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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56987 | 2 January 2024 04:33:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Containment Isolation Valves | The following information was provided by the licensee via phone and email: This 60-day optional telephone notification is being made in lieu of a Licensee Event Report (LER) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 2333 EST on January 1, 2024, an invalid actuation of group 6 primary containment isolation valves (PCIVs) (i.e., containment atmospheric control/monitoring (CAC/CAM) and post-accident sampling system (PASS) isolation valves) occurred. Reactor building ventilation isolated and standby gas treatment started per design. No manipulations associated with the isolation or reset logic were ongoing at the time. Troubleshooting determined that the group 6 isolation signal resulted from spurious relay contact actuation in the main stack radiation high-high isolation logic due to relay contact oxidation. The main stack radiation monitor is a shared component that sends isolation signals to Unit 1 and Unit 2. There were no Unit 1 actuations. Only the relay contacts associated with Unit 2 actuated. The relay has been replaced. The actuation was not initiated in response to actual plant conditions. It was not an intentional manual initiation and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. During this event the PCIVs functioned successfully, and the actuations were complete. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector had been notified. | Primary containment Reactor Building Ventilation | |
| ENS 56988 | 28 December 2023 13:15:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generators | The following information was provided by the licensee via phone and email: This 60-day optional telephone notification is being made in lieu of a Licensee Event Report (LER) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 0815 EST on December 28, 2023, an invalid actuation of the four emergency diesel generators (EDGs) occurred. It was determined that this condition was likely caused by spurious operation of the undervoltage relay for the startup auxiliary transformer feeder breaker to the `1D' balance of plant bus which was being fed by the unit auxiliary transformer at the time, per the normal lineup. This non-safety related EDG actuation logic was disabled, and additional investigation is planned during the upcoming refueling outage. The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. During this event, the four EDGs functioned successfully, and the actuations were complete. All emergency buses remained energized from offsite power and, therefore, the EDGs did not tie to their respective buses. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector had been notified. | Emergency Diesel Generator | |
| ENS 56287 | 9 November 2022 14:06:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Containment Isolation Valves | The following information was provided by the licensee via email: This 60-day optional telephone notification is being made in lieu of an LER (Licensee Event Report) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 0906 Eastern Time (EST) on November 9, 2022, an invalid actuation of Group 6 Primary Containment Isolation Valves (PCIVs) (i.e., Containment Atmospheric Control/Monitoring and Post Accident Sampling isolation valves) occurred. In addition, per design, Reactor Building Ventilation isolated and Standby Gas Treatment started. It was determined that this condition was caused by faulty test equipment that was being used during preparation for the Main Stack Radiation Monitor High Radiation Response Time test. This test requires connecting a recording device to monitor for the test start signal on a Unit 2 relay associated with the Main Stack High Radiation signal. The recorder faulted which caused the associated fuse to blow and resulted in Unit 2 receiving a Main Stack High Radiation signal and Group 6 PCIV actuation. It was verified that the radiation monitor was not in trip electrically (i.e., there was no high radiation condition). The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. During this event the PCIVs functioned successfully, and the actuations were complete. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector was notified. | Primary containment Reactor Building Ventilation | |
| ENS 56138 | 6 August 2022 10:28:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-DAY Optional Telephonic Notification of Invalid Actuation of Containment Isolation Valves | The following information was provided by the licensee via email: This 60-day optional telephone notification is being made in lieu of an LER submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for invalid actuations of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 0628 Eastern Daylight Time (EDT) on August 6, 2022, an invalid actuation of group 6 Primary Containment Isolation Valves (PCIVs) (i.e., containment atmospheric control/monitoring and post accident sampling isolation valves) occurred. The group 6 isolation signal resulted from the reactor building ventilation radiation monitor `A' channel exceeding the setpoint value. This condition recurred at