SECOND Loss of Offsite Power at the Byron Nuclear Power Plant Since January 23 – No Inclement Weather

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For the second time in a month, a power interruption caused operators at Byron Generating Station to declare an “unusual event,” officials said in a news release sent around 10 p.m. Tuesday.

Byron Unit 1 Emergency Diesels automatically started to respond to a Loss of Offsite Power (LOOP) at 17:31 CST.  Offsite Normal Power to 4.16kV Emergency Safety Buses 141 and 142 via Station Auxiliary Transformers (SAT) 142-1 and 142-2 respectively, was interrupted. Emergency Diesels 1A and 1B automatically started and energized ESF Buses 141 and 142.

Concurrently, 6.9kV Buses 157, 150, 156, 158, and 4.16kV Buses 144 and 143 Fast Transferred to the Unit Auxiliary Transformers (UAT) 141-1 and 141-2, which is supplied by the Unit 1 Main Generator and not the Switchyard.

The Fast Transfer kept the Unit 1 on line such that there was no Reactor Protection Signal generated by the RCP Bus Undervoltage sensors.

Unit 2 Cross Tie from its ESF Buses are being operated in order to provide power to the Unit 1 ESF Buses such that the Unit 1 EDGs can be secured and placed back in Stand By.

As an armchair QB, it appears that SAT 142-1 and 142-2 became de-energized due to an unknown fault. It would be interesting to know the Initial Breaker Lineup prior to the event but that has not been made public. It appears that 345kV Bus Section 6 was de-energized, which feeds both Unit 1 SATs. Please refer to attached simplified Electrical Drawing.

It is unclear whether BOTH units would have to be Shutdown in order to comply with Technical Specification 3.8.1 for Cross-Connected ESF Buses.

January Reactor 2 Shutdowns – 

On January 23, Byron Unit 2 experienced a LOOP where the Unit tripped. During the Root Cause investigation, a Design Flaw (Event 47636) was identified however, it was not traced to the cause of the Trip. In addition, a broken Insulator was identified as a possible cause.

The NRC sent a Special Investigation Team to review the circumstances around the loss of offsite power that led to a Unit 2 reactor shutdown on Jan. 30 at the Byron nuclear power plant.



Power Reactor Event Number: 47708
Facility: BYRON
Region: 3 State: IL
Unit: [1] [ ] [ ]
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: CHRIS COTE
HQ OPS Officer: CHARLES TEAL
Notification Date: 02/28/2012
Notification Time: 19:03 [ET]
Event Date: 02/28/2012
Event Time: 17:31 [CST]
Last Update Date: 02/28/2012
Emergency Class: UNUSUAL EVENT
10 CFR Section:
50.72(a) (1) (i) – EMERGENCY DECLARED
50.72(b)(2)(xi) – OFFSITE NOTIFICATION
50.72(b)(3)(iv)(A) – VALID SPECIF SYS ACTUATION
50.72(b)(3)(v)(D) – ACCIDENT MITIGATION
Person (Organization):
ANN MARIE STONE (R3DO)
SAMSON LEE (NRR)
CYNTHIA PEDERSON (R3RA)
BRUCE BOGER (NRR)
SCOTT MORRIS (IRD)
KEVIN BISCOE (FEMA)
DAN GATES (DHS)
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N Y 100 Power Operation 99 Power Operation
UNUSUAL EVENT DUE TO LOSS OF OFFSITE POWERByron Unit 1 declared an Unusual Event due to a loss of offsite power for greater than 15 minutes (EAL MU-1). The 1A and 1B emergency diesel generators auto-started and automatically restored power to ESF (Engineered Safety Feature) Busses 141 and 142. The 1A Auxiliary Feedwater pump auto-started due to an undervoltage signal to ESF bus 141. The 6.9 KV Busses (Non-ESF) and 4.16 KV Busses (Non-ESF) auto transferred to the Unit Auxiliary Transformers and Unit 1 remained online. The ESF reserve feed breakers are available and in the process of transferring ESF loads over to Unit 2 via the ESF cross-ties. This will allow shutdown of the 1A and 1B diesel-generators and allow alignment to standby status. Switchyard repairs are being initiated.

The licensee notified the State of Illinois, Ogle County, Oregon and Byron municipalities and the NRC Resident Inspector. The licensee plans on issuing a news release. Unit 2 remained online and was unaffected throughout the event.

Notified Nuclear SSA and NICC vie email.


Byron 1
4Q/2011 Plant Inspection Findings

MODIFICATION OF THE AUXILIARY FEEDWATER SYSTEM WITHOUT PRIOR NRC APPROVAL – Inspection Report# : 2011004 (pdf)

MODIFICATION OF THE AUXILIARY FEEDWATER SYSTEM WITHOUT PRIOR NRC APPROVAL -Inspection Report# : 2011004 (pdf)

DESIGN OF AUXILIARY FEEDWATER SYSTEM INCLUDED VOIDS IN SAFETY RELATED ALTERNATE SUCTION FLOWPATHS – Inspection Report# : 2011004 (pdf)

UNTIMELY CORRECTIVE ACTION FOR PREVIOUSLY IDENTIFIED NON-CITED VIOLATIONS (sECTION 40a2.1.B.3.I) – Inspection Report# : 2011008 (pdf)

FAILURE TO INITIATE ISSUE REPORTS –  Inspection Report# : 2011008 (pdf)

