О разработке контрольных уровней удельной суммарной альфа-активности проб воды для ряда источников централизованного хозяйственно-питьевого водоснабжения в Республике Хакасия

The aim of the work is to develop control levels of specific total alpha-activity of water samples for a number of sources of centralized drinking water supply in the Republic of Khakassia on the basis of the results of long-term laboratory studies. Materials and methods. The analysis is carried out on the basis of the results of laboratory studies of water sources of centralized drinking water supply of the population of the Republic of Khakassia, performed by accredited testing laboratories of institutions of the state sanitary and epidemiological service of the Republic for the period from 2001 to 2018, using alpha-beta radiometric, alpha-spectrometric methods with radiochemical preparation of counting samples, gamma-spectrometric method. The control levels of specific total alpha-activity of water samples from the sources of centralized drinking water supply in the Republic of Khakassia were established by the statistical maximum – the sum of the average value with a doubled standard deviation, with the volume of research more than 30, and the maximum value with the volume of research less than 30. Results. About half of the studied water samples from the sources of the centralized drinking water supply of the Republic of Khakassia, annually, are noted with exceeding the control level of specific total alpha-activity (0,2 Bq/kg). The values obtained in the studied samples vary up to 5,57 Bq/kg. During the observation period, samples of water exceeding the reference level of specific total alpha-activity (0.2 Bq/kg) were identified in settlements of the Altai, Askizsky, Beysky, Bogradsky, Ordzhonikidzevsky, Tashtypsky, Ust–Abakansky, Shira districts and the city of Sorsk, smt. Prigorsk (Chernogorsk). In previous studies, it was found that high levels of specific total alpha-activity in the country are mainly due to natural radionuclides uranium-238 ( 238 U), uranium-234 ( 234 U). In a number of settlements of the Republic, the sum of the ratio of specific activities of natural radionuclides to the corresponding levels of intervention exceeds 1,0. Average annual individual effective doses of internal exposure to natural radionuclides of drinking water, at or above 0,1 mSv/year (values in the range of 0,1-0,2 mSv/year), which does not require urgent radiation protection measures. At the same time, monitoring of indicators of radiation safety of water sources of water supply should be carried out in accordance with the established requirements. In this connection, in order to improve control, for the rapid assessment of the radiation situation and making timely decisions to ensure radiation safety of the population, the calculation of control levels of specific total alpha-activity was carried out. As a result of calculations, specific values of control levels for each of water source were obtained. The calculated values range from 0,2 to 2,6 Bq/kg. Conclusion. The control levels are “site standards” and are calculated for each of the source of water supply. Their excess will be considered as a signal of “negative change” of the radiation situation”, which may be associated with an increase of the specific activities of 234 U, 238 U, or the appearance of highly radiotoxic radionuclides: 226 Ra, 210 Po, 228 Ra.