How it began
The plant was built in the science city of Obninsk in Kaluga Oblast, about 110 kilometers southwest of Moscow, at the Institute of Physics and Power Engineering. Construction started at the end of 1950. The reactor first reached criticality on 2 May 1954. At 5:30 pm on 26 June 1954 the plant was connected to an electricity grid to provide power to residences and businesses.
Before it existed
Electricity had first been generated from a nuclear reactor in 1951, by the Experimental Breeder Reactor I at the National Reactor Testing Station in Idaho. That reactor produced about 100 kilowatts, enough to power the equipment in its own small building, but it was not connected to a grid. Before Obninsk, nuclear energy had been developed for military purposes since the first chain reaction in 1942.
How it works
The plant had a single reactor, AM-1, named from the Russian for peaceful atom. It was a prototype that used a graphite moderator and water coolant, with uranium enriched to 5 percent. Its thermal output was 30 megawatts and it delivered about 5 megawatts of electricity, which the International Atomic Energy Agency describes as enough to power 2,000 homes.
What changed first
According to the International Atomic Energy Agency, the connection meant that nuclear energy had crossed the divide from military uses to civilian applications. For around four years Obninsk remained the only nuclear power reactor in the Soviet Union. Much of its work was experimental: an engineer who worked there recalled that the main task was to carry out studies on 17 test loops installed in the reactor.
What lasted
The technology tested in the Obninsk pilot plant was later used on a much larger scale in the RBMK reactors, of which AM-1 was a forerunner. The next Soviet plant connected to the grid, Beloyarsk Unit 1 in 1964, had a capacity of 100 megawatts. A typical nuclear power plant by 2004 produced about 1,000 megawatts, and nuclear power generated about 16 percent of the world's electricity. Obninsk itself was shut down on 29 April 2002 after 48 years of operation.
