Tririum in urine in residents of Ozyorsk, the Chelyabinsk region in 2016

Objectives. To create the model of relation between volume activity of tritium in urine of Ozyorsk residents and physical and biological factors. To define the correspondence of internal exposure doses of Ozyorsk residents obtained from tritium to standards and requirements of present-day radiation security system. In the framework of the objectives the following tasks were solved: measurement of volume activity of tritium in the urine; detection of main factors affecting the volume activity of tritium in the urine; estimation of the distribution of committed effective dose equivalent of internal exposure due to tritium intake in 2016 among Ozyorsk residents under stable radiation environment.

Material and methods. 30 samples of urine were taken from resident of Ozyorsk Chelyabinsk region never employed at the Mayak Production Association in 2016. Measurement of tritium volume activity in the urine was performed using up-to-date ultra low level beta spectrometer Quantulus-1220. A questionary was developed that allowed collection of individual data on the water intake regime, on the occupational activity and the living conditions of people under study. Statistical processing was performed using software Excel-2013 and R. In order to develop models of dependency of tritium volume activity in urine of the residents from continuous and/or category variables we used correlation and regression methods of analysis. In order to compare two samples by mean value of tritium volume activity Student t-criterion was used. In order to verify normality of dose distribution Shapiro-Wilk test was used.

Results. Volume activity of tritium in urine of adult Ozyorsk residents in 2016 was in average 18.5 ± 1.1 Bq/dm³, volume activity of tritium in urine of children – 12.6 ± 2.3 Bq/dm³ in average. Major statistical characteristics of estimates of committed effective dose equivalent from tritium in Ozyorsk residents due to intake on 2016 under stable radiation environment obtained from a sample of 30 individuals were the following: minimum value made 0.07 µSv, mean value was 0.27 µSv, coefficient of variation made 36%, maximum value made 0.49 µSv. A model of dependence of tritium volume activity in urine of Ozyorsk residents from the water supply source was obtained.

Conclusions. Estimates of committed effective dose equivalent of internal exposure from tritium among Ozyorsk residents due to intake in 2016 made: mean value of committed effective dose equivalent was 0.027 and maximum value made 0.05% from the annual effective dose limit for residents under unifactor tritium intake. In 2016, the levels of tritium volume activity in the bodies of adult and children population of Ozyorsk city depended on volume activity of tritium in drinking water supply sourced more than on the age. As of 2016, under stable radiation environment at Mayak Production Association, tritium did not pose any threat for Ozyorsk population.

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