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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 40104 | 27 July 2003 22:39:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Optional Report | This 60-day optional report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of a specified system, specifically Primary Containment Isolation Valve (PCIV) Group II and III outboard valves. The inboard valves were unaffected by this event. On July 27, 2003, at 1839 hours, a spurious operation of Primary Containment Isolation System (PCIS) logic relay occurred. This normally energized relay momentarily changed state resulting in an isolation of the outboard Secondary Containment Isolation Valves (SCIVs) and outboard Group 2 and 3 PCIV's. Additionally, the "B" Standby Gas Treatment (SBGT) subsystem started due to the isolation. The affected systems responded as expected for the given conditions. The Group II/III PCIS isolation was reset by 1842 hours. The affected systems were promptly returned to a normal configuration. No other deficiencies or abnormalities were noted during the event. This event has been entered into the site-specific corrective action program for resolution (CR 169219) The NRC resident has been informed. | Secondary containment Primary Containment Isolation System Primary containment | |
| ENS 40198 | 25 September 2003 04:00:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.73(a)(1), Submit an LER | Initiation of a Technical Specification Required Shutdown at Peach Bottom 2 | On 09/25/03 @ 2210, while restoring reactor vessel instrumentation to service on Unit 3, an invalid ECCS actuation, (reactor vessel lo-lo-lo) occurred which caused all four (4) EDG to automatically start. All eight (8) 4 KV buses remained supplied from offsite sources. The Unit 3 ECCS pump auto starts were previously defeated per plant procedure and were not required to be operable per Tech Specs. The invalid ECCS initiation signal caused the offsite power Loss-of-Power instrumentation setpoints to transfer to the degraded voltage LOCA setpoints. With the degraded voltage LOCA setpoints initiated, the 4 KV E-bus fast transfer capability on a degraded voltage-NON-LOCA condition is defeated. With the inability to fast transfer the 4 KV E-buses on a degraded voltage NON-LOCA condition, both offsite sources are inoperable. Prior to restoring the reactor vessel level instrumentation, the E-2 diesel generator was inoperable. With both offsite source.; and one EDG inoperable, LCO 3.8.1 Required Action H.1 requires an entry into LCO 3.0.3 for Unit 2. With Unit 3 in MODE 5, LCO 3.0.3 is not applicable. After one (1) hour, actions were taken to initiate a plant shutdown per LCO 3.0.3. No negative reactivity was added as the preparations were administrative in nature. At 09/26/03 @ 0006, the invalid ECCS initiation was removed. And all offsite Loss-of-Power instrumentation has been returned to OPERABLE status. Following the automatic start of all four (4) EDGs, E-1, E-3, and E-4 were successfully shutdown per plant procedures. E-2 could not be shutdown per plant procedures and was shutdown locally. The cause of the inability to shutdown E-2 per plant procedures is under investigation. E-2 EDG remains inoperable. The NRC Resident Inspector was notified by the licensee.
This 60-day optional report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of a specified system, specifically the Units 2 and 3 Emergency Diesel Generators (EDGs).' 'On 9/25/03 at 2210 while restoring reactor vessel instrumentation to service on Unit 3, an invalid EDG start actuation signal on Reactor Vessel Lo-Lo-Lo level occurred which caused all four Emergency Diesel Generators to automatically start. Investigation into the cause of the event identified that the sequence of operating instrument valves associated with the instrument rack for level transmitters LT 72A and LT 72C resulted in the invalid reactor vessel lo-lo-lo reactor water level signal and subsequent EDG logic actuation. The EDGs initiated as expected for the given conditions. Off-site power was not affected and continued to supply power to the emergency busses. Once the reason for the EDG initiation was determined, the E-1, E-3, and E-4 EDGs were shut down per plant procedures from the Main Control Room by approximately 2255 hours. The E-2 EDG could not be shut down normally from the Main Control Room control switch. It was later shut down at the local control panel in the E-2 EDG bay at about 0030 hours on 9/26/03. Repairs to the E-2 EDG control switch were completed in accordance with the Corrective Action Program (CR 177605).' 'Notification of the event to the NRC was initially made at 0125 on 9/26/03 (EN # 40198). Since the initial report, it was determined that a Technical Specification LCO 3.0.3 condition did not exist since the off-site sources were operable. This event has been entered into the site-specific corrective action program for resolution (CR 1776 10). The licensee has informed the NRC Resident Inspector. | Emergency Diesel Generator | |
