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| Entered date | Event description | |
|---|---|---|
| ENS 54944 | 12 October 2020 03:46:00 | At 0026 (EDT) on October 12, 2020, D.C. Cook Unit 2 tripped automatically on low-low level of #24 steam generator which occurred after a lowering of main condenser vacuum. The reason for the lowering main condenser vacuum and the reason for the low steam generator #24 level is under investigation. 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. Notification is also being made as an eight (8) hour report under 10 CFR 50.72(b)(3)(iv)(A) due to actuation of the Auxiliary Feedwater System (AFW). The D.C. Cook Resident NRC Inspector has been notified. Unit 2 is being supplied by offsite power. All control rods fully inserted. Auxiliary Feedwater Pumps started as required and are operating properly. Decay heat is being removed via steam generator power operated relief valves (PORVs) due to condenser steam dump unavailability from low main condenser vacuum. All four Reactor Coolant Pumps remain running. Preliminary evaluation indicates all plant systems functioned normally following the reactor trip. D.C. Cook Unit 2 remains stable in Mode 3. No radioactive release is in progress as a result of this event. |
| ENS 54291 | 24 September 2019 15:02:00 | On September 24, 2019, at 0930 EDT, a non-licensed employee contract supervisor had a confirmed positive test result for illegal drugs during a random test. The employee's access to the plant has been denied. The licensee has notified the NRC Resident Inspector. |
| ENS 52456 | 22 December 2016 05:45:00 | With D.C. Cook Unit 1 in Mode 1 and 100 percent power and Unit 2 in Mode 4 during a refueling outage, the following emergency diesel generators (EDGs) were declared inoperable due to a discovered design and manufacturing issue involving some of the diesel fuel pumps/injectors in each of the following EDGs: Unit 1 CD (Train A) EDG, Unit 2 AB (Train B) EDG, and Unit 2 CD (Train A) EDG Due to both Unit 2 EDGs being inoperable, Unit 2 is required to be in Mode 5 by 1300 (EST) on 12/23/16. Unit 1 is required to restore its emergency diesel generator within 14 days (by 2300 (EST) on 1/04/17). In connection with both trains of Unit 2 EDGs being inoperable, this is being reported as an 8-hour report pursuant to 10CFR50.72(b)(3)(v)(D) as loss of safety function in connection with mitigating the consequences of an accident. The NRC Resident Inspector has been informed. Unit 1 maintenance will be prioritized over Unit 2 and Unit 2 will most likely proceed to Mode 5.
The condition reported in ENS 52456 pursuant to 10 CFR 50.72(b)(3)(v)(D) has been evaluated, and determined not to be a loss of safety function in connection with mitigating the consequences of an accident, and is being retracted. With D.C. Cook Unit 1 in Mode 1 and 100% power and Unit 2 in Mode 4 during a refueling outage, the following Emergency Diesel Generators (EDGs) were declared inoperable due to a discovered design and manufacturing issue involving some of the diesel fuel pumps/injectors in each of the following EDGs: Unit 1 CD (Train A) EDG, Unit 2 AB (Train B) EDG, and Unit 2 CD (Train A) EDG. Subsequent endurance testing was performed on selected Delivery Valve Holders (DVH), which were the affected components of the diesel fuel pumps/injectors, to evaluate the expected degradation of the DVHs during the EDG mission. This testing determined that the identified design and manufacturing issue would not have prevented the EDGs from performing their intended safety functions. Therefore, all EDGs were OPERABLE and did not result in a loss of safety function in connection with mitigating the consequences of an accident. The NRC Resident Inspector was notified of this retraction. Notified the R3DO (Kunowski). |
| ENS 50320 | 30 July 2014 08:16:00 | A non-licensed employee contractor foreman had a confirmed positive test result for alcohol during a random fitness-for-duty test. The employee's access to the plant has been terminated. This notification is being made under 10 CFR 26.719 (b)(2)(ii), significant FFD policy violations or programmatic failures, as a twenty-four (24) hour report. The licensee has notified the NRC Resident Inspector. |
| ENS 49687 | 1 January 2014 15:21:00 | At 11:00 EST on Wednesday, January 1, 2014, during a scheduled functional test of the Cook Nuclear Plant (CNP) Technical Support Center (TSC) ventilation system, the following two dampers failed to properly open when the system was placed in emergency mode (ventilation flow directed through the emergency filtration unit): 12-HV-TSC-SD-5, TSC Ventilation Emergency Flow To & From Air Conditioner 12-HV-TSC-AC-1 Volume Damper 12-HV-TSC-SD-7, TSC Ventilation Emergency Filtration Unit 12-HV-TSC-FIL Inlet Volume Damper The TSC ventilation system is therefore non-functional. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to an emergency response facility being non-functional. Repair activities are in progress for repair of the two dampers. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. The licensee has notified the NRC Resident Inspector.
