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| Event date | Region | State | Site | Reactor type | Event description | |
|---|---|---|---|---|---|---|
| ENS 58187 | 9 March 2026 13:33:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone and email: At 0833 CDT on 03/09/2026, it was determined that a licensed operator tested positive in accordance with the FFD testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 58186 | 8 March 2026 22:17:00 | NRC Region 3 | Illinois | Byron | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 1717 CDT on March 8, 2026, during the Byron Unit 1 refueling outage, it was determined that the control rod drive mechanism (CRDM) penetration 31 was degraded because liquid penetrant testing performed on the embedded flaw repair weld identified an unacceptable rounded indication, in accordance with American Society of Mechanical Engineers (ASME) Section III acceptance standards and an NRC-approved licensee relief request for a previously performed embedded flaw repair. Required repairs will be completed in accordance with the ASME code of record prior to returning the vessel head to service. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 58179 | 27 February 2026 23:23:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone and email: At 1723 CST on February 27, 2026, it was determined that a non-licensed supervisor tested positive in accordance with the FFD testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 58170 | 23 February 2026 15:34:00 | NRC Region 3 | Michigan | Fermi | GE-4 | The following information was provided by the licensee via fax or email: On February 23, 2026, at 1034 EST, it was determined that a non-licensed supervisor failed a test specified by the fitness for duty (FFD) testing program. The individual's unescorted site access has been terminated. The NRC Resident and Region 3 Inspectors had been notified. |
| ENS 58165 | 13 February 2026 21:19:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone and email: At 1519 CST on February 13, 2026, it was determined that a (non-licensed) supervisor tested positive in accordance with the FFD testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 58150 | 26 January 2026 15:58:00 | NRC Region 3 | Michigan | Cook | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: This is an initial report notification pursuant to 10 CFR Part 21.21. On January 26, 2026, Cook Nuclear Plant completed a Part 21 evaluation concerning an issue with the refurbishment kit used for K-Line series 600V Breakers supplied by ABB, Inc. An incorrect tension spring was supplied in one of the refurbishment kits. The refurbishment kits should be supplied with two tension springs: P/N 650216A00 and P/N 650216E00. The kit received was missing P/N 650216A00 and had two of P/N 650216E00. The incorrect 650216E00 spring could have been installed into a K-Line series 600V breaker in the location intended to accept the 650216A00 spring. The 650216E00 is a lighter spring and may not be capable of providing the tensioning force required to prevent an aged breaker from slow closing. A breaker's failure to charge and close properly could result in an arc fault condition. The breakers were inspected for the correct spring, which is visible from the front of the breaker between a gap in the mechanism cover and the charging handle. All breakers installed appear to have the correct springs installed. One spare breaker, not installed in the plant, appears to have had the incorrect spring installed. A written notification will be provided within 30 days. Affected Plants: Cook Nuclear Power Plant. The NRC Resident has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The wrong part numbers were identified in the refurbishment kits on December 1, 2025. A site engineer noted the wrong spring installed in a spare breaker as part of the Part 21 evaluation. Corrective actions included notifying the vendor and returning the unused refurbishment kits. |
| ENS 58121 | 18 January 2026 08:20:00 | NRC Region 3 | Michigan | Cook | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 0320 EST on January 18, 2026, DC Cook Unit 2 tripped automatically following receipt of reactor control instrumentation control group 1 and controller failure annunciators. The reason for the annunciators remains under investigation. This notification is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), reactor protection system actuation as a four-hour report, and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the auxiliary feedwater system, as an eight-hour report. The DC Cook Resident NRC Inspector has been notified. Unit 2 is being supplied by offsite power. All control rods fully inserted. All auxiliary feedwater pumps started properly. Decay heat is being removed via the steam dump system. Preliminary evaluation indicates equipment required for post trip response functioned normally following the reactor trip. DC Cook Unit 2 remains stable in Mode 3 while conducting the post trip review. No radioactive release is in progress as a result of this event. Unit 1 remains stable at 100 percent power and is unaffected. |