| ENS 40819 | 25 April 2004 05:05:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation | This 60-day optional report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 4/25/04, at approximately 0105 hours, the 343SU startup source tripped resulting in a fast transfer of expected 4 kV emergency busses to the alternate offsite power source. The fast transfer resulted in a half PCIS Group II isolation on both Units 2 and 3 as expected. The half isolation of PCIS Group II resulted in outboard isolation valves closing on Unit 2 and inboard isolation valves closing on Unit 3. The isolations involved various PCIS Group II process lines such as Reactor Water Cleanup (RWCU), Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD) and Containment Instrument Nitrogen. The Units 2 and 3 PCIS isolations were reset by approximately 0130 hours in accordance with procedures. All required isolation valves operated as designed. The offsite source (343SU) was lost as a result of a ground fault. Subsequent investigation determined that a raccoon had climbed a takeoff tower where the startup source transitions from an aerial line to underground cabling. The associated equipment was located in a small fenced area near the plant. The offsite source was inspected, tested and returned to an operable condition by approximately 2220 hours on 4/25/04. This issue has been entered into the site Corrective Action Program (CR 216811) for evaluation and implementation of further corrective actions. The licensee notified the NRC Resident Inspector. | Primary Containment Isolation System Reactor Water Cleanup | |
| ENS 41192 | 18 September 2004 08:57:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation Due to Off Site Power Source Fast Transfer | This 60-day optional report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 9/18/04, at approximately 0357 hours (EDT), the 343SU offsite-power source tripped resulting in a fast transfer of expected 4 kV emergency busses to the alternate offsite power source. The fast transfer resulted in system isolations on both units due to the affect on the PCIS instrumentation logic. The system isolations are an expected occurrence for a fast transfer. The isolations involved various process lines such as Reactor Water Cleanup (RWCU) and Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD). The Units 2 and 3 PCIS isolations were reset by approximately 0420 hours in accordance with procedures. All required isolation valves operated as designed. The offsite power source (343SU) was lost as a result of a momentary deenergization of the 220-34 Newlinville Transmission Line to clear a ground fault. The fault was approximately 29 miles from the PBAPS site and was caused by a lightning strike to a transmission tower near the Newlinville substation. Field inspections of the 220-34 Transmission Lines and Towers were performed and it was identified that there was a flash mark on the tower insulator confirming the lightning strike. It was determined that the protective relaying for the 220-34 Newlinville Transmission Line operated as designed. The 343SU offsite power source was returned to service by approximately 2115 hours on 9/18/04. This issue has been entered into the site Corrective Action Program (CR 254392) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification. | Primary Containment Isolation System Reactor Water Cleanup | |
| ENS 41193 | 28 September 2004 06:00:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation Due to Bus Voltage Dip During Recirc Mg Start | |||
| ENS 43910 | 11 December 2007 21:45:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Notification of an Invalid Actuation of Units 2 and 3 Primary Containment Isolation Systems | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 12/11/07, at approximately 1645 hours, the 13 Kv non-safety related AS4 feeder breaker tripped as a result of an electrical fault downstream of the breaker. The electrical fault resulted in a momentary voltage dip on the offsite power source (3SU). The momentary voltage dip resulted in PCIS Group II and III isolations on Units 2 and 3. Unit 2 experienced inboard PCIS isolations, while Unit 3 experienced outboard PCIS isolations. The isolations involved various process lines including Reactor Water Cleanup (RWCU), Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD), Drywell Sumps, and Containment Instrument Nitrogen. The Units 2 and 3 PCIS isolations were reset by approximately 1715 hours in accordance with procedures. All required isolation valves operated as designed. The AS4 breaker trip has been preliminarily determined to be an electrical fault of a fuse clip associated with a non-safety related transformer (00X029). This transformer provides power to equipment at the discharge canal control structure. This issue has been entered into the site Corrective Action Program (CRs 710316, 711652, 710769) for evaluation and implementation of further corrective actions. The NRC resident has been informed of this notification. | Primary Containment Isolation System Reactor Water Cleanup | |
| ENS 44465 | 24 July 2008 03:25:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation Due to Loss of One Offsite Power Circuit to Safety Buses | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 7/23/08, at approximately 2325 hours, Units 2 and 3 experienced invalid Primary Containment Isolation System (PCIS) partial isolations. Unit 2 experienced an outboard PCIS Group II isolation, while Unit 3 experienced inboard and outboard PCIS Group II isolations. The isolations involved various process lines including Reactor Water Cleanup (RWCU), Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD), Drywell Sumps, and Containment Instrument Nitrogen. The Units 2 and 3 PCIS isolations were reset by approximately 2350 hours in accordance with procedures. All required isolation valves operated as designed. The invalid PCIS isolations were a result of a fast transfer on associated 4 kV safety-related electrical buses for Units 2 and 3 caused by a loss of one of the two off-site power circuits that supply the 4 kV buses. This fast transfer resulted in a momentary voltage transient on electrical power supplies to the logic for the Units 2 and 3 PCIS. The two station off-site power circuits are fed from three offsite sources. The loss of the offsite power circuit was caused by failure of the 'A' phase of the '#1' transformer, which is associated with one of the three offsite power sources. This transformer is located at the North Substation. The transformer automatically isolated as a result of a fire associated with this transformer and resulted in the loss of two of the three offsite power sources. Subsequent to fire extinguishment, appropriate electrical switching was performed and the offsite power circuit was returned to an operable status by 0650 hours on 7/24/08. This issue has been entered into the site Corrective Action Program (CR 799684, 811332) for evaluation and implementation of further corrective actions including determining why two offsite sources were lost as a result of the transformer failure. The NRC resident has been informed of this notification. | Primary Containment Isolation System Reactor Water Cleanup | |
