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 Entered dateSiteRegionReactor typeEvent description
ENS 5406010 May 2019 15:30:00DresdenNRC Region 3At 0720 CDT (on 5/10/19), security was notified of a prohibited item (un-opened alcohol container) reported in the protected area. Security assumed escort of the non-supervisory (contract) individual and took custody of the prohibited item. The employee's access to the plant has been suspended. The NRC Resident Inspector has been notified.
ENS 540549 May 2019 07:01:00DresdenNRC Region 3On May 9, 2019 at 0348 CDT, an automatic scram was received on Unit 2 following a turbine trip. All rods inserted to their full-in positions. All Group 2 and Group 3 automatic isolations actuated as expected. Systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The NRC Resident Inspector has been notified. Decay heat is being removed using the steam bypass valves to the condenser and the safety relief valves did not lift as a result of the trip.
ENS 5385130 January 2019 17:41:00DresdenNRC Region 3At 0910 (CST) on January 30, 2019, the Dresden Station Heater Boiler 'B' tripped while placing the station Heater Boiler 'A' in service. With colder temperatures, the density of the supply air increased and contributed to a greater quantity of air entering the Reactor Building than what was previously being supplied with heating steam in service. The Reactor Building differential pressure (DP) degraded and dropped below 0.25 inches water column vacuum. This condition represents a failure to meet Technical Specification (TS) Surveillance Requirement 3.6.4.1.1. Entry into TS 3.6.4.1 Condition A was made due to Secondary Containment becoming inoperable. Standby Gas Treatment System was initiated to assist with Reactor Building DP control. Reactor Building DP was restored to greater than 0.25 inches water column vacuum. TS 3.6.4.1 Condition A was exited. This event is being reported under 10 CFR 50.72(b)(3)(v)(C), 'Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to ... control the release of radioactive material.' The NRC Resident Inspector has been notified."
ENS 5320412 February 2018 13:47:00DresdenNRC Region 3

EN Revision Text: UNANALYZED CONDITION FOR TORNADO GENERATED MISSILES On February 12, 2018, during evaluation of protection for Technical Specifications (TS) equipment from the damaging effects of tornado generated missiles, Dresden Station identified a non-conforming condition in the plant design such that specific TS equipment is considered to not be adequately protected from tornado generated missiles. Tornado generated missiles could strike the Unit 2, Unit 2/3, and Unit 3 Emergency Diesel Generator main fuel oil tank vents. This could result in crimping of the vents, which would affect the ability of the main fuel oil tanks to perform their function if a tornado would occur. This condition is reportable in accordance with 10 CFR 50.72(b)(3)(ii)(B) as a condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety and 10 CFR 50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. This condition is being addressed in accordance with NRC enforcement guidance provided in Enforcement Guidance Memorandum (EGM) 15-002, 'Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance,' and DSS-ISG-2016-01, 'Clarification of Licensee Actions in Receipt of Enforcement Discretion' per Enforcement Guidance Memorandum EGM 15-002, 'Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance,' Revision 1. Compensatory measures have been implemented in accordance with these documents. The NRC Resident Inspector has been informed of this notification.

  • * * RETRACTION ON 10/11/19 AT 1031 EDT FROM SAMANTHA COSENZA TO BETHANY CECERE * * *

The purpose of this notification is to retract event notification 53204 made on February 12, 2018, for Dresden Station. Additional review determined that the current design of all three Emergency Diesel Generators and associated Main Fuel Oil Storage Tanks Vents is consistent with the licensing basis for Dresden Station. There was no non-conformance of Dresden's tornado missile protection design, and the EDGs were operable at the time the event notification was made. Therefore, this event does not meet the criteria of 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D). The ENS 53204 report is being retracted. The NRC Resident Inspector has been informed of this notification." Notified R3DO (Hills).

ENS 531987 February 2018 15:04:00DresdenNRC Region 3GE-3At approximately 1040 CST, seven (7) Dresden Nuclear Power Station Offsite Emergency Notification sirens (i.e., Siren Nos. DR1, DR4, DR5, DR6, DR9, DR10, and DR11) were inadvertently activated. The Kendall County, IL Emergency Management Agency notified the Exelon Generation Company, LLC. Emergency Response Organization that at 1040 CST, a contract individual inadvertently cut a wire that resulted in the actuation of these seven sirens for three minutes. The contract organization personnel are addressing the issue with the sirens. The Kendall and Will County Emergency Management Agency contacted Exelon Generation Company regarding this event. This notification is being made in accordance with 10 CFR 50.72(b)(2)(xi) as an event where other government agencies were notified. The NRC Resident Inspector has been informed of this notification. The sirens are operable.
ENS 530481 November 2017 16:33:00DresdenNRC Region 3GE-3On November 1, 2017 at 1225 CDT, both the 2-220-58A Feed Water Inboard Check Valve and the 2-220-62A Feed Water Outboard Check Valve failed Local Leak Rate Testing (LLRT) acceptance criteria due to excessive leakage. These valves are considered primary containment isolation valves, and as such, are required to ensure that an adequate primary containment boundary is maintained. Technical Specification (TS) 5.5.12, 'Primary Containment Leakage Rate Testing Program,' establishes limits for Primary Containment leakage. Based upon the results of the LLRT, Dresden, Unit 2, may not have met the limits for primary containment leakage during the last operating cycle as specified in TS 5.5.12.C. Dresden Unit 2 is currently in Mode 5 for a refueling outage and per Dresden TS 3.6.1.1, 'Primary Containment,' Primary Containment is not required in the current mode of operation (i.e., Mode 5). However, in accordance with 10 CFR 50.72(b)(3)(ii)(A), this event is reportable as a condition that resulted in a principal safety barrier being seriously degraded. The NRC Resident Inspector has been notified.
ENS 5296412 September 2017 14:20:00DresdenNRC Region 3GE-3On September 12, 2017 at 1131 CDT, both Unit 3 Standby Liquid Control system (SLC) subsystems were declared inoperable for a through wall leak on the common discharge piping. With both subsystems inoperable, the SLC system was unable to fulfill its safety function. This event is reportable under 10 CFR 50.72(b)(3)(v)(A) for an event or condition that could have prevented the fulfillment of a safety function of a system that is needed to shut down the reactor and maintain it in a safe shutdown condition and under 10 CFR 50.72(b)(3)(v)(D) for a system that was unavailable for accident mitigation. The NRC Resident Inspector has been notified. With both trains of SLC inoperable, the licensee entered an 8-hr. action statement to restore at least one train to operability. If unable to do so, then the plant will enter a 12-hr. shutdown action statement.
ENS 5258228 February 2017 21:34:00DresdenNRC Region 3GE-3

