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| Entered date | Event description | |
|---|---|---|
| ENS 55910 | 24 May 2022 06:49:00 | The following information was provided by the licensee via email: On May 24, 2022, at 0414 EDT, while rolling the Unit 1 main turbine during the Unit 1 Cycle 31 refueling outage, the Unit 1 main turbine experienced high vibrations and the main turbine was manually tripped with reactor power at 12 percent. Main turbine vibrations persisted and the reactor was manually tripped, Main Steam Stop Valves were closed, and main condenser vacuum was broken. This notification is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System (RPS) actuation as a four (4) hour report, and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the Auxiliary Feedwater System, as an eight (8) hour report. The DC Cook Resident NRC Inspector has been notified. Unit 1 is being supplied by offsite power. All control rods fully inserted. Both Motor Driven Auxiliary Feedwater Pumps started properly. Decay heat is being removed via Steam Generator Power Operated Relief Valves. Preliminary evaluation indicates all plant systems functioned normally following the Reactor Trip. DC Cook Unit 1 remains stable in Mode 3 while conducting the Post Trip Review. No radioactive release is in progress as a result of this event. |
| ENS 55322 | 23 June 2021 01:55:00 | On June 22, 2021, at 2331 EDT, DC Cook Unit 2 Reactor was manually tripped due to a large steam leak in a crossover pipe of the Moisture Separator Re-heater (MSR) to the low pressure turbine. This notification is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System (RPS) actuation as a four (4) hour report, and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the Auxiliary Feedwater System, as an eight (8) 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 all plant systems 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 was not affected. |
| ENS 54241 | 26 August 2019 16:41:00 | A non-licensed contract employee supervisor had a confirmed positive for an illegal drug during pre-access testing. The employee's access to the plant was denied. |
| ENS 53334 | 13 April 2018 20:01:00 | At 1555 EDT, the Unit 2 'CD' Emergency Diesel Generator (EDG) automatically started and loaded to 4kV Safeguards bus T21C. Testing was in-progress and the start was unplanned. Unit 2 is currently defueled. Unit 1 remains stable at 100 percent power. The South Spent Fuel Pit Cooling Train lost power due to a load shed. The South Spent Fuel Pit Cooling Pump was restarted on 2 'CD' EDG at 1614 EDT. The North Spent Fuel Pit Cooling Train remained in-service the entire time. There was no observable change in Spent Fuel Pool temperature. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of an emergency diesel generator, as an eight (8) hour report. The NRC Resident Inspector has been notified. |
| ENS 51859 | 8 April 2016 20:50:00 | At 1657 EDT on April 8, 2016, an oil leak developed from the station's switchyard transformer no. 4. Approximately 25,000 gallons of oil has leaked within the transformer's containment berm. At 1820 EDT on April 8, 2016, DC Cook environmental personnel determined that approximately 2000 gallons of oil had leaked outside of the containment berm onto the ground. None of the oil has made it to any nearby drains. Leak has stopped and cleanup is ongoing. D.C. Cook has notified the State of Michigan and local authorities. The NRC Resident Inspector was notified. This notification is being made in accordance with 10 CFR 50.72(b)(2)(xi) due to notification of offsite agencies. |
| ENS 51106 | 31 May 2015 16:32:00 | At 1600 (EDT) on May 31, 2015, (DC Cook) operations commenced a shutdown of DC Cook Unit 1 to comply with LCO 3.8.1 Condition G, when the 14 day limit to complete Condition B Required Action could not be met. At 0010 (EDT) on May 18, 2015, Unit 1 AB Emergency Diesel Generator was removed from service for planned maintenance. LCO 3.8.1 Condition B was entered which allows 14 days to restore diesel to operable. At 1049 (EDT) on May 21, 2015, Unit 1 AB Emergency Diesel Generator tripped during post maintenance testing due to high bearing temperatures. Subsequent actions to repair and restore the diesel to operable status have been unsuccessful. This event is reportable under 10 CFR 50.72(b)(2)(i), the initiation of any nuclear plant shutdown required by the plant's Technical Specifications, as a four (4) hour report. The DC Cook Sr. Resident NRC Inspector has been notified. Unit 1 is expected to be in Mode 5 by 2030 EDT on June 1, 2015. There is no impact on Unit 2.
