Event Notification Report for September 25, 2025

AGREEMENT STATE REPORT - LOST EXIT SIGN

The following is a summary of information provided by the Colorado Department of Public Health and Environment (the Department) via email:

The Department received a notification from the licensee that one (1) exit sign containing 7.62 Ci of tritium was lost in Boulder, Colorado.

Manufacturer: Isolite Corporation
Model Number: 880-12-6
Isotope: H-3
Activity: 7.62 Ci

Event Report ID No.: CO250029

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 - LOST EXIT SIGNS

The following is a summary of information provided by the Colorado Department of Public Health and Environment (the Department) via email:

The Department received notification from the licensee that 10 exit signs containing 9.5 Ci of tritium each were lost in Boulder, Colorado.

Manufacturer: Isolite Corporation
Model number: 880-12-6
Isotope: H-3
Activity: 95 Ci

Colorado event report ID number: CO250030

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

EN Revision Imported Date: 10/21/2025

EN Revision Text: TWO TRAINS OF ECCS INOPERABLE

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

"On 9/23/2025 at 2214 CDT, the South Texas Project Unit 1 (STP-1) train 'B' reactor containment fan cooler (RCFC) chilled water supply outside containment isolation valve, 1-CC-MOV-0137, was declared inoperable due to a material condition. This rendered train 'B' component cooling water inoperable which cascaded to train 'B' emergency core cooling system (ECCS) subsystem to render it inoperable. STP-1 entered technical specification (TS) 3.5.2 action 'A' for train 'B' ECCS, requiring restoration within 7 days or apply the requirements of the Configuration Risk Management Program (CRMP).

"On 09/25/2025 at 1229 CDT, train 'A' essential chiller 12A was declared inoperable due to inability to maintain chiller water outlet temperature less than 52 degrees Fahrenheit. This cascaded down to the train 'A' ECCS subsystem to render it inoperable. STP-1 entered TS 3.5.2 action 'B' due to less than two of the required subsystems operable, to within 1 hour restore at least two subsystems to operable status or apply the requirements of the CRMP, or be in at least hot standby within the next 6 hours and in hot shutdown within the following 6 hours.

"On 09/25/2025 at 1329 CDT, STP-1 entered the CRMP based on two ECCS subsystems remaining inoperable longer than 1 hour. These subsystems are used for accident mitigation. Unit 1 remains in mode 1."

* * * RETRACTION ON 10/20/2025 AT 1636 EDT FROM MARC HILL TO JOSUE RAMIREZ * * *

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

"The purpose of this notification is to retract EN 57952, which was made on September 25, 2025, at 1736 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function.
"Therefore, this event was not a condition that could have prevented fulfillment of a safety function.
"The NRC Resident Inspector has been notified."

Notified R4DO (Vossmar)

AGREEMENT STATE REPORT - MEDICAL EVENT

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

"On October 3, 2025, the Department received notification from the licensee regarding a treatment error during stereotactic radiosurgery with a gamma knife system for a patient with a brain arteriovenous malformation (AVM). The patient was prescribed a total dose of 20 Gy over 2 fractions. The licensee stated that the event occurred on September 25, 2025, when during the first fraction, a coordinate system error between the stereotactic frame and immobilization masking resulted in radiation being delivered to an incorrect site in the brain, completely missing the AVM target volume. As a result, the prescribed 12 Gy for the first fraction was delivered to non-target brain tissue and 0 Gy reached the intended AVM target. The error was discovered on October 2, 2025, just before the patient was scheduled to undergo the second and final treatment fraction. Treatment was immediately suspended and both the referring physician, who is the surgeon, and the patient were immediately informed.

"Additional information will be provided in accordance with SA-300 reporting requirements."

Texas incident number: 10231

A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.