At 1825 (CST) on 02/28/2017, Dresden Station received unexpected alarm 923-5 C-1, RX BLDG DP LO (Reactor Building Differential Pressure Low). Reactor Building differential pressure was observed to briefly lose vacuum and return to a normal reading of 0.6 inches vacuum water gauge. At the time of the transient, Grundy County was under a Severe Weather Warning and gusts of wind were being monitored from the Main Control Room up to approximately 57 mph. The Reactor Building differential pressure returned to (greater than or equal to) 0.25 inches vacuum water gauge at 18:25 after 18 seconds with no operator action. Operators observed differential pressure reading to lose vacuum, below 0 inches vacuum water gauge, for approximately 3 seconds. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.1. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. This event is being reported in accordance with 10CFR50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. An issue report has been initiated and a 60-day Licensee Event Report will be submitted in accordance with 10CFR50.73(a)(2)(v)(C). The NRC Resident Inspector has been notified.

  • * * RETRACTION ON 4/14/17 AT 1429 EDT FROM BOBBY SHORT TO DONG PARK * * *

The purpose of this notification is to retract ENS notification 52582 made on 2/28/17 for Dresden Nuclear Power Station. The previous notification reported a potential loss of Reactor Building differential pressure due to high wind conditions and associated entry into Technical Specification 3.6.4.1 Condition A for failure to meet Surveillance Requirement 3.6.4.1.1 to maintain differential pressure above 0.25 inches vacuum water gauge. After further evaluation, it has been determined that the high winds caused a momentary low pressure pocket on the leeward side of the Reactor Building causing the differential pressure reading seen in the Main Control Room, but it did not challenge Reactor Building differential pressure or Secondary Containment. Reactor Building differential pressure indication utilizes four transmitters, one on each wall of the Reactor Building, and the most conservative reading is transmitted to the indicator in the Main Control Room. Wind conditions impacting a single transmitter would result in indication of low Reactor Building differential pressure in the Main Control Room. Procedures direct action to obtain local readings from all four Reactor Building differential pressure transmitters. After the low indication in the Main Control Room, Equipment Operators were dispatched to obtain local indication and all four transmitters were found to be indicating 0.6 inches vacuum water gauge. This was a short duration transient with no indications of an equipment failure that could impact Secondary Containment. The entire transient occurred within an 18 second window where differential pressure indication began at 0.6 inches vacuum water gauge, dropped to below 0 inches vacuum water gauge, and subsequently restored to 0.6 inches vacuum water gauge with no operator intervention. Furthermore, a significant change in Reactor Building differential pressure would impact readings on Drywell pressure because the Reactor Building pressure is used as a reference leg. Trends of Drywell pressure during the event indicated no adverse conditions implying that Reactor Building differential pressure was stable. Thus, it has been concluded that this was an indication issue and at no point during the transient would Secondary Containment have been unable to perform its safety function. Therefore, this event does not meet the criteria of 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function, and the ENS notification is being retracted. There is no longer a requirement for an associated 60-day Licensee Event Report in accordance with 10 CFR 50.73(a)(2)(v)(C). The NRC Resident Inspector has been notified. Notified R3DO (Jeffers).

ENS 525428 February 2017 17:06:00DresdenNRC Region 3GE-3

At 0851 CST on Wednesday, February 8th, 2017, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) Emergency Ventilation System was emergently declared inoperable due to a failure of the outside air damper to reposition. This resulted in the inability for the TSC ventilation to maintain the required air flow to support habitability during emergency conditions. Actions are being taken to repair damper to restore functionality of the TSC ventilation system. In the interim, station procedures provide guidance to relocate the TSC to an alternate facility. This event is being reported under 10 CFR 72(b)(3)(xiii), Any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability (e.g., significant portion of control room indication, Emergency Notification System, or offsite notification system). The NRC Resident Inspector has been notified.

  • * * UPDATE PROVIDED BY RYAN CHAMBERLAIN TO JEFF ROTTON AT 0418 EST ON 02/10/2017 * * *

At 0108 CST on February 10, 2017, Dresden TSC ventilation has been restored and is now functional. The NRC Resident Inspector has been notified. Notified R3DO (Kunowski).

ENS 5237016 November 2016 18:22:00DresdenNRC Region 3GE-3

At 1105 CST on Wednesday, November 16th, 2016, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) Emergency Ventilation System was emergently declared inoperable due to an unplanned loss of the pneumatic air supply compressor. The loss of the air compressor resulted in the emergency air filtration unit flow control damper failing to the full open position. In this condition, the emergency air filtration unit could exceed the max flow rate of 1100 SCFM and the max differential pressure of 6 inches H2O at rated flow rate resulting in degraded performance. This results in a potential loss of protective action function provided by the emergency ventilation filtration system and could impede the ability to perform Emergency Assessments should a radiological emergency event occur requiring the system to be in service. Actions are being taken to repair the pneumatic air system to restore functionality of the TSC ventilation system. In the interim, contingency actions are being developed to manually control the emergency air filtration unit flow control damper in a degraded condition. In the event that ventilation cannot be restored, Station Procedures provide guidance to relocate the TSC to an alternate facility. This event is being reported under 10 CFR 50.72(b)(3)(xiii), 'Any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability (e.g., significant portion of control room indication, Emergency Notification System, or offsite notification system).' The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM ADAM SCHUERMAN TO HOWIE CROUCH AT 0812 EST ON 11/17/16 * * *

The pneumatic air supply compressor has been repaired and tested satisfactorily. The Technical Support Center is now considered operable. The licensee will be notifying the NRC Resident Inspector. Notified R3DO (Peterson).

