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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56939 | 30 January 2024 14:37:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty | The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: On January 30, 2024, a non-licensed employee supervisor, after investigation, was determined to be in involved with a controlled substance. The employee's access to the site has been placed on administrative hold, pending further investigation. The NRC Resident Inspector has been notified. | ||
| ENS 56502 | 3 May 2023 16:30:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report | The following information was provided by the licensee via phone and email: A non-licensed, non-supervisor contractor was found to be in possession of alcohol in the protected area. The individual's site access has been terminated. The NRC Senior Resident Inspector has been notified. | ||
| ENS 56464 | 16 February 2023 12:05:00 | Other Unspec Reqmnt 10 CFR 50.73(a)(1), Submit an LER | 60 Day Notification for an Invalid Actuation of the Emergency Service Water System | The following information was provided by the licensee via email: 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 an invalid specific system actuation of the Emergency Service Water (ESW) System. On 2/16/2023, while performing a calibration planned maintenance (PM) for a jacket water pressure indicator during a D13 diesel generator system outage window, the 'C' ESW pump unexpectedly auto-started. Subsequent investigation identified that the affected jacket water pressure indicator shares a common sensing line with a jacket water pressure switch that provides a back-up to the engine speed switch for the engine running signal. At the time the jacket water pressure indicator calibration PM was being performed, the power circuits for D13 diesel generator instrumentation were energized. Pressurization of the energized jacket water pressure switch during the pressure indicator calibration activity resulted in initiation of a false engine running signal to the `C' ESW pump start logic. This event is considered an invalid system actuation because the 'C' ESW pump started in response to a false signal that the D13 EDG was running when the D13 EDG did not start. The actuation was not initiated in response to actual plant conditions or parameters and was not a manual initiation. The ESW system functioned as expected in response to the actuation. The affected ESW pump was shut down in accordance with plant procedures. There was no impact on the health and safety of the public or plant personnel. The licensee notified the NRC Resident Inspector. | Service water | |
| ENS 56360 | 6 February 2023 11:30:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Communications and Assessment Capabilities | The following information was provided by Constellation via email: On 02/06/2023 at 0416 EST, the Constellation Emergency Response Organization (ERO) Notification Database System uploaded data files into the Mass Notification System (Everbridge) which is used to notify ERO personnel when activated. At 0630, the individual reviewing the uploaded files discovered that the data files did not upload properly and that Everbridge may not notify all ERO individuals within the required 10 minutes of system initiation. Constellation resolved the issue by 0752. During the time period of 0416 to 0752, control room operators would have been unaware that the ERO notification was not successful. Therefore, this issue constitutes a loss of offsite communications capability and is reportable under 10 CFR 50.72(b)(3)(xiii), 'The licensee shall notify the NRC as soon as practical and in all cases within eight hours of the occurrence of any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability (e.g., significant portion of control room indication, Emergency Notification System, or offsite notification system).' This loss of offsite communications capability affected all Constellation nuclear stations. There was no impact on the health and safety of the public or plant personnel. Each affected station NRC Resident Inspectors have been or will be notified. | ||
| ENS 56283 | 2 November 2022 23:29:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-DAY Telephonic Notification - Invalid Specific System Actuation | The following information was provided by the licensee via email: This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid specific system actuation of the Emergency Service Water System (ESW). On 11/2/2022, during normal reactor operations, multiple main control room alarms were received for D12 Emergency Diesel Generator (EDG) running and Unit 1 Division 2 Safeguard Battery Ground. The D12 EDG did not start; however, the 'B' ESW Pump auto started. Subsequent troubleshooting determined that the cause of the D12 EDG running alarms and the inadvertent auto start of the 'B' ESW Pump was a malfunction on the D12 EDG speed switch. This event is considered an invalid system actuation because the 'B' ESW Pump started in response to a false signal that the D12 EDG was running when D12 EDG did not start. This was a complete actuation of the ESW System and the system functioned as expected in response to the actuation. The affected ESW Pump was shut down in accordance with plant procedures and the degraded D12 EDG speed switch was replaced. There was no impact on the health and safety of the public or plant personnel. The licensee notified the NRC Resident Inspector. | Service water Emergency Diesel Generator | |
