Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56637 | 25 July 2023 13:24:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Control Room Envelope Inoperable | The following information was provided by the licensee via email: At 0924 (EDT) on July 25, 2023, it was discovered that both trains of control room air conditioning system were simultaneously inoperable due to an inoperable control room envelope boundary. The boundary was restored at 0925 (EDT) on July 25, 2023. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. There has been no impact to Unit 3 which remains at 100% power.
The licensee determined in a subsequent engineering evaluation of the conditions that existed at the time, that the access hatch being open did not have an adverse impact upon the control room emergency ventilation system and the control room envelopes boundary's ability to perform their safety function including: Radiation dose to the occupants did not exceed the licensing basis, design basis accident calculated value. Protection of control room occupants from hazardous chemicals and smoke. Therefore, this condition is not reportable and NRC Event EN56637 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Lally) | Control Room Emergency Ventilation Control Room Envelope | |
| ENS 54738 | 5 June 2020 07:20:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | EN Revision Imported Date : 10/6/2020 CONTROL ROOM BOUNDARY DOOR FAILURE On June 5, 2020, at 0320 (EDT) a loss of control room envelope (CRE) was declared inoperable due to failure of door 204-36-007. The door was repaired at 0322 (EDT), restoring the CRE to operable. The NRC Resident Inspector, state, and local authorities were notified.
The purpose of this call is to retract a report made on June 5, 2020, NRC Event Number EN54738. NRC Event Report number EN54738 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room envelope boundary door was discovered to not be able to fully close due to the latching mechanism being stuck in the extended position. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) via an 8 hour prompt report as an 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. Upon further review, MPS2 determined that there was no loss of safety function. An engineering evaluation determined that even with the control room boundary door unable to be fully closed due to the latching mechanism being stuck in, the extended position, control room air in-leakage would not have been sufficient to prevent the control room emergency ventilation system from performing its safety function. Therefore, this condition is not reportable and NRC Event Number EN54738 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Dimitriadis).
The purpose of this call is to provide an update to the retraction for a report made on June 5, 2020, NRC Event Number EN54738. The retraction being updated was made on 7/9/2020 at 1443 hours. NRC Event Report number EN54738 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room envelope boundary door was discovered to not be able to fully close due to the latching mechanism being stuck in the extended position. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) via an 8 hour prompt report as an 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 Control Room Envelope). A subsequent engineering evaluation of the conditions that existed at the time, determined that the inability of the control room boundary door to fully close due to the latching mechanism being stuck in the extended position did not have an adverse impact upon the ability of the CRE to perform its safety function. The CRE remained operable throughout this event, and the ventilation system would have performed its safety function. Therefore, this condition is not reportable and NRC Event Number EN54738 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Lally). | Control Room Emergency Ventilation | ||
| ENS 53752 | 25 November 2018 01:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | En Revision Imported Date 1/22/2019 | EN Revision Text: LOSS OF CONTROL ROOM ENVELOPE DUE TO DOOR FAILURE On 11/24/18 at 2015 EST, a loss of Control Room Envelope (CRE) was declared due to failure of the control room boundary door, 204-36-008. (Abnormal Operating Procedure 8588A Mitigating Actions for Control Boundary Breach was implemented). The door was repaired at 2030 EST, restoring CRE to operable (status). A mechanical failure of the control room door latch prevented the door from closing. The licensee notified the NRC Resident Inspector.
