Abstract
The population of the Earth is exposed to external and internal radiation every day. Radiation doses differ over a wide range of cosmic radiation levels and the content of natural and anthropogenic radionuclides in the lithosphere, hydrosphere, atmosphere and biosphere. Ionizing radiation and radionuclides of natural and artificial origin inevitably causes exposure, increasing the probability of adverse health effects. Suppose the dose of radiation is low and is exposed for a long period of time (low power). In that case, the risk is significantly reduced, since the likelihood of repair of damaged tissues increases. However, there is a risk of long-term consequences, such as cancer, which can manifest in years or even decades. The paper aims to research the natural factors in the formation of radioactivity in the natural waters of Northern Kazakhstan and assess waterrelated doses to the population. The leading research methods for this issue are radiometric and radiochemical methods of analysis. Selective radiochemical analysis was used to determine the radionuclides of uranium, thorium, radium, lead, cesium and strontium, and a radiometer was used to determine radonuclides. During the study, 166 water sources over the past 5 years were analysed and systematized. The research object was drinking water sources of the population of Ayyrtau, Tayinsha, Yesil districts, and Musirepov district of the North Kazakhstan region. Four types of drinking water sources were investigated: well water, borehole water, spring water, borehole water used for centralized water supply. When calculating the dose of internal exposure, the data of the annual radiochemical analysis of various fresh water sources of four districts of the North Kazakhstan region from 2011 to 2016 were used.