| ENS 56163 | 14 October 2022 14:07:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Inoperable | The following information was provided by the licensee via email: Unit 1 High Pressure Coolant Injection (HPCI) was declared inoperable due to an inadvertent division 2 isolation signal and subsequent valve closure. This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of the safety function of a system that is needed to mitigate the consequences of an accident. The NRC Resident will be notified. | High Pressure Coolant Injection | |
| ENS 55685 | 3 January 2022 13:41:00 | 10 CFR 26.719, FFD Reporting requirements | Failed FITNESS-FOR-DUTY Test | The following information was provided by the licensee via email: On January 3, 2022, a Licensed Reactor Operator violated the station's Fitness for Duty policy. The employee's unescorted access to Limerick Generating Station has been terminated in accordance with station procedures. The event was determined to be reportable under 10 CFR 26.719(b)(2)(ii). The NRC Resident Inspector has been notified. | ||
| ENS 55484 | 23 September 2021 18:43:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection System Declared Inoperable | During planned testing of the Unit 1 HPCI (high pressure coolant injection) system, flow controller oscillations occurred which prevented successful completion of the surveillance test. Operators secured Unit 1 HPCI and declared the system inoperable. HPCI inoperable placed the licensee in a 14-day limiting condition for operation that was extended to 30 days after their risk-informed completion time evaluation was done. The licensee has notified the NRC Resident Inspector. | High Pressure Coolant Injection | |
| ENS 55345 | 13 May 2021 11:00:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Containment Isolation Signal | This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of containment isolation signal affecting more than one system. On May 13, 2021, during the restoration of the Unit 2 Refuel Floor High Radiation Isolation Logic an invalid isolation signal was received. The condition requiring an isolation signal was verified not to be present prior to restoring the logic; however, it was not recognized that a previous isolation signal was latched in and had not been reset. When the isolation logic was restored, the Primary Containment Isolation System (PCIS) isolated on the invalid signal. The systems successfully completed the isolation per the plant design and plant configuration. The following systems actuated due to the Unit 2 PCIS Group 6C Isolation: - Isolation of Containment Hydrogen and Oxygen Sampling Valves, - Start of the 2A Reactor Enclosure Recirculation System, - Trip of the Units 1 and 2 Refuel Floor HVAC, - Start of the A and B Trains of Standby Gas Treatment Systems. The NRC Resident Inspector was notified. | Primary Containment Isolation System HVAC Standby Gas Treatment System Reactor Enclosure Recirculation System | |
| ENS 55000 | 16 November 2020 10:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Inoperable | During normal plant start up on Limerick Unit 1, reactor pressure was raised above 200 psig prior to unisolating the Unit 1 high pressure coolant injection system (HPCI) which remained inoperable. Per TS 3.5.1, HPCI is required to be operable in Mode 2 above 200 psig. HPCI has since been restored to operable. The NRC Resident Inspector has been notified. | High Pressure Coolant Injection | |
| ENS 54996 | 13 November 2020 07:45:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to High Reactor Pressure Signal | At 0245 EST on November 13, 2020, the Limerick Unit 1 reactor automatically scrammed on a valid Reactor High Pressure signal (1096psig). The Reactor High Pressure signal was caused by the closure of the 1B Inboard Main Steam Isolation Valve (MSIV), causing reactor pressure to rise, exceeding the Reactor Protection System (RPS) setpoint of 1096psig. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Steam Bypass Valves to the Main Condenser and normal level control using the Feedwater System. The closure of the 1B Inboard MSIV appears to have been caused by a loss of Primary Containment Instrument Gas (PCIG) pneumatic supply to the valve. The licensee notified the NRC Resident Inspector, and will be notifying Berks, Chester, and Montgomery Counties, as well as the Pennsylvania Emergency Management Agency. | Feedwater Reactor Protection System Main Steam Isolation Valve Primary containment Main Condenser Main Steam | |
| ENS 54098 | 4 June 2019 05:45:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Scram During Rapid Plant Shutdown | At 0145 EDT, on 6/4/19, Unit 2 was manually scrammed during a Rapid Plant Shutdown. At 64 percent reactor power, a Rapid Plant Shutdown was initiated due to lowering Main Condenser vacuum as a result of the loss of a plant electrical panel that powers Offgas System controls. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Turbine Bypass Valves to the Main Condenser and normal level control using Feedwater and Condensate. Main Condenser Vacuum has been restored. The licensee notified the NRC Resident Inspector. Additionally, State and local government agencies were notified. Prior to restarting Unit 2, an evaluation needs to be done due to the Unit 1 Diesel currently out of service for maintenance. The Unit 1 Diesel is a power supply for some of the common systems under the Unit 2 Technical Specifications and therefore required. | Feedwater Main Condenser | |
