Tritium in the urine of the Mayak PA workers in the period from 2017 to 2019

Objectives. To define the levels of volume activity of tritium compounds and fraction of organically bound tritium in urine of chemical production workers of “Mayak Production Association” in present-day conditions; to identify the relationship between volume activity levels and professional occupation (department and profession). Material and methods. 245 urine samples from 171 workers of Mayak Production Association tritium production facility were collected in the period from 2017 to 2019. Volume activity of tritium compounds was measured by liquid scintillation method using spectrometer Quantulus-1220. The samples were distilled or dried and then combusted using an automatic preparation and oxidization system Sample Oxidizer A307. The “R” software was used for statistical analysis and for processing the measurement results and occupational factors. Chaddok’s scale was applied to determine the degree of correlation. The significance level was taken equal to 5%. Results. The value of total tritium volume activity in the urine and tritium volume activity in the water phase varied within 4 orders of magnitude (from ~30 Bq/dm3 to ~250 kBq/dm3). The value of volume activity of organically bound tritium in the urine varied within 2 orders of magnitude (from ~6 Bq/dm3 to ~3000 kBq/dm3). The fraction of organically bound tritium in the urine of the workers was within the range from 0,07% to 74%, and did not differ statistically significantly from lognormal distribution with parameters GM=2,7% and GSD=3,7. Very high rank correlation was detected between total volume activity of tritium compounds and tritium volume activity in the water phase in the urine. Noticeable rank correlations were detected between the total volume activity of tritium compounds in the urine and volume activity of organically bound tritium, as well as between tritium volume activity in the water phase and volume activity of organically bound tritium in the urine. The total tritium volume activity and tritium volume activity in the water phase in the urine of the workers of the 1st department and of the analytical laboratory of Mayak Production Association tritium production facility were statistically significantly higher than in the workers of the 2nd department according to median values. Statistically significant differences between medians of the total tritium volume activity in the urine and tritium volume activity in the water phase related to profession were observed only in the workers in the 1st department. Conclusion. Estimation of tritium volume activity in the water phase by the level of total tritium volume activity in the urine without sample preparation is possible with 95% reliability within limits of one order of magnitude towards the model value. Estimation of volume activity of organically bound tritium in the urine without sample preparation by the level of total tritium volume activity in the urine without sample preparation is possible with 95% reliability within limits of two orders of magnitude towards the model value. The effect of occupational factors to the levels of volume activity of tritium compounds in the urine of Mayak Production Association professional workers was detected.

Estimation of radiation dose from ingested tritium in humans by administration of deuterium-labelled compounds and food

Radiation doses from organically bound tritium (OBT) in foods have been a major concern near nuclear facilities. The current dose coefficient for OBT is calculated using a standard model from the International Commission on Radiological Protection, in which some biokinetic values are not based on human metabolic data. Here, the biokinetics of ingested OBT, and radiation doses from them, were estimated by administering labelled compounds and foods to volunteers, using a deuterium (D) tracer as a substitute for tritium. After the administration of D-labelled glucose, alanine, palmitic acid, or soybean, the D/H ratios in urine were measured for up to 119 days, and the biokinetic parameter values were determined for OBT metabolism. The slow degradation rates of OBT could not be obtained, in many volunteers administered glucose and alanine. The estimated committed effective dose for 1 Bq of tritium in palmitic acid varied from 3.2 × 10–11 to 3.5 × 10–10 Sv Bq−1 among volunteers and, for those administered soybean, it varied from 1.9 × 10–11 to 1.8 × 10–10 Sv Bq−1. These results suggest that OBT, present in some ingested ingredients, gives higher doses than the current dose coefficient value of 4.2 × 10–11 Sv Bq−1.