The purpose of this call is to retract a report made on November 25, 2018, NRC Event Number EN53752. NRC Event Report number EN53752 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room envelope boundary door was discovered to not be able to fully close due to the latching mechanism being stuck in the extended position. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) via an 8-hour prompt report as an 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. Upon further review, MPS2 determined that there was no loss of safety function. An engineering evaluation determined that even with the control room boundary door unable to be fully closed due to the latching mechanism being stuck in the extended position, control room air in-leakage would not have been sufficient to prevent the control room emergency ventilation system from performing its safety function. Therefore, this condition is not reportable and NRC Event Number EN53752 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified the R1DO (Carfang). | Control Room Emergency Ventilation | |
| ENS 53688 | 22 October 2018 04:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Inoperable Control Room Envelope Due to Failed Surveillance | On October 22, 2018 at 2241 hrs. EDT, a loss of Control Room Envelope (CRE) was declared due to failing to meet the requirements of (surveillance requirement) SR 4.7.6.1h during 72-month surveillance testing. Measured in-leakage exceeded the SR acceptance value. Abnormal Operating Procedure 2588A, 'Mitigating Actions for Control Room Envelope Boundary Breach', have been implemented. The licensee has notified Connecticut Department of Environmental Protection, Connecticut dispatch, Waterford dispatch, and the NRC Resident Inspector of this event. | ||
| ENS 52501 | 20 January 2017 13:35:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Failure of a Secondary Containment Door to Close | At 0835 (EST) on January 20, 2017, at Millstone Power Station Unit 3, subsequent to personnel passage through a door in the auxiliary building, the door failed rendering it unable to completely close. At this time, in accordance with Technical Specification 3.6.6.2 "Secondary Containment," the Shift Manager declared the secondary containment inoperable. The door was repaired and the door completely closed at 1256 (EST) on January 20, 2017, and secondary containment was declared operable. Since Secondary Containment was rendered inoperable, Dominion is reporting that this condition could have prevented the fulfillment of the safety function to control the release of radioactive material and mitigate the consequences of an accident. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D). The NRC Senior Resident Inspector has been notified. | Secondary containment | |
| ENS 51889 | 28 April 2016 00:07:00 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Energy Line Break Door Discovered Open | On April 27, 2016 at 20:07 (EDT), a high energy line break (HELB) door between the turbine driven auxiliary feedwater pump and the motor driven auxiliary feedwater pump rooms was discovered open and unattended. In the event of a HELB, this condition could have rendered both trains of auxiliary feedwater inoperable. The boundary was not operable for approximately 1 hour. Upon discovery, the door was closed restoring the boundary. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v) as any event or condition that alone could have prevented the fulfillment of the safety function of structures or systems that are needed to: (B) Remove residual heat; and (D) Mitigate the consequences of an accident. The NRC Senior Resident Inspector has been notified. The Licensee notified the Connecticut DEEP and Waterford Dispatch. | Auxiliary Feedwater | |
| ENS 51860 | 9 April 2016 19:23:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Determined to Be Inoperable During Surveillance Testing | During pre-planned surveillance testing of the Supplementary Leak Collection and Release System (SLCRS), an issue was found affecting the Secondary Containment boundary. Millstone Unit 3 is being moved to Mode 5 for a refuel outage where investigation and repairs will be made. This is reportable under 10CFR50.72(b)(3)(v)(C), a condition that could have prevented the fulfillment of a safety function for systems or structures to control the release of radioactive material, and 10CFR50.72(b)(3)(v)(D) to mitigate the consequences of an accident. The surveillance testing was being performed while Millstone 3 was being removed from service for an upcoming Refueling Outage. The licensee has notified the NRC Resident Inspector and State and Local authorities. | Secondary containment | |
| ENS 51187 | 28 June 2015 13:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Control Room Environmental Boundary Door Found Unlatched | During Security checks of Control Room doors, a boundary door was found not latched. This door is capable of being manually closed and latched. The door was in this condition for 4 hours and 25 minutes. The door is currently closed and latched. This is being reported as it could have prevented the fulfillment of a safety function to mitigate the consequences of an accident per 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. A condition report has been written and the door is posted to require manual checks to ensure it is latched until the door closing mechanism is repaired.
