Comparison of Radiation and Chemical Toxicity of Uranium Compounds on The Basis of Calculation by New ICRP Biokinetic Models

Purpose: Harmonization and improvement of the system for regulating the internal radiation exposure of workers and the basic requirements for ensuring radiation safety, taking into account the application of new international requirements and recommendations.

Material and methods: The article presents a comparison of the radiation and chemical toxicity of uranium compounds, obtained on the basis of calculating the levels of inhalation intake and committed effective dose depending on the types of compounds F, M, F/M and M/S in the AMAD range from 0.3 to 20 μm for typical isotopic compositions of natural (NU), depleted (DU), low enriched (LEU) and highly enriched (HEU) uranium, which lead to the maximum permissible concentration of uranium in the kidneys. The calculations were carried out using new ICRP biokinetic models, which give more physiologically realistic representations of uptake and retention in organs and tissues, and excretion.

Results: The dynamics of uranium activity in the kidneys was calculated for constant chronic inhalation intake over a 50-year period and for acute intake. It was shown that in case of chronic intake, the rate of accumulation of uranium in the kidneys, expressed in relative units, does not depend on the AMAD in the range from 0.3 to 20 μm and slightly depends on the types of compounds F, F/M, M and M/S, which include almost all chemical compounds of uranium. In case of acute intake, there is a rapid, within 1–3 days, an increase of uranium in the kidneys to a maximum value and then a gradual decrease to a value of 20 % of the maximum value in 20–60 days, depending on the type of compound F, M, F/M, M/S and AMAD in a wide range of values from 0.3 to 20 µm. To compare the radiation and chemical toxicity of uranium, the values of the committed effective dose were calculated, which is formed after intake of uranium aerosols of the types F, M, F/M and M/S and AMADs from 0.3 to 20 µm in an amount that creates the maximum concentration of uranium in the kidneys 0.3 µg/g for chronic intake and 3 µg/g for acute intake. The values of uranium intake per year in milligrams, which form the maximum concentration of uranium in the kidneys of 0.3 µg/g, in case of constant chronic intake of uranium aerosols, as well as the values of uranium intake in milligrams, which form the maximum concentration of uranium in the kidneys of 3 μg/g after a single intake of uranium aerosols in both case of the types F, M, F/M and M/S and AMAD in the range from 0.3 to 20 µm were calculated, which are evidently independent of the considered isotopic composition of the uranium.

Conclusion: It is shown that chemical toxicity prevails over radiation toxicity for the types of uranium compounds F and F/M for all considered uranium isotopic composition, except for HEU; for the type of compound M it is the same for mixtures of NU and DU, and for the type M/S radiation toxicity prevails for all considered uranium isotopic composition. In case of chronic intake at committed effective dose exposure rate of several mSv per year, workers can suffer from the chemical toxicity of uranium when working with F and F/M compounds and isotope compositions of natural (NU), depleted (DU) and low enriched (LEU) uranium already after 1–2 years of work. In case of acute intake, the chemical toxicity of uranium should be taken as a criterion for limiting exposure for compounds F and F/M, and also partially M (for uranium isotope compositions of NU, DU and LEU), which can significantly, by tens and hundreds of times, reduce the permissible limit of uranium intake.