On June 27, 1954, the Obninsk Nuclear Power Plant, located near the city of Obninsk in the Russian Soviet Federative Socialist Republic, began operation and supplied electricity to the local grid. Built under the auspices of the Soviet Academy of Sciences, the plant’s AM-1 (Atom Mirny) reactor produced about 5 megawatts thermal and about 5 megawatts electrical for demonstration and research purposes. Its start-up represented the first instance of a nuclear reactor delivering electricity to a public grid on a sustained, organized basis rather than solely powering experimental equipment or a ship. Design and Purpose The Obninsk facility was intended primarily as a research and demonstration reactor rather than a large-scale commercial station. Its design combined features of early test reactors with practical systems for heat removal and electricity generation. The reactor used enriched uranium as fuel and a water-cooled, graphite-moderated core. Engineers and scientists at the institute sought to demonstrate that controlled nuclear fission could be harnessed safely for peaceful electricity production, provide operational experience, and study reactor behavior under real-world conditions. Construction and Context Construction began in the late 1940s and early 1950s amid the broader postwar expansion of nuclear research in several countries. The Soviet program emphasized both military and civilian nuclear technology; Obninsk was presented domestically and internationally as a peaceful application of atomic energy. At the time, reactors in other countries existed for research or propulsion tests, but Obninsk is widely recognized in historical records as the first reactor to feed a power grid with electricity on a continuing basis. Operation and Legacy Obninsk operated in various modes over subsequent years, serving as a testbed for reactor components, fuel assemblies and operational procedures. While its electrical output was small by later standards, the plant provided important data and experience that informed the design of larger civil reactors. It remained in operation into the 1950s and 1960s and was officially shut down in 2002; parts of the site have since been preserved as a museum and historical complex. Historical Significance and Disputed Claims Historians and technical sources generally identify Obninsk as the first nuclear power plant to supply electricity to a grid for civilian use. There are related milestones often noted alongside Obninsk: earlier reactors had produced electricity in laboratory conditions or powered specific equipment (for example, experiments in the United States and the United Kingdom), and the U.S. Shippingport Atomic Power Station later became one of the first large-scale commercial plants. When discussing “firsts,” distinctions matter—between the first sustained grid supply, the first to power a city, the first commercial-scale plant, or first on a naval vessel—and Obninsk’s claim is specifically to having been the first to connect a nuclear reactor’s output to a public electricity grid for demonstration and research in 1954. Safety and Public Perception At the time, public information about reactor safety and environmental impacts was limited, especially in the Soviet context. The Obninsk project was framed as peaceful scientific progress and helped pave the way for broader civil nuclear programs. Technical and operational lessons learned there contributed to reactor design, training of personnel, and regulatory thinking in subsequent decades. Conclusion Obninsk’s start-up on June 27, 1954, is a well-documented milestone in the history of nuclear energy: a small research reactor that became the first to supply electricity to a public grid, demonstrating the feasibility of civilian nuclear power and influencing subsequent developments worldwide.