| ENS 44940 | 2 March 2009 15:55:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Primary Containment Isolation Signal Due to Maintenance Error | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Unit 3 Primary Containment Isolation System (PCIS). On 3/2/09, at approximately 1155 hours, Unit 3 experienced an invalid PCIS partial isolation. Associated with the momentary shorting of a terminal lead during maintenance, a fuse was blown and power was lost to nine Primary Containment Isolation Valves (PCIVs). This resulted in two of the PCIVs re-positioning to the closed position. The re-positioned PCIVs were the AO-3-07B-3509 (Inner Drywell Exhaust Valve) and the AO-3-16-5235 (Instrument Nitrogen System Suction Valve). Closure of these valves affected the Containment Atmospheric Control (CAC), Containment Atmospheric Dilution (CAD) and Containment Instrument Nitrogen systems. Closure of these valves was the expected response for loss of power to this portion of the PCIS control circuitry. The fuse was replaced and the valves were restored to an operable condition by 1235 hours on 3/2/09. The invalid PCIS isolation was a result of the momentary shorting of an energized terminal lead associated with preventive maintenance to replace a pressure switch associated with PCIV AO-3-07B-3519 (Nitrogen Supply Purge Valve). This issue has been entered into the site Corrective Action Program (CR 887441) for evaluation and implementation of further corrective actions. The NRC resident has been informed of this notification. | Primary Containment Isolation System Primary containment | |
| ENS 47907 | 13 March 2012 20:04:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Report - Invalid Primary Containment Isolation System Actuation | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Unit 2 Primary Containment Isolation System (PCIS). On 3/13/12, at approximately 1604 hours, Unit 2 experienced an invalid PCIS partial isolation. An equipment operator was in the process of making an adjustment to the Reactor Protection System (RPS) MG Set output voltage during daily rounds. As the rheostat was beginning to be rotated to increase the voltage, output voltage quickly dropped below the MG Set undervoltage trip setpoint. The BC757B and BC757D MG Set output breakers opened, resulting in the loss of the 2B RPS bus causing a half scram. The half scram signal resulted in closure of the instrument nitrogen primary containment isolation valve, secondary containment normal ventilation isolation valves and start of the 'B' Standby Gas Treatment supply fan. The invalid PCIS isolation was a result of the failure of the voltage adjustment rheostat for the MG Set output voltage. This issue has been entered into the site Corrective Action Program (AR 1340452) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification. | Secondary containment Reactor Protection System Primary Containment Isolation System Primary containment | |
| ENS 50089 | 9 March 2014 21:13:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification for an Invalid Actuation of an Emergency Service Water System | This 60-day report, as allowed by 10CFR 50.73(a)(1), is being made pursuant to 10CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of an emergency service water system. On 3/9/14, at approximately 1536 EST, the E2 Emergency Diesel Generator (EDG) was started for a post maintenance operability test. The 'A' safety-related Emergency Service Water (ESW) pump was being used to provide cooling to the EDG. At approximately 1613 EST and 1622 EST, unexpected automatic starts of the 'B' ESW pump and the non-safety related single train Emergency Cooling Water (ECW) pump occurred. The EDG run was terminated at 1622 EST to investigate the cause of the unexpected starts. It was determined that a failed angle drive adaptor resulted in invalid input to the speed switch, which resulted in the unplanned starts of the 'B' ESW pump and the ECW pump. Except for the failure of the angle drive adaptor, all systems and equipment operated as expected. The NRC resident has been informed of this notification. | Service water Emergency Diesel Generator | |
| ENS 51962 | 28 March 2016 17:20:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made pursuant to 10 CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of containment isolation valves in more than one system. On 3/28/16, at approximately 1320 (EDT), a loss of power occurred on the Unit 2 E124 480 volt load center due to an equipment operator inadvertently opening the main feed breaker during the process of applying a clearance to de-energize the E124-P-A motor control center for planned maintenance. Loss of the E124 load center resulted in Group II and Group III primary containment isolations due to an invalid ESF actuation signal. Systems impacted by the containment isolations included containment instrument nitrogen, containment atmospheric monitoring, reactor water cleanup, and secondary containment. Balance of plant impacts included partial loss of feedwater heating and a reduced condenser vacuum. Reactor power lowered to 86% as a result of the event and further decreased to approximately 80 percent when re-establishing the 3A, 4A and 5A feedwater heaters. Following direction from the control room, the E124 main feed breaker was promptly re-closed by equipment operators. Affected equipment was restored to its normal or planned configuration and containment isolations were reset at 1406. The containment isolation signal was generated as a result of the loss of power to the E124 load center and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The licensee has notified the NRC Resident Inspector. | Feedwater Secondary containment Primary containment Reactor Water Cleanup | |