After repairs were completed, the TSC was restored to service at 0130 EST on 1/2/14. The licensee has notified the NRC Resident Inspector. |
| ENS 49682 | 31 December 2013 10:50:00 | At 1050 EST on Tuesday, December 31, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems will be removed from service for scheduled maintenance. Under certain accidents conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. TSC ventilation system maintenance and post maintenance testing is scheduled to be completed by 1600 EST on December 31, 2013. The licensee has notified the NRC Resident Inspector. This notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii) due to the loss of an emergency response facility.
The TSC ventilation system maintenance and testing was completed satisfactorily and the system was restored to service at 1730 EST on 12/31/13. The licensee will notify the NRC Resident Inspector. Notified R3DO (Kunowski) |
| ENS 49170 | 3 July 2013 01:15:00 | At 0115 EDT on Wednesday, July 3, 2013, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems will be removed from service for scheduled maintenance. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. TSC ventilation system maintenance and post maintenance testing is scheduled to be completed by 2100 EDT on July 3, 2013. The licensee has notified the NRC Resident Inspector. This notification is being made in accordance with 10CFR50.72(b)(3)(xiii) due to the loss of an emergency response facility.
The TSC ventilation system maintenance and testing was completed satisfactorily and the system was restored to service at 1430 EDT on 7/3/13. The licensee has notified the NRC Resident Inspector. Notified R3DO (Kunowski) |
| ENS 48060 | 2 July 2012 01:49:00 | At 02:00 EDT on Monday, July 2, 2012, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems will be removed from service for scheduled maintenance. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. TSC ventilation system maintenance and post maintenance testing is scheduled to be completed by 15:00 EDT on Monday, July 2, 2012. The licensee has notified the NRC Resident Inspector. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to the loss of an emergency response facility.
The TSC ventilation system maintenance was completed satisfactorily and the system was restored to service at 1725 EDT on 7/2/12. The licensee will notify the NRC Resident Inspector. Notified R3DO (Daley). |
| ENS 47864 | 26 April 2012 01:21:00 | At 2246 EDT on April 25, 2012, D.C. Cook notified the State of Michigan and local authorities of an oil spill from the Unit 2 (Main Generator) Seal Oil system at 2110 EDT which resulted in a portion of this oil entering the absorption pond, which is in the owner controlled area. An oil sheen is present on the absorption pond which has a surface area of approximately 2 acres (87,000 square feet) and it is estimated that five to ten gallons of oil are on the absorption pond. The NRC Resident Inspector was notified. The licensee has contained the oil leak and clean up efforts are ongoing. |
| ENS 47794 | 1 April 2012 04:26:00 | At 0445 EDT on Sunday, April 1, 2012, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems will be removed from service for scheduled maintenance. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. TSC ventilation system maintenance and post maintenance testing is scheduled to be completed by 1900 EDT on Sunday, April 1, 2012. The licensee has notified the NRC Resident Inspector. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to the loss of an emergency response facility. * * * UPDATE FROM DEAN BRUCK TO PETE SNYDER ON 4/1/12 AT 1633 EDT * * * The TSC ventilation system maintenance was completed satisfactorily and the system was restored to service at 1620 EDT on 4/1/12. The licensee will notify the NRC Resident Inspector. Notified R3DO (Dickson). |
| ENS 46520 | 4 January 2011 08:15:00 | At 0800 EST on Tuesday, January 4, 2011, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems were removed from service for scheduled maintenance. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary . TSC ventilation system maintenance is scheduled to be completed by 1600 EST on Tuesday, January 4, 2011. The licensee has notified the NRC Resident Inspector. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to the loss of an emergency response facility,
The TSC ventilation system maintenance was completed satisfactorily and the system was restored to service at 1705 EST. The licensee will notify the NRC Resident Inspector. Notified the R3DO (Lipa) via e-mail. |
