Event Notification Report for April 10, 2025

AGREEMENT STATE REPORT - STUCK OPEN GAUGE SHUTTER

The following information was provided by the Arkansas Department of Health (the Department) via email:

"At 1725 CDT on 4/1/2025, Suzano Packaging notified the Department by email that the rotor pin for the shutter in one of their process gauges on digester #8 was sheared. The discovery was made while attempting to lock out the gauge for process maintenance.

"The affected gauge is as follows:

"OHMART-03240310036 SR2, SN-4731C0, Cs-137, 1000 microcuries.

"Licensee actions are as follows:

"A technical representative from BBP Sales [LLC, a dealer and servicer of OHMART Vega Corporation Scientific Instruments] determined on 4/1/2025 that the gauge cannot be repaired in place and steps have been implemented to acquire a replacement gauge.

"The process continues to run safely, with no additional exposure to workers, but with confined space entry being prohibited.

"Digester #8 remains in service with the affected gauge performing measurements as required.

"Upon receipt of the replacement gauge, maintenance will be scheduled with BBP Sales technical support to safely remove the affected process gauge from service and replace it with the new unit.

"The investigation is ongoing, and reporting will proceed in accordance with SA-300."

Arkansas Event Number: AR-2025-001

CONCURRENT REPORT FOR OFFSITE NOTIFICATION

The following information was provided by the licensee via phone and email:

"Notification per 10 CFR Part 70, Appendix A(c), NRC FCSS ISG-12, Rev 0 (Centrus ACO Procedure ACD2-RG-044, Appendix B, Section N):

"The licensee shall notify the NRC Operations Center of any event or situation: related to the health and safety of the public or onsite personnel, or protection of the environment, for which a news release is planned. Such an event may include an on-site fatality or inadvertent release of radioactively contaminated materials; if a notification to other government agencies has been or will be made, no matter the significance.

"The Ohio EPA [Environmental Protection Agency] will be notified by FBP [Fluor BWXT Portsmouth] Environmental that approximately 500 gallons of sewage had been released to the North Pond or Outfall 013.

"Recommended actions are to install straw bales in the discharge area, to contain and clean the area, and to monitor the North Pond for solids. Sandbags have been placed at the facility exit. Centrus Environmental has also notified Ohio EPA.

"The regulatory manager provided a courtesy notification of this concurrent Ohio EPA reporting to the NRC Region II Senior Inspector and the NRC HQ Senior Program Manager."

Condition Notification Number: 12535

EN Revision Imported Date: 4/10/2025

EN Revision Text: AUXILIARY FEEDWATER SYSTEM INOPERABLE

The following information was provided by the licensee via phone and email:

"On April 7, 2025, at 2000 EDT, it was discovered that all pumps in the auxiliary feedwater system were inoperable due to the loss of control power to the `B' train emergency feedwater (EFW) flow control valve which supplies the `D' steam generator. The redundant `A' Train EFW flow control valve for the `D' steam generator remains functional, as well as the capability of the auxiliary feedwater system to supply all steam generators.

"The `A' and `B' EFW flow control valves are arranged in a series configuration for each steam generator. Failure of any of the 8 EFW flow control valves to meet its surveillance requirements will render all EFW pumps inoperable per technical specifications (TS).

"This condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(B).

"The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

Troubleshooting is ongoing for the cause of the loss of control power. The licensee is currently in technical specification limiting condition for operation 3.7.1.2 action statement 'D' to restore at least one auxiliary feedwater pump to operable status as soon possible.

* * * RETRACTION ON 04/09/2025 AT 1049 EDT FROM BOB MURRELL TO JORDAN WINGATE * * *

The following information was provided by the licensee via phone and email:

"The purpose of this notification is to retract a previous report made on 04/08/2025 at 1344 EDT, EN 57652. Notification of the event to the Nuclear Regulatory Commision was initially made because of declaring all pumps in the emergency feedwater system inoperable in response to discovering the loss of control power to the `B' train emergency feedwater (EFW) flow control valve, which supplies the `D' steam generator. The redundant `A' train EFW flow control valve for the `D' steam generator remained functional, as well as the capability of the EFW system to supply all steam generators.

"Subsequent to the initial report, NextEra has concluded that the loss of control power to the `B' train EFW flow control valve did not prevent EFW from fulfilling its safety function. Specifically, the `A' train of EFW was fully capable of fulfilling all EFW safety functions.

"Therefore, this event is not considered a safety system functional failure and is not reportable pursuant 10 CFR 50.72(b)(3)(v)(B).

"The NRC Resident Inspector has been notified."

Notified R1DO (Schussler)

EN Revision Imported Date: 4/10/2025

EN Revision Text: PART 21 - GENERAL ELECTRIC TIME DELAY RELAY FAILURE

The following is a summary of the information provided by the licensee via email:

This is a report made in accordance with 10 CFR Part 21.21 on a failure of a Curtiss Wright (CW) supplied General Electric (GE) time delay relay.