ENS 523558 November 2016 12:50:00DresdenNRC Region 3GE-3On 11/8/16, Operators were performing Division I Undervoltage Testing Surveillance on Unit 3, when a 2 (psi) drywell signal was inserted, Reactor Building Ventilation tripped and SBGT initiated as expected. At 0510 (CST), reactor building to atmosphere differential pressure dropped below the (negative) 0.25 inches water. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.1. As a result, entry into Technical Specification 3.6.4.1 condition A was made due to Secondary Containment becoming inoperable. This event is being reported in accordance with 10CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. At 0532, the 2/3 Reactor Building material interlock inner door was closed and Reactor Building (differential pressure) was restored to greater than (negative).25 inches of water column. An issue report has been initiated. An investigation will be conducted and a 60 day Licensee Event report will be submitted in accordance with 10 CFR 50.73(a)(2)(v)(C). The NRC Resident Inspector has been notified.
ENS 5225319 September 2016 21:40:00DresdenNRC Region 3GE-3

At 1550 (CDT) on September 19, 2016, Dresden received the Methyl Iodide Penetration test results for the Control Room Emergency Ventilation (CREVS) charcoal. The test results did not meet technical specification acceptance criteria. This results in the inoperability of CREVS. CREVS is a single train system and therefore is reportable per 10CFR50.72(b)(3)(v)(D). The Air Filtration Unit (AFU) is required to operate during a design basis accident to maintain Main Control Room habitability. This places unit 2 and unit 3 in a 7 day LCORA (Limiting Condition of Operation Required Action) per Tech Spec 3.7.4 Required Action A.1. The licensee notified the NRC Resident Inspector.

  • * * UPDATE AT 1635 EDT ON 03/23/17 FROM HENRY WATERS TO S. SANDIN * * *

The licensee is retracting this report based on the following: The purpose of this notification is to retract ENS notification 52253 made on September 19th, 2016, for Dresden Nuclear Power Station. After further evaluation and testing, it has been determined that the Control Room Emergency Ventilation System (CREVS) charcoal would have fulfilled its safety function given the Methyl Iodide Penetration test results. The initial tests were performed with a 2 inch bed depth due to a difference in batches used in each charcoal filter, but testing at a 4 inch bed depth is the correct testing methodology for Dresden's configuration. At a 4 inch bed depth, the test results met the Technical Specification acceptance criteria with significant margin. Therefore, this event does not meet the criteria of 10 CFR 50.72(b)(3)(v)(D) and the ENS report is being retracted. The NRC Resident Inspector has been notified. Notified R3DO (Orlikowski).

ENS 5210720 July 2016 12:02:00DresdenNRC Region 3GE-3

At 1130 CDT on Wednesday, July 20, 2016, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system will be removed from service for planned maintenance activities. During the maintenance, the TSC ventilation will be shut down. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out-of-service time. The planned TSC ventilation outage is scheduled to be completed in approximately 14 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Planning (EP) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration, the Station Emergency Director will relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM RYAN CHAMBERLAIN TO DANIEL MILLS ON 07/21/2016 AT 1757 EDT * * *

At 1619 CST on July 21, 2016, Dresden TSC ventilation has been restored and is now functional." The licensee has notified the NRC Resident Inspector Notified R3DO (Stone).

ENS 5209818 July 2016 22:07:00DresdenNRC Region 3GE-3Testing of the Everbridge ERO (Emergency Response Organization) notification system identified that the system cannot notify all ERO individuals. This constitutes a loss of offsite communications capability. Compensatory measures (ERO phone lists) were put in place. The Everbridge system capability loss for Dresden Station was identified at 1500 CDT on July 18, 2016, due to an undetermined loss of system communications. Emergency Response Data System (EROS) capability was not lost. This event is reportable under 10 CFR 50.72(b)3(xiii) as a major loss of communication capability. On July 18, 2016 at 1957 CDT, an Everbridge ERO call in drill was initiated and verified successful at 2030 CDT. The NRC Resident Inspector has been notified. Some of the ERO personnel did not receive a test page. The requirement is to have all ERO personnel receive the page within ten minutes and to be fully staffed within one hour.
ENS 5204627 June 2016 12:21:00DresdenNRC Region 3GE-3

At 1050 CDT, (on 6/27/16), an Alert was declared at Dresden Unit 3. The Alert is due to Unit 3 experiencing a fire in the HPCI (High Pressure Coolant Injection) system, auxiliary oil pump motor. The fire is out. This notification is being made per 10 CFR 50.72(a)(1)(i). Dresden Unit 3 is stable and continues to operate at 100% power and HPCI has been declared inoperable. There is no impact on Dresden Unit 2. The licensee has notified the NRC Resident Inspector Notified DHS SWO, FEMA, USDA, HHS, DOE, DHS NICC, EPA, and FEMA National Watch Center, FDA EOC, NuclearSSA via email only.

  • * * UPDATE FROM MICHAEL HAYES TO JOHN SHOEMAKER AT 1433 EDT ON 6/27/16 * * *

Termination of MA-5 (Alert). Fire in HPCI room verified extinguished. HPCI system is inoperable. (Technical Specification) TS 3.5.1 condition G in effect, per 10 CFR 50.72(c)(i) - notification of termination of Alert. Dresden Unit 3 terminated the Alert at 1319 CDT, on 6/27/16. Dresden Unit 3 continues to operate at 100% power. The licensee will notify the NRC Resident Inspector. Notified R3DO (Kunowski), NRR (Miller), IRD (Grant), DHS SWO, FEMA, USDA, HHS, DOE, DHS NICC, EPA, and FEMA National Watch Center, FDA EOC, NuclearSSA via email only.

  • * * UPDATE FROM MICHAEL CSERNAK TO JOHN SHOEMAKER AT 1755 EDT ON 6/27/16 * * *

At 1042 (CDT) on 6/27/16, the U3 High Pressure Coolant Injection (HPCI) system was declared inoperable after the Auxiliary Oil Pump failed. This event is reportable per 10CFR50.72(b)(3)(v)(D); any event or condition that at the time of discovery could have prevented fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. This is an eight hour reporting requirement. The Dresden NRC Resident (Inspector) has been notified. Notified R3DO (Kunowski).

