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The following information was provided by the licensee via phone call and email: At 0800 on February 12, 2023, it was discovered that both trains of control room emergency ventilation system were simultaneously inoperable due to a safety injection relief valve discharging to a Unit 1 sump. This leakage in conjunction with design basis loss of coolant accident may result in radiological dose exceeding limits to the exclusion area boundary and to the control room, which is common to both Unit 1 and Unit 2. Therefore, this condition is being reported as an eight-hour, nonemergency notification per 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D) as an 'Unanalyzed Condition and a Condition that Could Have Prevented Fulfillment of a Safety Function.' There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * RETRACTION FROM ROBERT TAYLOR TO DONALD NORWOOD AT 0530 EDT ON 3/17/2023 * * *

Retraction of EN56350, Control Room Emergency Ventilation System Inoperable: Based on subsequent evaluation, it was determined that the control room emergency ventilation system remained operable due to the maximum measured leak rate being within the bounds of the analysis. The maximum measured leak rate of 32,594 cc/hr from the safety injection system did not challenge the calculated maximum engineered safety features leak rate of 45,600 cc/hr and remained within the current dose analysis limits. As such, this was not an unanalyzed condition and did not prevent the fulfillment of a safety function to mitigate the consequences of an accident. The NRC Resident Inspector has been notified. Notified R1DO (Bickett).

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.

• * * RETRACTION ON 07/09/2020 AT 1443 EDT FROM GERALD A. BAKER TO OSSY FONT * * *

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).

• * * UPDATE FROM MICHAEL GAGNON TO BRIAN P. SMITH AT 1444 EDT ON 10/01/2020 * * *

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).

At 2307 EDT on April 21, 2019, in Mode 1 at approximately 100 percent reactor power, Unit 1 automatically tripped due to a Main Turbine Trip. The Main Turbine Trip was a result of two out of three level instruments sensing a false high reactor water level. All control rods inserted as expected during the scram. Safety Relief Valves G and K lifted per design. The same level instruments that failed also tripped both Reactor Feed Pumps. As a result, reactor water level dropped below the Low Level 1 and 2 actuation setpoints. Per design, the Low Level 1 signal resulted in Group 2 (i.e., floor and equipment drain isolation valves), Group 6 (i.e., monitoring and sampling isolation valves) and Group 8 (i.e., shutdown cooling isolation valves) isolations. The Low Level 2 signals resulted in Group 3 (i.e. Reactor Water Cleanup) isolation, a secondary containment isolation signal, and an auto start of Standby Gas Treatment and Control Room Emergency Ventilation. Also, the Low Level 2 resulted in (high pressure coolant injection) HPCI and (reactor core isolation cooling system) RCIC automatically starting and injecting into the vessel. All systems responded as designed. This event is being reported in accordance with 10 CFR 50.72(b)(2)(iv)(B) for RPS actuation and 10 CFR 50.72(b)(3)(iv)(A) as an event that results in valid actuations of the Primary Containment Isolation System. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. Decay heat is currently being removed via the turbine bypass valves. Condensate and feed water are maintaining water level. The reactor is still at saturation temperature and 475 psi, lowering slowly. The reactor is still in a normal electrical lineup. There was no impact to Unit 2 as a result of this event.

• * * UPDATE ON 04/22/19 AT 0220 EDT FROM ALAN SCHULTZ TO JEFFREY WHITED * * *

The licensee updated the event report to include a 4-Hr Non-Emergency Notification in accordance with 10 CFR 50.72(b)(2)(iv)(A) for Emergency Core Cooling System, HPCI, Discharge to the Reactor Coolant System. Notified R2DO (Dickson), NRR EO (Miller) and IR MOC (Gott).

