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Event Notification Report for January 14, 2011

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
01/13/2011 - 01/14/2011

** EVENT NUMBERS **


46531 46534

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Power Reactor Event Number: 46531
Facility: DIABLO CANYON
Region: 4 State: CA
Unit: [1] [2] [ ]
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: PAULA GERFEN
HQ OPS Officer: JOE O'HARA
Notification Date: 01/10/2011
Notification Time: 19:39 [ET]
Event Date: 01/10/2011
Event Time: 13:21 [PST]
Last Update Date: 01/14/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(D) - ACCIDENT MITIGATION
50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
Person (Organization):
BOB HAGAR (R4DO)

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

BOTH TRAINS OF AUXILIARY BUILDING VENTILATION BECAME INOPERABLE

"On January 10, 2011, at 1321 PST, Diablo Canyon Power Plant, Unit 2, entered Technical Specification Limiting Condition of Operation (TS LCO) 3.0.3, when both trains of Auxiliary Building Ventilation System (ABVS) became inoperable following closure of damper M-4 and the ensuing loss of both exhaust fans E-1 and E-2. TS LCO 3.0.3 was exited on January 10, 2011, at 1342 following a status reset and selection of fan E-2. This provided a ventilation flowpath and use of both exhaust fans in the Safeguards mode. Both trains of Auxiliary Building Ventilation are operable. This 8-hour non-emergency report is made pursuant to 10 CFR 50.72(b)(3)(v)(D)."

The unit is not in a TS LCO. All 3 unit EDG's are operable and offsite power is in the normal lineup.

The NRC Resident Inspector has been notified.


* * * UPDATE FROM WES FIANT TO DONALD NORWOOD AT 0021 EST ON 1/14/2011 * * *

"On January 13, 2011, at 1603 PST, engineering determined that a single failure design vulnerability exists at Diablo Canyon Power Plant Units 1 and 2.

"Engineering review of the control logic of the ABVS determined that while in Buildings Only (non-safeguards) alignment or during system realignment from Safeguards Only to Buildings Only alignment, failure of damper M-4A or M-4B (series dampers) could result in the control logic securing both ABVS exhaust fans. This would prevent ABVS actuation on receipt of a valid safeguards actuation signal. When this occurs, a control room alarm is actuated, which requires the operators to reset the control logic from the control room, thereby re-enabling the capability of the ABVS to respond to a safeguards actuation signal. The Unit 2 event on January 10, 2011, at 1321, occurred due to this single failure vulnerability when the control system attempted to restore the ABVS alignment from Safeguards Only to the Buildings Only alignment. This design vulnerability is currently mitigated by maintaining the ABVS in either of the two safeguards alignments (Safeguards Only or Buildings and Safeguards).

"This single failure design vulnerability is an 8-hour non-emergency report made pursuant to 10CFR50.72(b)(3)(ii)(B) for an event that resulted in the nuclear power plant being in an unanalyzed condition for both Unit 1 and Unit 2."

The licensee will notify the NRC Resident Inspector. Notified R4DO (Hagar).

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Agreement State Event Number: 46534
Rep Org: TEXAS DEPARTMENT OF HEALTH
Licensee: STERIS ISOMEDIX OPERATIONS
Region: 4
City: EL PASO State: TX
County:
License #: L04268
Agreement: Y
Docket:
NRC Notified By: RAY JISHA
HQ OPS Officer: JOE O'HARA
Notification Date: 01/11/2011
Notification Time: 18:27 [ET]
Event Date: 01/10/2011
Event Time: 19:00 [CST]
Last Update Date: 01/11/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
AGREEMENT STATE
Person (Organization):
BOB HAGAR (R4DO)
LARRY CAMPER (FSME)

Event Text

AGREEMENT STATE REPORT - SPOOL VALVE FAILURE ON IRRADIATOR

"A pool type irradiator experienced a drive mechanism failure on one of the two racks. This caused the 1.2 M Curie of Co-60 to remain stuck in the retracted position. It remained there for one hour until the operators discovered that a spool valve was stuck. Once the valve was freed the source rack returned to the pool as normal. The licensee is investigating the equipment malfunction and will submit further information when available."

There wre no personnel injuries.

TX Incident No. 8809

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Thursday, March 29, 2012