| ENS 58102 | 29 December 2025 22:00:00 | NRC Region 3 | Illinois | LaSalle | GE-5 | The following information was provided by the licensee via phone and email: At 1600 CST on 12/29/2025, it was determined that a through-wall leak identified on a three-quarter inch vent valve off of the bonnet of the Unit 1 'B' reactor recirculation flow control valve qualifies as pressure boundary leakage resulting in a degraded reactor coolant system pressure boundary. Leakage repair will be completed prior to plant startup from the current outage. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel.? The NRC Resident Inspector has been notified. The State of Illinois will be notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: This event is related to EN 58100. |
| ENS 58100 | 28 December 2025 22:06:00 | NRC Region 3 | Illinois | LaSalle | GE-5 | The following information was provided by the licensee via phone and email: At 1606 CST with Unit 1 in mode 1 at 93 percent power, the reactor was manually tripped due to degrading containment parameters associated with a leak from the 'B' reactor recirculation pump line, which has been isolated. The trip was not complex, however the 'A' reactor recirculation pump tripped to OFF instead of down-shifting to slow speed. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Operations responded using emergency operations procedures and stabilized the unit in plant mode 3 (hot shutdown). Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Unit 2 is not affected. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 58090 | 16 December 2025 16:00:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone or email: On December 16, 2025, at 1000 CST, it was determined that a supervisor tested positive in accordance with the FFD testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 58074 | 9 December 2025 13:18:00 | NRC Region 3 | Ohio | Davis Besse | B&W-R-LP | The following information was provided by the licensee via phone and email: At 0818 EST on December 9, 2025, it was determined that a contract supervisor failed a test specified by the fitness for duty testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 58046 | 18 November 2025 14:48:00 | NRC Region 3 | Michigan | Palisades | CE | The following information was provided by the licensee via phone and email: On November 18, 2025, (non-licensed) supervisor violated the station's fitness for duty (FFD) policy. The employee's unescorted access to Palisades Nuclear Plant has been terminated. The event was determined to be reportable under 10CFR26.719(b)(2)(ii). The NRC Resident Inspector has been notified. |
| ENS 58043 | 17 November 2025 22:13:00 | NRC Region 3 | Illinois | Dresden | GE-3 | The following information was provided by the licensee via phone and email: At 1613 CST on November 17, 2025, it was discovered that the single train of high pressure coolant injection (HPCI) was inoperable. Due to this inoperability, the system was in a condition that could have prevented the fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). The isolation condenser was operable during this time period. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: A fuse in the turbine stop valve circuit blew during initial system testing for unit startup. |
| ENS 58038 | 14 November 2025 20:02:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone: On November 14, 2025, at 1351 CST, while in a system outage window, for the reserve auxiliary transformer 'B' bus work inspections, the emergency reserve auxiliary transformer tripped. This resulted in the loss of offsite power to all vital busses. At 1402 CST, a notice of unusual event was declared (MU.1) due to the loss of all offsite power to vital busses. All three emergency diesel generators actuated and energized the vital busses. Notified DHS SWO, DOE Ops Center, FEMA Operations Center, FEMA NWC, CWMD Watch Desk, HHS Ops Center, CISA Central Watch Officer, USDA Ops Center, EPA EOC, FDA EOC (email), DHS Nuclear SSA (email), DHS NRCC THD Desk (email), FEMA NRCC SASC (email), and FERC Reliability Monitoring Center (email).