ENS 5193416 May 2016 19:56:00DresdenNRC Region 3GE-3At 1457 (CDT) on 5-16-16, U-2 (Unit 2) High Pressure Coolant Injection (HPCI) system was declared inoperable after isolation of the system due to a steam leak on the HPCI steam inlet drain pot drain line. The event is reportable per 10CFR50.72(b)(3)(v)(D), Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences an accident. This is an eight hour report requirement. The Dresden NRC Resident Inspector has been notified.
ENS 519139 May 2016 17:34:00DresdenNRC Region 3GE-3At approximately 1430 CDT on 5/9/2016, the Dresden Station Main Control Room was notified by Exelon Corporate Emergency Preparedness of the inadvertent actuation of all 27 Full Sounding Sirens in Will County, Illinois. Exelon Emergency Preparedness was notified at 1309 CDT on 5/9/2016. The inadvertent actuation occurred on 5/7/16 at 2350 CDT during a training activity performed by Wescom (Western Will County Communications Center). This event is reportable per 10 CFR 50.72(b)(2)(xi), News Release or Notification of Other Government Agencies. This is a 4-hour reporting requirement. The Dresden NRC Resident has been notified.
ENS 5172110 February 2016 02:17:00DresdenNRC Region 3GE-3At 2142 (CST) on February 9, 2016, Reactor Building differential pressure did not meet the required 0.25 inches of vacuum water gauge due to failure of the control system. At 2205, the Unit 3 Reactor Building Ventilation System was secured and manually isolated. The Reactor Building differential pressure returned to (greater than or equal to) 0.25 inches of vacuum water gauge at 2207. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.1. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified.
ENS 5166419 January 2016 18:41:00DresdenNRC Region 3GE-3

At 0400 CST on Wednesday, January 20, 2016, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system will be removed from service for planned maintenance activities. During the maintenance, the TSC Ventilation will be shut down. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed in approximately 43 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Planning (EP) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration; the Station Emergency Director will relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE AT 0049 EST ON 1/22/16 FROM STEVEN MELL TO JEFF HERRERA * * *

At 2223 CDT on 1/21/16, Dresden TSC Ventilation was restored. The Dresden TSC Ventilation is functional at this time. The NRC Resident Inspector has been notified. Notified R3DO (Cameron).

ENS 5150930 October 2015 17:38:00DresdenNRC Region 3GE-3At 1429 CDT, Dresden Nuclear Power Station (DNPS) notified the Illinois Environmental Protection Agency (IEPA) of an upset condition involving the loss of power to the DNPS lift station. The lift station power was lost at approximately 1350 CDT, and in response, DNPS entered abnormal operating procedures to limit hot canal levels. Power was restored to the lift station at approximately 1500 CDT. There was no impact to the health and safety of the public or to the environment. The NRC Resident Inspector has been notified.
ENS 5142124 September 2015 05:52:00DresdenNRC Region 3GE-3During surveillance testing of the U2 HPCI (High Pressure Coolant Injection) system, the HPCI motor gear unit (MGU) was positioned from 100 percent to 75 percent demand to satisfy operability testing. The motor gear unit did not respond as system demand was returned to 100 percent. This indicated a failure of the MGU which requires declaration of inoperability of the HPCI System. This is a 14 day LCO. HPCI is a single train system and reportable under SAF 1.8 'Event or condition that could have prevented fulfillment of a safety function.' The licensee will be notifying the NRC Resident Inspector.
ENS 513745 September 2015 17:24:00DresdenNRC Region 3GE-3At 1010 (CDT) on September 5, 2015, Reactor Building differential pressure did not meet the required 0.25 inches of vacuum due to an open inspection hatch. At 1018 (CDT), an inspection hatch was found to have fallen open and (was) subsequently closed (manually) on the Reactor Building exhaust fan damper access hatch. The damper is outside of the Reactor Building secondary containment isolation boundary. Following closure of the hatch, Reactor Building differential pressure returned to greater than or equal to 0.25 inches of vacuum water gauge. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.1. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)c as a condition that could have prevented the fulfillment of a safety function. The NRC Senior Resident Inspector has been notified.
ENS 513714 September 2015 14:36:00DresdenNRC Region 3GE-3At 0810 (CDT) on September 4, 2015, two Secondary Containment doors in one access opening, were opened simultaneously. The interlock mechanism preventing both doors from operating simultaneously at the Unit 2 570 foot elevation Turbine to Reactor Building interlock did not operate as expected. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. Secondary Containment differential pressure was maintained within specification. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Senior Resident Inspector has been notified.
ENS 5123215 July 2015 01:04:00DresdenNRC Region 3GE-3

At 0004 (CDT) on Wednesday, July 15, 2015, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system will be removed from service for planned maintenance activities. During the maintenance, the TSC Ventilation will be shut down. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed in approximately 24 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Planning (EP) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration; the Station Emergency Director will relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM TRAVIS PRELLWITZ TO DONALD NORWOOD AT 1733 EDT ON 7/17/2015 * * *

At 1347 CDT on July 17, 2015, Dresden TSC Ventilation was restored. The Dresden TSC Ventilation is Functional at this time. The NRC Resident Inspector has been notified. Notified R3DO (Orth).