| ENS 54015 | 21 April 2019 13:20:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Limerick Onsite Non-Work Related Fatality | Event of Public Interest performed to notify State and Local agencies for emergency vehicle response required due to an on-site non-work related illness. The individual was unresponsive and was unable to be resuscitated due to the medical issue. The individual was outside the Radiological Controlled Area (RCA) and no radioactive material or contamination was involved. The NRC Resident Inspector was notified. | ||
| ENS 54083 | 18 April 2019 06:49:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a Unit 2 Containment Isolation Logic Due to a Blown Fuse | This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of Limerick Generating Station Unit 2 containment isolation logic. On April 18, 2019, while performing a relay replacement on the Division 2/4 Main Steam Line logic, a partial containment isolation occurred due to a blown fuse. The following systems had components that actuated due to the partial isolation: Reactor Water Clean-Up System Primary Containment Instrument Gas System Drywell Chilled Water System Reactor Enclosure Cooling Water System Core Spray System The Residual Heat Removal System received an isolation signal; however, the system remained in service because the isolation was defeated in accordance with plant procedures. This event resulted in partial Group 2A, 3, 7A, 8A, and 8B isolations. The systems successfully functioned per the plant design and plant configuration. The licensee notified the NRC Resident Inspector. | Primary containment Core Spray Residual Heat Removal Main Steam Line | |
| ENS 54014 | 22 February 2019 15:30:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a Unit 1 Containment Isolation Logic Due to a Blown Fuse | This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of Limerick Generating Station Unit 1 containment isolation logic. On February 22, 2019, while performing work on the 1C Main Seam Line Rad Monitor a partial containment isolation occurred due to a blown fuse. The blown fuse caused a single channel 'C' isolation signal for the Refueling Area Ventilation Exhaust High Radiation and the Reactor Enclosure Ventilation Exhaust-High Radiation logic. The following systems had components that actuated due to the partial isolation: - Plant Process Radiation Monitoring System - Nuclear Boiler System - Control Rod Drive Hydraulic System - Containment Atmospheric Control System - Primary Containment Instrument Gas System This event resulted in partial Group VIC and partial Group VIIIB isolations. All the components that would actuate on a single 'C' isolation signal responded as designed. The licensee notified the NRC Resident Inspector. | Primary containment Control Rod | |
| ENS 53556 | 21 August 2018 04:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Holding Pond Overflow | At 2322 EDT, Limerick Generating Station notified the Pennsylvania DEP (Department of Environmental Protection) that our plant waste water pond (holding pond) overflowed due to heavy rainfall in the area. Plant alignment changes were made and the holding pond stopped overflowing at 0017 EDT. Limerick Generating Station has not determined this release to contain oil, grease, or pollutants hazardous to the public. The licensee notified the NRC Resident Inspector. | ||
| ENS 53341 | 17 April 2018 14:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection System Declared Inoperable | Unit 1 HPCI (High Pressure Coolant Injection) was declared inoperable due to a Main Pump seal leak that was identified during surveillance testing. Unit 1 HPCI was declared inoperable at 1030 EDT. HPCI was secured and was manually re-aligned to an available status. At the time of this notification, repairs have been completed and the licensee is making preparations to re-perform the surveillance. The licensee has notified the NRC Resident Inspector. | High Pressure Coolant Injection | |
| ENS 53108 | 8 December 2017 18:10:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection Inoperable Due to a Leaking Check Valve | U/2 HPCI (Unit 2/High Pressure Coolant Injection) was declared inoperable due to leak by of the pump discharge check valve after pump shutdown from flow testing. This resulted in cycling of the minimum flow valve. The discharge valve was closed to prevent the continued cycling of the minimum flow valve. This condition was identified during normal surveillance testing. The licensee notified the NRC Resident Inspector. | High Pressure Coolant Injection | |
| ENS 52874 | 27 July 2017 17:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Core Injection System Declared Inoperable | (Unit 2) HPCI was declared inoperable due to improper valve alignment stemming from an incorrect sequence directed from a work order. (Unit 2) HPCI was inoperable for 20 minutes and was manually re-aligned to an operable status. The licensee notified the NRC Resident Inspector. | ||
| ENS 52871 | 25 July 2017 00:44:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification to the Pennsylvania Department of Environmental Protection | |||
| ENS 52738 | 8 May 2017 13:25:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Through-Wall Leakage Identified on Reactor Coolant System Pressure Boundary During Testing | On May 8th, 2017 at 0925 (EDT), during the performance of LGS (Limerick Generating Station) leakage testing of the reactor pressure vessel and associated piping, a through-wall leak was identified on an instrument line connected to the N16D nozzle. The reactor will be maintained shutdown until pipe repairs and testing are complete. The licensee informed the NRC Resident Inspector. | Reactor Coolant System Reactor Pressure Vessel | |