On 11/3/17, with the unit operating in Mode 1 at approximately 100 percent power, an issue was identified with the Station Vent Radiation Monitors. The noble gas channels utilize an efficiency factor for isotope Kr-85 instead of the required Xe-133. For the normal range radiation monitors, the efficiency factor is non-conservative, resulting in both monitors being declared inoperable at 1045 hours EDT. As a result, the Normal Control Room Ventilation System was shut down and isolated, and the Control Room Emergency Ventilation System started in accordance with Technical Specification Required Actions at 1122 hours. The inoperability of both Station Vent Normal Range Radiation Monitors represents a condition that at the time of discovery could have prevented the fulfillment of the safety function of a system needed to mitigate the consequences of an accident. The Station Vent Accident Range Monitors also utilize an efficiency factor for Kr-85 instead of Xe-133, but for the Accident Range Monitors the efficiency factor is conservative. Because alternate means exist to determine release rate, which include use of grab samples and field surveys, this degraded capability does not represent a major loss of emergency assessment capability. The NRC Resident Inspector has been notified.

• * * RETRACTION FROM NICK DOWNING TO DONALD NORWOOD AT 0927 EST ON 12/14/2017 * * *

On 11/3/2017, the efficiency factors for the Station Vent Normal and Accident Range Radiation Monitors were revised to the proper setting for the required isotope, the normal range monitors were declared Operable, and the Control Room Normal Ventilation System was returned to service. An evaluation of the issue with the Station Vent Normal Range Radiation Monitors was performed, which determined the Control Room Ventilation isolation setpoint is well below the point at which the dose to the Control Room Operators would exceed General Design Criteria (GDC) limits following a Design Bases Accident. The error introduced from using an incorrect efficiency value did not challenge the margin to the GDC limits; therefore, the Station Vent Normal Range Monitors remained operable, and this issue did not prevent the monitors from fulfilling their safety function to mitigate the consequences of an accident.

The NRC Resident Inspector has been notified. Notified R3DO (Stone).

On February 5, 2015 at 0109 EST, the Control Room Emergency Ventilation System (CREVS) was declared inoperable due to a higher than allowed identified in-leakage rate for the Control Room Envelope (CRE) when in the Normal Operating Mode. Unit 1 remains at 100 percent power and Unit 2 remains in Mode 3 for an unrelated planned maintenance outage. Unit 1 and Unit 2 share a common CRE. This in-leakage was detected during additional testing following the event documented in EN #51584. At the time of discovery, there is a reasonable expectation this condition could prevent the fulfillment of the safety function of a system that is required to mitigate the consequences of an accident, thus satisfying the reporting criteria for 10CFR50.72(b)(3)(v)(D). Actions to implement mitigating actions were immediately initiated in accordance with Technical Specification 3.7.10. CREVS has been placed in Recirculation Ventilation Mode, isolating the control room from outside air. The NRC Senior Resident Inspector has been notified of the condition.

• * * RETRACTION FROM DAVID HELD TO VINCENT KLCO AT 1411 EDT ON 4/4/16 * * *

Following the 8-hour 10 CFR 50.72 notification made on 02/05/2016 (EN 51712) regarding the Control Room Emergency Ventilation System (CREVS) inoperability, further engineering evaluation has determined the identified in-leakage does not result in exceeding the design criteria for dose to the control room personnel. Therefore the degraded Control Room Emergency Ventilation System remained operable with the identified air in-leakage as determined by the Control Room Envelope Habitability Program. As such, the safety function was never lost and the event notification is being retracted as it is not reportable pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident has been notified. Notified the R1DO (Jackson).

On December 3, 2015 at 2107 (EST), the Control Room Emergency Ventilation System (CREVS) was declared inoperable due to a higher than allowed identified in-leakage rate for the Control Room Envelope (CRE) when in the Normal Operating Mode. Both Unit 1 & Unit 2 remain at 100 percent power and they share a common CRE. At the time of discovery, there is a reasonable expectation this condition could prevent the fulfillment of the safety function of a system that is required to mitigate the consequences of an accident, thus satisfying the reporting criteria for 10CFR50.72(b)(3)(v)(D). Actions to implement mitigating actions were immediately initiated in accordance with Technical Specification 3.7.10. CREVS has been placed in Recirculation Ventilation Mode, isolating the control room from outside air. The NRC Senior Resident Inspector has been notified of the condition.

