The technology of modular high-Temperature nuclear reactors (VHTR), due to the high degree of safety and environmental friendliness, can provide a comprehensive supply of electricity and heat, as well as solve the actual problem of effective hydrogen generation. The purpose of this study is to analyze the possibility and prospects of using gas-cooled nuclear reactors in the energy area and primary production. In the article the algorithm of primary calculations of the main characteristics, such as: distribution of the neutron flux density in the reactor core (the volume of the nuclear reactor occupied by fuel elements) and the reflector along the radius; the critical radius of the nuclear reactor-the minimum radius of the reactor at which it supports a self-sustaining chain reaction of fuel nuclei; the volume of the nuclear reactor determined for the found critical radius of the reactor; the average density of the neutron flux in the volume of the nuclear reactor; macroscopic cross sections of the main interactions; average thermal power of a nuclear reactor. A comparative analysis of the results of the algorithm for different materials of fuel and reflector, as well as the percentage of fuel enrichment by the isotope of uranium-235 is made. As a result, it was found that the most suitable reflector is graphite because of its cost and safety as compared with beryllium. Uranium oxide is more effective than metallic uranium.