The following update is a summary of information provided by the licensee via phone and email: On November 16, 2025, at 0500 CST, the Unusual Event was terminated. All offsite electrical power has been restored, and the plant is in a normal electrical lineup. The NRC Resident Inspector was notified. Notified R3RA (Geissner), NRR (Groom), NSIR (Williams), R3DO (Ziolkowski), NRR EO (Mckenna), IR MOC (Grant), R3PAO (Mitlyng), R3DRSS (Heck). Notified DHS SWO, DOE Ops Center, FEMA Operations Center, FEMA NWC, CWMD Watch Desk, HHS Ops Center, CISA Central Watch Officer, USDA Ops Center, EPA EOC, FDA EOC (email), DHS Nuclear SSA (email), DHS NRCC THD Desk (email), FEMA NRCC SASC (email), and FERC Reliability Monitoring Center (email). |
| ENS 58040 | 14 November 2025 19:51:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone and email: At 1351 CST on 11/14/25, with the unit in mode 1 at 99 percent power, an actuation of the division 1, 2, and 3 emergency diesel generators (EDGs) occurred when a fault occurred on the emergency reserve auxiliary transformer (ERAT). The reserve auxiliary transformer `B' was de-energized and isolated for maintenance. The cause of the division 1, 2, and 3 EDGs auto-start was an actuation of the loss of voltage function undervoltage relays for each respective bus. The division 1, 2, and 3 EDGs automatically started as designed when the applicable loss of voltage signals were received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the division 1, 2, and 3 EDGs. The NRC Resident Inspector has been notified. |
| ENS 58036 | 12 November 2025 17:50:00 | NRC Region 3 | Michigan | Fermi | GE-4 | The following information was provided by the licensee via phone and email: On November 12, 2025, at approximately 1250 EST, during surveillance testing of the high-pressure coolant injection (HPCI) system the HPCI minimum flow valve (E4150F012) would not open during stroke testing. HPCI had been removed from service for quarterly surveillance testing at 0957, November 12, 2025. The unplanned inoperability condition began at 1250 when a stroke time test was attempted, and the valve did not reposition. Since HPCI is a single-train safety system, this meets the criterion for event notification per 10CFR50.72(b)(3)(v)(D) as a condition that, at the time of discovery, could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident, based on loss of a single train safety system. Reactor core isolation cooling was and has remained operable. The Senior NRC Resident Inspector has been notified. The failure is currently under investigation. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Limiting conditions for operation 3.5.1 and 3.6.1.3 were entered to address HPCI inoperable. The site remains on normal offsite power, and all emergency diesel generators remain available.
The following information was provided by the licensee via phone and email: Following the initial (event notification) EN, further analysis of the condition identified that the HPCI system would have been able to perform its safety function with the minimum flow valve failed closed. Therefore, HPCI is considered operable. No other concerns were noted during the event. HPCI remained operable and there was no loss of safety function. The event did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). Therefore, the NRC non-emergency 10CFR50.72(b)(3)(v)(D) report was not required and the NRC report 58036 can be retracted and no Licensee Event Report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted. The NRC Resident Inspector was notified. Notified R3DO (Sanchez Santiago) |
| ENS 58018 | 2 November 2025 19:46:00 | NRC Region 3 | Illinois | LaSalle | GE-5 | The following information was provided by the licensee via phone and email: At 1346 CST with Unit 1 in mode 1 at 100 percent power, the reactor automatically tripped on turbine control valve fast closure due to a generator lockout. The trip was not complex with all systems responding normally post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Operations responded using emergency operating procedures and stabilized the plant in mode 3. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Unit 2 is not affected. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 58015 | 29 October 2025 13:15:00 | NRC Region 3 | Minnesota | Monticello | GE-3 | The following information was provided by the licensee via phone and email: At 0815 CDT, on October 29, 2025, fitness-for-duty (FFD) program administrators identified that a contract employee, who was required to be part of the FFD program random testing pool, had been inadvertently removed from the pool on October 20, 2025. The employee's protected area access has been placed on hold in accordance with the station process. The issue has been placed into the site corrective action program for further review and evaluation to determine the cause. This event notification is being made in accordance with 10 CFR 26.719(b)(4). The NRC Resident Inspector has been notified. |