| ENS 52455 | 21 December 2016 18:50:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Due to Valve Failure | During review of the Limerick future modification list, a concern was raised with a proposed modification for HV-011-015A, ESW (Emergency Service Water) 'A' Discharge to 'B' RHR Service Water Return, which failed to fully close during routine testing. As a result of the failure to close, a clearance was applied and a 10CFR50.59 screening was performed to close and de-energize HV-011-015A and open and de-energize valve HV-011-011A, ESW 'A' Discharge to 'A' RHR (Residual Heat Removal) Service Water Return. This clearance isolated one of the two ESW return flow paths so that only one flow path is available to return cooling water flow to the spray pond. The 10CFR50.59 screening did not address that fire areas 12 (Unit 1 4kV D13 switch gear room) and 18 (Unit 2 4kV D23 switch gear room) are not in compliance with the existing fire safe shutdown (FSSD) analysis. The FSSD analysis credits both flow paths so that Emergency Service Water can be returned to the spray pond. With only one of the two return flow paths available, a single spurious fire induced valve operation can result in deadheading an ESW pump and starving an operating emergency diesel generator of cooling water. Running the emergency diesel generator with a loss of cooling water will initiate a diesel protective trip on high temperature. Compensatory measures are in place for the specific fire areas listed above. The licensee has notified the NRC Resident Inspector. | Service water Emergency Diesel Generator Spray Pond | |
| ENS 52270 | 29 September 2016 21:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Tsc Ventilation Indication Issue Identified Following Surveillance Testing | On 9/29/2016 at 1700 (EDT) the MCR (Main Control Room) was notified of a potential Technical Support Center (TSC) emergency ventilation indication issue following surveillance testing. At 2350 troubleshooting revealed a blown control power fuse which affected functionality of TSC HVAC emergency mode. The system was restored to operable as of 0043 on 9/30/16. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. If TSC relocation becomes necessary, then personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee informed the NRC Resident Inspector. | HVAC | |
| ENS 52101 | 18 July 2016 20:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Offsite Communications Capability | Testing of the Everbridge ERO (Emergency Response Organization) notification system identified the system was not able to notify all ERO individuals. This constitutes a loss of offsite communications capability. The issue was subsequently reported resolved by the vendor and site testing has verified resolution at 2037. The Everbridge system capability loss for Limerick was identified at approximately 1600 EDT on July 18, 2016, due to a loss of system communications. Emergency Response Data System (ERDS) capability was not lost. This event is reportable under 10 CFR 50.72(b)(3)(xiii) as a loss of communications capability. The NRC Resident inspector has been notified. | Emergency Response Data System | |
| ENS 51968 | 1 June 2016 13:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram Due to Unexpected Core Flow Change | Limerick Unit 2 was manually scrammed from 100 (percent) power at 0900 (EDT) on 6/1/2016 in accordance with plant procedure OT-112 'Unexpected/Unexplained change in core flow' when both 2A and 2B Recirculation Pump Adjustable Speed Drives (ASDs) tripped due to an electrical fault. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Steam Bypass valves to the Main Condenser and normal level control using Feedwater. The Manual RPS actuation is reportable under 10 CFR 50.72 (b)(2). All rods inserted fully on manual scram and the plant is in a normal shutdown electrical line up. Unit 1 was not affected by this event. The licensee plans to issue a press release. The licensee notified local counties and Pennsylvania Emergency Management Agency (PEMA). The NRC Resident Inspector has been notified. | Feedwater Main Condenser Main Steam | 05000353/LER-2016-001 |
| ENS 51847 | 4 April 2016 17:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Cooling Tower Water Released to a Non-Permitted Outfall | Notified the Pennsylvania Department of Environmental Protection that Limerick Cooling Tower water was released to a non-permitted outfall through the spray pond (Ultimate Heat Sink) due to system lineups associated with emergent maintenance activities. There was no radioactive material contained within the water released. Corrective actions are being taken to prevent further release via this outfall. The NRC Resident Inspector will be notified. | Spray Pond | |
| ENS 51952 | 28 March 2016 05:50:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Inboard Isolation Logic | On Monday, March 28, 2016, Unit 1 was in OPCON 5 (Refueling) conducting a refueling outage. A modification was being installed for an NSSSS (Nuclear Steam Supply Shutoff System) Test Box on Division 1A Group 1 NSSSS logic. At 0150 hours, a logic jumper was removed as directed by the work order and a logic fuse failed. The fuse failure caused an unplanned invalid actuation of the inboard isolation logic. The isolations were reset and the valves were restored to initial conditions at 0246 hours. On Sunday, April 3, 2016, at 0134 hours, one additional logic fuse opening event occurred during the testing which also caused an invalid actuation which was reset at 0405 hours. The fuse openings occurred during jumper manipulations as the modification was tested on the Division 1A and 1D logic during the refuel outage. The investigation determined the fuse openings were due to the testing process. The suspected