05000244/LER-2014-003
| R.E. Ginna Nuclear Power Plant | |
| Event date: | 09-10-2014 |
|---|---|
| Report date: | 11-06-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor |
| 2442014003R00 - NRC Website | |
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Unit Conditions Prior to the Event The reactor was in Operational Mode 1 at 100% power, 2235 psig and 574 degrees F. The plant had entered TS LCO 3.8.1 "AC Sources — MODES 1, 2, 3, and 4" Condition B "One DG inoperable", after declaring the "A" EDG inoperable due to planned, in-progress surveillance test STP-O-12.1 "EMERGENCY EDG GENERATOR A". There were no other structures, systems or components out of service that contributed to this event.
Description of the Event
On September 10, 2014, Ginna Unit 1 was at 100% power. The plant had entered TS LCO 3.8.1 at 2251 hours0.0261 days <br />0.625 hours <br />0.00372 weeks <br />8.565055e-4 months <br /> and STP-O-12.1 was commenced. The testing proceeded normally through synchronizing the "A" EDG to Bus 18. The next step in the procedure is to synchronize the "A" EDG to Bus 14. At 2353 hours0.0272 days <br />0.654 hours <br />0.00389 weeks <br />8.953165e-4 months <br /> upon attempting to close the Bus 14 supply breaker in accordance with the procedure, a J-9 Annunciator Alarm, SAFEGUARD BREAKER TRIP, was received in the control room.
Equipment Operators and Station Electricians were dispatched to Bus 14 to investigate the problem.
Electricians determined that the circuit breaker was properly aligned i.e., the tripper bar was found to be properly aligned for operation. Subsequently, the switch on the Main Control Board for the circuit breaker for Bus 14 supply from the "A" EDG was then placed into pull-stop.
On September 11, 2014 a Failure Modes Effects Analysis (FMEA) was performed to identify all possible failure mechanisms for the circuit breaker failure. A troubleshooting plan was then developed and implemented to determine the cause for the failure of the circuit breaker to close. This plan included contacting the OEM to assist in the investigation of the issue as it related to the operation of the circuit breaker. Non-intrusive troubleshooting revealed no obvious issues with the circuit breaker. In parallel with the troubleshooting plan, work was commenced on the morning of September 11, 2014, to prepare a spare breaker for installation at the "A" EDG output breaker position in Bus 14.
During the morning of September 11, 2014, follow-on troubleshooting was performed in conjunction with restarting the "A" EDG and attempting to reclose the breaker in accordance with STP-O-12.1. At approximately 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> on September 11, 2014, the "A" EDG was started with the original output breaker in service. The breaker closed appropriately on demand and operated as required in accordance with STP-O-12.1.
At approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on September 11, 2014, the spare circuit breaker was installed in bus 14.
The "A" EDG was started at approximately 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br /> and the circuit breaker closed on demand satisfactorily. Upon completion of the test the tripper bar was inspected to verify that it was properly aligned for operation.
At 2342 hours0.0271 days <br />0.651 hours <br />0.00387 weeks <br />8.91131e-4 months <br /> on September 11, 2014, the "A" EDG was declared operable and TS LCO 3.8.1 was exited for the "A" EDG.
At 0009 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> on September 12, 2014, TS LCO 3.8.1 was entered for "B" EDG being inoperable. At that time an inspection was performed of the "B" EDG output breaker in Bus 16. This was done to assure that the circuit breaker tripper bar was properly aligned for operation. It was found to be properly aligned.
At 0048 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> on September 12, 2014, "B" EDG was declared operable and TS LCO 3.8.1 was exited for the "B" EDG after the satisfactory inspection of the "B" EDG output circuit breaker.
The failed breaker was component 52/E1A1, model number DB-75, manufactured by Westinghouse.
Analysis of the Event
Past operability analysis indicated the "A" EDG had been inoperable since the last successful performance of STP-O-12.1 on August 13, 2014. This exceeded the TS LCO 3.8.1 "AC Sources — MODES 1, 2, 3, and 4" Condition B "One DG inoperable" requirement of 7 days and is reportable under 10 CFR 50.73(a)(2)(i)(B) "Any operation or condition which was prohibited by the plant's Technical Specifications." Engineering analysis performed after discovery provided high confidence the output breaker could have been closed manually from the control room if the "A" EDG had been required to perform a safety function.
A review of maintenance and surveillance procedures performed between August 13, 2014, and September 10, 2014, determined there were three instances where two required trains of equipment necessary to maintain the reactor in a safe shutdown condition were concurrently inoperable due to "A" EDG inoperability. All instances were for a brief period of time (approximately 4 — 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />). The "A" and "B" EDGs were concurrently inoperable on August 27, 2014, due to performance of routine surveillance testing on "B" EDG. The "A" and "B" Emergency Core Cooling System (ECCS) trains were concurrently inoperable on August 28, 2014, due to performance of routine surveillance testing on "B" ECCS train.
The "A" and "B" Residual Heat Removal (RHR) trains were concurrently inoperable on August 28, 2014, due to performance of routine surveillance testing on "B" RHR train. This is reportable under 10 CFR 50.73(a)(2)(v)(A) "Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition." None of the systems were required to perform any safety functions during the periods when both trains were concurrently inoperable and in all instances the length of time both trains were considered inoperable is within the allowance of LCO 3.0.3 for plant shutdown.
Based on the above considerations, this event is not considered to have had any significant effect on the health and safety of the public.
Cause of the Event
A causal analysis was performed by the station, with assistance from an OEM engineer. Based on testing performed as a part of the analysis and input from the vendor engineer it was determined that alignment related issues internal to the breaker were the apparent cause of the event.
The cause of this event is attributed to NUREG-1022 Cause Code B, Design, Manufacturing, Construction/Installation.
This event was entered into the site corrective action program (AR 02178745).
Corrective Actions
A spare circuit breaker was installed and STP-O-12.1 was performed to verify satisfactory operation.
Testing procedures have been modified to include post-test inspections to ensure the tripper bar is properly aligned for operation. Maintenance procedures will be modified to verify proper end to end play alignment.
Previous Similar Occurrences A review of Ginna LERs submitted during the last five years identified no similar events.