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Start date | Title | Description | Topic | |
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ENS 56915 | 5 January 2024 15:40:00 | Emergency Ventilation Systems Inoperable | The following information was provided by the licensee via phone and email: At approximately 1111 EST on 01/05/2024, a mechanical penetration room door was discovered unlatched. Based on security badge history, the door was last opened at 1040 EST. The unlatched door resulted in both trains of the station emergency ventilation system being inoperable due to being unable to maintain the shield building negative pressure area. With both trains simultaneously inoperable, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The door was closed and verified latched upon discovery to restore the systems to an operable status. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The station emergency ventilation system (EVS) was tested with the mechanical penetration room door unlatched. The test results showed that the station EVS attained the required negative pressure in the shield building within the time required by the Technical Specifications. Therefore, the station EVS remained operable with the door unlatched, and this issue did not prevent the system from fulfilling its safety function to control the release of radioactive material and mitigate the consequences of an accident. The NRC Resident Inspector has been notified. Notified R3DO (Orlikowski) | |
ENS 55775 | 9 March 2022 00:19:00 | FITNESS-FOR-DUTY Report - Contract Supervisor Failed FITNESS-FOR-DUTY Test | The following information was provided by the licensee via phone and email: A non-licensed, contract employee supervisor had a confirmed positive for alcohol during a follow-up fitness-for-duty test. The employee's access to the plant has been terminated. The NRC Resident Inspector has been notified.
The following information was received from the licensee via E-mail: This is a retraction of EN55775. The measured Blood Alcohol Level (BAC) of the individual was below the Fitness-For-Duty program limits, so this event did not constitute a violation of the Fitness-For-Duty program. The NRC Resident Inspector has been notified. Notified R3DO (Hills) and the FFD E-mail group. | |
ENS 53685 | 22 October 2018 04:00:00 | En Revision Imported Date 11/12/2018 | EN Revision Text: CONTROL ROOM ENVELOPE DECLARED INOPERABLE DUE TO DOOR LATCH FAILURE At 0856 EDT on October 22, 2018, it was discovered that the Control Room Envelope, a single-train system, was inoperable due to failure of a boundary door to latch; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D) as a loss of safety function. The door latch was repaired, and the Control Room Envelope declared operable at 0910 EDT. There was no impact on the health and safety of the public or plant personnel, as the door was capable of being closed at all times and the door was manned the entire time it could not latch. The NRC Resident Inspector has been notified.
Retraction of Event #53685, Control Room Envelope Declared Inoperable due to Door Latch Failure Based on subsequent field measurements taken for the boundary door, the force needed to open the unlatched door is sufficient to maintain the Control Room Envelope positive pressure. Therefore, the Control Room Envelope remained Operable with the boundary door unlatched, and this issue did not prevent the system from fulfilling its safety function to mitigate the consequences of an accident. The NRC Resident Inspector has been notified. Notified the R3DO (Hanna). | |
ENS 53051 | 3 November 2017 14:45:00 | Station Vent Radiation Monitor Efficiency Factor Non-Conservative | 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.
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). | Time of Discovery Grab sample |
ENS 52701 | 21 April 2017 06:02:00 | High Switchyard Voltage Renders Both Offsite Circuits Inoperable | On 4/21/17, high grid voltage conditions were experienced, resulting in voltages higher than those established for operability of the offsite circuits. Grid voltages have been observed at approximately 355.8 kV on the nominal 345 kV system. As a result, both qualified circuits between the offsite transmission network and the onsite Class 1E AC Electrical Power Distribution System were declared inoperable at 0202 hours (EDT). Main generator voltage control has been lowered to the minimum possible excitation with the unit operating at 100 percent power. The inoperability of both offsite circuits results in a loss of safety function in accordance with NRC reporting guidance. The voltage of the onsite Essential busses remains within acceptable values, and both Emergency Diesel Generators are operable. At 0715 (EDT) on 4/21/17, grid voltage has returned to an acceptable value and the equipment was declared operable. The NRC Resident Inspector has been notified.
Following the reporting of high switchyard voltage on 4/21/17, the licensee-established voltage limits were re-evaluated. The new high voltage limit has been established at 362.94 kV on the nominal 345 kV system, or 105.2 percent of nominal voltage, as compared to the previous maximum grid voltage of 103.3 percent. This new limit is above the 355.8 kV experienced on 4/21/17. Therefore, the equipment remained operable and no loss of safety function existed for the qualified circuits between the offsite transmission network and the onsite Class 1E AC electrical power distribution system, and the notification made per 10 CFR 50.72(b)(3)(v)(A-D) is being retracted. An evaluation of the past three years of switchyard voltage data was also performed, and it was concluded the AC power system and its connected safety-related equipment remained capable of performing its required safety functions during the three-year evaluation period. The NRC Resident Inspector has been briefed on the evaluation results and informed of this retraction. Notified the R3DO (Stone). | Offsite Circuit |
ENS 52247 | 16 September 2016 20:57:00 | Essential Busses Not Aligned to Power Transformers During Plant Startup | At 1657 Eastern Daylight Time (EDT) the plant entered Mode 4 (from Mode 5), and subsequently, at 1710 EDT, it was discovered that 480V AC essential busses E1 and F1 were being supplied from the shutdown operations transformers. The essential busses E1 and F1 are required to be aligned to the power operations transformers in Mode 4 for operability in accordance with TS 3.8.9. With both E1 and F1 essential busses aligned to the shutdown operations transformers with the plant in Mode 4, both trains of the essential electrical power distribution system were inoperable, resulting in a loss of safety function. At 1733 EDT both E1 and F1 essential busses were aligned to the power operations transformers as required by TS 3.8.9. This issue is being reported as a loss of safety function of the essential electrical busses. The NRC Resident Inspector has been notified of the event.