devices that caused the condition are not permanent plant equipment and there is no degradation of the actual circuit. They were part of a temporary configuration that was installed to support modification installation and acceptance testing. The temporary devices have been removed. The portion of the primary containment isolation system that received an actuation signal functioned successfully. All of the affected open isolation valves automatically closed. The isolation was a partial actuation. This 60-day ENS report is being made per 10CFR 50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to report invalid automatic actuations of systems listed in paragraph (a)(2)(iv)(B). The listed system that actuated was general containment isolation signals affecting containment isolation valves in more than one system. Primary containment isolation valves (PCIVs) closed on reactor water cleanup (RWCU), drywell chilled water (DWCW), primary containment instrument gas (PCIG), drywell sumps and the suppression pool cleanup systems. The licensee has notified the NRC Resident Inspector. | Primary Containment Isolation System Primary containment Reactor Water Cleanup | |
| ENS 51809 | 21 March 2016 01:54:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Technical Specification (Ts) Required Shutdown Due to Pressure Boundary Leakage | During a planned Unit 1 shutdown for a refueling outage, a 0.5 gpm 'pressure boundary leak' was identified on a 1 inch pipe connected to the '1A' RHR-Shutdown Cooling return line by the drywell leak inspection team during a drywell inspection at approximately 15% power. The leak exceeded the TS 3.4.3.2 'Operational Leakage' LCO of no pressure boundary leakage. TS action 'a' was entered which requires to be in at least Hot Shutdown within 12 hours and Cold Shutdown within the next 24 hours. Therefore, the event is reportable within 4 hours per 10CFR50.72(b)(2)(i) due to the initiation of a plant shutdown required by the plant's TS. The event is also reportable within 8 hours per 10CFR50.72(b)(3)(ii) due to an event that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded. TS 1.28 defines Pressure Boundary Leakage as leakage through a nonisolable fault in a reactor coolant system component body, pipe wall or vessel wall; therefore, the leak is a 'pressure boundary leak' as defined in TS. The licensee notified the NRC resident Inspector. | Reactor Coolant System | 05000352/LER-2016-003 |
| ENS 51773 | 7 March 2016 13:37:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Fatality Onsite | At the Limerick Generating Station, an individual experiencing a non-occupational illness was taken to a local medical facility. The individual was not contaminated. Subsequently, Limerick was informed that the individual has suffered a fatality. The individual was a contract employee and was located in a clean break area, within the protected area, when the individual became ill. The licensee has notified the NRC Resident Inspector and OSHA. | ||
| ENS 51749 | 22 February 2016 18:11:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Spurious Actuation of One Emergency Siren During Planned Maintenance | Limerick Generating Station Main Control Room was informed that a Limerick Emergency Preparedness Zone (EPZ) siren located in Skippack Township, Montgomery County, Pennsylvania was sounding by an off-site vendor. This notification is being made in accordance with SAF 1.9 due to a spurious actuation of Limerick Emergency Preparedness Zone (EPZ) siren. The alarm actuated for approximately 90 seconds following preventative maintenance. No actual plant emergency exists. All Limerick EPZ sirens remain functional; no other reportability threshold(s) have been met or exceeded. The licensee informed State and local authorities and the NRC Resident Inspector. | ||
| ENS 51614 | 19 December 2015 12:02:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to Low Reactor Water Level | At 0702 EST on 12/19/2015, the Unit 2 reactor automatically scrammed on a valid reactor low level signal (12.5 inches). The reactor low level signal was caused by the trip of the in-service 2A Reactor Feedwater Pump, causing reactor level to lower, exceeding the low reactor level setpoint of 12.5 inches. The shutdown was normal. The plant is stable in Hot Shutdown with normal reactor level, pressure control via the Main Steam Bypass Valves to the Main Condenser and normal level control using the Condensate System. High level trip of the 2A Reactor Feedwater Pump was caused by high reactor level of +54 inches following opening of bypass valves during reactor start-up and pressurization. The cause is still being investigated. All systems functioned as expected following the reactor scram. The licensee notified the NRC Resident Inspector. | Feedwater Main Condenser Main Steam | |
| ENS 51368 | 3 September 2015 23:01:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection (Hpci) Declared Inoperable | At 1901 EDT on 9/3/2015, the Unit 2 HPCI system inboard steam supply valve isolated due to a high steam flow instrument failure. The inboard steam supply valve closed and isolated as expected. There were no indications of a steam leak. Drywell parameters and affected Reactor Enclosure rooms and piping areas were inspected with no indications of a steam leak. In addition, the steam leak detection system did not indicate any rising temperatures for any of the affected areas. The issue has caused Unit 2 HPCI to be declared inoperable and unavailable. Unit 2 has entered into a 14 day (Technical Specification) Limited Condition of Operation per T.S. 3.5.1. The licensee notified the NRC Resident Inspector. | High Pressure Coolant Injection | |