• * * RETRACTION ON 1/7/16 AT 1110 EST FROM SHAWN SNOOK TO DONG PARK * * *

Following the 8-hour 10CFR50.72 notification made on 12/4/2015 (EN 51584) regarding the Control Room Emergency Ventilation System (CREVS) inoperability, an engineering evaluation determined inleakage did not exceed limits described in the Beaver Valley licensing basis. Therefore, the degraded Control Room Emergency Ventilation System remained Operable with the identified air inleakage as determined by the Control Room Envelope Habitability Program. As such, the safety function was never lost and the event notification is being retracted as it is not reportable pursuant to 10CFR50.72(b)(3)(v)(D). FENOC is planning to repair the degraded components of the system. The NRC Resident (Inspector) has been notified." Notified R1DO (Dimitriadis).

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.

• * * RETRACTION FROM THOMAS CLEARY TO VINCE KLCO ON 7/8/2015 AT 1314 EDT * * *

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).

On April 3, 2015, at 1500 EDT, the Control Room Emergency Ventilation System on St. Lucie Unit 1 will be declared inoperable due to pre-planned maintenance during the current refueling outage. The Technical Support Center (TSC) ventilation system is part of the Unit 1 Control Room Emergency Ventilation System, therefore, the TSC ventilation system has been rendered non-functional during the course of the work activities. The TSC ventilation is expected to be returned to service in approximately 24 hours. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing emergency planning procedures. Should the TSC become uninhabitable, the TSC staff will relocate to an alternate TSC location in accordance with applicable site procedures. This notification is being made in accordance with 10 CFR 50.72 (b)(3)(xiii) due to the potential loss of an emergency response facility. An update will be provided once the TSC ventilation system has been restored to normal operation. The NRC Resident Inspector has been notified.

• * * UPDATE PROVIDED BY DAVE FIELDS TO JEFF ROTTON AT 2240 EDT ON 4/03/2015 * * *

The TSC ventilation system has been restored to normal operation as of 2230 EDT on April 3, 2015. The NRC Resident Inspector has been notified. Notified R2DO (Walker).

On September 04, 2014, at 1905 hours (CDT), the Control Room Emergency Ventilation (CREV) system was declared inoperable due to the Air Handling Unit (AHU) tripping upon restoration of Control Room Ventilation following testing of Reactor Building Ventilation instrumentation. Troubleshooting is in progress at this time. Technical Specification 3.7.4, Condition A, was entered which requires the CREV system to be restored to an operable status in seven (7) days. Additionally, Technical Specification 3.7.5, Condition A, was entered which requires CREV AC to be restored to an operable status in 30 days. This notification is being made in accordance with 10CFR50.72(b)(3)(v)(D), '(any) event or condition that could have prevented fulfillment of a safety function,' because the CREV system is a single train system required to mitigate the consequences of an accident. The licensee has notified the NRC Resident Inspector.

• * * RETRACTION PROVIDED BY MARK BRIDGES TO JOHN SHOEMAKER AT 1721 EDT ON 10/23/2014 * * *

The purpose of this notification is to retract the ENS notification made on September 4, 2014 (ENS 50427). Upon further investigation it was verified that the function of Control Room Emergency Ventilation System was not affected as discussed in Chapters 6 and 15 of the Updated Final Safety Analysis Report. Therefore, the threshold for reporting the issue as an event or condition that could have prevented the fulfillment of a safety function was not met (NUREG 1022 Revision 3 - Event Report Guidelines Section 3.2.7). The licensee has notified the NRC Resident Inspector and applicable State authorities. Notified R3DO (Pelke)