ENS 5117323 June 2015 10:26:00DresdenNRC Region 3GE-3At 0342 (CDT), as a result of severe weather conditions in the area, Exelon Generation Company, LLC (EGC) identified that the Emergency Notification System (ENS), Health Physics Network (HPN) phone systems, and their associated back-up system, the commercial phone system, had failed at Dresden Nuclear Power Station (DNPS). A loss of the primary phone system concurrent with the loss of the associated back-up system is a reportable condition in accordance with 10 CFR 50.72 (b)(3)(xiii) - Major Loss of Emergency Preparedness Capabilities. As a result of the failed communication systems, DNPS contacted the NRC to notify them of the issue and provided an alternate phone number for the Shift Manager for use until the systems were restored. As of 0743 (CDT), ENS, HPN, and the commercial phone systems were restored and verified to be working properly. The licensee notified the NRC Resident Inspector.
ENS 507926 February 2015 16:53:00DresdenNRC Region 3GE-3At 1227 CST on 06 Feb 2015, Dresden Unit 2 automatically scrammed due to a Reactor Water Level transient. Set up activities for weekend maintenance were being performed on the feedwater system at the time of the event. All rods inserted to their full-in positions. Systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. The ultimate heat sink was maintained. The source of the transient was a loss of Feedwater Level Control and the reactor automatically scrammed on low reactor water level. Cause of the failure is under investigation. All three feed pumps tripped as a result of the transient. The 2B reactor feed pump was restored following the transient in accordance with station operating procedures. Level is being maintained with normal feedwater. High Pressure Coolant Injection initiated on a valid low-low reactor water level. Manual operator action was taken to prevent unneeded injection into the reactor coolant system. Group 2 Primary Containment and Group 3 Shutdown Cooling and Reactor Water Clean-up system isolations occurred as expected. Unit 2 and 2/3 (swing diesel) EDGs started as expected, but did not load onto their associated busses as offsite power was maintained. The licensee has notified the NRC Resident Inspector.
ENS 5075926 January 2015 05:04:00DresdenNRC Region 3GE-3

At 0355 (CST) on Monday, January 26, 2015, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system was removed from service for planned preventative maintenance activities on the TSC air handling unit, air compressor units, and TSC air filtration unit. During the maintenance, the TSC Ventilation will be shut down. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 38 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Planning (EP) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration; the Station Emergency Director will evacuate and relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM RYAN SEARS TO JOHN SHOEMAKER AT 2012 EST ON 1/27/15 * * *

At 1740 CST on January 27th, 2015, Dresden TSC Ventilation was restored. The Dresden TSC Ventilation is functional at this time. The NRC Resident Inspector has been notified. Notified the R3DO (Dickson).

ENS 5073313 January 2015 22:10:00DresdenNRC Region 3GE-3At 1904 Central Time 13 Jan 2015, Dresden Unit 2 was manually scrammed by Operators due to a Reactor Water Level transient. All rods inserted to their full-in positions. All systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. The source of the transient was a failure of both controllers in the Feedwater Level Control system. Cause of the failure is under investigation. This condition is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (R) when the reactor is critical. There was no on-going work or testing during this time which could be attributed to the failure of the level controllers. Unit 2 is in a normal post scram electrical line-up and maintaining pressure and temperature. RHR cooling is available if required. Unit 3 was unaffected by this transient. The licensee informed the NRC Resident Inspector.
ENS 5028921 July 2014 06:42:00DresdenNRC Region 3GE-3

At 0525 (CDT) on Monday, July 21, 2014, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system was removed from service for planned preventative maintenance activities on the TSC air handling unit, air compressor units, and TSC air filtration unit. During the maintenance, the TSC Ventilation was shut down. The TSC air filtration fan and dampers are non-functional, rendering the TSC HVAC accident mode nonfunctional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 48 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Planning (EP) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration; the Station Emergency Director will evacuate and relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM MATT KERCHENFAUT TO DONALD NORWOOD AT 2035 EDT ON 7/22/2014 * * *

At 1540 CDT on July 22, 2014, Dresden TSC Ventilation was restored. The Dresden TSC Ventilation is functional at this time. The NRC Resident Inspector has been notified. Notified R3DO (Orth).

ENS 501808 June 2014 17:03:00DresdenNRC Region 3GE-3

This notification is being made pursuant to 10 CFR 50.72(b)(2)(xi) because Dresden Nuclear Power Station is in the process of informing the Illinois Emergency Management Agency (lEMA) and Illinois Environmental Protection Agency (IEPA) of recent groundwater monitoring results at Dresden Station. Additionally, the station intends to issue a press release. As part of the Station's extensive environmental monitoring and sampling program, sample results from an onsite sampling well near the 2/3 contaminated water storage tank (CST) indicate elevated levels of tritium. This is an on-site leak, requiring the notification of the State of Illinois. Based on sampling data obtained, the tritium is currently confined to Exelon property. The IEPA/lEMA regulation requires notification when a release to soil, groundwater or surface water goes offsite at greater than 200 pCi/L or remains on-site greater than 0.002 Curies. Based upon the sampling results from the monitoring well near the 2/3 CST with a concentration of approximately 0.0000013 Curies/liter it is likely that the 0.002 Curie on-site threshold has been exceeded. The Station continues to track this issue by monitoring the existing wells and initiation of mitigative actions to contain any release and ensure it remains on-site. At this time, the source of the tritium has not been identified. Investigation continues to determine if an off-site release occurred. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE AT 1951 EDT ON 6/9/2014 FROM THOMAS DITCHFIELD TO MARK ABRAMOVITZ * * *

At 1830 (CDT), the station notified IEPA/IEMA, pursuant to 35 ILL. ADM. Code 1010.202, that from the time period of April 2, 2014, to June 8, 2014, elevated levels of tritium existed at the discharge of the plant. As part of the site investigation that was done in response to the event reported in EN 50180, it has been determined that no greater than 0.1 Curies were discharged from the site. The majority of this discharge was to the Kankakee River via the sewage treatment plant effluent. A small amount, determined to be less than 2%, was discharged to the Morris Illinois sewage treatment facility. This release is associated with the elevated tritium levels discovered on June 7, 2014 and reported to the IEPA on June 8, 2014. The system is currently isolated, and is not discharging to the Kankakee River. The licensee notified the NRC Resident Inspector. Notified the R3DO (Daley).