| ENS 51168 | 21 June 2015 20:25:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Secondary Containment Isolation | In response to a trip of Unit 2 reactor enclosure HVAC (Heating, Ventilation and Air Conditioning), subsequent loss of reactor enclosure delta-p and rising reactor enclosure room temperatures, a Unit 2 manual secondary containment isolation was initiated per station procedures. This manual isolation also resulted in an isolation signal to containment atmosphere control (CAC) system valves and primary containment instrument gas (PCIG) system valves. System responses were as expected. Unit 2 secondary containment delta-p and room temperatures were restored via the standby gas treatment system (SGTS), and Unit 2 secondary containment integrity remains intact and operable. Investigation of the trip of Unit 2 reactor enclosure HVAC is ongoing. This is being reported under 50.72(b)(3)(iv)(A) for containment isolation signal affecting containment isolation valves in more than one system. The licensee informed the NRC Resident Inspector. | Secondary containment Primary containment HVAC Standby Gas Treatment System | |
| ENS 50981 | 13 April 2015 06:20:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram Initiated | Following a pre-planned scram for entry into the U2 Refueling Outage, the 'B' Reactor Protection system (RPS) was unable to be reset due to a deficiency with the '2H' Intermediate Range Power Monitor. Due to this failure to reset RPS, a manual full scram was initiated as required by plant procedures. The licensee notified the NRC Resident Inspector. | Reactor Protection System | |
| ENS 50956 | 5 April 2015 19:37:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Alert Declared Due to Fire in Motor Control Center | An Alert was declared due to a fire in a Unit 2 Division 2 Safeguard (250 volt) DC Motor Control Center. This has made the High Pressure Core Injection system inoperable and unavailable. The fire is out. The emergency response organization has been activated and investigation / repair planning will commence. Unit 2 is stable with no other system affects. The fire was extinguished by on-site personnel. No off-site responders were required. The Reactor Core Isolation Cooling system remains operable. A Fire Watch has been stationed to monitor for fire reflash. There were no injuries resulting from this event. There was no effect on Unit 1. The licensee notified the NRC Resident Inspector and State and local government agencies. Notified the following organizations: DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, FDA EOC, FEMA NWC, and Nuclear SSA.
The Alert was terminated at 1742 EDT. The licensee notified the NRC Resident Inspector and State and local government agencies. Notified R1DO (Kennedy), IRD (Gott), and NRR EO (Morris). Notified the following organizations: DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, FDA EOC, FEMA NWC, and Nuclear SSA. | Reactor Core Isolation Cooling | |
| ENS 50951 | 3 April 2015 14:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Inoperable Seismic Instrumentation Identified During Historical Review | Limerick Generating Station (LGS) has completed a review of recent seismic monitor performance. The seismic monitor is currently capable of fulfilling its emergency assessment support function. The review of the system performance over the last three years identified two occasions when the system was degraded and incapable of performing its emergency assessment support function such that emergency classification at the UNUSUAL EVENT and ALERT levels could not be declared within fifteen minutes as required with site instrumentation. The seismic monitor was determined to be degraded and incapable of performing its emergency assessment support function on the following dates: 1) January 17, 2014 - Unit 1 100% power, Unit 2 97% power 2) March 22, 2014 - Unit 1 Refueling, Unit 2 100% power These unplanned inoperable conditions of the seismic monitor were entered into the LGS Corrective Action Program (CAP) when they occurred. While Exelon procedural direction allowed the use of offsite sources to obtain seismic data when the seismic monitor is incapable of assessing emergency plan Emergency Action Levels (EALs), this was not explicitly referenced in the approved EALs. The loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(xiii). This report is required per 10 CFR 50.72(a)(1)(ii) as an event that occurred within 3 years of the date of discovery. For the two dates above, the 1/17/14 failure was related to function of the system CPU (central processing unit) and the 3/22/14 failure was due to a failed instrument backup battery. There was no seismic event on either of these two dates. The licensee informed the NRC Resident Inspector. | ||
| ENS 50847 | 24 February 2015 02:40:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram on Reactor High Pressure Signal | At 2140 EST on 02/23/2015, Unit 1 reactor automatically scrammed on a valid reactor high pressure signal (1096#). The reactor high pressure signal was caused by the closure of the 1C inboard main steam isolation valve (MSIV), causing reactor pressure to rise, exceeding the reactor protection system (RPS) setpoint of 1096# pressure. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the main steam bypass valves to the main condenser and normal level control using the feedwater system. The closure of the 1C inboard MSIV appears to have been caused by a loss of primary containment instrument gas (PCIG) pneumatic supply to the valve. Instrument air was aligned to the remaining MSIV's. Limerick Unit 1 will remain in Hot Shutdown until repairs can be made. All rods inserted into the core during the scram. No relief or safety valves actuated during the transient. The electric grid is stable and supplying all plant loads. There was no affect on Unit 2. The licensee notified the NRC Resident Inspector, Pennsylvania Emergency Management Agency, and Berks, Chester and Montgomery counties. | Feedwater Reactor Protection System Main Steam Isolation Valve Primary containment Main Condenser Main Steam | 05000352/LER-2015-001 |