Event Report number 51187 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room environmental boundary door was found unlatched. This was reported in accordance with 10CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function to mitigate the consequences of an accident. Upon further review, MPS2 has concluded that there was no loss of safety function, because even with the control room boundary door unlatched, the control room emergency ventilation system would have been able to perform its safety function during accident conditions. The MPS2 control room is pressure neutral and the hydraulic door closure mechanism was verified adequate to ensure the door would close and remain closed during accident conditions (even though it was not latching). Therefore, this condition is not reportable and NRC Event Number 51187 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector. Notified the R1DO (Cahill). | Control Room Emergency Ventilation | |
| ENS 50836 | 20 January 2015 01:18:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Energy Line Break Boundary Door Not Latching | A High Energy Line Break (HELB) boundary door was discovered not latching. HELB boundary affects both trains of safety related (480V) switchgear and was not operable for approximately seven minutes. (The licensee) entered the technical specification action statement, restored the door to functional, and exited the technical specification action statement. The licensee notified the NRC Resident Inspector, the State of Connecticut and local officials. | 05000423/LER-2015-001 | |
| ENS 50737 | 15 January 2015 13:08:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | A&B Switchgear Room Boundary Door Latch Discovered Not Functioning Properly | On January 15, 2015 a high energy line break door affecting both trains of safety related switchgear rooms was discovered not latching after passage. The boundary was not operable for approximately 19 minutes. The door has been repaired. Dominion is reporting that this condition could have prevented the fulfillment of the safety function to mitigate the consequences of an accident pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Senior Resident Inspector has been notified. The State of Connecticut Department of Energy, and Environmental Protection and Waterford Dispatch were also notified. | ||
| ENS 50712 | 1 January 2015 23:25:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Main Control Room Boundary Door Did Not Properly Latch | During (surveillance) checks of Control Room doors, a boundary door did not latch after being accessed until the door was opened and closed. This is being reported as it could have prevented the fulfillment of a safety function to mitigate the consequences of an accident per 10CFR50.72(b)(3)(v)(D). The door is currently closed and latched. The door was in this condition for between 5 and 10 seconds. The licensee notified the Connecticut Department of Environmental Protection, Town of Waterford and the NRC Resident Inspector.
Upon further review, Millstone Power Station Unit 2 has concluded that there was no loss of safety function, because even with the control room door latch degraded, the control room door and its closing mechanism would still be able to maintain the control room envelope's boundary intact. Therefore, this condition is not reportable and NRC Event Number 50712 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector. The licensee notified the NRC Resident Inspector. Notified R1DO (Jackson). | ||
| ENS 50676 | 12 December 2014 14:57:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Energy Line Break Isolation Door Inoperable | The boundary door between the A and B safety related switchgear rooms was found not to be latching. This door is credited in the high energy line break (HELB) analysis. Both trains of safety related switchgear were affected for approximately 36 minutes. The technical specification action statement was entered, the door was repaired, and the action statement was exited. The licensee notified the NRC Resident Inspector. | 05000423/LER-2014-004 | |
| ENS 50360 | 13 August 2014 04:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Control Room Boundary Door Failed to Latch | A Control Room Boundary Door failed to latch and maintain the Control Room boundary. This condition was reportable in accordance with 10CFR50.72(b)(3)(v)(D). The door was repaired and the Control Room boundary was restored on 8/13/14 at 0552 (EDT). The licensee notified the NRC Resident Inspector, State of Connecticut, and local agencies. | ||
| ENS 50002 | 5 April 2014 14:25:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Enclosure Building | In preparation for a scheduled outage, maintenance personnel removed the upper and lower boots of the main steam safety valves. Upon discovery, Operations personnel declared the Enclosure Building inoperable. Maintenance re-installed the boots and the integrity of the Enclosure Building was restored and the building returned to service. The licensee notified the NRC Resident Inspector, the State of Connecticut, and the town of Waterford. | Main Steam Safety Valve | |
| ENS 49783 | 1 February 2014 15:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Control Room Door Blocked Open for Planned Maintenance | Door in Control Room boundary blocked open for scheduled maintenance. No impact as door is opened under administrative control OP3314F, Section 4.24. Door has been closed following maintenance. Door opened under administrative control could have prevented the fulfillment of Safety Function to Mitigate the Consequences of an Accident. A door credited for Control Room Boundary was blocked open under administrative controls as part of a Pre-Planned maintenance activity. Technical Specification 3.7.7, Control Room Emergency Ventilation System, is applicable and allows 'The Control Room Envelope (RE) boundary may be opened under administrative control' NUREG 1022, Revision 3, states inoperability of a single train system is reportable even though the plant's Technical Specifications may allow the condition to exist for a limited time. Although the plant was operated within the licensing basis, since the Control Room Envelope was rendered inoperable, Dominion is reporting that this condition could have prevented the fulfillment of the safety function to mitigate the consequences of an accident. The licensee has notified the NRC Resident Inspector, State government, and Local government.