| ENS 58008 | 27 October 2025 06:17:00 | NRC Region 3 | Illinois | Dresden | GE-3 | The following information was provided by the licensee via phone and email: At 0117 CDT on 10/27/2025, with Unit 2 in mode 3 at 0 percent power, an actuation of the RPS system occurred during restoration of the scram instrument volume high level bypass switch to normal. The cause of the RPS system actuation was a valid high level in the scram instrument volume. All control rods had been previously inserted and the RPS system automatically initiated a scram signal as designed when the scram instrument volume high level signal was received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the RPS system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 58006 | 25 October 2025 16:30:00 | NRC Region 3 | Michigan | Palisades | CE | The following information was provided by the licensee via phone and email: On 10/25/25, at approximately 1230 EDT, 3 empty alcohol bottles were found in the protected area by a contract employee. Site security was notified and took possession of the empty bottles which were removed from the protected area. The individual who accidentally brought in the empty alcohol bottles with other non-alcoholic empty bottles was tested for FFD and was negative. This event is reportable in accordance with 10 CFR 26.719(b). The NRC Resident Inspector has been notified. |
| ENS 58002 | 22 October 2025 20:35:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone and email: At 1535 CDT on 10/22/2025, with Unit 1 in mode 1 at 86 percent power, the reactor was manually tripped due to low turbine electro-hydraulic control (EHC) oil system reservoir level, caused by a leak developing in the heater bay. The trip was not complex, with all systems responding normally post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Operations responded using the emergency operating procedure for reactor pressure vessel control and stabilized the plant in mode 3. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves, which have a separate EHC oil system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57998 | 22 October 2025 08:52:00 | NRC Region 3 | Michigan | Palisades | CE | The following information was provided by the licensee via phone and email: On October 22, 2025, at 0452 EDT, chemistry determined that a report to the State of Michigan, Department of Environment, Great Lakes, and Energy, would be required based on exceeding the National Pollutant Discharge Elimination System permit limit for hydrazine. This exceedance did not exceed any NRC regulations or reporting criteria. This notification is being made solely as a four-hour, non-emergency notification for a notification to another government agency. This event is a 4-hour non-emergency report in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector will be notified. |
| ENS 57996 | 21 October 2025 20:32:00 | NRC Region 3 | Michigan | Palisades | CE | The following information was provided by the licensee via phone and email: On 10/21/2025 at 0930 EDT an individual fell into the reactor cavity. The reactor cavity is full of water. They ingested some amount of cavity water. The individual was decontaminated by radiation protection personnel but had 300 counts per minute detected in their hair. At 1632 EDT they were sent off site to seek medical attention. This is an eight-hour notification, non-emergency, for the transportation of a contaminated person offsite. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xii). The NRC Resident Inspector has been notified. |
| ENS 57978 | 10 October 2025 07:30:00 | NRC Region 3 | Illinois | Braidwood | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 0230 CDT, on October 10, 2025, it was determined that the control rod drive mechanism (CRDM) penetration '69' was degraded because liquid penetrant testing performed on the embedded flaw repair weld identified an unacceptable indication in accordance with American Society of Mechanical Engineers (ASME) Section Ill acceptance standards and NRC approved licensee relief request for a previously performed embedded flaw repair. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel.? The NRC Resident Inspector has been notified. |
| ENS 57967 | 6 October 2025 08:21:00 | NRC Region 3 | Illinois | Clinton | GE-6 | The following information was provided by the licensee via phone and email: At 0321 CDT on 10/6/2025, with Unit 1 in mode 1 at 23 percent power, the reactor automatically tripped due to reactor water level rising to the reactor protection system auto-scram setpoint, prior to the manual scram being completed. The trip was not complex with all systems responding normally post-trip. The trip occurred as the station was transitioning level control from the motor driven reactor feed pump to the `A' turbine driven reactor feed pump as part of plant startup. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Operations responded using emergency operating procedure 1 (reactor pressure vessel control) and stabilized the plant in mode 3. Decay heat is removed by discharging steam to the main condenser using the turbine bypass valves. The digital feedwater level control system response is still under investigation. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57941 | 22 September 2025 14:30:00 | NRC Region 3 | Ohio | Davis Besse | B&W-R-LP | The following information was provided by the licensee via phone and email: At approximately 1030 EDT on September 22, 2025, it was determined an employee had an unopened bottle of beer inside the protected area on September 20, 2025. The individual's authorization for site access has been restricted, pending the results of an investigation. The NRC Resident Inspector and the NRC Region III Security Inspector have been notified. |