approximately 1305 EDT on August 12, 2022. In both instances, the `B' channel, located in the same plenum, remained steady and below the setpoint value through the entire event. This, along with readings made by radiation protection technicians, confirmed that there were no actual high radiation conditions in the reactor building exhaust in either instance. Following each invalid actuation, upon returning unit 2 reactor building ventilation to service, the `A' channel readings returned to be consistent with the `B' channel. It was determined that these invalid actuations likely resulted from degradation of circuit components associated with the radiation monitor. The `A' channel radiation monitor was replaced on September 22, 2022. During these two events, the PCIVs functioned successfully and the actuations were complete. The actuations were not initiated in response to actual plant conditions, they were not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, these events have been determined to be invalid actuations. These events did not result in any adverse impact to the health and safety of the public. | Primary containment Reactor Building Ventilation | |
| ENS 55859 | 7 March 2022 04:40:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation 60-DAY Telephone Notification | The following information was provided by the licensee via fax or email: This 60-day telephone notification is being made in lieu of an LER submittal per 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for invalid actuations of systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 0040 Eastern Standard Time (EST) on March 7, 2022, Unit 1 received inadvertent High-Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) initiation signals. Subsequently, at approximately 0148 EST on March 7, 2022, Unit 1 received inadvertent Low-Pressure Coolant Injection (LPCI) and Core Spray initiation signals. In addition, all four Emergency Diesel Generators auto started, Group 10 (Instrument Air) Primary Containment Isolation System actuations occurred, and the Residual Heat Removal (RHR) Service Water Booster pumps tripped resulting in a brief interruption (approximately 9 minutes) to the Shutdown Cooling (SDC) heatsink. Jumpers, installed per planned refueling outage activities, prevented discharge of Emergency Core Cooling Systems into the reactor. HPCI, RCIC, and RHR Loop `A' were removed from service and under clearance. RHR SDC remained operable via RHR Loop `B' and forced circulation was maintained in the reactor. At the time of these events, Unit 1 was shutdown for refueling and the `A' and `C' reactor water level transmitters had been isolated in preparation for planned replacement. Leak-by of the instrument isolation valves occurred on both transmitters. Leak-by on the `C' instrument occurred at a faster rate with the `A' instrument providing the confirmatory signals resulting in Low Level 2 (LL2) and Low Level 3 (LL3) indication at approximately 0040 EST and 0148 EST, respectively. All actuations occurred as designed for LL2 and LL3 signals. During these events, reactor water level remained stable at the Reactor Vessel Head Flange and the `B' and `D' reactor water level transmitters remained off-scale-high, as expected under these conditions. Therefore, the actuations were not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system (i.e., there was no low reactor water level condition). Considering the above, these actuations were invalid. There was no impact on the health and safety of the public or plant personnel. | Service water Emergency Diesel Generator Primary Containment Isolation System Reactor Core Isolation Cooling Shutdown Cooling Core Spray Residual Heat Removal Emergency Core Cooling System | |
| ENS 55756 | 4 January 2022 18:16:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-DAY Optional Telephonic Notification for Invalid Actuation of Containment Isolation Valves | The following information was provided by the licensee via email: This 60-day optional telephone notification is being made in lieu of an LER (Licensee Event Report) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 1316 Eastern Standard Time (EST) on January 4, 2022, during performance of isolation logic periodic testing associated with Primary Containment Isolation System Groups 2 and 6, an invalid actuation of Group 6 Primary Containment Isolation Valves (PCIVs) (i.e., Containment Atmospheric Control/Monitoring (CAC/CAM) and Post Accident Sampling (PASS) isolation valves) occurred. This resulted in a Division I CAC isolation signal, a full CAM isolation, and a full PASS isolation. Reactor Building Ventilation isolated and Standby Gas Treatment started per design. No manipulations associated with the isolation or reset logic were ongoing at the time. Troubleshooting determined that the Group 6 isolation signal resulted from a high resistance contact on a relay associated with the main stack radiation high-high isolation logic. This condition interrupted electrical continuity and prevented the Group 6 logic from resetting. Following cleaning of the relay contacts, the isolation logic remained in the reset state. The main stack radiation monitor is a shared component that sends isolation signals to Unit 1 and Unit 2. It was verified that the radiation monitor was not in trip electrically and there were no Unit 2 actuations. Therefore, the actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. As a result, this event has been determined to be an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector was notified. | Primary Containment Isolation System Primary containment Reactor Building Ventilation | |