ENS 500853 May 2014 15:15:00DresdenNRC Region 3GE-3At 1209 CDT on 3 May 2014, Dresden Unit 2 automatically scrammed on a Generator-Turbine Load Mismatch signal following a main generator trip. All rods inserted to their full in positions. All systems operated as expected. Reactor vessel inventory and pressure are being maintained in automatic. The cause of the scram was due to a main generator trip that occurred during a voltage regulator channel transfer. Troubleshooting is in progress to determine the exact cause of the generator trip. This condition is being reported pursuant to 10CFR50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The plant is in a normal shutdown electrical lineup. Main feedwater is being used to maintain reactor vessel level and decay heat is being removed by the main condenser via the turbine bypass valves. There was no impact on Unit 3 which remains stable at 100 percent power. The licensee notified the NRC Resident Inspector.
ENS 5003012 April 2014 13:24:00DresdenNRC Region 3GE-3At 1012 CDT on April 12, 2014, Dresden Unit 2 automatically scrammed on TR-2 sudden pressure relay actuation. All rods inserted to their full-in positions. Following the reactor scram, the 'A' reactor recirculation pump did not run back to minimum speed automatically. Operators took action to run the recirculation pump to minimum speed manually. All other systems operated as expected. Reactor vessel inventory and pressure are being maintained in automatic. The cause of the scram was due to a trip of the sudden pressure relay for Main Power Transformer 2. Troubleshooting is in progress to determine the cause (of the trip of the sudden pressure relay). This condition is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. Normal offsite power remains available. There was no impact on Unit 3. The NRC Resident Inspector has been informed.
ENS 4996327 March 2014 09:42:00DresdenNRC Region 3GE-3At 0151 (CDT) on March 27, 2014, indication was received in the Control Room that two Secondary Containment doors, in the 2/3 Diesel Generator Interlock, were opened simultaneously. An equipment operator, in the field at the time of the event, reported that while opening the reactor building side interlock doors, individuals were able to open the diesel side interlock doors. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2, since two doors in a singular access opening were allowed to open. As a result, entry into Technical Specification 3.6.4.1 Condition A was made due to Secondary Containment being inoperable. The doors were open for approximately 5 seconds and were immediately secured. Secondary Containment differential pressure was maintained throughout the event. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified.
ENS 497873 February 2014 02:41:00DresdenNRC Region 3GE-3

At 0043 (CST) on Monday, February 3, 2014, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system was removed from service for planned preventative maintenance activities on the TSC ventilation system condensing unit. The TSC air handing and filtration units will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 88 hours. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing Emergency Preparedness (EP) procedures and checklists. If radiological conditions require TSC facility evacuation during ventilation system maintenance; the Station Emergency Director will evacuate and relocate the TSC staff in accordance with established procedures. The licensee notified the NRC Resident Inspector.

  • * * UPDATE ON 2/4/14 AT 1939 EST FROM DAN MILLER TO DONG PARK * * *

At 1800 CST on February 4, 2014, Dresden TSC ventilation was restored. The Dresden TSC ventilation is functional at this time. The NRC Resident Inspector has been notified. Notified R3DO (Orlikowski).

