Event Notification Report for June 21, 2025

VALID EMERGENCY DIESEL GENERATOR START

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

"At 2204 EDT on 6/22/2025, with unit 1 and unit 2 operating at 100 percent power, the 'A' reserve station service transformer (RSST) was lost which resulted in the loss of power to the '1J' emergency bus. As a result of the power loss, the '1J' emergency diesel generator (EDG) automatically started as designed and restored power to the '1J' emergency bus. During the event, the unit 1 'A' charging pump (1-CH-P-1A) automatically started as designed due to the loss of power event. Security footage reported a bright white flash associated with the 'A' RSST at the time of the event.

"The valid actuation of these ESF components due to loss of electrical power is reportable per 10 CFR 50.72(b)(3)(iv)(A).

"The '1J' emergency bus off-site power source was restored to service via an alternate source and the '1J' EDG was secured and returned to automatic. Restoration of offsite power to operable is complete. 1-CH-P-1A was secured and returned to automatic. Both units are currently stable, and an investigation is underway to determine the cause of the loss of the 'A' RSST."

Unit 2 was unaffected. The NRC resident inspector was notified.

UNUSUAL EVENT - UNIT 4 CONTAINMENT ISOLATION FAILURE DUE TO BUS LOCKOUT

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

On 6/21/2025, at 1438 EDT, Turkey Point experienced an unplanned reactor trip and a spurious safety injection signal when the '4A' 4 kV bus locked out. An Unusual Event, SU8.1, was declared at 1453 EDT due to two open, motor-operated steam generator sample containment isolation valves not closing on the phase 'A' containment isolation signal due to the loss of power. There were no abnormal parameters that would require a safety injection signal.

Turkey Point unit 3 was unaffected and remains at 100 percent power. Turkey Point unit 4 is stable in mode 3.

The state and one county were notified, and the other county will be notified.

The NRC Resident Inspector was notified.

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

The licensee manually closed the valves due to loss of power to the bus, and they are investigating the cause of the reactor trip.

* * * UPDATE ON 06/21/2025 AT 1639 EDT FROM CHAD HELLMAN TO KAREN COTTON * * *

Turkey Point unit 4 exited the Unusual Event at 1609 EDT.

Notified R2RA (Lara), NRR (Bowman), NSIR (Erlanger), R2DO (Blamey), NRR EO (Felts), IR MOC (Whited), R2 PAO (Gasperson).

Notified DHS SWO, FEMA Operations Center, CISA Central Watch Officer, FEMA NWC, DHS Nuclear SSA (email), CWMD Watch Desk (email).

* * * UPDATE ON 06/21/2025 AT 1835 EDT FROM ADAM ABRAMS TO KAREN COTTON * * *

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

"On June 21, 2025, at 1438 EDT, while Turkey Point Unit 4 was in mode 1 at 100 percent power, the reactor automatically tripped due to lockout of the '4A' 4 kV bus. The cause of the bus lockout is unknown. The trip was complicated with all systems responding normally post-trip, except for containment isolation valves powered from the '4A' 4 kV bus. Operations stabilized the plant in mode 3. Decay heat is removed by discharging steam from the steam generators to atmosphere. Unit 3 is not affected. This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B).

"An actuation of the auxiliary feedwater (AFW) system occurred during the reactor trip and safety injection signal. The AFW pumps automatically started as designed when the low steam generator, safety injection, and '4A' 4 kV bus undervoltage signals were received. This event is being reported pursuant to 10 CFR 50.72(b)(3)(iv)(A).

"The NRC Resident Inspector has been notified."

Notified R2DO (Blamey).

AGREEMENT STATE REPORT - DAMAGED GAUGE

The following information was provided by the Illinois Emergency Management Agency (the Agency) via phone and email:

"The Agency was contacted on 6/21/25 by a gauge user at Klingner and Associates to report that a Humboldt 5001EZ gauge was hit by a truck and damaged on a construction site in Williamsfield, IL. A truck struck the gauge, damaging the handle and the right side of the case. The source rod was not extended when the incident occurred, and the licensee reported that the source appeared to be properly shielded. The licensee followed their emergency procedures, called the radiation safety officer, and then called the Agency for further instructions. The licensee reported that they did not have a survey instrument. The transport case was reported as undamaged, and the gauge was able to be placed in its shielded transport container. The gauge was then transported back to secure storage with strict directions to not open or handle until a reactive inspection could be performed.

"Agency staff arrived at the licensee's authorized gauge storage site on 6/23/2025 to assess the gauge condition and determine reportability under 32 Ill. Adm. Code 340.1220(c)(2). Both sources appeared undamaged, however, the sliding shield at the bottom of the gauge was observed to be approximately 25 percent open and the handle could no longer be used to fully close the shutter, due to the gauge handle being sheared off at the time of impact. A survey of the bottom of the gauge indicated a maximum reading of 150 mrem/hr at contact using a Ludlum model 3-IS-1 ion chamber. Agency inspectors confirmed that the incident did not result in contamination, loss of radioactive material, or exposures in excess of regulatory limits. A leak test will be conducted prior to transport for repair/disposal. With the gauge in its transportation case, Agency inspectors measured a TI (transport index) of 2.0 which would require a radioactive yellow III label and placarding [for shipment]. Discussions are ongoing regarding adding additional shielding and reducing the TI to 1.0 or less, to facilitate shipment using a radioactive yellow II label.

"Agency inspectors confirmed that the event is reportable under 32 Ill. Adm. Cod 340.1220(c)(2). No items of non-compliance resulted from the reactive inspection. Agency inspectors verified that the gauge user maintained adequate visual surveillance of the gauge and followed the licensee's emergency procedures. The licensee was advised of the requirement to submit a written report within 30 days.

"Pending additional information, this matter may be considered closed."

Illinois Reference Number: IL250025