| ENS 55191 | 17 February 2021 19:07:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Containment Isolation Valves | This 60-day optional telephone notification is being made in lieu of an LER submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 1507 EDT on February 17, 2021, during performance of isolation logic periodic testing associated with Primary Containment Isolation System Groups 2 and 6, an invalid actuation of Group 6 Primary Containment Isolation Valves (PCIVs) (i.e., Containment Atmospheric Control/Monitoring and Post Accident Sampling isolation valves) occurred. The Group 6 isolation signal resulted from the reactor building ventilation radiation monitor `B' Channel exceeding the setpoint value. This condition likely resulted from the radiation monitor electronics being impacted by humidity levels, which exceeded the instrument design requirements that developed in the area over time as a result of the Unit 2 reactor building ventilation being secured per the test procedure. The `A' Channel, located in the same plenum, remained steady and below the setpoint value through the entire event. This, along with readings made by a Radiation Protection Technician, confirmed that there was no actual high radiation condition in the reactor building exhaust. Upon returning Unit 2 reactor building ventilation to service, the `B' Channel readings returned to be consistent with the `A' Channel. The PCIVs functioned successfully and the actuation was complete. The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector was notified. | Primary Containment Isolation System Primary containment Reactor Building Ventilation | |
| ENS 54675 | 5 March 2020 14:25:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Telephonic Notification of an Invalid Specified System Actuation | This 60-day optional telephone notification is being made in lieu of an LER (licensee event report) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 1025 Eastern Standard Time (EST) on March 5, 2020, with Unit 1 shutdown in Mode 5 for refueling, an invalid actuation of Group 6 Primary Containment Isolation Valves (PCIVs) (i.e., Containment Atmospheric Control/Monitoring and Post Accident Sampling isolation valves) occurred. The invalid actuation occurred when power was lost as a result of the Inboard Isolation Logic Fuse being removed per a planned clearance hang to support maintenance. The PCIVs functioned successfully and the actuation was complete. The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | Primary containment | |
| ENS 54144 | 10 May 2019 00:00:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Optional Notification Due to Actuation of an Emergency Diesel Generator | This 60-day optional telephone notification is being made in lieu of an LER submittal, as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 2000 EDT on May 9, 2019, an invalid actuation of emergency diesel generator (EDG) 1 occurred. At the time, EDG 1 was removed from service for planned maintenance. The invalid actuation occurred when the starting air clearance was being lifted while simultaneously performing a Post Maintenance Test (PMT) where an external DC power source was applied to a relay that provided continuity directly to the starting air solenoids. As a result, the air start solenoids were energized causing EDG 1 to start. EDG 1 started and functioned successfully. The actuation was complete; EDG 1 successfully started and ran unloaded. The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator | |
| ENS 52778 | 6 April 2017 16:12:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generators | This 60-day optional telephone notification is being made in lieu of an LER submittal, as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). On April 6, 2017, at 1212 Eastern Daylight Time (EDT), an invalid actuation of emergency diesel generators (EDGs) 1, 2. 3. and 4 occurred. In support of maintenance associated with the onsite electrical distribution system, activities were in progress to power the 2C balance-of-plant (BOP) bus from the startup auxiliary transformer (SAT) followed by de-energization of the 2D BOP bus. However, flexible links between the SAT and the 2D BOP bus had not been installed. As a result, under voltage sensing relay (27SX) was not energized and an invalid SAT secondary side under voltage EDG auto start signal was generated. There was no actual under voltage on the SAT, no loss of power, and all emergency buses continued to be powered by the unit auxiliary transformer (UAT). The EDGs responded properly to the auto-start signal. The actuation was complete, in that the EDGs successfully started and ran unloaded. The EDGs were returned to standby status by 1415 EDT. Since no actual under voltage condition existed which required the EDGs to start, and the start was not in response to actual plant conditions satisfying the requirements for initiation, this event has been determined to be an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee notified the NRC Resident Inspector. | Emergency Diesel Generator | 05000325/LER-2017-004 |
