Event Notification Report for September 10, 2024

AGREEMENT STATE - STUCK OPEN GAUGE

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

"On September 11, 2024, the Agency was contacted by a representative for the Exxon Mobile refinery in Channahon to advise of a fixed gauge containing 20 mCi of Cs-137 [sealed source] had a reportable equipment failure. Specifically, on September 10, 2024, during routine shutter checks, the handle that operates the shutter broke off, leaving the gauge in the open position. The gauge is mounted to a production vessel which is full of commodity. There were no exposures, and due to the vessel being in use, personnel exposure is not a concern. The manufacturer has been contacted for repairs. The licensee met the notification requirements. This report will be updated with the source serial number and verification of repair and replacement upon receipt."

Illinois Event Item Number: IL240021

OFFSITE NOTIFICATION

The following information was provided by the licensee via email:

"On September 10, 2024, Columbia Generating Station determined that no more than approximately thirty (30) gallons of silicone oil was inadvertently released into a plant service water system due to a failed heat exchanger on a plant installed air compressor. The plant service water system returns water to a water basin that contains at a minimum 300,000 gallons of water. The water basin is connected to the Columbia River via a blowdown line. The compromised heat exchanger and compressor have been isolated and secured from the plant service water system. Although not confirmed, it is suspected that an unknown quantity of silicone oil may have been released to the Columbia River. A visual inspection of the basin did not identify any oil sheen or film, and there are no additional actions needed to mitigate this issue. It does not appear the oil released poses a threat to human health or the environment, however, because there could have been a discharge of an unknown quantity of silicone oil into the Columbia River, this matter is immediately reportable under [Revised Code of Washington] 90.56.280 to the U.S. Coast Guard National Response Center, Washington State Department of Ecology, and to the State of Washington Energy Facility Site Evaluation Council (EFSEC) under the site's National Pollutant Discharge Elimination System (NPDES) permit section S3.F.2.b.

"This condition is being reported pursuant to 10 CFR 50.72(b)(2)(xi) for notification of other government agencies concerning an event related to the health and safety of the public or protection of the environment. Notifications to off-site agencies are in progress."



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

The NRC resident inspector will be notified.

60-DAY OPTIONAL TELEPHONIC NOTIFICATION OF INVALID ACTUATION OF CONTAINMENT ISOLATION VALVES

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

"This 60-day optional telephone notification is being made in lieu of a licensee event report (LER) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B).

"At approximately 1342 EDT, on September 10, 2024, the reactor water cleanup (RWCU) inboard primary containment isolation valve (PCIV), and the reactor recirculation pump sample inboard PCIV, unexpectedly closed. At the time of this event, work was in progress replacing a control relay in the residual heat removal (RHR) shutdown cooling inboard isolation PCIV circuitry. This relay replacement required lifting the leads of several wires. The neutral side of the relay was electrically connected with the actuation logic for the inboard RWCU and reactor recirculation pump sample PCIVs; the lifting of this lead resulted in the unexpected closure of these PCIVs.

"The actuation was not initiated in response to actual plant conditions, nor an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the system. Therefore, this event has been determined to be an invalid actuation.

"During this event the PCIVs functioned successfully, and the actuations were complete. This event did not result in any adverse impact to the health and safety of the public.

"The NRC Resident Inspector was notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
Unit 2 was not affected.