| ENS 50670 | 11 December 2014 14:45:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Both Secondary Containment Airlock Doors Opened Simultaneously | Station personnel simultaneously opened the inner and outer air lock doors from Unit 2 Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared inoperable per Unit 2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 352' momentarily open at the same time. Reactor Enclosure D/P (differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total time was approximately 5 seconds. The secondary containment doors do not have a mechanical interlock and this event has been classified as a human performance error. The licensee notified the NRC Resident Inspector | Secondary containment | 05000353/LER-2014-007 |
| ENS 50518 | 8 October 2014 08:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Sodium Hypochlorite Leak with Potential to Enter the Environment | This notification is being made as a result of notifications to other government agencies. A sodium hypochlorite leak occurred on site at Limerick Generating station on 10/7/14, that had the potential to enter the environment. The leak has been isolated. A flow control valve in the U1 cooling tower chemical treatment system caused the leak. The sodium hypochlorite that leaked was deposited into the onsite Holding Pond. The Holding Pond was being discharged at the time of the leak in accordance with procedures to support normal plant operations. The leak was discovered at 2110 hours (EDT on 10/7/14) and isolated at 2115 hours. The Holding Pond discharge was secured at 2125 hours. Sampling of the Holding Pond confirmed the presence of sodium hypochlorite. Since the Holding Pond was being released at the time of the leak, there is a potential that greater than 67 gallons of sodium hypochlorite could have been released to the Schuylkill River. This report is being made due to the potential that a reportable quantity of sodium hypochlorite could have discharged to the Schuylkill River while the Holding Pond was releasing during the sodium hypochlorite leak. Evaluations are being performed to quantify this actual volume of sodium hypochlorite that was discharged as a result of the leak. The licensee has notified the NRC Resident Inspector and state and local authorities. | ||
| ENS 50376 | 17 August 2014 08:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Technical Support Center Emergency Ventilation System Inoperable | On 8/17/2014 at 0400 EDT, the Technical Support Center (TSC) emergency ventilation system was identified as inoperable. Troubleshooting of this equipment found a blown control power fuse. The system has been restored to operational status as of 0555 EDT on 8/17/2014. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee notified the NRC Resident Inspector. | ||
| ENS 50007 | 8 April 2014 10:18:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Shutdown Action Initiated Because Hpci and Rcic Were Simultaneously Inoperable | U1 entered Technical Specification 3.0.3, and initiated actions to reduce power via control rod insertion in preparations to enter startup within the following 6 hours. Entry into Tech Spec 3.0.3 was a result of both HPCI and RCIC injection systems being inoperable at the same time. During startup from the U1 refueling outage, RCIC and HPCI full flow testing was unable to be completed at rated reactor pressure prior to the expiration of the 12 hour allowance per Tech Spec Surveillances 4.7.3.b* and 4.5.1.b.3** respectively. This occurred due to testing issues encountered while attempting to perform the rated pressure pump valve and flow tests. U1 HPCI testing was completed satisfactorily at 0830, and HPCI was restored to operable. Plant shutdown was terminated at 0830 (EDT) as conditions for 3.0.3 no longer existed. The licensee will notify the NRC Resident Inspector. | Control Rod | |
| ENS 49871 | 5 March 2014 04:34:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Unit 1 Manually Scrammed During a Rapid Shutdown in Response to a Turbine Ehc Failure | At 2334 EST on 3/4/14 Unit 1 was manually scammed during a Rapid Plant Shutdown. The Rapid Plant Shutdown was initiated due to an Electro Hydraulic (Control) (EHC) System failure resulting in all Low Pressure Turbine lntercept Valves failing closed. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Steam Bypass Valves to the Main Condenser and normal level control using Feedwater. The licensee informed both State and local agencies and the NRC Resident Inspector. A press release will be issued by the licensee. | Feedwater Main Condenser Main Steam | 05000352/LER-2014-004 |
| ENS 49842 | 19 February 2014 15:19:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Technical Support Center Emergency Ventilation Failure | On 2/19/2014 at 1019 EST, the Technical Support Center emergency ventilation system failed to operate during TSC Ventilation Operability Check per EP-MA-124-1001-F-02 performed by Limerick Emergency Preparedness staff. Troubleshooting of this equipment deficiency found a blown control power fuse. The fuse failure is attributed to its age. The system has been restored to operational status as of 1430 EST on 2/19/2014. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee notified the NRC Resident Inspector. | ||