| ENS 52051 | 9 May 2016 10:26:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Primary Containment Isolation Valves (Pcivs) | This 60-day telephone notification is being made in lieu of a Licensee Event Report (LER) submittal in accordance with 10 CFR 50.73(a)(1) to notify the NRC of an invalid actuation of PCIVs, reportable under 10 CFR 50.73(a)(2)(iv)(A). On May 9, 2016, at 0626 Eastern Daylight Time (EDT), an unexpected trip of the Unit 1 Reactor Protection System (RPS) Bus A occurred, resulting in closure of several PCIVs on loss of power, per design. In addition, the following actuations also occurred per design: - insertion of a half reactor scram signal. - initiation of the standby gas treatment (SBGT) system . - isolation of the secondary containment. - initiation of the control room emergency ventilation (CREV) system smoke and radiation mode. - trip of the operating reactor water cleanup system (RWCU) pump due to closure of its isolation valve. The event resulted from a failed relay coil in the drive motor run logic for the RPS power supply motor-generator (MG) set. The failed relay blew a fuse, which de-energized the RPS drive motor contactor and MG set. This resulted in de-energizing the RPS power supply in the 'A' channel and produced the actuations listed previously, per design. Affected systems and components were restored to their normal configurations by 1000 EDT on May 9, 2016. Since no plant or process conditions existed that required the PCIV isolations (e.g., high drywell pressure or low reactor water level), this event is being reported per 10 CFR 50.73(a)(1) as an invalid actuation. This issue has been entered into the site Corrective Action Program (CR 2027653) for evaluation and implementation of further corrective actions. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector has been notified. | Secondary containment Reactor Protection System Primary containment Reactor Water Cleanup Control Room Emergency Ventilation | |
| ENS 51739 | 9 January 2016 14:46:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generator | This 60-day optional telephone notification is being made in lieu of an LER submittal, as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). On January 9, 2016, at 0946 Eastern Standard Time (EST), an invalid actuation of EDG 2 occurred. During the performance of procedure 0PT-12.2.1B, 'ECCS D/G #2 Logic Test,' procedure steps were performed out of sequence. As a result, the EDG 2 control logic was not properly defeated to prevent the auto-start prior to testing portions of the Emergency Core Cooling System (ECCS) EDG 2 logic. EDG 2 responded properly to the auto-start signal. The actuation was complete, in that the EDG started and ran unloaded. EDG 2 was returned to standby status at 1130 EST. Since no actual bus under voltage condition existed which required the EDG to start, and the start was not in response to actual plant conditions satisfying the requirements for initiation, this event has been classified as an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator Emergency Core Cooling System | 05000325/LER-2017-004 |
| ENS 51505 | 10 September 2015 01:03:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a General Containment Isolation Signal Affecting More than One System | This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe invalid actuation containment isolation signals affecting containment isolation valves in more than one system. On September 9, 2015 at 2103 hours Eastern Daylight Time (EDT), Unit 1 experienced a loss of electrical power to motor control center 1CB when the substation E6 feeder breaker tripped. The loss of power resulted in closure of primary containment isolation valves (PCIVs) in Unit 1 Primary Containment Isolation System (PCIS) Group 2 (i.e. Drywell Equipment and Floor Drains, Residual Heat Removal (RHR) Discharge to Radwaste, RHR Process Sample, and Traversing lncore Probe), Group 3 (i.e., Reactor Water Cleanup), and Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems). It has been determined that affected PCIVs appropriately closed. However, the limit switch within the motor operator of the inboard RWCU PCIV (i.e. 1-G31-F001) malfunctioned; resulting in an inaccurate remote position indication. Testing has confirmed that 1-G31-F001 properly closed and can perform its intended safety function. These PCIV isolations were the result of a substation E6 feeder breaker trip to motor control center 1CB and not in response to actual plant conditions (i.e., to mitigate the consequences of an event) and, therefore, were invalid. This event did not result in any adverse impact to the health and safety of the public. The NRC Resident Inspector was notified. | Primary Containment Isolation System Primary containment Residual Heat Removal Reactor Water Cleanup | |