The licensee is retracting this report based on the following: The purpose of this call is to retract the report made on February 1, 2014, NRC Event Number 49783. Event Report number 49783 describes a condition in which the Millstone Power Station Unit 3 (MPS3) Control Room Envelope was voluntarily rendered inoperable under administrative control. Using the criteria of NUREG-1022 Rev. 3, this condition report is not related to inoperability being due to one or more personnel errors, including procedure violations; equipment failures; inadequate maintenance; or design, analysis, fabrication, equipment qualification, construction, or procedural deficiencies and was declared inoperable as part of a planned evolution for maintenance or surveillance testing and done in accordance with an approved procedure and the plant's technical specifications. Therefore, this condition Is not reportable and NRC Event Number 49783 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector. The licensee notified the NRC Resident Inspector. Notified R1DO (Ferdas). | Control Room Emergency Ventilation | |
| ENS 49774 | 29 January 2014 16:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Boundary Was Temporarily Blocked Open | Title: Door Opened Under Administrative Control Could Have Prevented Fulfillment of Safety Functions to Control the Release of Radioactive Material and Mitigate the Consequences of an Accident On January 29, 2014, it was determined a door credited as a Secondary Containment Boundary was temporarily blocked opened multiple times since January 25, 2014 under administrative control. Technical Specification 3.6.6.2 'Secondary Containment' is applicable and requires the system to be restored to operable status within 24 hours. In each instance where the door was blocked open, the requirements of Technical Specification 3.6.6.2 were entered and complied with. NUREG 1022 Revision 3 states inoperability of a single train system is reportable even though the plant's Technical Specifications may allow the condition to exist for a limited time. Although the plant was operated within the licensing basis, since Secondary Containment was rendered inoperable, Dominion is reporting that this condition could have prevented the fulfillment of the safety function to control the release of radioactive material and mitigate the consequences of an accident. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D). The NRC Senior Resident Inspector has been notified.
The licensee is retracting this report based on the following: The purpose of this call is to retract the report made on January 29, 2014, Event Number 49774. Event Report number 49774 describes a condition in which the Millstone Power Station Unit 3 (MPS3) Secondary Containment was voluntarily rendered inoperable under administrative control. Using the criteria of NUREG-1022 Rev. 3, this condition report is not related to inoperability being due to one or more personnel errors, including procedure violations; equipment failures; inadequate maintenance; or design, analysis, fabrication, equipment qualification, construction, or procedural deficiencies and was declared inoperable as part of a planned evolution for maintenance or surveillance testing and done in accordance with an approved procedure and the plant's technical specifications. Therefore, this condition is not reportable and NRC Event Number 49774 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector. The licensee informed the NRC Resident Inspector. Notified R1DO (Ferdas). | Secondary containment | |
| ENS 49678 | 29 December 2013 12:44:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Switchgear Room Door Discovered Unlatched | A condition was discovered on December 29, 2013 that could have prevented the fulfillment of safety functions to shutdown the reactor and maintain it in a safe shutdown condition and mitigate the consequences of an accident. On December 29, 2013, a water tight door between the East Switchgear and Service Building was discovered not dogged (unlatched). Upon discovery, the safety function was immediately restored by properly dogging (latching) the subject door. The subject door between the East Switchgear and Service Building protects both trains' of safety related switchgears. The access Key Log indicates the door was in the condition for approximately 60 minutes. If the door is inoperable, then T.S. 3.0.3 applies. This condition is being reported pursuant to 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3))(v)(D). The NRC Resident lnspector has been notified (by the licensee). The licensee has notified state and local authorities. The door is required to be properly secured to protect the East Switchgear from a potential High Energy Line Break and was left improperly dogged by a security officer while making rounds. Millstone Unit 3 did not enter T.S.3.0.3 and continues to operate at 100%.
