Igor Kurchatov and his apprentice Georgy Flyorov discovered the basic ideas of the uranium chain reaction and the nuclear reactor concept in the 1930s. In 1942 Kurchatov declared: "At breaking up of kernels in a kilogram of uranium, the energy released must be equal to the explosion of 20,000 tons of trotyl." This announcement was practically verified during the atomic bombing of Hiroshima.
When war broke out between Germany and the USSR in 1941, Kurchatov switched his research first to protecting shipping from magnetic mines, and later to tank armour. In 1943 the NKVD obtained a copy of a secret British report by the MAUD Committee concerning the feasibility of atomic weapons, which led Stalin to order the commencement of a Soviet nuclear programme (albeit with very limited resources). Ioffe recommended Kurchatov to Molotov, and Kurchatov was appointed director of the nascent programme later that year.
The Soviet atomic bomb project remained a relatively low priority until information from spy Klaus Fuchs and later the destruction of Hiroshima and Nagasaki goaded Stalin into action. Stalin ordered Kurchatov to produce a bomb by 1948, and put the ruthless Lavrenty Beria in direct command of the project. The project took over the town of Sarov in the Gorki Oblast (now Nizhny Novgorod Oblast) on the Volga, and renamed it Arzamas-16. The team (which included other prominent Soviet nuclear scientists such as Julii Borisovich Khariton and Yakov Borisovich Zel'dovich) was assisted both by public disclosures made by the U.S. government and by further information supplied by Fuchs, but Kurchatov and Beria (fearing the intelligence was misinformation) insisted his scientists retest everything themselves. Beria in particular would use the intelligence as a third-party check on the conclusions of the teams of scientists.
On August 29, 1949 the team detonated First Lightning, its initial test device (a plutonium implosion bomb) at the Semipalatinsk Test Site. Kurchatov later remarked that his main feeling at the time was one of relief, as he was confident that had the weapon failed, Stalin would have had him shot.
Kurchatov subsequently worked on the Soviet hydrogen bomb program (1953), but later worked for the peaceful use of nuclear technology, and advocated against nuclear bomb tests.
Among the projects held under Kurchatov were the first cyclotron in Moscow (1949), the first Atomic Reactor in Europe (1946), the first industrial Nuclear power plant in the world (1954), the first Nuclear reactor for Submarines in the world (1959), Nuclear Icebreakers (Lenin, both the world's first nuclear powered surface ship and the first nuclear powered civilian vessel, 1959).
During the A-bomb programme, Kurchatov swore he wouldn't cut his beard until the program succeeded, and he continued to wear a large beard (often cut into eccentric styles) for the remainder of his life, earning him the nickname "The Beard". Kurchatov died in Moscow in 1960 of a blood clot in his brain, and his ashes were buried in the Kremlin Wall Necropolis on Red Square. Two towns bear his name: Kurchatov Township, the headquarters of the STS, and Kurchatov near Kursk (the site of a nuclear power station). The Kurchatov crater on the Moon and the asteroid 2352 Kurchatov are also named after him.