Event Notification Report for July 14, 2025

EN Revision Imported Date: 7/14/2025

EN Revision Text: PART 21 REPORT - SOLENOID VALVE FAILS TO OPERATE AFTER EXTENDED DE-ENERGIZATION

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

This report relates to the failure of a single air-operated valve identified by Dominion Energy at North Anna due to failure of the associated solenoid valve. The solenoid valve periodically failed to reposition, or only partially repositioned, after periods of extended de-energization.

As part of testing, the ASCO NP8321 solenoid valve series and all ASCO NP-series solenoid valves were qualified to sit in a normally energized position and were not tested for extended periods of de-energization. The U-cup seal was tested and ASCO determined that this U-cup seal experienced performance limitations at low air operating pressures (below 40 psi) and the valve did not shift completely to an energized state.

An alternative valve (NP8300) is recommended by ASCO for this customer application. In the interim, ASCO recommends increasing the inlet air pressure to the valve to at least 80 psi not to exceed the maximum 150 psi to conservatively ensure proper operation of the NP8321 series valve in a de-energized state.

ASCO concludes based on design and known operating experience that only the NP8321 model valve exhibits this condition.

ASCO does not have adequate knowledge of the actual installation and operating condition of this valve to determine whether this condition would create a `substantial' safety hazard as defined in 10 CFR 21.3. The report is intended to provide investigation results and recommendations. Each end user needs to perform their own evaluation based on the information provided in this notification.

Bryan Causey
Quality Engineer
Bryan.Causey@Emerson.com

The only plant known to be affected at the time of the report is North Anna.

* * * UPDATE ON 07/11/2025 AT 0907 EDT FROM BRYAN CAUSEY TO IAN HOWARD * * *

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

ASCO performed extensive testing on this valve with a variety of U-cup seals and found all U-cup seals used for the NP8321 series have low pressure de-energized dormancy performance limitations.

For applications where the valve is at 80 psi, ASCO will be updating guidance to indicate that a minimum pressure rating of 80 psi must be maintained when switching from the de-energized state to the energized state for normally closed valves. For normally open valves, 80 psi must be maintained when switching from the energized state to the de-energized state. ASCO ensures application at or above 80 psi would meet its equipment qualification requirements.

For applications between 40 and 80 psi the utility has not observed any low-pressure dormancy issues on valves that have already experienced the applications longest possible period of de-energization, ASCO advises that the valve remain in service for the rest of its equipment life, during this time ASCO recommends looking for an appropriate alternative valve and solution for this system. ASCO recommends an NP8300 or NP8316 valve as a suitable replacement. For applications at or below 40 psi, the utility should consult with ASCO at the earliest opportunity.

The NP8300 is a potential replacement for the NP8321 series but it is not a drop-in replacement. The NP8300 series consumes twice the wattage of NP8321 and has a lower flow rate. If the lower flow and higher wattage of the NP8300 are acceptable limitations for the utility's application, then ASCO would recommend a NP8300 valve.

If the application requires the same wattage and can manage higher flow, a NP8316 can replace a NP8321 but the higher flow rate may require changes to the specific system in place. The NP8316 does have a lower minimum operating pressure differential of just 10 psi instead of 15 psi, but the flow is several times higher than the NP8321. For this solution to work, the system would need to be tolerant of this higher flow and ensure that the minimum operating pressure differential of 10 psi (measured between in the inlet port and exhaust port) is maintained with appropriate piping/regulators and exhaust pipes capable of ensuring that the minimum pressure is maintained. This could include changing out piping and regulators for larger sized pipes and regulators to match the higher Cv [valve flow coefficient] of the NP8316 series.

ASCO concludes that for applications at or above 80 psi, the NP8321 series valve meets its full equipment requirements. For applications below 80 psi, ASCO recommends replacing the value based on the above guidelines.

Notified R2DO (Davis) and the Part 21 groups (email).

AGREEMENT STATE REPORT - STOLEN MOISTURE DENSITY GAUGE

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

"On July 7, 2025, at about 0710 CDT, a report was made by the licensee that an Istrotek model 3500 moisture density gauge containing a 10 mCi Cs-137 source and a 40 mCi Am241/Be source had been discovered stolen at 0518 CDT on July 7, 2025, from the bed of a pickup truck at the residence of an employee in Fort Worth, Texas. The securing chains and locks had been breached overnight and the gauge taken.

"The gauge handle was secured by a lock; no immediate public health issue is anticipated.

"A report was made to the Fort Worth Police Department."

Texas incident number: 10208

THIS MATERIAL EVENT CONTAINS A 'Less than Cat 3' LEVEL OF RADIOACTIVE MATERIAL

Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf

AGREEMENT STATE REPORT - STUCK OPEN SHUTTERS

The following information was provided by the South Carolina Department of Environmental Services (the Department) via phone and email:

"The licensee informed the Department via email on July 3, 2025, (a phone notification was not made to the Department), that two fixed gauging devices were disabled or failed to function as designed. The licensee reported that a 2 curie cesium-137 Kay-Ray/Sensall Inc. model number: 7700Y-1000, serial number: S95K1307 was stuck in the open position (exposed), and a 100 millicurie Cs-137 Texas Nuclear model number: 570-571157C, serial number: B2988 is stuck in a partially open position (exposed). Both of the devices are attached to a process vessel.

"The licensee also informed the Department that a 100 millicurie Cs-137 Texas Nuclear model number: 570-571157C, serial number: B2987 has a visible crack in the source housing and is attached to a process vessel.

"The licensee performed ambient dose rate surveys and reported results similar to the Sealed Source and Device Registry (SSDR) certificates.

"The licensee did not report any overexposures or ongoing health/safety concerns.

"This event is still under investigation by the Department."

South Carolina Event Number: TBD

AGREEMENT STATE REPORT - STUCK OPEN SHUTTER

The following information was received from the Minnesota Department of Health (MDH), Radioactive Materials Unit via email:

"On Monday, July 7, 2025, at 1000 [CDT], the licensee discovered a gauge with a stuck shutter. The gauge is a Texas Nuclear fixed gauge with a 200 mCi Cs-137 source. Maintenance was planned on the apron feeder near the gauge. The maintenance group requested the electrical group close the shutter on this gauge. The electrical crew was unable to close the shutter after multiple attempts and decided to remove the gauge and place it in a container containing lead plates. The radiation safety officer (RSO) took readings 1 foot from the top and sides of the container. The highest reading was 0.3 mR/hr. The container was labeled as radioactive material and taped off with red tape. The RSO reached out to QAL-TEK to dispose of the unit. QAL-TEK stated they may be able to come out in less than two weeks."

Minnesota Event Report ID: MN250004

AUTOMATIC REACTOR TRIP

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

"At 1418 EDT on 7/13/2025, with Unit 2 in mode 1 at 100 percent power, the reactor automatically tripped due to a main turbine trip. The trip was not complicated 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 steam dump system and the auxiliary feedwater (AFW) system. Unit 1 is 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). The expected actuation of the AFW system (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A).

"There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
The cause of the main turbine trip was due to the loss of both main feed pumps due to a loss of secondary power. The cause of the loss of secondary power is still being investigated.