Upon further review the fact that the switchgear room door was closed but not latched did not render the switchgear within the room inoperable, and therefore, there was no loss of safety function. The engineering evaluation determined the switchgear would have been protected for high energy line break, flooding, and tornado pressure drop events. Additionally, the carbon dioxide fire suppression capability would have also been maintained. The details of the engineering review will be provided to the NRC Senior Resident Inspector. Notified R1DO (DeFrancisco). | ||
| ENS 49674 | 23 December 2013 20:00:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Historical Gaps in High Energy Line Break Barrier | At 1930 EST on June 7, 2012, it was determined that a series of gaps in a high energy line break (HELB) barrier rendered equipment in the west 480 VAC switchgear room inoperable. There is evidence that this condition had existed since initial construction. The openings were sealed and the equipment restored to operable status at 1605 EST on June 8, 2012. This condition was previously reported to the NRC pursuant to 10 CFR 50.73(a)(2)(i)(B) in LER 2012-001-00. Upon further engineering analysis, it was determined that for limited exposure times safety functions could have been prevented for certain postulated high energy line breaks. Therefore, this condition is also being reported pursuant to 10 CFR 50.73(a)(2)(v)(A),(D), and 10 CFR 50.72(b)(3)(v). The NRC Senior Resident Inspector has been notified. | ||
| ENS 49562 | 20 November 2013 19:19:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Boundary Not Maintained | System affected: Secondary Containment Boundary / SLCRS (Supplementary Leak Collection and Release Systems) Causes: Door in secondary containment boundary found not latched. Effect of Event on Plant: No impact on the plant as SLCRS was not required for the duration that the door was not functional. Actions Taken or Planned: Door is now closed and latched. Will repair degraded latch. This condition was identified around 1100 EST on 11/19/13. The NRC Resident Inspector has been notified. State and local authorities were notified by the licensee. | Secondary containment | |
| ENS 48215 | 21 August 2012 04:38:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Both Emergency Diesel Generators Inoperable | At 0038 EDT on 08/21/12, EDG "A" was declared inoperable after the Engineered Safeguards Actuation System (ESFAS) fuse failed . EDG "B" had been inoperable for planned maintenance since 2223 EDT on 08/15/12. With both EDGs inoperable, Unit 2 entered Tech Spec LCO 3.8.1.2 which requires suspension of all operations involving core alteration and positive reactivity additions. At 0713 EDT on 08/21/12, the licensee declared EDG "B" Operable exiting the Tech Spec LCO. The cause of the ESFAS fuse failure on EDG "A" is under investigation. The licensee will notify state and local agencies and has informed the NRC Resident Inspector.
The purpose of this call is to retract the report made on 8/21/2012, Event Number 48215. Upon further review, the fuse failure did not render the 'A' Emergency Diesel Generator (EDG) inoperable in MODE 5. If called upon, the safety functions would have been met. The Engineered Safeguards Actuation System (ESFAS) was repaired prior to restart of the unit. Notified R1DO (Conte). | Emergency Diesel Generator | |
| ENS 47656 | 9 February 2012 22:55:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Main Steam Line Pressure Transmitters Found Inoperable | A condition was discovered on February 9, 2012 that could have prevented fulfillment of the safety function to shutdown the reactor and maintain it in a safe shutdown condition and mitigate the consequences of an accident. During maintenance performed on the main steam line pressure transmitters on both trains, the one-time use only EEQ seals were not replaced rendering the transmitters inoperable. These transmitters initiate safety injection and main steam isolation functions in the event of a main steam line break. Since all transmitters were inoperable this condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(A) and (D). The condition existed for about a week. Subsequently the required number of transmitters have been repaired and are operable. The NRC Senior Resident Inspector was notified and was present in the control room during the repair activity. The licensee also notified the State of Connecticut. | Main Steam Line Main Steam | |
| ENS 46680 | 18 March 2011 05:45:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Control Room Boundary Rendered Inoperable | On March 17, 2011 during a control room walk-down, it was discovered that a halon bottle located in the control room was removed from its associated piping for scheduled work. The open piping penetrates the control room boundary rendering it inoperable. Technical Specification 3.7.6.1 'Control Room Emergency Ventilation System' is applicable in Modes 1, 2, 3, 4, 5 and 6 was entered. Since control room boundary was rendered inoperable, Dominion is reporting that this condition could have prevented the fulfillment of the safety function to mitigate the consequences of an accident. Upon discovery the piping was capped re-establishing the control room boundary. Further engineering review will be conducted to more fully evaluate the impact on the control room boundary. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). Offsite power is normal and all emergency diesel generators are operable. There was no increase in plant risk. The NRC Senior Resident Inspector has been notified.
