Chain reaction, nuclear first controlled

Controlled Nuclear Chain Reaction The First 50 Years, American Nuclear Society, La Grange Park, lU., 1992. 

Shortly after Japan s December 7,1941 attack on Pearl Harbor, the U.S. became more driven to expedite its timetable for developing the first fission weapon because of fear that the U.S. lagged behind Nazi Germany in efforts to create the first atomic bomb. On December 2, 1942 at 3 49 p.m., Enrico Fermi and Samuel K. Allison achieved the world s first controlled, self-sustained nuclear chain reaction in an experimental reactor using natural uranium and graphite. 

Because the isotope uranium-235 is fissionable, meaning that it produces free neutrons that cause other atoms to split, it generates enough free neutrons to make it unstable. When the unstable U-235 reaches a critical mass of a few pounds, it produces a self-sustaining fission chain reaction that results in a rapid explosion with tremendous energy and becomes a nuclear (atomic) bomb. The first nuclear bombs were made of uranium and plutonium. Today, both of these fuels are used in reactors to produce electrical power. Moderators (control rods) in nuclear power reactors absorb some of the neutrons, which prevents the mass... 

One day as the Italian physicist Enrico Fermi and George Uhlenbeck (who had come to the United States on a visit) were looking out a window overlooking Manhattan, Fermi remarked, You realize, George, that one small fission bomb could destroy most of what we see outside Fermi was soon to be doing some of the preliminary experimental work that preceded the American atomic bomb project. It was Fermi who produced the first controlled nuclear chain reaction. 

In 1942, Enrico Fermi demonstrated the first controlled chain reaction in the Fermi reactor, and that was shortly followed in 1945 by the start-up of the Soviet uranium-graphite reactor in Moscow. The enthusiasm for nuclear energy in 1950s was so great that scientists would say that nuclear is too cheap to meter . 

Compacted UO2 was used in the assembly of the first nuclear exponential lattice in July 1941. The first self-sustaining controlled nuclear chain reaction was achieved in the CP-1 uranium-graphite reactor on December 2, 1942, using 32,652 kg (36 tons) of uranium oxide (both UO2 and UsOs), as well as uranium metal. 

Fermi, Enrico. (1901-1954). An Italian physicist who later became a U.S. citizen. He developed a statistical approach to fundamental problems of physical chemistry based on Pauli s exclusion principle. He discovered induced or artificial radioactivity resulting from neutron impingement, as well as slow or thermal neutrons. He was professor of physics at Columbia (1939) and awarded the Nobel Prize in physics in 1938. He was the first to achieve a controlled nuclear chain reaction, directed the construction of the first nuclear reactor at the University of Chicago (1942), and worked on the atomic bomb at Los Alamos. He also carried on fundamental research on subatomic particles using sophisticated statistical techniques. Element 100 (fermium) is named after him. 

The first major step in developing usable, controllable nuclear power took place on December 2,1942, in a squash court underneath an unused football field at the University of Chicago. It was there that Enrico Fermi, an Italian physicist, successfully carried out a sustained and controlled fission chain reaction. 

These experiments gave direct evidence of an explosive chain reaction. They gave an energy production of up to twenty million watts, with a temperature rise in the hydride up to 2 C per millisecond. The strongest burst obtained produced 10 neutrons. The dragon is of historical importance. It was the first controlled nuclear reaction which was supercritical with prompt neutrons alone. 

Controlled nuclear chain reaction (Enrico Fermi) In 1926 Fermi helped develop Fermi-Dirac statistics, which describe the quantum behavior of groups of electrons, protons, or neutrons. He now produces the first sustained nuclear chain reaction. 

History s first critical chain reaction was carried out in an atomic pile, which was literally a stack or pile of uranium-containing graphite blocks and blocks of pure graphite that served as a neutron moderator (see I Figure 10.11). The pile was constructed in a squash court beneath the stands of an athletic fieldhouse at the University of Chicago, and the experiments were carried out by a team of scientists led by Italian physicist Enrico Fermi. In December 1942, the team observed that nuclear reactions in the pile had become self-sustaining, or critical. The control rods, composed of strong neutron absorbers, were pushed into the pile to stop the reaction. 

The first two chapters serve as an introduction to the basic physics of the atom and the nucleus and to nuclear fission and the nuclear chain reaction. Chapter 3 deals with the fundamentals of nuclear reactor theory, covering neutron slowing down and the spatial dependence of the neutron flux in the reactor, based on the solution of the diffusion equations. The chapter includes a major section on reactor kinetics and control, including temperature and void coefficients and xenon poisoning effects in power reactors. Chapter 4 describes various aspects of fuel management and fuel cycles, while Chapter 5 considers materials problems for fuel and other constituents of the reactor. The processes of heat generation and removal are covered in Chapter 6. 

The second paper of 1940 [3 ], entitled Kinetics of Uranium Chain Decay, is no less significant than the first. This pioneering work yielded a whole series of brilliant results for the first time, the need to take into account the role of delayed neutrons in the kinetics of chain nuclear reactions was shown (it is precisely the delayed neutrons which ensure easy control of nuclear reactors), the influence of heating on the kinetics of a chain process was considered in detail, and a number of conclusions were reached which are of much importance for the theory of reactor control. This same paper predicted the formation in the process of chain fission of new, previously unknown, nuclei which strongly absorb neutrons, a prediction which was later fully confirmed. 

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