| ENS 49706 | 9 January 2014 16:35:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Entry Into & Exit from Technical Specification 3.6.5.1.1 Due to Open Air Lock Doors | Station Personnel simultaneously opened the inner and outer air lock doors from Unit 2 (U2) Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared Inoperable per U2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 352' momentarily open at the same time. Reactor Enclosure D/P(differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total (Limiting Condition for Operation) time was approximately 5 seconds. The NRC Resident Inspector has been informed. | Secondary containment | 05000353/LER-2014-002 |
| ENS 49691 | 4 January 2014 04:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Siren Activation Caused by Equipment Malfunction | Limerick Generating Station Main Control Room was informed that a Limerick Emergency Preparedness Zone (EPZ) Siren located in South Coventry, Chester County Pennsylvania area was sounding by an off-duty plant employee and confirmed by the Chester County 911 Dispatch Center. Notification occurred at 2300 hours on 1/13/14. This notification is being made in accordance with SAF 1.9 due to a spurious actuation of Limerick Emergency Preparedness Zone (EPZ) Siren. The siren maintenance contractor has been contacted to investigate and silence the sounding alarm. No actual Plant emergency exists. The siren activation was caused by equipment malfunction. (The) remaining 164 of 165 Limerick EPZ Sirens remain functional, no other reportability threshold(s) have been met or exceeded. The licensee has notified the NRC Resident Inspector and state and local authorities. | ||
| ENS 49659 | 18 December 2013 19:09:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Unit 2 Secondary Containment Integrity | Station Personnel simultaneously opened the inner and outer air lock doors from Unit 2 Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared inoperable per U2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on the 352 foot elevation being momentarily open at the same time. Reactor Enclosure D/P (differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total LCO time was approximately 5 seconds. The licensee notified the NRC Resident Inspector. | Secondary containment | 05000353/LER-2014-001 |
| ENS 49651 | 18 December 2013 14:39:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Unit 1 Secondary Containment Integrity | Station Personnel simultaneously opened the inner and outer air lock doors from Unit 1 Reactor Enclosure to the Radwaste Enclosure. Reactor Enclosure Secondary Containment Integrity was declared inoperable per U1 TS 3.6.5.1.1, due to failure to meet surveillance requirement U1 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 217 (foot elevation, being) momentarily open at the same time. Reactor Enclosure D/P (delta pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U1 TS 4.6.5.1.1.b.2. Total LCO time was approximately 5 seconds. The licensee has notified the NRC Resident Inspector. | Secondary containment | 05000352/LER-2014-002 |
| ENS 49644 | 17 December 2013 01:00:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report - Licensed Operator Tested Positive for Alcohol | A licensed operator had a confirmed positive for alcohol during a random fitness for duty test. The employee's access to the plant has been restricted. The licensee has notified the NRC Resident Inspector. | ||
| ENS 49526 | 10 November 2013 18:51:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Integrity Momentarily Declared Inoperable | Station personnel simultaneously opened the inner and outer air lock doors from the unit 1 reactor enclosure to the radwaste enclosure. Reactor enclosure secondary containment integrity was declared INOPERABLE per TS 4.6.5.1.1.b.2 due to report of both containment airlock doors on the 217 foot elevation being momentarily open at the same time. Reactor enclosure D/P (differential pressure) remained steady at .35 inches water column. Reactor enclosure secondary containment integrity was declared OPERABLE following verification that at least one airlock door to each access of secondary containment was closed per U1 TS 4.6.5.1.1.b.2. Total LCO time was approximately 10 seconds. The licensee has notified the NRC Resident Inspector. | Secondary containment | |
| ENS 49318 | 3 September 2013 10:46:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Access Air Lock Doors Opened Simultaneously Resulting in Momentary Degradation | During planned maintenance activities, station personnel simultaneously opened the inner and outer airlock doors from unit 2 reactor enclosure to the U2 reactor enclosure HVAC room, resulting in a lowering of reactor enclosure delta pressure to below the tech spec minimum required value. The airlock doors were closed within approximately 5 seconds and reactor enclosure delta pressure recovered to greater than the tech spec minimum required value within approximately 20 seconds. Unit 2 secondary containment was declared inoperable for the time that reactor enclosure delta pressure was below the tech spec minimum required value, and was declared operable when reactor enclosure delta pressure recovered to greater than the tech spec minimum required value. Total Limiting Condition of Operation time was approximately 20 seconds. The licensee has notified the NRC Resident Inspector. | Secondary containment HVAC | 05000353/LER-2013-002 |