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U.S. Transuranium and Uranium Registries Conference Contributions

7th European Radiation Protection Week, Dublin, Ireland, October 9–13, 2023

Martin Šefl and Sergei Tolmachev participated in the 7th European Radiation Protection Week in Dublin, Ireland. Dr. Šefl gave a platform presentation about organ activity estimates in a group of workers exposed to high-fired oxides.

Comparison of Organ Activity Estimates based on Bioassay Monitoring with Post-mortem Tissue Analyses

Martin Šefl (USTUR), Maia Avtandilashvili (USTUR), Joey Y. Zhou (DOE), Sergey Y. Tolmachev (USTUR)

Purpose: Monitoring data, such as urinary excretion and in-vivo body measurements are usually the primary source of information for radiation epidemiology of nuclear workers. The United States Transuranium and Uranium Registries (USTUR) complements monitoring data with post-mortem tissue radiochemical analyses for modeling of actinide biokinetics and estimation of radiation doses.

Material and Methods: Uncertainties in organ activities, and radiation dose estimates from internally deposited 239Pu were evaluated using a group of nine former nuclear workers. These individuals voluntarily donated their tissues to the USTUR. All nine workers were exposed to ‘high-fired’ PuO2 aerosols during the same glove-box fire accident. Plutonium bioassay data for each individual included at least five positive urine measurements. For six workers, the fire was their only intake, two had an additional wound intake, and one had an additional inhalation incident.

Results: The measured 239Pu activities ranged from 9.4 to 123 Bq in the liver, from 9.2 to 215 Bq in the skeleton, and from 92.9 to 7540 Bq in the lungs. Bayesian inference was used to obtain distributions of estimates of activities and doses. Latin hypercube sampling was employed to create priors of main absorption parameters (rapidly dissolved fraction, and slow dissolution rate) and selected particle transport rates. Distributions of organ activities and organ equivalent doses were generated. The distributions of 239Pu activities based on bioassay measurements were compared to the measured post-mortem 239Pu activities in the lungs and liver+skeleton.

Conclusion: Means of the modeled distributions differed from measured values on average by 49% for the lungs, and by 66% for the liver+skeleton. [USTUR-0647-23]