| ENS 52961 | 14 July 2017 18:53:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of Containment Isolation Valves | This report is being made as required by 10 CFR 50.73(a)(2)(iv)(A) to describe an automatic actuation of containment isolation valves in more than one system. Because the actuation was invalid, this 60-day telephone notification is being made instead of a written LER (Licensee Event Report), in accordance with 10 CFR 50.73(a)(1). On 07/14/17, at approximately 1453 hours (EDT), an electrical transient occurred due to an off-site lightning strike that de-energized one of the station's two qualified off-site power sources. This resulted in an automatic fast transfer of four 4 kV electrical buses to the alternate off-site source. The fast transfer occurred as designed without complications. The loss of power had numerous impacts on plant equipment that occurred in accordance with plant design, including a Group 2 primary containment isolation on both units. The Group 2 isolation affected multiple systems, including Reactor Water Cleanup, Instrument Nitrogen, and the Drywell Floor Drain. The fault on the off-site transmission line immediately cleared after the lightning strike and at 1457 hours (EDT) the transmission system operator gave the station permission to reclose the breaker to the off-site source. Following system restorations and equipment walkdowns, plant operators re-established normal connections to the off-site source on 7/14/17 at 2322 hours (EDT) in accordance with station procedures. The containment isolation occurred as a result of the loss of an off-site power source and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The NRC Resident Inspector has been informed of this notification. | Primary containment Reactor Water Cleanup | |
| ENS 54820 | 8 June 2020 08:24:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Specified System Actuation | This report is being made as required by 10 CFR 50.73(a)(2)(iv)(A) to describe an automatic actuation of containment isolation valves in more than one system. Because the actuation was invalid, this 60-day telephone notification is being made instead of a written LER (licensee event report), in accordance with 10 CFR 50.73(a)(1). On 06/08/2020, at approximately 0424 EDT, a trip of the Unit 3 'A' reactor protection system (RPS) MG-Set resulted in a partial activation of the primary containment isolation system and inboard containment isolation valves closed in multiple systems. All affected Group III containment isolation valves were verified to be closed. It was determined that the normal power supply for the Unit 3 'A' RPS had failed. Power was transferred from the normal to the alternate source and the RPS 'A' channel was reset. Investigation determined that the 3A RPS MG Set motor contactor coil winding had failed due to an internal short circuit. The motor contactor has been replaced. The containment isolation was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The NRC Resident Inspector has been informed of this notification. | Reactor Protection System Primary Containment Isolation System | |
| ENS 56280 | 12 November 2022 04:33:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-DAY Telephonic Notification | 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 50.73(a)(2)(iv)(A) for an invalid actuation of a primary containment isolation signal affecting more than one system. On November 11, 2022, at 2333 hours EST, Peach Bottom experienced an unplanned loss of the #343 Off-Site Startup Source. Due to the temporary loss of power during automatic bus transfers, several systems experienced Primary Containment Isolation System (PCIS) Group II and Group III (GP II/III) isolation signals. Plant Systems impacted by isolation valve closure included: Reactor Water Clean Up (RWCU), Containment Atmospheric Control (CAC), Traversing In-Core Probe (TIP) Purge, Primary Containment Floor and Equipment Drains, and the Instrument Nitrogen system. All equipment responded as designed. Plant conditions which initiate PCIS GP II isolation signals are Reactor Vessel Low Water Level, High Drywell Pressure, RWCU system High Flow or RWCU Non-Regenerative Heat Exchanger High Outlet Temperature. The PCIS GP III actuations are initiated by the Reactor Vessel Low Water Level, Primary Containment High Pressure, Reactor Building Ventilation High Radiation or Refuel Floor Ventilation High Radiation. At the time of the event, none of these actual plant conditions existed; therefore, the actuation of the PCIS was invalid. The loss of the #343 Off-Site Startup Source was caused by a failed printed circuit card in the programable logic controller (PLC) for the 3435 breaker. There is no time-based maintenance strategy for PLC replacement. The PLC circuit card was replaced, and the breaker restored to full qualification and service. Preventive maintenance strategy will be enhanced to address the identified vulnerability. The licensee has notified the NRC Resident Inspector. | Primary Containment Isolation System Primary containment Reactor Building Ventilation |