CBRN event in Czech Republic on Mon 1st September 2025

The museum in Roztoky near Prague operates an irradiation chamber that is used to destroy insects in collection items with gamma radiation. For this purpose, a sealed radionuclide source of Co-60 with an actual activity of 127 TBq on the date of the event is used.

On 1. 9. 2025, a radiation worker was exposed to radiation by entering the irradiation chamber to bring another object into it for irradiation at a time when the emitter was extended in the working position and irradiation was taking place. The worker was moving in a field of ionizing radiation for about 1 to 2 minutes. The worker was equipped only with a personal film dosimeter, he left the operational dosimeter in the office. After closing the shielding door, he realized his mistake and reported the incident to his superior.
After evaluating the personal film dosimeter that the worker was wearing, an effective dose of 320 mSv was determined, and no deterministic effects were observed.
An inspection by SÚJB inspectors found that several negative factors coincided, which led to the worker's irradiation:
1. Due to a technical fault in the switch, the blocking of the shielding door was inoperative at the time when the IZ source was extended in the working position. This allowed the shielding door to the chamber to be opened during irradiation.
2. due to a switch malfunction, the light signaling the position of the emitter on the panel did not work, the worker did not notice this and thought that the source was not extended in the working position.
3. switching off the workplace monitoring system (switching off was carried out by the worker who was irradiated during the incident)
4. violation of the obligation to be equipped with a personal operational dosimeter.