| ENS 57905 | 5 September 2025 06:30:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone and email: At 0130 CDT on September 5, 2025, it was discovered that the single train high pressure coolant injection (HPCI) system was inoperable. Due to this inoperability, the system was in a condition that could have prevented the fulfilment of a safety function. Therefore, this condition is being reported as an 8-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). Unit 1 reactor core isolation cooling was operable during this time period. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The Illinois Emergency Management Agency has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The inoperability was caused by a malfunctioning turbine steam admission valve during a surveillance. Unit 1 is in a 14-day limiting condition for operations. |
| ENS 57881 | 21 August 2025 03:08:00 | NRC Region 3 | Michigan | Fermi | GE-4 | The following information was provided by the licensee via phone and email: On 08/20/2025 at 2308 EDT, the Fermi 2 active seismic monitoring system provided indication of a potential seismic activity event. Plant abnormal procedures were entered, and compensatory measures were met and remain in place. Neither the United States Geological Survey (USGS) nor the next closest nuclear power plant could confirm/validate the readings obtained at Fermi. The seismic monitoring system was declared inoperable to validate the calibration of the system. Fermi 2 has two active seismic monitors: one on the reactor pressure vessel pedestal and one in the high pressure core injection (HPCI) room. Only the HPCI room seismic monitor was declared inoperable. The HPCI room accelerometer is the sole trigger for the seismic recording system (which outputs peak accelerations experienced during a seismic event) and the associated control room alarm. This is used in assessment of the magnitude of an earthquake for emergency action level HU 2.1. The loss of the active seismic monitoring system is reportable within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(xiii). No seismic activity has been felt on-site, and the USGS recorded no seismic activity in the area. The NRC Resident Inspector has been notified. An alternative means of monitoring seismic event entry is still available per the emergency plan via USGS. |
| ENS 57879 | 20 August 2025 12:11:00 | NRC Region 3 | Michigan | Cook | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: A non-licensed employee had a confirmed positive for alcohol during a random fitness-for-duty (test). The employee's access to the plant has been terminated. The NRC Resident Inspector has been notified. |
| ENS 57865 | 12 August 2025 20:21:00 | NRC Region 3 | Ohio | Davis Besse | B&W-R-LP | The following information was provided by the licensee via phone and email: At 1621 EDT on 8/12/2025, a technical specification required shutdown was initiated at Davis-Besse Nuclear Power Station Unit 1. Technical specification limiting condition for operation 3.3.11 for steam generator (SG) low level instrumentation channel requirements was not met, and condition 'B' was entered on 8/12/2025 at 1600 with required actions to be in mode 3 with a completion time of 6 hours and be in mode 4 with a completion time of 12 hours. This event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(i). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The affected SG level instrumentation is for emergency feedwater automatic initiation. The instruments were declared inoperable due to a reference leg leak in containment. |
| ENS 57841 | 30 July 2025 21:45:00 | NRC Region 3 | Illinois | Dresden | GE-3 | The following information was provided by the licensee via phone and email: At 1645 CDT on July 30, 2025, it was discovered that the single train of the ultimate heat sink was inoperable. Due to this inoperability, the system was in a condition that could have prevented the fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(B). There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The proximal cause of the inoperability was due to a buildup of grasses in the crib house from the river. Operators were able to clear the crib house bar rack intake and restore operability within eight minutes. |
| ENS 57839 | 30 July 2025 17:30:00 | NRC Region 3 | Illinois | Braidwood | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: On July 30, 2025, at 1230 CDT, with Unit 1 in mode 1 at 100 percent power, the reactor automatically tripped due to an over temperature delta 'T' reactor protection system actuation while critical. This event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Actuation of the auxiliary feedwater (system) occurred during the reactor trip response. The cause of the auxiliary feedwater auto-start was a LO-2 steam generator water level. The 1A and 1B auxiliary feedwater pumps started as designed when the LO-2 steam generator water level signal was received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the auxiliary feedwater system. Operators responded using procedures 1BwEP-0 and 1BwEP ES-0.1 to stabilize the unit in mode 3. Decay heat is being removed by discharging steam to the main condenser using the main steam dump valves. Unit 2 is not affected. All systems responded as expected with the exception of steam pressure channel 1Pl-545A and steam flow channel 1Fl-523A, which both failed high during the lightning storm and subsequent transient. Actions per 1BwOA lnstrument-2 are in progress to address these failures. