I appreciated the item “Replacing high-risk radioactive materials remains a challenge” in the September 2021 issue of Physics Today (page 23). In 1972 my career at the University of Rochester started with periodic source replacements in the Tandem Van de Graaff accelerator, which used iridium-192. My colleagues and I also used the same nuclide in radiation-therapy breast implants. I had to assist in the operating room to ensure no iridium seeds were lost. Over the years we dealt with blood irradiators and several cobalt and cesium therapy machines and with many smaller sealed sources.

The only “lost” source that I can recall is a cesium-137 capsule used for a three-day cervical implant. It was removed from the patient on a weekend, and procedures were not followed. An inventory on Monday morning revealed that one source was missing. We found it under a conveyor belt that workers used to sort laundry by hand. The source was not damaged, and none of the workers received a significant radiation dose. The incident does, however, support the challenge referenced in the article—a challenge that is easily met by following procedure.

Physics Today