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Event Notification Report for April 13, 2011

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
04/12/2011 - 04/13/2011

** EVENT NUMBERS **


46747 46748

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Power Reactor Event Number: 46747
Facility: FORT CALHOUN
Region: 4 State: NE
Unit: [1] [ ] [ ]
RX Type: (1) CE
NRC Notified By: ERICK MATZKE
HQ OPS Officer: JOE O'HARA
Notification Date: 04/12/2011
Notification Time: 14:34 [ET]
Event Date: 04/12/2011
Event Time: 09:15 [CDT]
Last Update Date: 04/12/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(D) - ACCIDENT MITIGATION
Person (Organization):
GEOFFREY MILLER (R4DO)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N N 0 Cold Shutdown 0 Cold Shutdown

Event Text

UNSEALED FLOOD BARRIER PENETRATION

"During investigations of flood barrier penetrations, a flood barrier sealing a diesel driven fire pump exhaust was found to be cracked. This exhaust pipe penetrates the west wall of the intake structure. Flooding through the penetration could have impacted the ability of the station's raw water pumps to perform their design accident mitigation functions.

"This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v).

"The penetration is at an approximate elevation of 1012 feet mean sea level (MSL). The river level has been less than 997 feet MSL since prior to December 1, 2010. The raw pumps are operable. There are not any indications of conditions that might result in a flood. Actions are in progress to plug the penetration."

The NRC Resident Inspector has been notified.

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Power Reactor Event Number: 46748
Facility: COMANCHE PEAK
Region: 4 State: TX
Unit: [ ] [2] [ ]
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: ED LESSMANN
HQ OPS Officer: BILL HUFFMAN
Notification Date: 04/13/2011
Notification Time: 01:57 [ET]
Event Date: 04/12/2011
Event Time: 22:15 [CDT]
Last Update Date: 04/13/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Person (Organization):
GEOFFREY MILLER (R4DO)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
2 N N 0 Refueling 0 Refueling

Event Text

ESF ACTUATION FOLLOWING LOSS OF A SAFEGUARD BUS DURING EDG TESTING

The following event occurred with the unit in a "No Mode" defueled condition.

"On the 12th of April at 2215 (Central Time) Comanche Peak Nuclear Power Plant Unit 2 had a Train B ESF Actuation (Black Out) reportable per 10CFR50.72(b)(3)(iv) for [the 6.9KV Train B] Emergency AC Electrical power systems including Emergency Diesel Generator (EDG).

"At the time of the event, Unit 2 was in 'No Mode' - the core was off loaded and post maintenance testing was being performed on the 2-02 Emergency Diesel Generator. The scope of the EDG testing was to verify proper operation of the EDG when it was the sole supply to the Unit 2 Train B 6.9KV safeguards buses. Unit 2 Train B 6.9 KV buses have 3 AC sources - XST1 (138KV) preferred source, XST2 (345KV) alternate source and the 2-02 Emergency Diesel Generator.

"The 2-02 EDG was started normally and was operating in parallel with XST1 (preferred AC source) just before the event. The event was triggered when the preferred AC supply breaker to the Train B 6.9KV Safeguard bus was opened per plan. The opening of the preferred feeder breaker resulted in the 2-02 EDG being the sole AC source to the Train B 6.9KV bus. Immediately following this breaker operation, the EDG tripped on an Auto Voltage Regulator failure. This caused the Train B 6.9KV safeguard bus to de-energize which resulted in the automatic closure of the alternate AC (XST2) feeder breaker. This in turn triggered the Train B Solid State Sequencer to sequence on Train B Black Out loads - as designed.

"The Train B Black Out Solid State Sequencer operated as designed. No abnormalities were noted. All available equipment operated as designed.

"The 2-02 EDG is currently tagged out and the problem associated with the [Auto Voltage Regulator] failure is being investigated.

"[The] Resident NRC Inspector has been informed and is currently located on site."

No fuel movement was in progress during this event. Train A safeguard power was unaffected and available throughout. Non-safety related power was also not affected. The only operational impact was the loss of a Train B spent fuel pool cooling pump for approximately 10 minutes. The spent fuel pool temperature increased approximately 1/2 degree during before cooling was restored.

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