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57832 | 29 July 2025 01:58:00 | NRC Region 3 | Minnesota | Monticello | GE-3 | The following information was provided by the licensee via phone and email: At 2058 CDT on 7/28/2025, a spurious trip of the reactor building exhaust ventilation (system) caused a subsequent trip of the reactor building supply ventilation (system). This ventilation system failure resulted in the degradation of reactor building differential pressure and at 2200 CDT the differential pressure exceeded the technical specification limit, resulting in the inoperability of Secondary Containment. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72 (b)(3)(v). Failure of the ventilation system also resulted in elevated temperatures in the steam chase area of the plant. Operators reduced power to slow the temperature rise, however, at 2324 CDT on 7/28/2025 with Unit 1 in mode 1 at 41 percent power, the reactor was manually scrammed due to steam chase temperatures reaching the procedural limit. The scram was not complex, with all systems responding normally post-scram. Reactor water level is being maintained via the feedwater system. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. This condition is being reported as a four-hour, non-emergency notification per 10 CFR 50.72 (b)(2)(iv)(B). There has been no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Steam chase temperature has begun to lower, and the licensee intends to cooldown to mode 4 for maintenance. |
| ENS 57813 | 16 July 2025 14:59:00 | NRC Region 3 | Minnesota | Prairie Island | Westinghouse PWR 2-Loop | The following information was provided by the licensee via phone and email: At 0959 CDT on 7/16/2025, with Unit 1 in mode 1 at 100 percent power, the reactor tripped coincident with operation of a bus 11 knife switch during performance of (surveillance procedure) SP 1857, 4KV bus 11/12 undervoltage and underfrequency relay test. The trip was not complicated with all systems responding normally post trip. Operators responded and stabilized the plant. Decay heat is being removed by discharging steam using the steam dump system and the main feedwater system. Unit 2 is not affected. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the auxiliary feed water system (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact to the health and safety of the public or plant personnel. The NRC Senior Resident Inspector has been notified. |
| ENS 57804 | 7 July 2025 19:45:00 | NRC Region 3 | Michigan | Fermi | GE-4 | The following information was provided by the licensee via phone and email: On 7/7/2025 at 1545 EDT, one of the division 2 residual heat removal (RHR) complex pump room dampers was noted to be full-closed instead of at the expected full-open position based on outside air temperatures. An operator walkdown confirmed that the division 2 RHR pump room temperature controller was attempting to open the damper. Per plant procedures, the affected RHR service water (RHRSW), emergency equipment service water (EESW), and emergency diesel generator service water pumps (DGSW) were declared inoperable. Division 2 EESW supports the safety function for all division 2 safety systems, including high pressure coolant injection (HPCI). Therefore, HPCI was also declared inoperable. Since HPCI is a single-train safety system, this meets the criterion for event notification per 10 CFR 50.72(b)(3)(v)(D). The damper will be blocked to the position required based on current and projected outside air temperature, this will return the systems to operable. The cause of the damper failure is unknown and under investigation. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Multiple technical specification limiting conditions for operation (LCOs) were entered as a result of this event. Fermi Unit 2 expects to be able to exit the LCOs within the required timeframes.
The following retraction was provided by the licensee via phone and email: Following the initial event notification, further analysis of the condition identified that since the residual heat removal complex room temperature (85 degrees F) was less than the limit bounded by a calculation (<104 degrees F), and the dampers were blocked in a position in accordance with plant procedures within 24 hours of the event, there is reasonable assurance that the high pressure coolant injection (HPCI) system would be able to perform its safety function. Therefore, HPCI is considered operable for the condition. No other concerns were noted during the event. HPCI remained operable and there was no loss of safety function. The event did not involve a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident under 10 CFR 50.72(b)(3)(v)(D). Therefore, the NRC non-emergency 10CFR50.72(b)(3)(v)(D) report was not required and the NRC event report 57804 can be retracted and no licensee event report under 10 CFR 50.73(a)(2)(v)(D) is required to be submitted." Notified R3DO (Zurawski) |