The Licensee is retracting this report based on the following: On March 17, 2011 during a control room walk down at Millstone Power Station Unit 2, it was discovered that a halon bottle located in the control room was removed from its associated piping for scheduled work. Since the associated piping penetrates the control room boundary, operators declared the control room boundary inoperable. Upon discovery, the piping was capped re-establishing the control room boundary. Operators made a report in accordance with 10CFR50.72(b)(3)(v)(D). Subsequently, an engineering evaluation has been completed that concludes that the piping opening created by the removal of the halon bottle would not have prevented the fulfillment of the safety function to mitigate the consequences of an accident. Therefore, the condition reported in event report 46680 is being retracted. The NRC Resident Inspector has been notified. Notified R1DO (Powell). | Emergency Diesel Generator Control Room Emergency Ventilation | |
| ENS 46034 | 7 October 2009 14:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Historical Condition Previously Reported in Ler 2009-003 Should Also Have Been Reported in Accordance with 10 Cfr 50.72 (B)(3)(V)(D) | On October 7, 2009, two independent diesel generators were rendered inoperable. This was reported in LER 2009-003 as a condition prohibited by plant technical specifications and a common cause that resulted in two independent trains becoming inoperable. Upon further review, the condition which existed at Millstone Power Station Unit 2 and reported to the NRC in LER 2009-003, should also have been reported per the requirements of 10CFR50.72(b)(3)(v)(D). A supplement to LER 2009-003 will be submitted. The NRC Resident Inspector has been notified. | ||
| ENS 43059 | 21 December 2006 07:05:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Accident Mitigation - Auxiliary Feedwater System | A condition was identified (at 0205 on 12/21/06) involving improper placement of temporary scaffolding that could have resulted in all three Auxiliary Feedwater (AFW) pumps becoming inoperable during a high energy line break (HELB) in the Turbine-Driven Auxiliary Feedwater (TDAFW) pump room. Scaffolding, erected to perform maintenance on the floor above the TDAFW pump room, had two vertical members placed on the high energy line break blowout panel in the TDAFW pump room roof that could potentially have restricted the ability of the panel to lift during a HELB event in the TDAFW pump room. Failure of the panel to lift during the event may cause the structural limit of the walls separating the TDAFW pump room from the motor driven AFW pump room to be exceeded. This could have resulted in all three AFW pumps becoming inoperable. At 0530 on 12/21/06, scaffolding removal was complete and AFW operability was restored. This condition is being conservatively reported, pending further evaluation, per 10CFR50.72(b)(3)(v) as a condition that at the time of discovery could have prevented the fulfillment of a safety function. The licensee notified the NRC Resident Inspector. | Auxiliary Feedwater | |
| ENS 42882 | 7 October 2006 05:51:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Scaffold Prevents Main Steam Isolation Valve Closure | Temporary scaffolding was constructed near the loop-1 Main Steam Isolation Valve (MSIV) on 8/30/2006 while the Unit was in Mode 1. On 10/7/2006 surveillance testing on the MSIVs was conducted in Mode 3 and the loop-1 MSIV failed to fully stroke closed. It was determined that temporary scaffolding was interfering with full valve travel. The scaffolding was removed and the surveillance test verified full valve motion. The licensee notified the NRC Resident Inspector and will notify state and local officials. | Main Steam Isolation Valve |