Estimate of Tritium Intake in the Air from Coastal Plants of Lake Kyzyltash in 2021

Abstract

The goal of the research was determination of the level of annual tritium intake in the air from coastal plants of Lake Kyzyltash in 2021 and compliance of tritium content in the air of the coastal area of Lake Kyzyltash in 2021 with radiation safety standards. In the period May-September, 2021, a study of coastal plants near Lake Kyzyltash, a technological reservoir of the Mayak Production Association, was conducted. Within 100 m from the lakeside, humidity level of plants ranged from 41% to 87%, tritium volume activity level in the water of plants and transpiration water varied from 96 Bq/l to ~8.0 kBq/l and from 64 Bq/l to ~9.0 kBq/l, correspondingly. Based on the Cheddock scale, rank correlations between tritium volume activity and: time from the beginning of a vegetation period (weak reverse); distance from the lakeside (marked reverse); humidity of the plants (moderate positive), were revealed. To predict tritium intake in the air in the form HTO during the post-vegetative period, exponential decrease models of humidity and tritium volume activity in the plants with time were developed. The estimates of general periods of semi-decrease in humidity and tritium volume activity in the water of the plants, were 262 and 64 days, correspondingly. Total annual HTO intake in the air in 2021 from coastal plants was 6.92 E+11Bq, with contribution 0.35% of annual tritium intake from Lake Kyzyltash surface. The plants from the zone 0…~5m contribute 81.8% of total annual intake from coastal plants of Kyzyltash Lake (5.66E+11Bq). Annual HTO intake from the plants of Lake Kyzyltash coastline (0…~5m) only, was 5.66E+11Bq and was consistent with tritium release in 2021 from the Kursk Nuclear Power Plant (5.32E+11Bq), and tritium intake from all coastal plants of Lake Kyzyltash – with release from the Leningrad Nuclear Power Plant (6.90E+11Bq). In the course of two expeditions, if there were no precipitations, the mean HTO volume activity in the air of Lake Kyzyltash coastal areas was ~60 Bq/ m3, which is ~30 times less than permissible volume activity in the inhaled air for population 1.9E+3Bq/m3, according to NRB-99/2009. In the case of a hypothetical residence on the lakeside of Lake Kyzyltash in 2021 and a permanent level of tritium volume activity in natural environments, an annual committed effective dose of internal radiation conditioned by inhalation of super-heavy water vapor, will be 31 μSv/year for a critical group of children aged 1-2 years and 8.7 μSv/year for adult residents, according to NRB-99/2009. These estimates are conservative as far as they do not take into account the ice-free period during which there is practically no evaporation of water from Lake Kyzyltash surface and intake from plants.