11 * * *

"[At 2053 PDT,] Columbia has terminated the Unusual Event declared at 1607 [PDT] on 04/07/11. Conditions throughout the plant have remained stable. Columbia has confirmed there is no hazard to personnel safety nor a challenge to safe plant operation."

The licensee will notify the NRC Resident Inspector.

Notified R4DO (OKeefe), NRR EO (Blount), IRD (Grant), DHS (Jenkins), and FEMA (O'Connell).

* * * UPDATE FROM MATT HUMMER TO JOE O'HARA AT 2318 ON 4/8/11 * * *

"At 1922 EDT on April 7, 2011, NRC was notified of an Unusual Event at Columbia Generating Station (EN#46739), The NRC was notified the event was terminated at 2353 EDT on April 7, 2011.

"Based on further investigation, this event is being retracted.

"The stator cooling water system contains a mixture of water and hydrogen when in operation. The system had been removed from service, drained and blanketed with nitrogen prior to commencing maintenance. There was no active source of hydrogen in the system. Although the system had been tested for hydrogen and none was detected, the event occurred when workers cut into a section of the system piping where a small amount of residual hydrogen remained.

"Immediately following the event, tape was placed over the cut to prevent any debris from entering the pipe. Hydrogen measurements were taken in the vicinity of the cut section of pipe and in the general area and concentrations were below hazardous levels. The only elevated reading occurred directly at the cut location when the tape was removed, This indicated that hydrogen, residual in nature, was confined to the inside of the pipe. Since the system was not in use and the residual hydrogen was confined, plant operations were not affected,

"As a result of this event, no personnel were injured, no equipment was damaged, and there was no impact to structures needed for plant operation.

"The licensee will notify the NRC Resident Inspector, the media, and local, state, and other government agencies of this update."

Notified R4DO(O'Keefe)

LOSS OF THE CONTROL ROOM EMERGENCY VENTILATION SYSTEM

"At approximately 1740 hours on April 7, 2011, a loss of the Control Room Emergency Ventilation (CREV) system occurred. At the time of the event, the plant was performing 0MST-DG13R. 'DG-3 Loading Test.' During performance of this test, the 480 VAC Emergency Bus E-7 main feeder breaker tripped unexpectedly. As a result, the CREV emergency makeup damper 2-VA-2J-D-CB closed on this loss of power, resulting in two CREV subsystems required by TS 3.7.3, 'CREV System,' being inoperable. As a result, this condition could have prevented the fulfillment of the safety function for this system. Brunswick has a shared control room, but only Unit 1 was required to enter TS 3.7.3 Required Action C.1. for two CREV subsystems inoperable (i.e., be in Mode 3 within 12 hours). Unit 2 was operating in Mode 4 for a scheduled refueling outage and did not meet any applicability conditions for TS 3.7.3.

"Operability of the CREV subsystems was restored and the related LCO was exited at 1931 hours following the restoration of CREV damper 2-VA-2J-D-CB. Investigation of the E-7 bus trip is ongoing. This report 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 the 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 1 hour and 51 minutes. Plant staff took immediate action to return the equipment to service. For the brief time the CREV systems were inoperable, performance of plant personnel and equipment in the Control Room was not adversely affected."

The licensee notified the NRC Resident Inspector.

DEFECT IN ROTORK'S 30NA1 MOTOR COVER CASTING

A manufacturing defect was discovered in Rotork's 30NA1 motor cover casting part number 4748. When stroking the valve, the motor cover supports the loads developed from the stator torque and the rotor thrust reactions. The failure occurred at the rotor end bearing support. Investigation has shown that the casting was not manufactured to the drawing specification.

The manufacturer is searching their spares database to determine where it has supplied the motors and will inform the utilities once this list is complete.

AGREEMENT STATE REPORT - FIXED GAUGE SHUTTER FAILURE

The following report was received from the State of Texas via email:

"On July 19, 2011, the Agency [Texas Department of Health] received a call from the licensee's Radiation Safety Officer reporting that during a routine inspection on April 7, 2011, the shutter handle on an Ohmart/Vega Gauge model SHLG-1 broke off. The gauge serial number is 0678GK and contains 300 mCi of Cs-137. The gauge failed in the normally open position. The gauge was subject to condensation from a steam leak from above which caused the handle to rust. A vendor shut the gauge shutter on June 30, 2011. The gauge will be removed for disposal since the tank is no longer used. The failure did not create any additional exposure to any individual. Additional information will be provided as it is received in accordance with SA-300."

Texas Incident No.: I-8872