This update is to correct the information contained in the block titled 'Power/Mode After'. The power and mode after the event requiring notification (TECHNICAL SPECIFICATION REQUIRED SHUTDOWN DUE TO INABILITY TO RESTORE UNIT 1 AB EDG WITHIN THE COMPLETION TIME PRESCRIBED IN LCO 3.8.1 CONDITION B) was 99% power and mode 1. The licensee has notified the NRC Resident Inspector. D.C. Cook Unit 1 is currently in Mode 3 and conducting a normal cooldown to Mode 4. Notified R3DO (Passehl).
DC Cook Unit 1 reactor was shut down (Mode 3) at 0231 hours (EDT) June 01, 2015 and achieved Mode 5 at 0410 hours (EDT) June 02, 2015 to comply with LCO 3.8.1 Condition G with all systems operating normally. The licensee has notified the NRC Resident Inspector. Notified R3DO (Passehl). |
| ENS 51004 | 23 April 2015 05:25:00 | On April 23, 2015 DC Cook Unit 2 Reactor was manually tripped due to an uncontrolled cooldown due to two (2) failed open steam dump valves. The cause of the failure is still under investigation. This event is reportable under 10 CFR 50.72(b)(2)(i) Tech Spec Required Shutdown, as a four (4) hour report; 10 CFR 50.72(b)(2)(iv)(B), Reactor Protection System (RPS) actuation, as a four (4) hour report; and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the Reactor Protection System (RPS), as an eight (8) hour report. The electrical grid is stable and Unit 2 continues to be supplied by offsite power. All control rods fully inserted. Decay heat is being removed via steam generator Power Operated Relief Valves due to steam dump valves being manually isolated. Preliminary evaluation indicates all plant systems 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. The DC Cook Resident NRC Inspector has been notified. There is no indication of primary to secondary leakage and there is no impact on Unit 1. |
| ENS 50822 | 13 February 2015 15:55:00 | At 1123 EST on 2/13/2015, an emergency medical report was received in both unit's Control Rooms that an individual was having a personal medical issue outside the protected area. Onsite Emergency Medical personnel were dispatched to the scene. Off-site medical assistance was immediately requested. CPR was administered and the individual was transferred by off-site medical ambulance service to a local hospital. The Operations Shift Manager received confirmation of a fatality at 1315 EST on 2/13/2015. Notification was made to the Michigan Occupational Safety and Health Administration (MIOSHA). Both Units remain at 100% power. This Event Notification is being made due to the fatality and notification to a government agency. The NRC Resident Inspector has been notified. The individual was at the workout facility when this incident occurred. |
| ENS 50498 | 28 September 2014 10:55:00 | On 9/28/14 at approximately 0830 EDT, the Operations Shift Manager was made aware that the Berrien County Sheriff's Department (BCSD) had been notified of an Emergency Siren that had actuated. BCSD was notified by local residents. BCSD reset the emergency siren and a local police officer verified the siren was no longer actuating. The cause of the actuation is under investigation at this time. The siren remains in service pending further investigation. There are a total of 70 sirens and all remain functional. This notification is being made under 10 CFR 50.72(b)(2)(xi), Offsite Notification, as a four (4) hour report. The licensee notified the NRC Resident Inspector. |
| ENS 50462 | 16 September 2014 16:34:00 | At approximately 1420 (EDT) on September 16, 2014, a worker collapsed in an office building inside the protected area. Initial response by on-site responders found the person unresponsive. Subsequent response by off-site medical responders determined the person had died. Licensee was notified of fatality at 1519 (EDT). The fatality was due to an apparent personal medical issue and not work related. The individual was not contaminated. The individual was transported off-site via Medic One, a local ambulance. The NRC Senior Resident Inspector was notified. Plant operation was not impacted by the event. This notification is being made in accordance with 10 CFR 50.72(b)(2)(xi) due to notification of offsite agencies. The Licensee plans to make a press release. The licensee also notified Michigan OSHA, and other local authorities. |
| ENS 42949 | 30 October 2006 14:25:00 | At 1304 CT on 10/30/06, the licensee declared an Alert due to a fire in a breaker compartment in safety-related 480 VAC Bus 2B-53. The bus feeder breaker tripped open, resulting in the loss of some safety equipment, including one train of emergency feedwater. The fire was immediately extinguished. The licensee notified the NRC Resident Inspector.