| ENS 57772 | 20 June 2025 18:53:00 | NRC Region 3 | Illinois | Byron | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: At 1353 CDT on 6/20/2025, it was determined that a supervisor tested positive in accordance with the fitness-for-duty (FFD) testing program. The individual's authorization for site access has been terminated. The NRC Resident inspector has been notified. |
| ENS 57766 | 17 June 2025 17:57:00 | NRC Region 3 | Illinois | LaSalle | GE-5 | The following information was provided by the licensee via phone and email: This is an eight-hour, non-emergency notification for a loss of emergency assessment capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the technical support center (TSC) supply fan belt failed (at approximately 1257 CDT on 6/17/2025) which affects the functionality of an emergency response facility. Corrective maintenance activities have been completed as of 6/17/25 at 1619 (CDT) to replace the TSC supply fan belt. The TSC supply fan has been re-started and this condition is no longer applicable. If an emergency would have been declared requiring TSC activation during this period, the TSC would have been staffed and activated using existing emergency planning procedures unless the TSC became uninhabitable due to ambient temperature, radiological, or other conditions. If relocation of the TSC were necessary, the Emergency Director would have relocated the TSC staff to an alternate location in accordance with applicable site procedures. The emergency response organization team was notified of the maintenance and the possible need to relocate during an emergency. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57836 | 6 June 2025 16:00:00 | NRC Region 3 | Michigan | Cook | Westinghouse PWR 4-Loop | The following information was provided by the licensee via phone and email: This is an initial report notification pursuant to 10 CFR Part 21.21. Cook Nuclear Plant completed an internal evaluation concerning an issue with an emergency diesel generator (EDG) voltage regulator (VR) supplied by Paragon Energy Solutions, LLC. An issue was identified during a surveillance test conducted on April 22, 2025, concerning a thermal overload (TOL) for the VR which spuriously trips causing a condition where the EDG VR can no longer control the generator voltage, resulting in the inability of the EDG to supply automatic onsite emergency AC power. A failure analysis was completed on June 6, 2025, determined that the cause of the spurious trips is associated with a heater dimensional tolerance deficiency lowering the activation threshold of the TOL bimetallic strip and a workmanship deficiency associated with a braided control wire restricting the movement of the TOL pressure bar. Extent of condition examinations were performed and one additional TOL was found to be impacted. The two impacted TOLs have been replaced. A written notification will be provided within 30 days. Affected Plants: Cook Nuclear Power Plant. The NRC Resident has been notified. |
| ENS 57728 | 22 May 2025 09:13:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone: At 0359 CDT, Quad Cities Unit 2 experienced a fire in one of their battery cells during a planned discharge test. An Unusual Event (HU.3) was declared at 0413 CDT and the fire was extinguished by the fire brigade at 0422 CDT. The effected battery bank was isolated at the time of the event and all other electrical systems are functioning normally. Unit 2 remains in Mode 1 at 100 percent power and Unit 1 was unaffected. No injuries have been reported. The NRC Senior Resident Inspector, state, and local authorities have been notified. The event was terminated at 0520 CDT due to the fire being out and no other plant equipment being affected. Notified DHS SWO, FEMA Operations Center, CISA Central Watch Officer, FEMA NWC (email), DHS Nuclear SSA (email), CWMD Watch Desk (email). |
| ENS 57718 | 19 May 2025 15:45:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone and email: At 1045 CDT on May 19, 2025, with Unit 1 at 100 percent power, the reactor was manually tripped on lowering reactor water level caused by a loss of electrical power to the condensate and feedwater pumps. The trip was not complex with all systems responding as expected post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for the group II isolation, group III isolation, and Unit I emergency diesel generator (EDG) automatic start. Operations responded using emergency operating procedures and stabilized the plant in hot shutdown. Decay heat is being removed through the automatic depressurization system and the residual heat removal system. Coincident with the transient on Unit 1, Unit 2 experienced a trip of a reactor feed pump resulting in a runback of the reactor recirculation pumps. Unit 2 is currently stable at 80 percent power. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector and the Illinois Emergency Management Agency were notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: On Unit 1, all control rods fully inserted on the scram and outboard main steam isolation valves closed on a loss of power. The initial bus trip was caused by control power perturbations due to a ground on the associated battery system.