Engineering reviewed the actual conditions during the approximate 36 minutes the 480V AC essential busses were being supplied from the shutdown operations transformers. Grid voltages were higher than assumed minimum voltages, and electrical loading during Mode 4 conditions were reduced from expected full power operation loading. As a result, Engineering determined that all equipment remained capable of performing its required functions while connected to the shutdown operations transformers. Because the equipment remained capable of satisfying the requirements for Operability, no condition existed that could have prevented the fulfillment of a safety function. Therefore, no loss of safety function existed for the 480V AC essential buses, and the notification made per 10 CFR 50.72(b)(3)(v)(A-D) by the Davis-Besse Nuclear Power Station on 9/16/2016 (EN# 52247) is being retracted. The NRC Resident Inspector has been briefed on the evaluation results and informed of this retraction. Notified the R3DO (Jeffers). | |
ENS 49828 | 14 February 2014 08:25:00 | Shield Building Construction Opening | On 02/14/2014, an unfilled area was discovered in the concrete along the top of the shield building construction opening on the annulus side. The condition was discovered during the current steam generator replacement outage, and is likely due to not completely repouring the shield building wall opening in 2011. Analysis shows this condition is bounded by previous calculations that demonstrate the containment function is maintained such that the protection of the health and safety of the public was not in question. Further analysis is planned to reconfirm previous calculations. The NRC Resident Inspector has been notified.
The FirstEnergy Nuclear Operating Company is retracting the 8-hour non-emergency notification made on 02/14/2014 (EN# 49828). Engineering evaluation of the unfilled concrete area along the top of the shield building construction opening determined the condition did not prevent the shield building from performing all design functions as described in the Updated Safety Analysis Report. Therefore, this issue did not represent a condition that significantly degraded plant safety, and the notification made per 10CFR 50.72(b)(3)(ii)(B) is being retracted. The NRC Resident Inspector has been briefed on the evaluation results and informed of this retraction. Notified the R3DO (Kunowski). | |
ENS 40161 | 16 September 2003 04:30:00 | Reactor Coolant System Pressure Increase Caused a Valid Signal | At 1150 hours on 9/15/03 during Reactor Coolant System (RCS) pressure increase to approximately 700 psig, the Core Flood (CF) Tank 1 outlet motor-operated valve (CF1B) opened when the breaker for the valve was closed. Because RCS pressure was not high enough to actuate the pressure switch setpoint of 770 psig to open this valve, it was believed this was an invalid signal, and therefore the valve opening was not reportable under the criteria of 10 CFR50.72 After further review, at 0030 hours on 9/16/03 it was determined the sensed pressure was within the setpoint range of the switch, making this a valid signal to open the valve. The CF Tank pressure at the time (approximately 600 psig) was less than the RCS pressure of approximately 700 psig, therefore no discharge into the RCS occurred, and this event is not reportable per 10 CFR50.72(b)(2)(iv). The CF System is a passive system, but is used in conjunction with other Emergency Core Cooling Systems to mitigate significant events. Therefore, this event involving the opening of the CF Tank discharge valve CF1B is being conservatively reported in accordance with 10 CFR50.72(b(3)(2)(iv)(A) as a valid actuation of a train of the Emergency Core Cooling System. Upon opening of this valve, CF Tank 1 level and pressure were observed lowering with a corresponding rise in the Reactor Coolant Drain Tank, most likely due to leakage past a check valve. CF1B was closed according to procedures and the source breaker for the valve opened. The NRC Resident Inspector was notified by the licensee.
The actuation of the interlock for the Core Flood Tank 1 Outlet Isolation Valve did not constitute an actuation of the Core Flood System. The valve opened automatically as designed to ensure the Core Flood System was capable of performing its safety prior to being manually opened by the Operators. As part of the Emergency Core Cooling Systems, the primary function of the Core Flood System is to deliver cooling water to the reactor core in the event of a Loss of Cooling Accident per the Updated Safety Analysis Report. However, plant conditions (namely, Reactor Coolant System pressure lowering below Core Flood Tank pressure) did not exist that would have required the Core Flood System to perform its safety function. Therefore, the automatic opening of this valve does not constitute the actuation of the Emergency Core Cooling System, so this event is not reportable per 10CFR50.72(b)(3)(iv)(A). Therefore, NRC Event Number 40161 is retracted." R3DO (Anne Marie Stone) & NRR EO (Herb Berkow) notified. The NRC Resident Inspector will be informed of this retraction by the licensee. |