| ENS 49800 | 11 December 2013 13:18:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Primary Containment Isolation System (Pcis) Valves During I&C Maintenance | This 60-day report, as allowed by 10 CFR 50.73(a)(1 ), is being made per 10 CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid closure of Unit 2 Primary Containment Isolation System (PCIS) valves. On December 11, 2013, at 0818 EST, an instrument technician was adjusting the output voltage of the 'A' 120-volt Reactor Protection System (RPS) motor-generator (MG) set, which is the normal power supply for the 'A' RPS bus. As the adjustment potentiometer was being moved, output voltage momentarily dropped below the setpoint of an Electrical Protection Assembly (EPA) on the 'A' RPS bus. The EPA tripped and removed power from the 'A' RPS bus. Removing power from the RPS bus resulted in PCIS valves receiving a close signal. Affected valves or systems were a Reactor Water Sample valve, Main Steam Line Drain valves, Containment Atmospheric Control System valves, Drywell Equipment Drain and Floor Drain valves, and a Reactor Water Cleanup System valve. Other systems affected were Standby Gas Treatment, Control Room Emergency Ventilation, and Radiation Monitoring on Main Steam Lines, Main Stack, Reactor Building Vent, and Main Condenser. All actuations that resulted from the loss of power to RPS Bus 'A' were completed as expected. This event resulted from the attempt to adjust the voltage control potentiometer on the RPS MG set. When a technician attempted to adjust the potentiometer, the movement caused the RPS MG set to momentarily and unexpectedly experience a low voltage on the output, tripping the output breakers. Power was restored to the affected RPS bus by 0858 EST on December 11, 2013, and all affected systems were subsequently returned to service. Since no actual plant or process conditions existed which would have caused the various actuations described above, this event is being reported per 10 CFR 50.73(a)(1) as an invalid actuation. This issue has been entered into the site Corrective Action Program (CR 651284) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification. | Reactor Protection System Primary Containment Isolation System Reactor Water Cleanup Control Room Emergency Ventilation Main Steam Line Main Condenser | |
| ENS 49168 | 8 May 2013 01:14:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generators | This 60-day telephone notification is provided in accordance with 10 CFR 50.73(a)(1) to report an invalid actuation of the Emergency Diesel Generators (EDGs) reportable under 10 CFR 50.73(a)(2)(iv)(A). Due to the shared configuration of the onsite AC Electrical Distribution System, this event is applicable to both Units 1 and 2. On May 7, 2013, at approximately 2114 hours Eastern Daylight Time (EDT), while Operations personnel were making preparations for Unit 2 main turbine generator synchronization to the grid, a Main Generator Reverse Power Trip occurred. Main Generator Reverse Power Trip was actuated after adjusting the Manual Voltage Regulator on the Main Generator. The reverse power relay operates the Generator Primary Lockout which initiates a turbine trip and start of all four EDGs. These features functioned as designed. The main generator breaker was open at the time of the event; as such, electrical power was not lost to the emergency busses. All four EDGs started and operated as expected. Because electrical power was never lost to the emergency busses and none of the EDGs loaded to their respective emergency busses, the actuations were considered to be partial. The EDGs were returned to their standby line-up by 2229 hours on May 7, 2013. Since no actual bus under voltage condition existed which required the EDGs to start and the start was not in response to actual plant conditions satisfying the requirements for initiation, this event has been classified as an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator Main Turbine | |
| ENS 48972 | 4 March 2013 13:04:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generators | This 60-day telephone notification is provided in accordance with 10 CFR 50.73(a)(1) to report an invalid actuation of the Emergency Diesel Generators (EDGs) reportable under 10 CFR 50.73(a)(2)(iv)(A). Due to the shared configuration of the onsite AC Electrical Distribution System, this event is applicable to both Units 1 and 2. On March 4, 2013, at approximately 0804 EST, while performing a planned maintenance activity associated with the Unit 2 Start-Up Auxiliary Transformer (SAT), the SAT lock-out relay was inadvertently energized. This occurred when a Transmission Maintenance electrician closed the fault pressure device oil isolation valve without having previously opened the fault pressure cutoff switch. This action resulted in energizing the SAT lock-out relay and, per design, started all four EDGs. All four EDGs started and operated as expected. Because electrical power was never lost to the emergency busses and none of the EDGs loaded to their respective emergency busses, the actuations were considered to be partial. The EDGs were returned to their standby line-up by 1023 (EST) hours on March 4, 2013. Since no actual bus under voltage condition existed which required the EDGs to start and the start was not in response to actual plant conditions satisfying the requirements for initiation, this event has been classified as an invalid actuation. This event did not result in any adverse impact to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator | |
| ENS 44213 | 15 March 2008 20:35:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation System (Pcis) Actuation | This 60-day telephone notification is being made under reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1). On March 15, 2008, while resetting the main turbine in preparation for performing 1MST-RPS25R, 'RPS Turbine Stop Valve and Control Valve Closure Chan Cal,' a Group 1 isolation was received. Main Steam Lines (MSLs) A and B were isolated for local leak rate testing, however, the MSLs C and D were not. The inboard and outboard Main Steam Isolation Valves (MSIVs) for the C and D MSL closed as a result of this event. The isolation occurred during work associated with replacement of the main generator output breakers 22A and 22B. In order for the breakers to be removed, wiring that provides breaker position information was disconnected from the turbine control system (EHC). This resulted in a 'breaker closed' input to EHC. When the main turbine was reset, several logic interactions occurred resulting in the Group 1 isolation. No actual plant condition existed which required a Group 1 isolation and, with the Unit in Mode 4, Group 1 isolation is not required to be operable. Therefore, this actuation is considered to be invalid. The affected MSIVs and PCIS instrumentation operated properly. This was a full Group 1 isolation with only the MSIVs associated with the C and D MSLs closing since the A ad B lines were isolated when the actuation occurred. The invalid PCIS actuation was entered into the corrective action program (i.e., NCR 270475). The safety significance of this event was minimal. Plant equipment performed as expected. Group 1 isolation was not required to be operable in Mode 4. The Group 1 isolation was reset and a jumper was installed to prevent a subsequent invalid Group 1 isolation. Procedures will be developed or revised to disable the Group 1 Isolation during modes in which it is not required and to reset the main turbine during outages. The NRC Resident Inspector has been notified at this report. | Main Steam Isolation Valve Primary Containment Isolation System Main Turbine Main Steam Line | 05000324/LER-2008-001 |
| ENS 43791 | 21 September 2007 18:10:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Emergency Diesel Generators | This telephone notification is being made in accordance with 10CFR50.73(a)(1) to report an invalid actuation of the Emergency Diesel Generators (EDGs) reportable under 10CFR50.73(a)(2)(iv)(A). On September 21, 2007, at approximately 1310 EDT, while Operators were in the process of synchronizing the main turbine generator, a Generator Field Overexcitation trip occurred due to a failed transistor on the manual voltage regulator circuit board. This resulted in a primary and backup generator lockout and turbine trip. All four EDG's started and operated as expected. Because electrical power was never lost to the emergency buses and none of the EDGs loaded onto their respective emergency buses, the actuations were considered to be partial. The EDGs were returned to their standby line-up by 1615 on September 21, 2007. Since no actual bus undervoltage condition existed which required the EDG's to start and the start occurred inadvertently as a result of a single component failure, this event has been classified as an invalid actuation. This invalid EDG start event was entered into the corrective action program (i.e., NCR 247573) Initial Safety Significance Evaluation - The safety significance is considered to be minimal. The EDGs started and operated normally. Offsite electrical power to the Emergency buses was never lost. Corrective Actions - The main turbine generator manual voltage regulator circuit board was replaced. The licensee notified the NRC Resident Inspector. | Emergency Diesel Generator Main Turbine | |
| ENS 41692 | 12 May 2005 08:11:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.73(a)(1), Submit an LER | Technical Specification Required Shutdown Due to Loss of Emergency Bus E1 | On May 12, 2005, at 0411 hours, electrical power was lost to the 4160 VAC Emergency Bus E1. Emergency Diesel Generator 1 was inoperable for maintenance at the time of the electrical power loss. This power loss to Emergency Bus E1 affected both Units 1 and 2. Unit 1 The loss of power to E1 resulted in Division 1 Primary Containment Isolation Valve (PCIV) actuations. The actuations included the Primary Containment Isolation System (PCIS) Group 2 (i.e., Drywell Equipment and Floor Drain, Traversing In-core Probe, Residual Heat Removal (RHR) Discharge to Radwaste, and RHR Process Sample), Group 3 (i.e., Reactor Water Cleanup), and Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems) valves, as well as the Reactor Building Ventilation System isolation (i.e., Secondary Containment isolation) and the automatic start of Standby Gas Treatment (SGT) System train B. The actuations of PCIVs and Reactor Building Ventilation System isolation were complete and the affected equipment responded as designed to the invalid signal (i.e., the valves and dampers that were open, at the time of the event, closed). Additionally, SGT System train B started and functioned successfully. Loss of power to E1 also resulted in entry into LCO 3.0.3 (i.e., be in Mode 2 within 7 hours, Mode 3 within 13 hours, and Mode 4 within 