Alexander Ilyich Leipunsky (7.12.1903-14.08.1972) was a Soviet physicist and an academician of the Academy of Sciences of the Ukrainian SSR (1934). He was born in the village of Dragli (now in the Polish People's Republic). He graduated from the Leningrad Polytechnic Institute (1926) and worked at the Leningrad Physico-Technical Institute, in 1929—41 at the Kharkov Physico-Technical Institute (director in 1932-37) and in 1941-52 as head of a department at the Institute of Physics of the Academy of Sciences of the Ukrainian SSR (director in 1944-49); from 1952 he was at the Institute of Physics and Power Engineering in Obninsk (scientific director of the institute from 1959) and at the same time, from 1946, head of a chair at the Moscow Engineering Physics Institute.
His research concerned atomic and nuclear physics and nuclear power engineering. In 1932, together with A. K. Walter, K. D. Sinelnikov and G. D. Latyshev, he was the first in the USSR to split the nucleus of lithium with artificially accelerated protons; in 1936 he gave the first indirect confirmation of the neutrino hypothesis from measurements of the energy of recoil nuclei in beta decay; and in 1939 he predicted the nuclear chain reaction. In 1946 — 48 he arrived at the idea of fast-neutron reactors, pointing out the physical features of a nuclear chain reaction on fast neutrons and the advantage of using liquid metals as coolants in fast reactors. He carried out wide-ranging research on the physics of fast reactors, which ended in methods of calculation and in the construction of a number of experimental fast-neutron reactors, in particular BR-1, BR-5 and BOR-60 (the Lenin Prize, 1960). In his last years he did much work on the creation of the first Soviet industrial fast-neutron power reactor, the BN-350, which combines the functions of a nuclear power station and a desalination plant for sea water.
Hero of Socialist Labour (1963). He founded a school of nuclear physicists.