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| Entered date | Event description | |
|---|---|---|
| ENS 54820 | 6 August 2020 13:10:00 | This report is being made as required by 10 CFR 50.73(a)(2)(iv)(A) to describe an automatic actuation of containment isolation valves in more than one system. Because the actuation was invalid, this 60-day telephone notification is being made instead of a written LER (licensee event report), in accordance with 10 CFR 50.73(a)(1). On 06/08/2020, at approximately 0424 EDT, a trip of the Unit 3 'A' reactor protection system (RPS) MG-Set resulted in a partial activation of the primary containment isolation system and inboard containment isolation valves closed in multiple systems. All affected Group III containment isolation valves were verified to be closed. It was determined that the normal power supply for the Unit 3 'A' RPS had failed. Power was transferred from the normal to the alternate source and the RPS 'A' channel was reset. Investigation determined that the 3A RPS MG Set motor contactor coil winding had failed due to an internal short circuit. The motor contactor has been replaced. The containment isolation was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The NRC Resident Inspector has been informed of this notification. |
| ENS 52961 | 11 September 2017 15:00:00 | This report is being made as required by 10 CFR 50.73(a)(2)(iv)(A) to describe an automatic actuation of containment isolation valves in more than one system. Because the actuation was invalid, this 60-day telephone notification is being made instead of a written LER (Licensee Event Report), in accordance with 10 CFR 50.73(a)(1). On 07/14/17, at approximately 1453 hours (EDT), an electrical transient occurred due to an off-site lightning strike that de-energized one of the station's two qualified off-site power sources. This resulted in an automatic fast transfer of four 4 kV electrical buses to the alternate off-site source. The fast transfer occurred as designed without complications. The loss of power had numerous impacts on plant equipment that occurred in accordance with plant design, including a Group 2 primary containment isolation on both units. The Group 2 isolation affected multiple systems, including Reactor Water Cleanup, Instrument Nitrogen, and the Drywell Floor Drain. The fault on the off-site transmission line immediately cleared after the lightning strike and at 1457 hours (EDT) the transmission system operator gave the station permission to reclose the breaker to the off-site source. Following system restorations and equipment walkdowns, plant operators re-established normal connections to the off-site source on 7/14/17 at 2322 hours (EDT) in accordance with station procedures. The containment isolation occurred as a result of the loss of an off-site power source and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The NRC Resident Inspector has been informed of this notification. |
| ENS 51962 | 27 May 2016 09:22:00 | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made pursuant to 10 CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of containment isolation valves in more than one system. On 3/28/16, at approximately 1320 (EDT), a loss of power occurred on the Unit 2 E124 480 volt load center due to an equipment operator inadvertently opening the main feed breaker during the process of applying a clearance to de-energize the E124-P-A motor control center for planned maintenance. Loss of the E124 load center resulted in Group II and Group III primary containment isolations due to an invalid ESF actuation signal. Systems impacted by the containment isolations included containment instrument nitrogen, containment atmospheric monitoring, reactor water cleanup, and secondary containment. Balance of plant impacts included partial loss of feedwater heating and a reduced condenser vacuum. Reactor power lowered to 86% as a result of the event and further decreased to approximately 80 percent when re-establishing the 3A, 4A and 5A feedwater heaters. Following direction from the control room, the E124 main feed breaker was promptly re-closed by equipment operators. Affected equipment was restored to its normal or planned configuration and containment isolations were reset at 1406. The containment isolation signal was generated as a result of the loss of power to the E124 load center and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The licensee has notified the NRC Resident Inspector. |
| ENS 50089 | 6 May 2014 12:50:00 | This 60-day report, as allowed by 10CFR 50.73(a)(1), is being made pursuant to 10CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of an emergency service water system. On 3/9/14, at approximately 1536 EST, the E2 Emergency Diesel Generator (EDG) was started for a post maintenance operability test. The 'A' safety-related Emergency Service Water (ESW) pump was being used to provide cooling to the EDG. At approximately 1613 EST and 1622 EST, unexpected automatic starts of the 'B' ESW pump and the non-safety related single train Emergency Cooling Water (ECW) pump occurred. The EDG run was terminated at 1622 EST to investigate the cause of the unexpected starts. It was determined that a failed angle drive adaptor resulted in invalid input to the speed switch, which resulted in the unplanned starts of the 'B' ESW pump and the ECW pump. Except for the failure of the angle drive adaptor, all systems and equipment operated as expected. The NRC resident has been informed of this notification. |
| ENS 47907 | 8 May 2012 12:33:00 | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Unit 2 Primary Containment Isolation System (PCIS). On 3/13/12, at approximately 1604 hours, Unit 2 experienced an invalid PCIS partial isolation. An equipment operator was in the process of making an adjustment to the Reactor Protection System (RPS) MG Set output voltage during daily rounds. As the rheostat was beginning to be rotated to increase the voltage, output voltage quickly dropped below the MG Set undervoltage trip setpoint. The BC757B and BC757D MG Set output breakers opened, resulting in the loss of the 2B RPS bus causing a half scram. The half scram signal resulted in closure of the instrument nitrogen primary containment isolation valve, secondary containment normal ventilation isolation valves and start of the 'B' Standby Gas Treatment supply fan. The invalid PCIS isolation was a result of the failure of the voltage adjustment rheostat for the MG Set output voltage. This issue has been entered into the site Corrective Action Program (AR 1340452) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification. |