ANO-2 Technical Specification 3.6.3.1 action compliance is in progress which includes plans to commence plant shutdown starting at approximately 1908 hours (CT). Parallel repair efforts are underway to restore the necessary portions of 2B-53 power to allow exiting the Technical Specification 3.6.3.1 LCO's. The licensee notified the NRC Resident Inspector. Notified R4 DO (D. Powers) and R4 IRC (Kennedy).
At 1925 hours (CT) on 10/30/06, Shutdown of Unit 2 to Hot Standby was commenced in accordance with Technical Specification 3.6.3.1 Action D. This notification satisfies the requirement of 10CFR50.72(b)(2). The licensee notified the NRC Resident Inspector. Notified R4 DO (D. Powers) and R4 IRC (Kennedy).
At 1925 hours (CT), Shutdown of Unit 2 was commenced in accordance with Technical Specification 3.6.3.1. The termination criteria of OP-1903.010, Section 6.3 have been met and the Alert has been terminated (at 2000 CST). The licensee will notify the NRC Resident Inspector. Notified R4 DO (D. Powers), R4 IRC (Kennedy), NRR EO (Lubinski), NSIR (Leach, Blount, Wilson), HQ PAO (Brenner), Comm TA's (Lee, Brown, Skeen, Hatchett, Piccone), EDO Staff (Lamb - message), DHS SWO (Bozzo), FEMA (Casto), DOE (Foote), NRC (McCrossen), USDA (Giles), HHS (Harris) |
| ENS 42237 | 31 December 2005 19:16:00 | The EFW actuation occurred when the 'B' MFW pump RPM rose then dropped to ~4000 rpm. The MFW pump then recovered immediately. This transient caused EFIC (Emergency Feedwater Initiation Control) to actuate and both EFW pumps received start signals on invalid low SG level from the EFIC low range level instruments. These instruments measure level based upon a dp (differential pressure) across an orifice and are not considered reliable at 95% power and full MFW flow. All other SG level instruments indicate SG level was above EFIC setpoint during the MFW pump transient. This can be concluded by reviewing the OTSG (Once Through Steam Generator) level prior to and during the transient. Prior to the transient the EFIC low range level instruments indicated a level of ~24 inches. During the transient the EFIC low range level instruments indicated as low as 4 inches. However, the Startup Range level only lowered from ~122 inches prior to the transient to ~120 inches. Both EFW pumps were immediately overridden and stopped once it was verified this was not an actual under feed condition to the OTSGs. No EFW injection into the OTSGs occurred due to the EFW actuation. There was no ongoing maintenance at the time which would have explained the "B" MFW pump transient. The licensee informed the NRC Resident Inspector.
