Tritium in vegetation at various types of radioactive contamination sites under arid climate conditions

This article presents research findings on tritium (3H) in plants at the Semipalatinsk Test Site (STS), including the perimeter of the 'Degelen' site, the riverside zone of the Shagan River, and a conditionally 'background' area-the southeastern part of the STS (SEP). The 3H content in plants was determined in tritiated free water (TFWT) and organically bound 3H (OBT). Plant samples were measured using an ultra-low-level liquid scintillation spectrometer. Maximum 3H concentrations in plants were detected at the 'Degelen' site (TFWT up to 51 ± 5 kBq/kg, ОBТ up to 15 ± 1 kBq/kg) and Shagan River (TFWT up to 39 ± 4 kBq/kg, ОBТ up to 13 ± 1 kBq/kg). The presence of 3H was recorded not only at underground nuclear sites but also in the conditionally 'background' area (TFWT up to 0.18 ± 0.02 kBq/kg, ОBТ up to 0.088 ± 0.028 kBq/kg). Research suggests that water plays a key role in 3H migration processes in the natural system of interest. The OBT/TFWT values for the study area varied on average from 0.3 to 0.7. The dose rate of internal irradiation of the studied plants varied from 6.3 × 10-6 (SEP) to 1.2 × 10-2 µGy/day (at the boundary of the 'Degelen' site), which is significantly lower than the safe exposure level for biota.