Soviet Atomic Bomb
In the late 1930s and early 1940s many physicists already understood in general the atomic bomb should look like. The idea was to quickly concentrate in one place a certain amount (a critical mass) of fissionable materials by neutrons (with the emission of new neutrons) of the material. After that it will start an avalanche-like increase in the number of atoms decay - a chain reaction with the release of huge amounts of energy - an explosion. The problem was getting enough fissile material.
The only such substance naturally occurring in an acceptable amount of a uranium isotope with mass number (the total number in the nucleus of protons and neutrons) 235 (U-235). In natural uranium content of this isotope does not exceed 0.71% (99.28% uranium-238) to the same natural uranium content in the ore is at best 1%. Isolation of uranium-235 from natural uranium was quite a challenge. An alternative to uranium as soon became clear, was plutonium-239. In nature, it almost does not occur (it is 100 times less than U-235). Getting acceptable concentrations is possible in a nuclear reactor via neutron irradiation of uranium-238. The construction of such a reactor is another problem.
The third problem was that how it is possible to collect in one place the necessary mass of fissile material. In the course of even a very rapid convergence subcritical parts of them begin the fission reaction. The resultant energy release can not afford most of the atoms "participate" in the process of division, and they fly away before he could react.
In 1940 V.Shpinel and V.Maslov from Kharkiv Institute of Physics and Technology submitted an application for the invention of the atomic ammunition through the use of a chain reaction of spontaneous fission supercritical mass of uranium-235 which is formed of several sub-critical separated explosive impermeable to neutrons are destroyed by detonation (although the "performance" of the charge was highly questionable, evidence for the invention was received only in 1946). The Americans for their first bombs supposed to use the so-called cannon scheme. It actually used a gun barrel by means of which one of the subcritical fissile material shoots into another (it soon became clear that for plutonium, such a scheme is not suitable because of the lack of sufficient closing speed).
In 1937 the Radium Institute (Leningrad), the first cyclotron in Europe was launched. On November 25, 1938 decision of the Presidium of the Academy of Sciences (AS) of the USSR has created a permanent commission on the atomic nucleus. It includes S.Vavilov, A.Iofe, A.Alihanov, I.Kurchatov et al. (In 1940 they were joined by V.Hlopin and I.Gurevich). By this time the nuclear research carried out more than a dozen research institutes. In the same year at the Academy of Sciences of the USSR was formed by heavy water commission (later transformed to the Commission on Isotopes).
In September 1939, construction began on a powerful cyclotron in Leningrad, and in April 1940 it was decided to build a pilot plant for the production of about 15 kg of heavy water a year. But due to the outbreak of the war, these plans were not realized. In May 1940, Semenov, Y. Zeldovich, Yu.Khariton (Institute of Chemical Physics) proposed a theory of the development of a nuclear chain reaction in uranium. In the same year work was boosted by work on the search for new deposits of uranium ore.
On June 30, 1940, the Uranium Committee headed by Khlopin, with Vernadskiy and Ioffe as his associates, was created at the USSR Academy of Sciences. Among its members were academicians P.K. Kapitza, A.E. Fersman, I.V. Kurchatov, Y.B. Khariton, and others. But the actual start of the Soviet atomic project is considered to have happened on September 28, 1942, when the State Defense Committee (SDC) acknowledged the necessity of resuming the “research work for getting hold of nuclear energy” interrupted by the war.
The topmost issue was selecting a scientific supervisor for the project. This person must combine the talents of an outstanding scientist and organizer. There were several candidates, including eminent academicians. Ioffe insisted on appointing 39-year-old Kurchatov — he was confident in him. And he happened to be right.
In the USSR, every school student knew Kurchatov’s name. Igor Kurchatov, his associates, and the institute he created became a legend already in the 1950’s. It’s impossible to conceive how this person literally carried on his shoulders the entire Soviet atomic project. Igor Vasilyevich Kurchatov was an outstandingly educated scientist, which is why he was able to understand and solve the most complicated problems of the atomic power industry, encompassing the broadest range of areas of knowledge — chemistry, physics, geology, informatics. In essence, he was an interdisciplinary scientist, and this was a requirement for organizing a new atomic science.
Kurchatov combined his brilliant talent of an organizer with the widest scientific erudition, intuition, the gift of gathering real supporters and concentrating all efforts on reaching the most important objective of that time. This is generally an extremely rare phenomenon in world science. During the toughest war years, he created from scratch such a perfect science system, which handled the military task of building a nuclear weapon on an extremely tight schedule.
April 15, 1941 the Council of People's Commissars (SNK) issued a decree of of the building in Moscow a powerful cyclotron. But after the beginning of the Great Patriotic War almost all the work in the field of nuclear physics have been discontinued. Many nuclear physicists were at the front, or were diverted to other, as it seemed, more pressing issues.
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