On 12/31/05, an 8-hour notification (EN# 42237) was made by Arkansas Nuclear One reporting an automatic actuation of Emergency Feedwater (EFW). The report was submitted pursuant to the requirements of 10 CFR 50.72 (b)(3)(iv)(A) Valid System Actuation. The actuation of EFW occurred as a result of a "B" Main Feedwater (MFW) pump transient which caused an invalid low Steam Generator (SG) level signal from the Emergency Feedwater Initiation and Control (EFIC) instrumentation. As discussed in the original event report, the low SG level EFIC instruments do not provide valid indication at 95% power and full MFW flow. As a result of the elevated flow rate during this perturbation, an invalid indication below the low SG level setpoint was produced resulting in the system actuation. All other SG level instrumentation indicated that actual SG levels remained within the normal operating band, confirming that no low level condition existed and that this event represented an invalid actuation. Accordingly, this update revises Event Notification 42237 to be submitted pursuant to 10 CFR 50.73 (a)(2)(iv)(A) and the 60-day Optional 10 CFR 50.73 (a)(1) requirement - Invalid Actuation of EFW. EFID and EFW systems functioned as designed in response to the invalid low SG level signal. The original event report stated that there was no EFW injection into the steam generators as a result of the actuation; however, subsequent reviews of historical Safety Parameter Display System (SPDS) data indicated that the electric EFW pump (P-7B) fed the steam generators for approximately 5 seconds during the event. The licensee notified the NRC Resident Inspector. R4DO (Shannon) notified. |
| ENS 41907 | 10 August 2005 12:34:00 | While performing silent activation tests on two new electronic sirens associated with the Alert and Notification System this morning, a siren cancel signal was sent out to stop the siren test on the two sirens. Mechanical sirens 2Z4 and 2Z8 (not the new electronic sirens) located in the areas around Oakland Heights Elementary School in Russellville and the HWY 7T curve read the signal as an activation and subsequently activated. Pope County 911 called the Arkansas Department of Health (ADH) to advise that they had received calls concerning the activation. The normal siren verifiers for those sirens called ADH to report the sounding. ADH contacted ANO regarding the siren activation and issued a press release to four local radio stations. The signals sounded for 5 - 10 minutes. The licensee notified the NRC Resident Inspector. |
| ENS 41475 | 9 March 2005 16:40:00 | The following information was obtained from the licensee via facsimile (licensee text in quotes): On Tuesday 3/8, a local radio station carried a message about inadvertent siren soundings on the previous weekend. Neither the Arkansas Department of Health (ADH) staff nor ANO EP staff received any notifications relative to the inadvertent sounding or the number or location of the sirens. The ADH considers the sirens to be operable. A possible cause was reported as loss of electric service in some areas. ANO has some history that indicates power surges may cause inadvertent actuation of the sirens. The licensee has notified the NRC Resident Inspector. |
| ENS 41473 | 9 March 2005 09:36:00 | The following information was obtained from the licensee via facsimile (licensee text in quotes): ANO (Arkansas Nuclear One) Unit 2 shutdown on 3/9/05 at approximately 0038 (CST) to begin the 2R17 refueling outage. While performing the Mode 3 Hot Shutdown Walk down on ANO Unit 2, evidence of leakage was discovered around three (3) pressurizer heater sleeves. The amount of leakage was minor since no indication of moisture was present and the build up of boric acid was minimal. Investigations are underway as to the repair of the affected nozzles. The licensee notified the NRC Resident Inspector.
The following information was obtained from the licensee via facsimile (licensee text in quotes): ANO Unit 2 shutdown on 3-9-05 at approximately 0038 to begin the 2R17 refueling outage. While performing the Mode 3 Hot Shutdown Walk down on ANO Unit 2, evidence of leakage was discovered around three (3) pressurizer Heater Sleeves. The amount of leakage was minor since no indication of moisture was present and the build up of boric acid was minimal. Investigations are underway as to the repair of the affected nozzles. Update on 3/12/2005 @ 2140: During the followup inspection performed on 3-12-2005, eight pressurizer heater nozzles had evidence of boric acid leakage at the annulus between the nozzle and pressurizer. One plug was also discovered with evidence of boric acid leakage. The nozzle at this location was plugged during the late 1980's. The reactor is presently in cold shutdown. The NRC Resident Inspector was notified.
The following information was obtained from the licensee via facsimile (licensee text in quotes): Following decontamination activities performed on 3-15-2005, 1 (one) additional pressurizer heater nozzle had evidence of leakage at the annulus between the nozzle and pressurizer. The licensee notified the NRC Resident Inspector. Notified R4 DO (T. Farnholtz) |