Event Notification Report for May 28, 2024

STUCK SHUTTER

The following is a summary of information obtained from the licensee via phone:

The assistant radiation safety officer (ARSO) received a notification from their Tilden Mine site that a Ohmart Vega (model SH-F1B-0) containing 1 mCi of Cs-137 had a stuck open shutter. The ARSO is evaluating whether to contact Vega to schedule a technician to service the shutter or to amend their NRC license to allow them to service the shutter. The nuclear gauge is in a location inaccessible to personnel and there is no additional exposure risk to personnel or the public.

EN Revision Imported Date: 7/25/2025

EN Revision Text: AGREEMENT STATE REPORT - UNPLANNED EXPLOSION AND CONTAMINATION

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

"On 2/19/2025, Agency staff conducted a routine inspection at Hot Shots NM, LLC. At the time of inspection, it was discovered that on 5/28/2024, a pharmacist used a standard hot plate in lieu of a heat block in order to tag 2 curies of Tc-99m to Sestamibi. The heating caused the glass vial to explode, resulting in a major spill. The event resulted in contamination of the clean room and contamination to (2) individual's face and hair.

"The matter was discussed the next day [2/20/2025] with supervisory staff, and it was determined that the licensee failed to report the event as required under [32 Illinois Administrative Code] 340.1220(c)4 and likely 340.1220(b)2, both requiring notification to the Agency within 24 hours. This matter is reportable to the U.S. NRC within 24 hours.

"Due to a lack of records or licensee evaluation of dose from absorption through skin required under 32 Illinois Administrative Code 340.220(d), there is no current estimate to the amount of occupational exposure to the contaminated workers. Inspectors are actively gathering survey readings, specific activity, and variables that may allow an estimation of potential dose to workers. No workers reported to the hospital as a result of the incident. The investigation is ongoing, and updates will be provided as they become available."

Illinois Reference Number: IL250009

* * * UPDATE FROM GARY FORSEE TO BRIAN P. SMITH AT 1628 EDT ON JULY 24, 2025 * * *

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

"After a detailed investigation and multiple reports from the licensee, very few data points were available to bound the shallow dose equivalent (SDE - skin dose) to the two contaminated workers. Working from the data available, the licensee's consultant estimated Individual 1 received 290 mrem skin dose and Individual 2 received between 7090 and 170,290 mrem skin dose. As stated by the licensee's consultant, 'due to the lack of available survey and occupational monitoring records for the duration of the exposure for Individual 2, and the occupational exposure records for the remainder of the calendar year, it is assumed that this individual received an annual SDE of at least the occupational limit of 50,000 mrem. Without further information, the assigned dose for Individual 2 in this event is based on the worst-case scenario of 170,290 mrem, which does not take into account any potential attenuation or air gap as a result of settling on hair'. The only variables available to assist the Agency in a shallow dose equivalent estimate were the 2 curies of Tc-99m contained within the 3.6 milliliter vial, as well as statements from employees noting contamination on skin, neck, and hair up to 8.5 hours post-incident. Initial personnel decontamination efforts were conducted up to 25 minutes after the ruptured vial containing the Tc-99m. Since no survey readings or personnel exposure assessments were documented, the Agency was unable to conclusively determine if an employee received a 50-rem skin dose as a result of this incident. However, given the dose to the skin per microliter per hour (based on the range from two references), and noting contamination was noted on employee's hair, face, and neck even after initial decontamination attempts (decontamination was 25 minutes post incident), and noting the employee continued to work approximately 8.5 hours before completing decontamination; there is a high likelihood this incident 'may have caused, or threatened to cause' a shallow dose equivalent to the skin in excess of 50 rem. No workers reported to the hospital as a result of the incident and there was no evidence of deterministic effects. As a result of the information above, this report is being updated to include a likely occupational exposure in excess of the regulatory limits. Root cause was failure to follow established procedures for large spills. The licensee detailed corrective action including new training and procedures. Pending appropriate enforcement action, this investigation is considered complete."

Notified R3DO (Zurawski), NMSS Events Notification, NMSS (Allen)