| ENS 46477 | 14 December 2010 02:02:00 | At 2119 EST on December 13, 2010, operators manually started all Auxiliary Feedwater (AFW) pumps in response to a loss of the Unit 1 East Main Feedwater Pump. Operators were responding to decreasing condenser vacuum on the East Main Feedwater Pump and reducing turbine load when the East Main Feedwater Pump was manually tripped at approximately 21 inches of vacuum Hg. Operators entered the abnormal operating procedure for Loss of One Main Feedwater Pump, which directs starting all three AFW pumps. Plant power was stabilized at approximately 49%. The licensee will be notifying the NRC Senior Resident Inspector. This notification is being made in accordance with 10CFR50.72(b)(3)(iv)(A) due to the valid actuation of the AFW system in response to equipment failure. No maintenance was in progress, and the cause of the decreasing condenser vacuum in the MFP was due to debris in the traveling water screen. |
| ENS 45429 | 13 October 2009 08:20:00 | At 0744 (EDT) on Tuesday, October 13, 2009, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) air conditioning and charcoal filtration systems were removed from service for scheduled maintenance. Under certain accident conditions the TSC may become unavailable due to the inability of the air conditioning and charcoal filtration systems to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary. TSC ventilation system maintenance is scheduled to be completed at 1500 (EDT) on Tuesday, October 13, 2009. This notification is being made in accordance with 10CFR50.72(b)(3)(xiii) due to the loss of an emergency response facility. The licensee notified the NRC Senior Resident Inspector.
The CNP TSC ventilation system was returned to functional status following scheduled maintenance at 1333 (EDT) on Tuesday, October 13, 2009. This follow-up notification is being made to provide closure from the initial notification under 10CFR50.72.(b)(3)(xiii) due to the loss of an emergency response facility. The licensee has notified the NRC Senior Resident Inspector of the return to service of the TSC Ventilation System. Notified R3DO (Eric Duncan) |
| ENS 44542 | 6 October 2008 04:49:00 | At 0445 on Monday, October 6, 2008, the Cook Nuclear Plant (CNP) Technical Support Center (TSC) ventilation system and charcoal filter was removed from service for scheduled preventive maintenance. The charcoal bed filtration system is also out of service in support of the maintenance on the TSC ventilation system. Under certain accident conditions the TSC may become unavailable due to the inability of the filtration system to maintain a habitable atmosphere. Compensatory measures exist to relocate TSC personnel to the unaffected unit's control room if necessary based upon results of procedurally required monitoring of TSC radiological conditions. The TSC ventilation system maintenance is scheduled to complete at 16:00 on Monday, October 6,2008. The licensee has notified the NRC Senior Resident Inspector. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to the loss an emergency response facility.
The TSC Ventilation System and Charcoal Filter was returned to functional status at 14:35 on Monday, October 6, 2008. This follow up notification is being made to provide closure from the initial notification under 10 CFR 50.72 (b)(3)(xiii) due to the loss of an emergency response facility. The licensee has notified the NRC Resident Inspector. Notified R3DO (Lara). |
| ENS 42536 | 29 April 2006 14:19:00 | D.C. Cook Unit 2 was in Mode 4 and heating up after Unit 2 Cycle 16 refueling outage when 2-IMO-340 (East RHR pump to Charging Pump Suction Header) was throttled open. RHR suction was aligned to Loop 2 Hot Leg with wide range RCS pressure at 337 psig and RCS average temperature 280 degrees Fahrenheit. Charging header safety valve 2-SV-56 lifted with a setting of 220 psig and relieved to the Pressurizer Relief Tank (PRT) between 10:56:00 and 10:58:30. 2-IMO-340 was then closed. Approximately, 120 gallons of reactor coolant were directed to the PRT during the approximate 2.5 minutes, resulting in a flow rate of approximately 48 gpm, greater than the 25 gallon per minute identified leak rate limit for an Unusual Event (10 CFR 50.72(a)(1)(i)). Time of discovery for leakage quantity and reportability was 13:21 on 4/29/06. Therefore, for approximately 2.5 minutes, D.C. Cook Unit 2 met the conditions for an Unusual Event. However, this fact was discovered after leakage was stopped. Unit 2 is stable in Mode 4 at 340 degrees Fahrenheit and 405 psig RCS pressure. An Unusual Event was NOT declared, but the conditions for an Unusual Event were met under Emergency Condition Criteria S-8 between 10:56:00 and 10:58:30 on 4/29/06. This ENS notification is being made within one hour of the discovery of the undeclared event. The licensee will notify the NRC Resident Inspector.