FAILURE TO ENSURE THAT THE DESIGN OF THE AF SUCTION PIPING WAS ADEQUATE TO PREVENT AIR ENTRAINMENT FOLLOWING A SEISMIC OR TORNADO EVENT –  Inspection Report# : 2011003 (pdf)

Failure to Specify and Perform Required Independent Quality Verification Hold Point Inspections. –  Inspection Report# : 2011009 (pdf)

Failure to Follow Procedure Requirements for Temporary Scaffolds that Remain in Place for Over 90 Days. –  Inspection Report# : 2011009 (pdf)

EDG Usable Fuel Calculations Failed to Consider Appropriate EDG Frequency Variations. –  Inspection Report# : 2011009 (pdf)

Failure to Adequately Document and Justify Continued Operability of the Auxiliary Feedwater System. –  Inspection Report# : 2011015 (pdf)

AUXILIARY FEEDWATER PUMP LUBE OIL HEAT EXCHANGER CONFIGURED INCORRECTLY –  Inspection Report# : 2011002 (pdf)

INADEQUATE INSTRUCTIONS FOR MEASURING ECCS VOIDS –  Inspection Report# : 2011002 (pdf)

FAILURE TO EVALUATE THE EFFECTS OF DYNAMIC LOADS AT THE CS DISCHARGE PIPING – Inspection Report# : 2011002 (pdf)

Changes to EAL Basis Decreased the Effectiveness of the Plan without Prior NRC Approval –  Inspection Report# : 2010502 (pdf)

Changes to EAL Basis Decreased the Effectiveness of the Plan without Prior NRC Approval – Inspection Report# : 2010502 (pdf)

OUT-OF-DATE/EXPIRED RESPIRATOR CARTRIDGES – Inspection Report# : 2011002 (pdf)

Byron 2
4Q/2011 Plant Inspection Findings

FAILURE TO IDENTIFY ELEVATED RISK STATUS – Inspection Report# : 2011004 (pdf)

MODIFICATION OF THE AUXILIARY FEEDWATER SYSTEM WITHOUT PRIOR NRC APPROVAL – Inspection Report# : 2011004 (pdf)

MODIFICATION OF THE AUXILIARY FEEDWATER SYSTEM WITHOUT PRIOR NRC APPROVAL – Inspection Report# : 2011004 (pdf)

DESIGN OF AUXILIARY FEEDWATER SYSTEM INCLUDED VOIDS IN SAFETY RELATED ALTERNATE SUCTION FLOWPATHS – Inspection Report# : 2011004 (pdf)

UNTIMELY CORRECTIVE ACTION FOR PREVIOUSLY IDENTIFIED NON-CITED VIOLATIONS (sECTION 40a2.1.B.3.I) – Inspection Report# : 2011008 (pdf)

FAILURE TO INITIATE ISSUE REPORTS – Inspection Report# : 2011008 (pdf)

Inadequate Extent of Cause for 2A EDG Lube Oil Leak – Inspection Report# : 2011016 (pdf)

FAILURE TO ENSURE THAT THE DESIGN OF THE AF SUCTION PIPING WAS ADEQUATE TO PREVENT AIR ENTRAINMENT FOLLOWING A SEISMIC OR TORNADO EVENT – Inspection Report# : 2011003 (pdf)

Failure to Specify and Perform Required Independent Quality Verification Hold Point Inspections. – Inspection Report# : 2011009 (pdf)

Failure to Follow Procedure Requirements for Temporary Scaffolds that Remain in Place for Over 90 Days. – Inspection Report# : 2011009 (pdf)

EDG Usable Fuel Calculations Failed to Consider Appropriate EDG Frequency Variations. – Inspection Report# : 2011009 (pdf)

Failure to Adequately Document and Justify Continued Operability of the Auxiliary Feedwater System. – Inspection Report# : 2011015 (pdf)

INADEQUATE INSTRUCTIONS FOR MEASURING ECCS VOIDS – Inspection Report# : 2011002 (pdf)

Self-Revealing Failure of the 2A Diesel Generator Upper Lube Oil Cooler – Final Significance Determination issued in report 2011-012 on March 14, 2011.
Inspection Report# : 2011016 (pdf)
Inspection Report# : 2011011 (pdf)
Inspection Report# : 2011012 (pdf)

SELF-REVEALED LOW FLOW TO REACTOR CONTAINMENT FAN COOLER – Inspection Report# : 2011002 (pdf)

FAILURE TO EVALUATE THE EFFECTS OF DYNAMIC LOADS AT THE CS DISCHARGE PIPING – Inspection Report# : 2011002 (pdf)

Changes to EAL Basis Decreased the Effectiveness of the Plan without Prior NRC Approval – Inspection Report# : 2010502 (pdf)

Changes to EAL Basis Decreased the Effectiveness of the Plan without Prior NRC Approval – Inspection Report# : 2010502 (pdf)

OUT-OF-DATE/EXPIRED RESPIRATOR CARTRIDGES – Inspection Report# : 2011002 (pdf)

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1 Comment

  1. When a light switch or electric outlet at a house quit working, there’s a little nagging worry that something may be amiss in the system, and there’s a little remote tiny chance of something causing a fire, if something else doesn’t work. But at worst, the house burns down.

    When this happens at an NPP or SFP in the Midwest, the Midwest is destroyed, and a bread basket of the world taken out of use.

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