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Event Notification Report for June 2, 2006

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
06/01/2006 - 06/02/2006

** EVENT NUMBERS **


42479 42512 42610 42613

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!!!!! THIS EVENT HAS BEEN RETRACTED. THIS EVENT HAS BEEN RETRACTED !!!!!
Power Reactor Event Number: 42479
Facility: DUANE ARNOLD
Region: 3 State: IA
Unit: [1] [ ] [ ]
RX Type: [1] GE-4
NRC Notified By: W. BENTLEY
HQ OPS Officer: JOHN MacKINNON
Notification Date: 04/05/2006
Notification Time: 21:23 [ET]
Event Date: 04/05/2006
Event Time: 18:55 [CDT]
Last Update Date: 06/01/2006
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
Person (Organization):
ANNE MARIE STONE (R3)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N Y 96 Power Operation 96 Power Operation

Event Text

ABNORMAL OPERATING PROCEDURE (AOP) FOR STATION BLACKOUT COULD NOT BE PERFORMED IN SPECIFIED TIME PERIOD


"DAEC (Duane Arnold Energy Center) abnormal operating procedure AOP 301.1 for Station Blackout specifies that 30 minutes are allowed to establish alternate ventilation for RCIC (Reactor Core Isolation Cooling) /HPCI (High Pressure Coolant Injection) rooms, switchgear rooms, battery rooms, and the Main control room. During validation demonstration conducted on April 5, 2006 for the NRC Components team (from NRC Region 3 Office) the 30 minutes requirement was not met with the control room alternate ventilation taking about 60 minutes and with the other areas also exceeding their time requirements. This event is reportable as an unanalyzed condition that significantly degraded plant safety pursuant to 10 CFR 50.72(b)(3)(ii) reportability notification."

The NRC Resident Inspector was notified of this event by the licensee.

* * * RETRACTION FROM MURRELL TO HUFFMAN AT 1442 EDT ON 6/01/06 * * *

"Duane Arnold Energy Center is retracting event number 42479 which was reported to the NRC Operations Center on 4/5/06 at 1855. This event is now determined to be not reportable because further evaluation to assess the significance of the delays in establishing alternate control room ventilation determined that the delay did not result in an adverse temperature increase in the affected areas. Specifically, the control room and back panel area temperature rise was evaluated using a detailed mass and heat transfer model of the affected areas. The evaluation confirmed that delays in establishing alternate control room ventilation did not adversely impact station commitments to 10 CFR 50.63 or accident responses outlined in UFSAR Section 15.3.2. Other areas required to have alternate ventilation established within 30 minutes had previously been successfully validated. Therefore, this event is not reportable as an unanalyzed condition that significantly degraded plant safety. The analyses and the bases for this retraction can be found under the plant corrective action program."

The licensee notified the NRC Resident Inspector. R3DO (Kozak) notified.

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!!!!! THIS EVENT HAS BEEN RETRACTED. THIS EVENT HAS BEEN RETRACTED !!!!!
Power Reactor Event Number: 42512
Facility: FT CALHOUN
Region: 4 State: NE
Unit: [1] [ ] [ ]
RX Type: [1] CE
NRC Notified By: ERICK MATZKE
HQ OPS Officer: BILL HUFFMAN
Notification Date: 04/19/2006
Notification Time: 15:58 [ET]
Event Date: 04/19/2006
Event Time: 09:45 [CDT]
Last Update Date: 06/01/2006
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL
50.72(b)(3)(v)(D) - ACCIDENT MITIGATION
Person (Organization):
KRISS KENNEDY (R4)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N Y 100 Power Operation 100 Power Operation

Event Text

POSTULATED SCENARIO WHERE CONTAINMENT SPRAY SYSTEM MAY BE UNABLE TO FULFILL DESIGN SAFETY FUNCTION

"During a review of the operation of the plants emergency cooling system for the containment an unanalyzed single failure was discovered. The identified single failure scenario could result in the containment spray system being unable to fulfill its design safety functions.

"In the event of loss of offsite power occurring after the initiation of an accident signal, the 480V undervoltage relays serve to trip open containment spray pump breakers (as well as other ESF breakers) in order to prepare the breakers for resequencing after the diesel generator output breakers have closed onto their associated buses. The undervoltage trip bypass function performed by the sequencer timer relay contacts serves to prevent tripping ESF breakers due to inadvertent actuation of the undervoltage trip circuits and allows ESF breakers to trip only when sequencers have been reset by a loss of voltage at the 4160V bus level.

"In situations where a loss of power occurs at the 480 volt level without a coincident loss of power at the associated 4160 volt level, ESF loads supplied from the lost 480 volt bus, such as containment spray pumps, do not receive a trip signal due to the undervoltage blocking feature of the sequencing relays. For most ESF loads, this is not a problem and can be considered part of a single failure scenario affecting only one train of ESF equipment. In the case of containment spray pumps SI-3B and SI-3C, however, the failure of the associated breakers to trip during a single failure of bus 1B4B, results in the operation of a single spray pump, SI-3A with two containment spray valves open. This results in one pump operation to two containment spray headers.

"Operating the containment spray system in a one pump, two header configuration creates the possibility of inadequate system performance. This configuration may result in overloading the running pump (due to runout) and inadequate NPSH to the running pump. This condition was intended to be prevented by a modification which installed an interlock between spray pumps SI-3B and SI-3C and spray valve HCV-344. The modification apparently failed to consider the single failure of specific 480 Volt buses.

