| | Site | Start date | Title | Description |
|---|
| ENS 56612 | Summer | 11 May 2023 16:50:00 | Part 21 - CAP Screw Improper Length | The following information was provided by the licensee via email:
This is a non-emergency notification required by 10 CFR 21.21(d)(3)(i). A written notification in accordance with 10 CFR 21.21(d)(3)(ii) will be provided within 30 days. Steam generator emergency feedwater header discharge isolation check valves (XVC01009A-EF, XVC01009B-EF, and XVC01009C-EF) were designed specifically for and supplied to VC Summer Nuclear Station (VCSNS) by Flowserve under purchase order 4500653391 to replace the previous valves in the emergency feedwater system during refueling outage 27. On May 11, 2023, after valve installation, but prior to initial service, the socket head cap screws were identified as being shorter than the required design length. Valve drawings indicate a design length of 1.25" while the socket head cap screws received were 0.875". The correct length cap screws were installed prior to initial service. VCSNS completed a substantial safety hazard evaluation and determined that the improper length of the cap screws constituted a substantial safety hazard. This deviation in cap screw length resulted in a partial engagement of the cap screw to the cylinder rod extension and could potentially affect valve operation.
The NRC Senior Resident Inspector has been notified. |
| ENS 56453 | Summer | 5 April 2023 10:51:00 | Manual Reactor Trip | The following information was provided by the licensee via email:
At 0651 EDT on April 5, 2023, with Unit 1 in mode 1 at 85 percent power, the reactor was manually tripped due to loss of main feedwater pump 'C'. The trip was not complex, with all systems responding normally post-trip. Main feedwater pump 'B' had previously been removed from service in preparation for a planned shutdown as a part of refueling outage RF27.
Operations responded and stabilized the plant. Decay heat is being removed by the emergency feedwater system.
Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) resulting from valid actuation of the reactor protection and emergency feedwater systems.
There was no impact on the health and safety of the public or plant personnel.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
The licensee continues to investigate the loss of main feedwater pump 'C'.
The licensee notified the NRC Resident Inspector. |
| ENS 55750 | Oconee | 22 February 2022 03:07:00 | Manual Reactor Trip | The following information was provided by the licensee via fax or email:
At 2207 (EST) on 2/21/2022 with Unit 2 in Mode 1 at 68 percent power, the reactor was manually tripped due to lowering water level in the 2A Steam Generator. The trip was not complex with all systems responding normally post-trip.
Operators responded and stabilized the plant. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Units 1 and 3 were not affected.
Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non- emergency notification per 10 CFR 50.72(b)(2)(iv)(B).
There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."
- * * UPDATE ON 3/23/22 AT 1643 EDT FROM CHRIS MCDUFFIE TO TOM KENDZIA * * *
The following information was provided by the licensee via phone and email:
On 2/21/2022, Unit 2 was in Mode 1 increasing reactor power following startup from a forced outage. At 2205 (EST) with Unit 2 at 68 percent power, a feedwater control valve failed to properly control feedwater flow to the 2A Steam Generator and the Integrated Control System initiated an automatic runback. At 2207 (EST), the reactor was manually tripped from 39 percent power due to lowering water level in the 2A Steam Generator. Immediately following the manual reactor trip, an actuation of the Emergency Feedwater System (EFW) occurred. The 2A and 2B Motor Driven Emergency Feedwater (MDEFW) pumps automatically started as designed when the 'low steam generator level' signal was received for the 2A Steam Generator. The trip was not complex with all systems responding normally post-trip. Operators responded and stabilized the plant. Decay heat was removed by discharging steam to the main condenser using the turbine bypass valves. Units 1 and 3 were not affected. Unit 2 was restarted on 2/27/2022 following repairs.
Due to the Reactor Protection System actuation while critical, this event was reported on 2/22/2022 as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Following further evaluation, it was determined that a valid EFW actuation occurred, therefore this event is now also being reported as a late 8-hour non-emergency notification of a valid actuation of the EFW system in accordance with 10 CFR 50.72(b)(3)(iv)(A).