On 12/10/24, Constellation notified CW about the failure of the relay. Constellation stated the relay failed a planned maintenance test. The induction disc was unable to complete the full travel towards the under-voltage trip due to obstruction from the stationary contact, which slipped down along the shaft upon which it was mounted, and made contact with the induction disc.

On 2/13/25, CW received the failed CW supplied GE time delay relay from Constellation.

Further research discovered that LaSalle had a similar failure in 2002, but there have not been any other reported failures in the nuclear industry until this one.

On 4/07/25, Revision 2 of the failure analysis written by Constellation Power Labs stated similar results as those of 12/10/24. The bracket, even when fully tightened, could not hold its position on the shaft. The root cause of the failure could not be determined.

Because CW cannot establish a root cause, the following checks are recommended:

1) CW has modified the dedication plan to apply mild vertical force to assure that the clamp is secure as part of the dedication process.

2) End users should provide a similar mechanical test to be sure that the clamp remains secure during periodic surveillance and maintenance activities.

These actions should preclude a possible recurrence of this failure mechanism.

Relay information:
Part number: 12IAV69A1A
Manufacturer's serial number: AIAV111700032
CW tag number: CJ678001
CW serial number: 03

Affected facilities: Unknown

Responsible Curtis-Wright representative:

Mark Papke
QA Manager
Curtiss-Wright
4600 East Tech Drive, Cincinnati, OH 45245

* * * UPDATE ON 04/09/25 AT 0818 EDT FROM MARK PAPKE TO JOSUE RAMIREZ * * *

Curtiss Wright (CW) provided a copy of the undervoltage relay failure analysis Revision 2 written by Constellation Power Labs to the Nuclear Regulatory Commission. The report included conclusions, observations, and a test plan.
In addition, CW sent out a test procedure to the customer. CW has indicated that customers should perform a routine maintenance check on the contact/clamp.

Affected facilities: Constellation Fleet

Notified R1DO (Schussler), R2DO (Franke), R3DO (Hills), R4DO (Vossmar), and Part 21 group (Email).

MANUAL REACTOR SCRAM

The following information was provided by the licensee via phone and email:

"On April 08, 2025, at 1607 CDT, River Bend Station (RBS) was operating at 81 percent reactor power when a manual reactor protection system (RPS) actuation was inserted due to the loss of all normal service water pumps. Standby service water initiated and operated as expected. The scram was uncomplicated and all other plant systems responded as designed. Immediately after the scram, a reactor water level 3 isolation signal was received as expected.

"Reactor pressure is being maintained by the main turbine bypass valves. Reactor water level is being maintained by condensate and main feed water. RBS is currently in mode 3. No radiological releases have occurred due to this event. The loss of all normal service water is currently under investigation.

"This event is being reported under 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A), as an event or condition that results in actuation of the RPS while the reactor is critical and as a specified system actuation due to the expected reactor water level 3 isolation signal immediately following the reactor scram.

"The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

RBS intends to maintain temperature and pressure and remain in mode 3 while the event is under investigation.

VALID ACTUATION OF EMERGENCY AC ELECTRICAL POWER SYSTEMS

The following information was provided by the licensee via phone and email:

"At 1924 MST on April 8, 2025, a loss of power (LOP) occurred to 'Train-A' 4.16 kV class 1E electrical bus while re-energizing 'Train-A' balance of plant (BOP) engineered safety features actuation system (ESFAS) from pre-planned maintenance. The LOP occurred when the circuit breaker supplying off-site power to the 'Train-A' 4.16 kV class 1E bus tripped when 'Train-A' BOP ESFAS system was re-energized. Operators restored power to 'Train-A' 4.16 kV class 1E bus with 'EDG-A' [emergency diesel generator for 'Train-A'] at 1934 MST. Operators restored all necessary plant loads which had lost power. Per the Palo Verde emergency plan, no emergency classification was required.

"At the time of the LOP, the reactor was defueled with the core offloaded to the spent fuel pool.

"Unit 2 and Unit 3 are not impacted by this event and remain in mode 1, 100 percent power.

"The cause of the circuit breaker supplying off-site power to the 'Train-A' 4.16 kV class 1E bus tripping is under investigation. NRC Resident Inspector has been notified.

"This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in a valid actuation of emergency AC electrical power systems."

FAILED FITNESS FOR DUTY

The following information was provided by the licensee via phone and email:

"On April 8, 2025, at 1333 CDT, it was determined that a licensed operator violated the station's fitness-for-duty program. The employee's access to the plant has been terminated.

"This event is being reported under 10 CFR 26.719(b)(2)(ii)."

"The NRC Resident has been notified."