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

Abstract

This article presents research findings on tritium ( 3 H) 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 3 H content in plants was determined in tritiated free water (TFWT) and organically bound 3 H (OBT). Plant samples were measured using an ultra-low-level liquid scintillation spectrometer. Maximum 3 H 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 3 H 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 3 H 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.