There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
Notified the R2DO (Miller). |
| ENS 55800 | Oconee | 13 February 2022 21:25:00 | Emergency Feedwater System Actuation | The following information was provided by the licensee via email and phone:
At 1625 (EST) on 2/13/2022, with Unit 2 in Mode 3 at 0 percent power and plant heat up to normal operating temperature in progress, an actuation of the Emergency Feedwater System (EFW) occurred. The reason for the EFW auto-start was lowering water level in the 2A and 2B Steam Generators due to failure of the 2A Main Feedwater Pump to respond as required to maintain Steam Generator water level as Steam Generator pressure increased during plant heat up. The 2A and 2B Motor Driven Emergency Feedwater (MDEFW) pumps automatically started as designed when the 'low steam generator level' signal was received for the 2A and 2B Steam Generators.
Following further evaluation, it was determined that a valid EFW actuation occurred, therefore this event is being reported as a late 8-hour non-emergency notification of a valid actuation of the EFW system in accordance with 10 CFR 50.72(b)(3)(iv)(A).
There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 55580 | Summer | 15 November 2021 22:28:00 | Manual Reactor Trip Due to Main Transformer Fault | At 1728 EST on 11/15/2021, with Unit 1 in Mode 1 at 47 percent power, the reactor was manually tripped due to a main transformer fault. The trip was not complex, with all systems responding normally post-trip. Operations responded and stabilized the plant. Decay heat is being removed by the emergency feedwater system through the main condenser.
Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B).
Additionally, due to the valid actuation of the emergency feedwater system, this event is being reported as a non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A).
There was no impact on the health and safety of the public or plant personnel. The NRC Senior Resident Inspector has been notified."
- * * UPDATE ON 11/16/21 AT 1649 EST FROM BRUCE BENNETT TO KERBY SCALES * * *
At approximately 0900 (EST) on 11/16/2021, it was identified that mineral oil from the faulted main transformer had surpassed the capability of the oil containment system and discharged into Lake Monticello. It is estimated that less than 50 gallons of mineral oil entered the Lake. The oil is contained with booms and cleanup is ongoing. The EPA National Response Center and the South Carolina Department of Health and Environmental Control have been notified. This is considered a news release or notification to other government agencies; therefore, this event is reportable under 10 CFR 50.72(b)(2)(xi).
The NRC Senior Resident Inspector has been notified.
Notified R2DO (Miller). |
| ENS 55028 | Arkansas Nuclear | 10 December 2020 22:08:00 | Automatic Reactor Scram Due to Low Steam Generator Water Level | On December 10, 2020 at 1608 CST, Arkansas Nuclear One, Unit 2 (ANO-2) experienced an automatic reactor scram from 100 percent power due to Low Steam Generator Water Level in 2E-24A Steam Generator. Emergency Feedwater actuated automatically due to low water level in the A Steam Generator. Due to inadequate control of the B Main Feedwater Control System, water level in the B Steam generator rose to a level requiring manual trip of the B Main Feedwater pump. Emergency Feedwater responded as designed to feed both steam generators automatically.
All other systems responded as designed. All electrical power is being supplied from offsite power and maintaining unit electrical loads as designed.
Unit 2 is currently stable in Mode 3 (Hot Standby) maintaining pressure and temperature via Emergency Feedwater and secondary system steaming.
There are no indications of a radiological release on either unit as a result of this event.
This report satisfies the reporting criteria of both 10 CFR 50.72(b)(2)(iv)(6) for the Reactor Protection System actuation and 10 CFR 50.72(b)(3)(iv)(A) for the actuation of the Emergency Feedwater System.
The Arkansas Nuclear One NRC Senior Resident Inspector has been notified.
- * * UPDATE FROM JOHN LINDSEY TO DONALD NORWOOD AT 1605 EST ON 12/11/2020 * * *
The purpose of this (report) is to provide an update to NRC Event Number 55028.
The cause of the inadequate control of the B Main Feedwater Control System to control B Steam Generator Level was verified to be associated with the failure that led to the A Steam Generator low level condition.
After taking action to trip the B Main Feedwater Pump, Emergency Feedwater was manually actuated for the B Steam Generator and the Emergency Feedwater System was verified to maintain proper automatic control of both Steam Generator levels.
At the time of the initial event notification, plant temperature and pressure control had been transferred from Emergency Feedwater to Auxiliary Feedwater along with secondary system steaming.