37 hours) due to all required reactor coolant leakage detection instrumentation/systems being inoperable. At 0440 hours, it was discovered that all three Control Room Air Conditioning (AC) subsystems became inoperable due to failure of the control building air compressors and Technical Specification LCO 3.0.3 was entered. At 0515 hours, it was determined that both Control Room Emergency Ventilation (CREV) subsystems became inoperable when the dampers drifted shut. At 0546 hours, a control building air compressor was started and the control room air conditioning and CREV subsystems were returned to operable status. Operators initiated a plant shutdown for Unit 1, as required by Technical Specifications at 0948 hours. Unit 2 Conditions and activities associated with the Control Room AC and CREV systems apply to Unit 2 as well as Unit 1. Reporting Requirements Met by this Notification 10 CFR 50.72(b)(2)(1), the initiation of any nuclear plant shutdown required by the plant's Technical Specifications, applies to Unit 1. 10 CFR 50.72(b)(3)(v)(D), a condition that, at the time of discovery, could have prevented the fulfillment of the safety function of systems that are needed to mitigate the consequences of an accident (i.e., Control Room AC and CREV), applies to both Units 1 and 2. 10 CFR 50.73(a)(i), invalid actuation of general containment isolation signals affecting containment isolation valves in more than one system, applies to Unit 1. INITIAL SAFETY SIGNIFICANCE EVALUATION Currently Unit 2 is operating at steady state with Unit 1 being shut down. Specified systems actuated as designed. No adverse impact to the control room environment occurred during the period (i.e., one hour and 35 minutes) the affected ventilation system was inoperable. The other redundant emergency busses are operable. Prior to the event reactor coolant leakage level for Unit 1 was well within operating limits. The actions as required by the applicable Technical Specifications have been established. CORRECTIVE ACTIONS Activities are currently under way to determine the cause of the E1 power loss and restore electrical power to Emergency Bus E1. Causes and actions to preclude recurrence will be addressed in accordance with the corrective action program and provided to the NRC in the associated licensee event report. The licensee notified the NRC Resident Inspector.
On May 12, 2005, at 0411 hours, electrical power was lost to the 4160 VAC Emergency Bus E1. Emergency Diesel Generator 1 was inoperable for maintenance at the time of the electrical power loss. This power loss to Emergency Bus E1 affected both Units 1 and 2. A non-emergency notification (Event Number 41692) was made to the NRC Operations Center at 112:2 hours. This follow-up notification discusses plant recovery from the Emergency Bus E1 power loss. Unit 1 Loss of power to E1 resulted in entry, into LCO 3.0.3 (i.e., be in Mode 2 within 7 hours, Mode 3 within 13 hours, and Mode 4 within 39 hours) due to all required reactor coolant system (RCS) leakage detection instrumentation being inoperable. Operators initiated a plant shutdown for Unit 1, as required by Technical Specifications at 0948 hours. A Notice of Enforcement Discretion (NOED) was requested from the NRC to waive compliance with the shutdown requirements associated with RCS leakage detection instrumentation in order to provide more time for an orderly plant shutdown. In lieu of the RCS leakage detection shutdown requirements (i.e., be in Mode 2 by 1111 hours), Unit 1 would adhere to the shutdown requirements associated with loss of Emergency Bus E1 (i.e.,, be in Mode 3 by May 13, 2005, at 0011 hours). The requested NOED was verbally granted by the NRC on May 12, 2005 at 1050 hours, so shutdown activities for Unit 1 continued versus the insertion of a manual reactor scram, with the unit at approximately 65 percent of rated thermal power. Power was restored to Emergency Bus E1 and the LCO associated with RCS leakage detection instrumentation was exited on May 12, 2005 at 1740 hours. The LCO associated with loss of power to Emergency Bus E1 was exited at 2015 hours. Unit 2 The LCO associated with loss of power to Emergency Bus E1 also applied to Unit 2, and was exited at 2015 hours, CORRECTIVE ACTIONS Emergency Diesel Generator 1 was made available, but not operable, on May 13, 2005, at 0117 hours. The licensee notified the NRC Resident Inspector. Reg 2 RDO (Moorman) was notified. | Reactor Coolant System Secondary containment Emergency Diesel Generator Primary Containment Isolation System Primary containment Reactor Building Ventilation Residual Heat Removal Reactor Water Cleanup Control Room Emergency Ventilation | 05000325/LER-2005-004 |
