Staff at the New Milford Cancer Center in New Milford,
CT were performing their daily quality assurance checks on their Varian Medical Systems high dose rate (
HDR) afterloader when the 7.2 Ci (estimated)
Ir-192 source became stuck in the safe position. New Milford contacted the vendor who dispatched a support team to investigate.
The Varian RSO surveyed the area and found the dose rate at 5 cm was 1.5 mR/hr which was within normal parameters with the source in the shielded position. While attempting to free the source, it became stuck outside of the shielded position. Dose rates increased to 20 mR/hr at the entrance to the maze, 280 mR/hr at the turn (approximately 15 feet from the HDR) and 5.4 R/hr at 0.5 meters. The service manager was able to use the emergency hand crank to return the source to its shielded position. During the retrieval, the RSO received 9 mR while the service manager received 27 mR.
Based on past issues and current symptoms, Varian technicians replaced the drive mechanism and will be installing a new source wire.
Once all repairs are made, the HDR will be placed into service with the Varian team on hand during the first post-maintenance use.
Varian, an NRC licensee, is making this report since New Milford Cancer Center (license number 0617892-01) did not exceed any reporting thresholds due to this event.
The vendor has notified R1 (Modes). See similar events in
Event Notifications 46695 and 46758.