The licensee notified the NRC Resident Inspector.
Notified R4DO (Kellar). |
| ENS 52718 | Seabrook | 29 April 2017 22:44:00 | Manual Reactor Trip Due to Steam Generator Hi-Hi Level Signal and Feedwater Isolation | At 1844 (EDT) on 04/29/2017, while the unit was in a low power condition exiting from a refueling outage, the reactor was manually tripped following a P-14 signal (Steam Generator Hi-Hi Level) and a resulting feedwater isolation signal. All control rods were verified to be fully inserted. The cause of the ('B') steam generator high level is currently being investigated.
Emergency feedwater actuated at 1845 due to a low-low water level in steam generator 'D'. Plant equipment response is being evaluated and the plant is stabilized in Mode 3 with decay heat removal through the steam dump system to the condensers. There was no release and the emergency feedwater system has been restored to standby.
The event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow up notification will be made via the ENS or under the reporting requirements of 10 CFR 50.73.
The licensee notified the NRC Resident Inspector. |
| ENS 51765 | Seabrook | 2 March 2016 18:12:00 | Valid Actuation of Emergency Feedwater | On 3/2/2016, (at) 1312 hours EST, while in the process of a plant cooldown, a valid actuation of the emergency feedwater system (EFW) occurred when B steam generator levels were reduced to 20 (percent). The lowering level was a result of the unanticipated tripping of the start up feed pump on low condensate storage level while it was the feed source to the steam generators. The start up feed pump was restarted and feed flow had been restored when the actuation took place. The EFW flow was secured per procedure and the start up feed pump remains the feed source to the steam generators.
This is reportable under 50.72(b)(3)(iv)(A).
The licensee notified the NRC Resident Inspector. |
| ENS 51695 | Three Mile Island | 2 December 2015 02:19:00 | Invalid Emergency Feedwater Actuation | On December 1, 2015, at 2119 EST, with Unit 1 in power operation mode, during a planned maintenance activity, an invalid Heat Sink Protection System (HSPS) actuation occurred. At the time of the event, electrical maintenance technicians were verifying a HSPS relay contact state using an electrical test meter. The contact was being verified open by recording both voltage and resistance readings across the contact. The technicians first measured voltage. No voltage was found, indicating the relay contact was open, as expected. The technicians then measured for resistance across the open contact. Test meters have lower circuit impedance when measuring resistance as opposed to voltage, which can result in electrically bridging across open contacts. When the meter was installed across the open contact to obtain the resistance reading, the HSPS actuation circuit logic was completed and the inadvertent HSPS actuation occurred. The HSPS actuation resulted in the steam driven Emergency Feedwater (EFW) pump automatically starting and control valves receiving actuation set point signals. There was no emergency feed water injection into the steam generators. At the time of the inadvertent HSPS actuation, steam generator operating levels were above the HSPS actuation setpoint.
The specific train and system that actuated was the Heat Sink Protection System, Emergency Feedwater System Actuation on Loss of All Reactor Coolant Pumps (RCP) Train A.
The HSPS Loss of all RCP Train A actuation was complete.
The EFW valves and EFW steam driven pump started and functioned successfully.
This is reported under 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of HSPS Loss of all RCP Train A and in accordance with 10 CFR 50.73(a)(1), this notification of the invalid actuation is provided in lieu of a written LER.
The Licensee notified the NRC Resident Inspector. |
| ENS 51506 | Point Beach | 29 October 2015 08:48:00 | Actuation of the Auxiliary Feedwater System Due to Main Transformer Lockout | At 0348 CDT, while Point Beach Unit 2 was performing outage activities, it experienced a Main Power Transformer lockout and associated loss of busses (2A-01, 2A-02, 2B-01 and 2B-02). The loss of the two non-vital 4160 V buses resulted in actuation of the Unit 2 undervoltage logic which resulted in actuation of the Auxiliary Feedwater System. The Auxiliary Feedwater System functioned normally upon actuation.
This condition was determined to be reportable per 10CFR50.72(b)(3)(iv)(A)(6), PWR auxiliary or emergency feedwater system actuation.
This event did not affect the operating Unit 1.
The NRC Senior Resident Inspector has been notified. |