ENS 4973216 January 2014 15:50:00DresdenNRC Region 3GE-3The following 60-day report is being made under 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of the Unit 2, Division 1 and Division 2, Emergency Diesel Generators (EDG) that occurred on November 17, 2013, at 1000 CST. As allowed by 10 CFR 50.73(a)(1) this notification is being made via telephone. (a) The specific train(s) and system(s) that were actuated. On November 17th, during the required twenty-two year replacement of the ATWS (anticipated transient without scram) level transmitters, the Unit 2, Division 1 and Division 2, Emergency Diesel Generators (EDG) auto-started as a result of maintenance activities. The failure to remove trip relays, in addition to the sequence for the timing of the replacements, resulted in an unexpected and invalid low water level trip. Subsequently, this resulted in an automatic initiation of the Unit 2, Division 1 and 2, EDGs. (b) Whether each train actuation was complete or partial. Upon receiving the invalid low water level signal, both divisions of EDGs responded as expected for existing plant conditions. Therefore, the actuation was considered a complete actuation of both Division 1 and Division 2 EDGs. (c) Whether or not the system started and functioned successfully. Both Divisions of EDGs auto-started, achieved rated speed, and idled based upon offsite power being available to the safety related busses. Therefore, this is being considered a successful actuation of the Division 1 and Division 2 EDGs. The NRC Resident Inspector has been notified.
ENS 4959130 November 2013 22:43:00DresdenNRC Region 3GE-3At 1553 CST on November 30, 2013, during the performance of the High Pressure Coolant Injection (HPCI) fast initiation test, HPCI did not produce the required flow rate as specified by Technical Specification Surveillance Requirement 3.5.1.6. The HPCI subsystem is designed to ensure adequate core cooling when operated with other available Emergency Core Cooling Systems (ECCS), and during this event, all other ECCS systems remained operable. The cause of this event is currently under investigation. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of the safety function of structures or systems needed to mitigate the consequences of an accident. The NRC Resident Inspector has been notified. The flow rate achieved during the test was 3000 gpm and the required minimum flow rate is 5000 gpm.
ENS 4959028 November 2013 10:56:00DresdenNRC Region 3GE-3At 0258 CST on November 28, 2013, two individuals were removing materials from the main steam isolation valve room (X-Area) and defeated an interlock which allowed them to open two secondary containment doors simultaneously. The X-Area personnel access doors connect secondary containment to the turbine building and are part of the secondary containment boundary. At the time of this event, Dresden Unit 2 was in Mode 4 and secondary containment was not required. However, Dresden Unit 3 was in Mode 1 which requires secondary containment to be operable. Throughout this event, secondary containment differential pressure was maintained within technical specifications surveillance requirement 3.6.4.1.1 limits, and the individuals remained in the area with the capability to close the personnel access doors. This condition represents a failure to meet surveillance requirement 3.6.4.1.2, since both doors in a singular access opening were allowed to open. As a result, entry into technical specification 3.6.4.1 condition A was made, for Unit 3, due to secondary containment being inoperable. The doors were secured at 0311 and secondary containment was declared operable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of the safety function. The NRC Resident Inspector has been notified.
ENS 4958526 November 2013 19:02:00DresdenNRC Region 3GE-3On November 26, 2013, with Unit 2 shutdown for refueling, leakage was identified on the 2-0203-3C Electromatic Relief Valve (ERV) during a Reactor Pressure Vessel (RPV) pressure test. The leak is located on the line connecting the ERV main body to the pilot valve, and is approximately 1 drop per second. Each unit is designed with relief valves which actuate to control reactor coolant system pressure during transient conditions and are located on the main steam lines between the reactor vessel and the first isolation valve within the drywell. The cause of this event is under investigation. The condition is being reported under 50.72(b)(3)(ii)(A) given the defect was associated with the primary coolant system pressure boundary. The NRC Resident Inspector has been notified.
ENS 4954316 November 2013 17:53:00DresdenNRC Region 3GE-3At 10:19:02 (CST) on November 16, 2013, indication was received in the Control Room that two Secondary Containment doors, in one access opening, were open simultaneously. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected. A worker was staged in the interlock to operate the doors as an interim action while a modification to prevent additional failures was being developed. The worker reported that while opening the reactor building side door the Turbine Building side door opened several inches. Both doors were immediately closed and the interlock was removed from use. Secondary Containment differential pressure remained within Technical Specification required values during the short time both doors were open. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2. As a result, entry into Technical Specification 3.6.4.1 Condition A was made momentarily due to Secondary Containment being inoperable. The doors were secured at 10:19:07 (CST) and Secondary Containment was declared Operable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of the safety function. The NRC Resident Inspector has been notified.
ENS 4953514 November 2013 11:01:00DresdenNRC Region 3GE-3On November 14, 2013, both the 2-220-58B Feed Water Inboard Check Valve and the 2-220-62B Feed Water Outboard Check Valve failed Local Leak Rate Testing (LLRT) acceptance criteria. These valves are considered primary containment isolation valves and, as such, are required to ensure that an adequate primary containment boundary is maintained. Technical Specification (TS) 5.5.12, 'Primary Containment Leakage Rate Testing Program,' establishes limits for Primary Containment leakage. Based upon the results of the LLRT, Dresden, Unit 2, may not have met the limits for primary containment leakage during the last operating cycle as specified in TS 5.5.12.c. Dresden Unit 2 is currently in Mode 5 for a refueling outage and per Dresden TS 3.6.1.1, 'Primary Containment,' Primary Containment is not required in the current mode of operation (i.e., Mode 5). However, in accordance with 10 CFR 50.72(b)(3)(ii)(A), this event is reportable as a condition that resulted in a principal safety barrier being seriously degraded. The NRC Resident Inspector has been notified (by the licensee).
ENS 495035 November 2013 15:50:00DresdenNRC Region 3GE-3At 08:42 (CST) on November 5, 2013, indication was received in the Control Room that two Secondary Containment doors, in one access opening, were opened simultaneously. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected. A worker in the field reported that the Turbine Building side door was opened, and simultaneously the Reactor Building side door opened several inches and then quickly re-closed. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2. As a result, entry into Technical Specification 3.6.4.1, Condition A, was made momentarily due to Secondary Containment being inoperable. The doors were secured at 08:42 and Secondary Containment was declared Operable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified. See similar events 49153 and 49379. The licensee is tracking the failure as Incident Report 01581320.
ENS 4937923 September 2013 22:13:00DresdenNRC Region 3GE-3At 16:55:59 (CDT) on September 23, 2013, indication was received in the Control Room that two Secondary Containment doors, in one access opening, were opened simultaneously. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2. As a result, entry into Technical Specifications 3.6.4.1 condition A was made due to Secondary Containment being inoperable. The doors were secured at 16:56:04 and Secondary Containment was declared operable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified.
ENS 4918814 July 2013 16:29:00DresdenNRC Region 3GE-3

At 1600 CDT on Sunday, July 14, 2013, the Dresden Nuclear Power Station (DNPS) Technical Support Center (TSC) emergency ventilation system will be removed from service for planned preventative maintenance activities on the TSC air handling unit and air compressor units. During the maintenance, the TSC ventilation will be shut down. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 48 hours. Contingency plans are in place so that if an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing EP (Emergency Preparedness) procedures and checklists. If radiological or environmental conditions require TSC facility evacuation during ventilation system restoration, the Station Emergency Director will evacuate and relocate the TSC staff in accordance with station procedures. The NRC Resident Inspector has been notified.

  • * * UPDATE AT 1056 EDT ON 7/17/13 FROM PILLION TO HUFFMAN * * *

The planned TSC ventilation outage, for maintenance activities on the TSC air handling unit and air compressor units, has been extended and is now scheduled to complete on Saturday, July 20, 2013. During this maintenance, the TSC air filtration fan and dampers will continue to be non-functional. The licensee has notified the NRC Resident Inspector. R3DO (Hills) has been notified.

  • * * UPDATE FROM MATT KERCHENFAUT TO DONALD NORWOOD AT 1905 EDT ON 7/19/13 * * *

At 1135 CDT on July 19, 2013, Dresden TSC ventilation was restored. The Dresden TSC ventilation is functional at this time. The NRC Resident Inspector has been notified. Notified R3DO (Hills).

ENS 4915328 June 2013 14:18:00DresdenNRC Region 3GE-3At 0749 CDT on June 28, 2013, indication was received in the Control Room that two Secondary Containment doors, in one access opening, were opened simultaneously. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected. This condition represents a failure to meet Surveillance Requirement 3.6.4.1.2. As a result, entry into Technical Specifications 3.6.4.1 Condition A was made due to Secondary Containment being declared inoperable. The doors were secured at 0749 CDT (total time with both doors open was 7 seconds) and Secondary Containment was declared operable. This event is being reported in accordance with 10 CFR 50.72(b)(3)(v)(C) as a condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified.
ENS 4884522 March 2013 19:58:00DresdenNRC Region 3GE-3

Control Rod Drive (CRD) Check valves 3-0399-593 and 3-0399-594 are installed on the CRD supply header inside the reactor building to prevent unfiltered radiological release from primary containment past secondary containment through the CRD supply header. The (Design Basis Accident) DBA (Loss of Coolant Accident) LOCA dose analysis does not postulate the CRD supply piping as a release path. These valves were added in response to NRC IN 90-78. Their function is described in the Dresden UFSAR section 4.6.4.6. CRD check valves 3-0399-593 and 3-0399-594 failed their as found In Service Testing (IST) seat leakage test during refuel outage D3R22. Based on the condition of as-found failed seat leakage tests, Engineering determined that CRD check valves 3-0399-593 and 3-0399-594 would not have been able to perform their design functions as described in the UFSAR to maintain the offsite dose and control room dose within regulatory limits. The valves were repaired in D3R22 and successfully retested. The licensee notified the NRC Resident Inspector.