| ENS 41357 | 13 December 2004 21:15:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation | The following information was provided by the licensee: On December 13, 2004, at 1615 hours, during clearance restoration activities following 24V DC battery maintenance, Battery 22B-1 output breaker located on 24/48V DC Distribution Panel 22B, Circuit 5 was inadvertently opened resulting in the invalid actuation of the Unit 1 logic associated with the 24V DC bus. The actuations included the Primary Containment Isolation System (PCIS) Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems) valves, the Reactor Building Ventilation System Isolation (i.e., Secondary Containment isolation), and the automatic start of both Standby Gas Treatment (SGT) System trains A and B. The actuations of PCIS Group 6 valves and Reactor Building Ventilation System Isolation were complete and the affected equipment responded as designed to the invalid signal (i.e., the valves and dampers that were open, at the time of the event, closed). Additionally, SGT System trains A and B started and functioned successfully. After verification of the expected equipment responses, the breaker was reset, the actuation logic was reset, and the equipment/systems were returned to the status required by plant conditions. Discussion of the causes and corrective actions associated with this event are documented in the corrective action program in action request 145898. The (NRC) resident inspector has been notified. | Secondary containment Primary Containment Isolation System Reactor Building Ventilation | |
| ENS 40541 | 11 January 2004 11:37:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation | This report is being made in accordance with 10CFR50.73 (a)(1), which states, in part, "in the case of an invalid actuation reported under 10 CFR50.73(a)(2)(iv), other than actuation of the reactor protection system (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER." These invalid actuations are being reported under 10CFR50.73(a)(2)(iv)(A). NUREG-1022, Rev. 2, states that the report should provide the following information: -The specific train(s) and system(s) that were actuated -Whether each train actuation was complete or partial -Whether or not the system started and functioned successfully. On January 11, 2004, at 0637 hours, the Reactor Building Exhaust Radiation Monitor (i.e., 1-D12-RM-K609B) signal input spiked resulting in the invalid actuation of the logic associated with the instrument channel. The actuations included the Primary Containment Isolation System (PCIS) Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems) valves, the Reactor Building Ventilation System isolation (i.e., Secondary Containment isolation) and the automatic start of both Standby Gas Treatment (SGT) System trains A and B. The actuations of PCIS Group 6 valves and Reactor Building Ventilation System isolation were complete and the affected equipment responded as designed to the invalid signal (i.e., the valves and dampers that were open, at the time of the event, closed). Additionally, SGT System trains A and B started and functioned successfully. After verification of the expected equipment responses, 1-D12-RM-K609B was reset, the actuation logic was reset, and the equipment/systems were returned to the status required by plant conditions. A radiological survey of the monitored area was completed with no abnormal conditions noted. Discussion of the causes and corrective actions associated with this event are documented in the corrective action program in action request (i.e., AR) 115087. The resident inspector has been notified. | Secondary containment Reactor Protection System Primary Containment Isolation System Reactor Building Ventilation | |
| ENS 40496 | 22 December 2003 03:04:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Reactor Building Exhaust Radiation Monitor Signal Resulting in Pcis Isolations | This report is being made in accordance with �50.73 (a)(1), which states, in part, 'In the case of an invalid actuation reported under �50.73 (a)(2)(iv), other than actuation of the reactor protection system (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event Instead of submitting a written LER.' These invalid actuations are being reported under �50.73 (a)(2)(iv)(A). NUREG-1022, Rev. 2, states that the report should provide the following information: - The specific train(s) and system(s) that were actuated - Whether each train actuation was complete or partial - Whether or not the system started and functioned successfully. On December 21, 2003, at 2204 hours, the Reactor Building Exhaust Radiation Monitor (i.e., 1-D12-RM-K609B) signal input spiked resulting in the invalid actuation of the logic associated with the instrument channel. The actuations included the Primary Containment Isolation System (PCIS) Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems) valves, the Reactor Building Ventilation System isolation (i.e., Secondary Containment isolation) and the automatic start of both Standby Gas Treatment (SGT) System trains A and B. The actuations of PCIS Group 6 valves and Reactor Building Ventilation System isolation were complete and the affected equipment responded as designed to the invalid signal (i.e., the valves and dampers that were open, at the time of the event, closed). Additionally, SGT System trains A and B started and functioned successfully. After verification of the expected equipment responses, 1-D12-RM-K609B was reset, the actuation logic was reset, and the equipment/systems were returned to the status required by plant conditions. A radiological survey of the monitored area was completed with no abnormal conditions noted. Discussion of the causes and corrective actions associated with this event are documented in the corrective action program in action request (i.e., AR) 114005. The resident inspector has been notified. |