This work is devoted to the analysis of the methodology for calculating the dose of external radiation exposure to humans. In the course of the work, nuclear power facilities were investigated and the need for calculating radiation doses as a basis for ensuring radiation safety was determined. When solving the tasks, such research methods as system analysis, mathematical modelling, and calculation were used. The calculation of the functions of changes in internal radiation doses was carried out using the Matlab program. As a result of the work, the dependences of external radiation doses on time are obtained. The high processing speed and reliability of the data obtained allows the use of these methods in assessing the safe distance to nuclear power facilities for the living population. Also, the methods of calculating the dose of external radiation confirm their efficiency in the development of recommendations on radiation safety of the population.