Co-discoverer of spontaneous fission, a pillar of the Soviet atomic project
After they removed the neutron source, their ionization chamber kept firing. To rule out cosmic rays, they hauled the apparatus 50 meters underground into Moscow's Dinamo metro station, where the signal persisted: uranium fissions all by itself.
Soviet nuclear physicist. In 1940, together with Georgy Flyorov, he discovered the spontaneous fission of uranium-235, a finding that established the scientific foundation for the Soviet atomic bomb project. Drafted into the Red Army in 1941 and recalled to Kazan in 1942, he developed the associated-particle method for measuring neutron source yields and created express techniques for plutonium detection under Kurchatov. In 1947 he founded the neutron physics and nuclear fission laboratory at the Khlopin Radium Institute, which he led for nearly four decades, and in 1949 he established the nuclear physics department at the Lensovet Technological Institute, training generations of Soviet nuclear engineers.
Activities and affiliations
Career Timeline
- 1919–1928Porcelain and glass painter, Malaya Vishera glass factory
- 1931–1936Leningrad State University, Physics Faculty; diploma supervised by Igor Kurchatov
- 1936–1941Postgraduate researcher, Khlopin Radium Institute (RIAN), under Kurchatov and Khlopin
- 1940Co-discovered spontaneous fission of uranium with Flyorov (USSR State Discovery No. 33)
- 1941–1942Served in Red Army, lieutenant; recalled to Kazan for the atomic bomb project
- 1947–1986Founded and headed the Neutron Physics and Nuclear Fission Laboratory, RIAN
- 1949–1984Founded and chaired the Nuclear Physics Department, Lensovet Technological Institute
- 1948Awarded Doctor of Physical and Mathematical Sciences
Related historical events
- 1941–1945The Great Patriotic WarRed Army lieutenantHe served as a lieutenant in the Red Army from 1941 to 1942.
- 1943–1949The Soviet Atomic ProjectPhysicist whose discovery of spontaneous fission laid the foundation for the atomic bomb projectIn 1940, together with Flyorov, he discovered the spontaneous fission of uranium, and later co-signed a letter to Stalin urging nuclear research.
The Lensovet Institute Research School and Precision Fission Measurements, 1949-1990s
In 1949 Petrzhak founded the engineering physicochemistry faculty at the Leningrad Lensovet Technological Institute (LTI), and until 1974 he headed one of its three departments, nuclear physics. The new faculty was meant to supply engineering personnel for the then-infant atomic industry, and the nuclear physics department was charged with teaching nuclear physics, radioactivity, the interaction of ionizing radiation with matter and nuclear electronics inside a chemical institute. The department also influenced the scientific and teaching standards of the faculty's other chairs, and hundreds of graduates passed through it.
With the commissioning of a 15 MeV betatron at the LTI in 1952-1953, departmental research entered a new phase. Under Petrzhak's direction, staff and students measured the photofission product yields of uranium-238 and thorium-232 and studied the delayed neutrons emitted in the photofission of uranium-235 and plutonium-239. Those results entered nuclear data handbooks and long served as the photofission characteristics of those nuclides. In 1961 he organized a problem laboratory of nuclear power engineering attached to his department, widening its research range.
From the late 1960s into the early 1990s, Petrzhak and his staff carried out a large programme of precision absolute measurements of the fission cross sections of key nuclides of the nuclear fuel cycle, for fixed-energy neutrons and for neutrons of the californium-252 fission spectrum. In 1995, as part of work on a concept for transmuting spent nuclear fuel, precision measurements began of the prompt neutron spectra of minor actinides; he took part in preparing the first projects in that field and remained involved as a consultant until the last days of his life. He trained dozens of candidates and doctors of sciences at the institute, and his research results were set out in more than 300 publications.