The following was received from the
Washington State Department of Health, Office of Radiation Protection, via email:
Dosimetry results for the month of October 2021 for one employee showed ring extremity dosimeter readings of 77,156 millirads for one hand and 29,391 millirads for the other hand. The employee was interviewed and it appears that the radiation exposures were received during experiments involving yttrium-90 radiolabeling and injections into mice on October 25-27, 2021. The activity used during the experiments is not known at this time, but they had received a shipment of 40 milliCuries of yttrium-90 just before these experiments.
This event is still being investigated by the licensee, but some [preliminary] calculations using the `beta activity to dose-rate' online calculator in Rad Pro Calculator suggest that the high dosimetry results could have been caused if the outside of the employee's ring extremity dosimeters were contaminated with as little as a few thousandths of a microCurie of yttrium-90. This possibility of contamination on the ring extremity dosimeters is also supported by the employee's low whole body dosimeter results for the month of October 2021, which were 0 millirems deep dose, 45 millirems lens dose, and 97 millirems shallow dose. The much lower dosimetry results of a coworker who was working alongside of the exposed employee also suggest that contamination on the ring extremity dosimeters of the exposed employee may have been the cause. The coworker's results were ring extremity dosimeter readings of 6025 millirads on one hand and 889 millirads on the other hand, and whole body dosimeter results of 0 millirems deep dose, 32 millirems lens dose, and 68 millirems shallow dose.
Washington Reference Document Number: WA-21-025