This Bachelor’s thesis examines the area of small- and medium-sized nuclear reactors and their roles in the early development of nuclear energy. The work covers current small- and medium-sized reactors in operation and considers future developments in this area. Included is an analysis of the possibilities for their use and applications in various areas of human activity. The work focuses on new projects of small- and medium-sized reactors, especially on projects considered for the near future. They are evaluated for nuclear weapons proliferation resistance, as well as their economic and technical advantages. Furthermore, an analysis was carried out of the possible uses of small reactors in propulsion of spaceships, and their use in various...