Event Notification Report for November 17, 2023

MANUAL REACTOR SCRAM

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

"On November 17, 2023, at 2215 CST, River Bend Station (RBS) was operating at 30 percent reactor power performing plant startup activities when an isolation of low-pressure feedwater string `A' occurred. The team entered applicable alternate operating procedures and inserted control rods to exit the restricted region of the power to flow map. Feedwater temperature continued to lower until it challenged the prohibited region of the AOP-0007 graph requiring a reactor scram. The team inserted a manual reactor scram at 2355 from 24 percent reactor power. All control rods fully inserted and there were no complications. All systems responded as designed. Currently RBS Unit 1 is stable with reactor level being maintained 10 to 51 inches with feed and condensate, and pressure being maintained 500 to 1090 psig using steam drains.

"This event is being reported under 10 CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS) when the reactor is critical and 10 CFR 50.72(b)(3)(iv)(A) Specified System Actuation as result of Group 3 isolations.

"The NRC Senior Resident inspector has been notified.

"No radiological releases have occurred due to this event from the unit."

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

The electric plant is in a normal lineup for current plant conditions with all emergency diesel generators available. The cause of the initial isolation of low-pressure feedwater string "A" is still under investigation.

MEDICAL EVENT - Y-90 POTENTIAL UNDERDOSE

The following information was provided by the UP (Upper Peninsula) Health Systems Marquette via phone in accordance with Headquarters Operations Officers Report Guidance:

On 11/17/23 at 1100 EST at UP Health System Marquette, the radiation safety officer (RSO) determined that a patient received a dose that differed from the prescribed dose by more than 20 percent. The patient was prescribed a dose of 11.34 mCi of Y-90. The target organ was a tumor located in the patient's liver. The dose was administered to the target organ as expected, however, calculations on the remaining radioactivity left over from the administration estimated that the patient received a dose of only 2.82 mCi (24.9 percent of the prescribed dose). The RSO notified the referring physician, and the referring physician will notify the patient. The RSO is currently investigating the cause of the underdose and will submit a 15-day written report to follow up once the investigation is complete.

* * * RETRACTION ON 11/20/23 AT 1111 EST FROM BILL PYLE TO BILL GOTT * * *

The following information was provided by the UP (Upper Peninsula) Health Systems Marquette via phone:

The initial dose estimate was based on incorrect measurements and has been revaluated and the dose was in the acceptable range.

Notified R3DO (Feliz-Adorno) and NMSS Events Notification (via email).

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.