  • * * RETRACTION FROM RILEY RUFFIN TO HOWIE CROUCH ON 5/20/13 AT 1140 EDT * * *

Based on an evaluation of the current plant design and the overly conservative assumptions made in the 1996 dose estimate, the dose that would be experienced as a result of a DBA LOCA with LOOP (Loss of Offsite Power) due to back leakage through the control rod drive system to the condensate storage tanks (CST) has been reassessed. The initial estimations of dose did not consider the as-built piping configuration of the CRD system. The backflow would be greatly reduced due to the lower differential pressure between the Drywell and CSTs that would exist following a DBA-LOOP. This differential pressure experienced following a DBA-LOOP would not result in a significant backflow due to excess flow check valves and restricting orifices in the current CRD piping configuration. Additionally, in the event that any backflow did occur, the volume of water in the CST would provide a high decontamination factor and dilution. Therefore backflows that could be experienced following a DBA-LOOP would not produce doses that would exceed current limits. Based on this assessment, the unanalyzed condition that was reported on March 22 (EN 48845) is being retracted. The Licensee has notified the NRC Resident Inspector. Notified R3DO (Kozak).

ENS 4863528 December 2012 18:02:00DresdenNRC Region 3GE-3On December 28, 2012, at approximately 1410 hours CDT, Dresden Station was informed by Station Security that a Contract Supervisory (non-licensed) individual had a confirmed positive Fitness-For-Duty test for a controlled substance. This event affects both Dresden and Braidwood Stations. The individuals access to both Dresden and Braidwood Stations has been terminated. The licensee notified the NRC Resident Inspectors.
ENS 4842620 October 2012 15:09:00DresdenNRC Region 3GE-3The notification is being made pursuant to 10 CFR 50.72(b )(2)(xi) due to the fact that Exelon Nuclear has informed the Illinois Emergency Management Agency (lEMA) and the Illinois Environmental Protection Agency (IEPA) of the discovery of a hole in the 'A' Waste Sample Tank resulting in a potential inadvertent release of tritium at Dresden Station. Any release is currently contained within the plant's restricted area. The notifications to lEMA and IEPA were made at 1340 hours CDT on October 20, 2012. The tank was out of service and had been emptied for internal inspection. Therefore at the time of discovery, there was no active leak. The IEPA/lEMA regulations require notification when newly occurring, event-related unpermitted releases of radionuclides are identified. A release has not been confirmed but is suspected. A review of the historical groundwater monitoring well data trends and trending analysis from wells in proximity to the tank indicates no impact on groundwater. Further investigation of the groundwater in the area of the tank is ongoing to determine if an actual release has occurred. The potential leak was not released to an unrestricted area; therefore there is no anticipated adverse impact to the health and safety of the public. Since there was no release to an unrestricted area, 10 CFR Part 20 limits were not impacted. The licensee has notified the NRC Resident Inspector. The Waste Sample Tank normally contains processed rad waste water. The hole was found at the bottom of the tank.
ENS 4836130 September 2012 23:22:00DresdenNRC Region 3GE-3At 1804 hrs. CDT on Sunday, September 30, 2012, security personnel reported a fire in the mechanical maintenance shop. Fire Brigade responded and due to the severity of the fire, Coal City Fire Department was called for assistance. The fire was successfully extinguished at 1834 hrs. There were no personnel injured in the fire. The fire did not affect any structures, systems, or components that are required to provide for nuclear safety. At no time was the health and safety of the public adversely affected by this condition. The maintenance shop is not attached to safety related structure of the operating units; therefore Dresden Station Unit 2 and Unit 3 were not affected by the fire. At approximately 1930 hrs., information was released to the media due to fire in the mechanical maintenance shop requiring Coal City Fire Department assistance. This condition is reportable under 10 CFR 50.72(b)(2)(xi) due to a release of information to the media. No official press release was made. The cause of the fire is under investigation. The licensee has notified the NRC Resident Inspector.
ENS 4808010 July 2012 10:30:00DresdenNRC Region 3GE-3At 0236 CDT on Tuesday, July 10 2012, the Dresden Nuclear Power Station (DNPS) U3 Isolation Condenser System automatically isolated due to a inadvertent partial Group 5 Primary Containment Isolation System (PCIS) isolation, causing the inboard isolation valves to close. The PCIS isolation was caused during the performance of DIS 1300-07, 'U3 Isolation Condenser Steam/Condensate Line High Flow Calibration,' due to a failed test switch. The test switch failed to bypass the PCIS signal generated during the surveillance. All valves responded as expected due to this condition. The isolation condenser was declared inoperable and Technical Specification 3.5.3, Condition A was entered. HPCI was verified to be operable to satisfy the requirements of TS 3.5.3, Condition A.2. This condition is reportable under 10 CFR 50.72(b)(3)(v)(B) due to a condition occurring that could have prevented fulfillment of a safety function needed for residual heat removal. The licensee notified the NRC Resident Inspector.
ENS 4800910 June 2012 10:00:00DresdenNRC Region 3GE-3On Sunday June 10, 2012 at 0112 (Central Time), a through-wall leak was discovered on a piping elbow upstream of the High Pressure Coolant Injection (HPCI) Inlet Drain Pot Inboard Drain valve to the Main Condenser, AOV 3-2301-29. This piping elbow is safety-related, ASME Code Class 2 piping. Dresden Technical Requirements Manual 3.4.a, Condition B requires the leak to be isolated which renders the HPCI system inoperable. The Unit 3 HPCI system was isolated and declared inoperable at 0300 (Central Time), and Technical Specification 3.5.1 Condition G has been entered. The HPCI system is a single train system. The event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D), any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. The licensee notified the NRC Resident Inspector.