Based on additional investigation, it has not been confirmed that the initial bus trip was caused by a ground on the associated battery system. The cause remains under investigation. Notified R3DO (Szwarc)
The scram was initially reported as manual; however, further investigation determined that it was automatically initiated. Notified R3DO (Szwarc) |
| ENS 57647 | 5 April 2025 09:00:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | ? The following information was provided by the licensee via phone and email: At 0400 CDT on 4/05/2025, it was discovered that both trains of reactor building to suppression chamber vacuum breakers were simultaneously inoperable. Due to this inoperability, the system was in a condition that could have prevented the fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Both trains were restored to operable on discovery. The inoperability was a result of a configuration control issue following their refueling outage. The licensee will investigate the cause of the configuration control issue. |
| ENS 57638 | 29 March 2025 13:15:00 | NRC Region 3 | Ohio | Perry | GE-6 | The following information was provided by the licensee via phone and email: At 0915 EDT, on March 29, 2025, with Unit 1 in mode 5 at zero percent power, an actuation of the emergency diesel generator system occurred during Unit 2 startup transformer testing. The reason for the auto-start was the loss of an electrical bus during testing. The division 3 diesel generator automatically started as designed on low safety bus voltage. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the emergency diesel generator system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57618 | 19 March 2025 16:36:00 | NRC Region 3 | Minnesota | Monticello | GE-3 | The following information was provided by the licensee via phone and email: At approximately 1136 CDT on March 19, 2025, with Unit 1 in mode 1 at 97 percent power, a reactor water level transient occurred which resulted in an automatic reactor scram on low reactor pressure vessel water level. The scram was uncomplicated with all systems responding as expected. The cause of the event is under investigation. Containment isolation valves actuated and closed on a valid group 2 signal. Operations responded and stabilized the plant in mode 3. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. This event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) due to the reactor protection system actuation while critical, and an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for the Group 2 isolation signal. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The state of Minnesota as well as Wright and Sherburne counties will be notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At the time of the event, condensate flushing evolutions were ongoing. It should be noted that prior to the reactor scram, a single feedwater pump tripped which would lower reactor water level. |
| ENS 57614 | 18 March 2025 16:59:00 | NRC Region 3 | Minnesota | Prairie Island | Westinghouse PWR 2-Loop | The following information was provided by the licensee via phone and email: At 1059 (CDT) on March 18, 2025, it was determined that a licensed operator failed a (random) test specified by the fitness-for-duty testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 57616 | 18 March 2025 14:30:00 | NRC Region 3 | Ohio | Perry | GE-6 | The following information was provided by the licensee via phone and email: At 0930 EDT, March 18, 2025, it was determined that a contract supervisor failed a (random) test specified by the fitness-for-duty testing program. The individual's authorization for site access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 57606 | 13 March 2025 18:00:00 | NRC Region 3 | Illinois | LaSalle | GE-5 | The following information was provided by the licensee via phone and email: A licensed employee violated the FFD policy. The employee's access to the plant has been terminated. The NRC Resident Inspector has been notified. |
| ENS 57586 | 4 March 2025 16:30:00 | NRC Region 3 | Minnesota | Monticello | GE-3 | The following information was provided by the licensee via phone and email: On March 4, 2025, fitness-for-duty (FFD) program administrators identified a site employee who was required to be part of the FFD program random testing pool, had been inadvertently removed from it on August 5, 2024. The employee's protected area access has been placed on hold in accordance with the station process. The issue has been placed into the site corrective action program for further review and evaluation to determine the cause. This event notification is being made in accordance with 10 CFR 26.719(b)(4). The NRC resident inspector has been notified. |
| ENS 57515 | 26 January 2025 20:50:00 | NRC Region 3 | Illinois | Quad Cities | GE-3 | The following information was provided by the licensee via phone and email: On January 26, 2025, at 1450 CST, it was discovered that the Control Room Emergency Ventilation Air Conditioning (CREVAC) system was inoperable. Due to this inoperability, the system was in a condition that could have prevented the fulfillment of a safety function, and therefore, this condition is being reported as an eight-hour non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). The CREVAC system is a single train system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 57498 | 16 January 2025 17:50:00 | NRC Region 3 | Minnesota | Monticello | GE-3 | The following information was provided by the licensee via phone and email: On January 16, 2025, at 1150 CST, Xcel Energy performed a notification to the State of Minnesota Duty Officer per the National Pollutant Discharge Elimination System (NPDES) Permit (# MN0000868). This notification is being made solely as a four-hour, non-emergency report for notification to other government agency in accordance with 10 CFR 50.72(b)(2)(xi). There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The offsite notification is a requirement per the NPDES permit to report any instance of waste water release to the state. There was a release of waste water from a pumping house which was subsequently cleaned up by site personnel. |
| ENS 57494 | 15 January 2025 19:02:00 | NRC Region 3 | Illinois | Dresden | GE-3 | The following information was provided by the licensee via phone and email: At 1302 CST on 1/15/2025, it was determined that a (non-licensed) supervisor tested positive (for a controlled substance) in accordance with the Fitness for Duty (FFD) testing program. The individual's authorization for site access has been terminated. The NRC Senior Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: This was determined during random FFD testing. The individual performed no safety related work. |