"Spray valve HCV-344 has been disabled in the closed position so that no external signals will allow the valve to be opened. Disabling this valve places the plant in a 24 hour LCO (Technical Specification 2.4.2.d) starting at 0950 CDT."

The licensee notified the NRC Resident Inspector.

* * * RETRACTION FROM MATZKE TO HUFFMAN AT 1439 EDT ON 6/01/06 * * *

"On April 19, 2006, Ft. Calhoun station reported that an unacceptable single failure scenario had been identified that could result in the containment spray system being unable to fulfill its design safety functions. The failure scenario required that there be a loss of power at the 480 volt AC level without a coincident loss of power at the associated 4160 volt AC level. This resulted in the potential for one pump operation to two containment spray headers.

"Following a review of failures that would cause this it was determined that of all the possible failure mechanisms that could impact the capability of affected 480 volt AC bus, such that both trains of containment spray pump could be adversely affected, the only failure mechanism that has unacceptable consequences is a failure of multiple phases of AC power failing in an open circuited manner without a fault occurring and, consequently, without supply breakers opening. This failure mechanism has been determined not to be credible. Therefore, it is not necessary to assume that this type of failure could occur as part of a design basis event. Therefore, no credible single failure could result in the failure of the containment spray system to perform its intended safety function. The report of April 19, 2006 is being retracted June 1, 2006."

The licensee notified the NRC Resident Inspector. R4DO (Spitzberg) notified.

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Power Reactor Event Number: 42610
Facility: WATTS BAR
Region: 2 State: TN
Unit: [1] [ ] [ ]
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: DANA WHITE
HQ OPS Officer: MARK ABRAMOVITZ
Notification Date: 05/30/2006
Notification Time: 20:02 [ET]
Event Date: 05/30/2006
Event Time: 17:00 [EDT]
Last Update Date: 06/02/2006
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
50.72(b)(3)(iv)(A) - VALID SPECIF SYS ACTUATION
Person (Organization):
CHARLIE PAYNE (R2)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 M/R Y 100 Power Operation 0 Hot Standby

Event Text

MANUAL REACTOR TRIP ON HIGH TURBINE VIBRATION

"At approximately 1700 hours on May 30, 2006, with Watts Bar Nuclear Plant Unit 1 operating normally at 100% power, main turbine vibration increased to a value above the procedure limit and reactor operators manually tripped the reactor in accordance with site procedure requirements. All control rods inserted and the auxiliary feedwater system automatically actuated per design. No other significant equipment issues were identified and the reactor was stabilized in mode 3.

"This event is reportable under 10 CFR 50.72(b)(2)(iv)(B) for the manual reactor trip (4-hour report) and under 10 CFR 50.72(b)(3)(iv)(A) for the RPS and AFW actuations (8-hour report).

"Watts Bar had been monitoring indications of slightly elevated turbine vibration on the main turbine, but the reason for the increase above the procedure limit of 14 mils is not known at this time. TVA will be investigating the cause of the increased vibration to make necessary repairs before turbine startup."

Decay heat is being removed by dumping steam to the main condenser. No safety or relief valves lifted.

The licensee notified the NRC Resident Inspector.

* * * UPDATE FROM LICENSEE (R. CREWS) TO M. RIPLEY 0020 EDT 06/02/06 * * *

"As a result of the initial assessment of the turbine vibration discussed above, TVA has identified damage to the turbine end of the 'C' low pressure turbine. This is consistent with the initial indications of high vibration on the number 7, 8 and 9 bearings and not thought to be associated with previous condition monitoring of the number 11 bearing. Assessment and repair of secondary plant components damaged in the transient are in progress."

The licensee will notify the NRC Resident Inspector. Notified R2DO (C. Ogle)

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Power Reactor Event Number: 42613
Facility: HATCH
Region: 2 State: GA
Unit: [1] [2] [ ]
RX Type: [1] GE-4,[2] GE-4
NRC Notified By: PAUL UNDERWOOD
HQ OPS Officer: BILL HUFFMAN
Notification Date: 06/01/2006
Notification Time: 12:33 [ET]
Event Date: 06/01/2006
Event Time: 09:43 [EDT]
Last Update Date: 06/01/2006
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(xiii) - LOSS COMM/ASMT/RESPONSE
Person (Organization):
CHARLES R. OGLE (R2)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N Y 100 Power Operation 100 Power Operation
2 N Y 100 Power Operation 100 Power Operation

Event Text

TECHNICAL SUPPORT CENTER HVAC INOPERABLE

"During surveillance testing of 1R43S001B Emergency Diesel Generator 1B (swing EDG) from Unit 2 controls, 1R24S026 EDG 1 B Motor Control Center (MCC) did not transfer from Unit 1 power supply to Unit 2 power supply resulting in 1R24S026 being de-energized. MCC 1R24S026 provides power to Technical Support Center (TSC) HVAC which resulted in TSC HVAC being inoperable. Corrective work activities are in progress to expeditiously return the TSC HVAC back to service.

"If an emergency condition requiring activation of the Technical Support Center (TSC) occurs during the time the HVAC is inoperable, then contingency plans call for utilization of the TSC as long as radiological conditions allow. The Technical Support Center Activation procedure provides instructions to direct TSC management to the Control Room and TSC support personnel to the Simulator Building to continue TSC activities if it is necessary to relocate from the TSC so that TSC functions can be continued."

The licensee notified the NRC Resident Inspector.

Page Last Reviewed/Updated Friday, March 30, 2012
Friday, March 30, 2012