EN# 42536 reported that D.C. Cook Unit 2 satisfied the conditions for entry into an Unusual Event under Emergency Condition Criteria S-B, identified RCS leakage exceeding 25 GPM. This was identified after system alignment had been restored, ending the event, and was reported as an after the fact declaration that the conditions for an Unusual Event had been satisfied, but not declared. Subsequent review of this event has determined that the conditions for Emergency Condition Criteria S-B were not satisfied in that no identified RCS leakage occurred during this event. The diversion of 120 gallons of CVCS (Chemical Volume and Control System) inventory was the result of plant alignment by Operations personnel which was immediately recognized and terminated. Plant systems and components functioned as designed to terminate this event. The licensee will notify the NRC Resident Inspector. Notified R3DO (H. Peterson). |
| ENS 42125 | 8 November 2005 07:10:00 | At 03:58 on 11-08-05, D.C. Cook Unit 2 experienced an automatic, reactor trip due to Reactor Coolant Pump Bus Undervoltage. The cause of the reactor trip its under investigation. This requires a 4-hour report under 10CFR50.72(b)(2)(iv)(B). All four reactor coolant pumps have remained running. The Unit 2 Turbine Driven Auxiliary Feedwater Rump (TDAFP) started automatically due to low-low levels in at least two steam generators which is expected for a reactor trip from 100% power. The 'B' train Emergency Diesel Generator (2AB EDG) automatically started and loaded "B" train emergency bus T21A. These automatic actuations of the reactor protection system, TDAFP start, and 2A13 EDG start require an 8-hour report under I OCFR50.72(b)(3)(iv)(A). 'B' train emergency bus T21B was declared inoperable after it failed to be energized automatically on the start of the 2AB EDG. The cause of this failure is under investigation. The 'A' train Emergency Diesel Generator (2CD EDG) had been inoperable for scheduled maintenance during the time of the event. It was restored to operable status at 06:06. All control rods fully inserted. Steam generators are discharging steam to the main condenser using steam dumps. The licensee notified the NRC Resident Inspector. |
| ENS 40716 | 29 April 2004 18:09:00 | D.C. Cook Unit 2 was performing post-maintenance testing on a solenoid valve associated with a letdown orifice valve and realigning letdown flowpath when safety valve 2-SV-51 (Regenerative Heat Exchanger Letdown Outlet Safety Valve) lifted on 4/29/04 at 15:57 EDT, relieving 323 gallons of water to the Pressurizer Relief Tank over a five (5) minute period before letdown was isolated. Average leak rate was approximately 65 gallons per minute, greater than the 25 gallon per minute identified leak rate limit for an Unusual Event (10CFR50.72(a)(1)(i)). This was a rapidly concluded event of a five (5) minute duration. Time of discovery for leakage quantity and reportability was 17:10 on 4/29/04. Therefore, for a five (5) minute period, D.C. Cook Unit 2 met the conditions for an Unusual Event. However, this fact was discovered after leakage was stopped. Unit 2 is stable at approximately 100% reactor thermal power with the excess letdown system in service. An Unusual Event was NOT declared, but the conditions for an Unusual Event were met between 15:57 and 16:02 on 4/29/04. This ENS notification is being made within one hour of the discovery of the undeclared event. The licensee notified the NRC Resident Inspector. |