July 21, 2005
NRC INFORMATION NOTICE 2005-21: PLANT TRIP AND LOSS OF PREFERRED ACPOWER FROM INADEQUATE SWITCHYARD MAINTENANCE
ADDRESSEES
All holders of operating licensees for nuclear power reactors, except those who havepermanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to informaddressees about loss of power events as a result of inadequate preventive and corrective maintenance practices on switchyard breakers and current transformer It is expected that recipients will review the information for applicability to their facilities and consider actions, asappropriate, to avoid similar problem However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.DESCRIPTION OF CIRCUMSTANCES On May 5, 2004, Dresden Unit 3 was at full power and Dresden Unit 2 was shutdown when anautomatic reactor scram and a subsequent loss of offsite power event occurred during activities to reconfigure breakers in the 345 kV switchyar Operations personnel manually opened switchyard breaker 8-15 in accordance with the switching orde However, when the A and B phases opened, the C phase of switchyard breaker 8-15 failed to fully open within the required time. This failure produced current imbalances in Unit 2 and Unit 3 switchyard ring busses (tied together through a breaker), which led to the opening of several other switchyard breaker Unit 3 scrammed due to turbine load reject, and offsite power was lost to the Unit 3 safety- related emergency core cooling system (ECCS) busse The failed breaker was an I-T-E Imperial Corporation (current vendor ABB) sulfur hexafluoride (SF6) gas circuit breaker (type 362GA). This breaker used independent pole operators for each of the three phase The breaker was built and installed in the Dresden 345 kV switchyard in the late 1970's.On May 6, 2004, the licensee and personnel of the transmission and distribution company,Exelon Energy Delivery (EED), discovered that ABB, the current breaker vendor, had issued a product advisory in July 2003 for I-T-E Imperial Corporation GA and GB breakers to warn that the operating mechanisms may experience delayed trip or in some cases failures to trip due to age and application related problem In addition, the advisory noted that the breakers at ML051740051 IN 2005-21
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| list | - Information Notice 2005-02, Pressure Boundary Leakage Identified on Steam Generator Bowl Drain Welds (4 February 2005, Topic: Boric Acid, Stress corrosion cracking, Pressure Boundary Leakage)
- Information Notice 2005-04, Single-Failure and Fire Vulnerability of Redundant Electrical Safety Buses (14 February 2005, Topic: Safe Shutdown)
- Information Notice 2005-05, Improving Material Control and Accountability Interface with Criticality Safety Activities at Fuel Cycle Facilities (10 March 2005)
- Information Notice 2005-07, Results of Hemyc Electrical Raceway Fire Barrier System Full Scale Fire Testing (1 April 2005, Topic: Fire Barrier, Hemyc)
- Information Notice 2005-08, Monitoring Vibration to Detect Circumferential Cracking of Reactor Coolant Pump and Reactor Recirculation Pump Shafts (5 April 2005)
- Information Notice 2005-09, Official Exhibit - ENT000527-00-BD01 - NRC Information Notice 2005-09, Indications in Thermally Treated Alloy 600 Steam Generator Tubes and Tube-to Tubesheet Welds (Apr. 7, 2005) (7 April 2005)
- Information Notice 2005-11, Internal Flooding/Spray-Down of Safety-Related Equipment Due to Unsealed Equipment Hatch Floor Plugs And/Or Blocked Floor Drains (6 May 2005)
- Information Notice 2005-11, Internal Flooding/Spray-Down of Safety-Related Equipment Due to Unsealed Equipment Hatch Floor Plugs and/or Blocked Floor Drains (6 May 2005, Topic: Internal Flooding)
- Information Notice 2005-12, Excessively Large Criticality Safety Limits Fail to Provide Double Contingency at Fuel Cycle Facility (17 May 2005, Topic: Hemyc)
- Information Notice 2005-13, Potential Non-Conservative Error in Modeling Geometric Regions in the Keno-V. a Criticality Code (17 May 2005, Topic: Hemyc)
- Information Notice 2005-14, Fire Protection Findings on Loss of Seal Cooling to Westinghouse Reactor Coolant Pumps (1 June 2005, Topic: Safe Shutdown, Probabilistic Risk Assessment, Significance Determination Process, Fire Protection Program)
- Information Notice 2005-15, Three-Unit Trip and Loss of Offsite Power at Palo Verde Nuclear Generating Station (1 June 2005)
- Information Notice 2005-16, Outage Planning and Scheduling - Impacts on Risk (20 June 2005, Topic: Time to boil)
- Information Notice 2005-17, Manual Brachytherapy Source Jamming (23 June 2005, Topic: Brachytherapy)
- Information Notice 2005-18, Summary of Fitness-For-Duty Program Performance Reports for Calendar Years 2001, 2002 and 2003 (15 July 2005, Topic: Fitness for Duty, Contraband, Stolen)
- Information Notice 2005-20, Electrical Distribution System Failures Affecting Security Equipment (19 July 2005)
- Information Notice 2005-21, Plant Trip and Loss of Preferred AC Power From Inadequate Switchyard Maintenance (21 July 2005)
- Information Notice 2005-21, Plant Trip and Loss of Preferred AC Power from Inadequate Switchyard Maintenance (21 July 2005)
- Information Notice 2005-22, Inadequate Criticality Safety Analysis of Ventilation Systems At Fuel Cycle Facilities (29 July 2005, Topic: Brachytherapy)
- Information Notice 2005-22, Inadequate Criticality Safety Analysis of Ventilation Systems at Fuel Cycle Facilities (29 July 2005, Topic: Brachytherapy)
- Information Notice 2005-24, Nonconservatism in Leakage Detection Sensitivity (3 August 2005, Topic: Pressure Boundary Leakage)
- Information Notice 2005-26, Results of Chemical Effects Head Loss Tests In a Simulated PWR Sump Pool Environment (16 September 2005)
- Information Notice 2005-26, Results of Chemical Effects Head Loss Tests in a Simulated PWR Sump Pool Environment (16 September 2005)
- Information Notice 2005-27, Low-Dose-Rate Manual Brachytherapy Equipment-Related Medical Events (7 October 2005, Topic: Fire Barrier, RAMQC, Hemyc, Brachytherapy)
- Information Notice 2005-28, Inadequate Test Procedure Fails to Detect Inoperable Criticality Accident Alarm Horns (31 October 2005, Topic: Fire Barrier, RAMQC, Hemyc, Brachytherapy)
- Information Notice 2005-29, Steam Generator Tube and Support Configuration (27 October 2005)
- Information Notice 2005-30, Safe Shutdown Potentially Challenged by Unanalyzed Internal Flooding Events and Inadequate Design (7 November 2005, Topic: Safe Shutdown, Internal Flooding)
- Information Notice 2005-30, Safe Shutdown Potentially Challenged By Unanalyzed Internal Flooding Events and Inadequate Design (7 November 2005, Topic: Safe Shutdown, Internal Flooding)
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