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Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. The use of the nuclides produced is varied. The largest variety is used in research. By tonnage, separating natural uranium into enriched uranium and depleted uranium is the largest application. In the following text, mainly the uranium enrichment is considered. This process is crucial in the manufacture of uranium fuel for nuclear power plants, and is also required for the creation of uranium-based nuclear weapons. Plutonium-based weapons use plutonium produced in a nuclear reactor, which must be operated in such a way as to produce plutonium already of suitable isotopic mix or grade. While different chemical elements can be purified through chemical processes, isotopes of the same element have nearly identical chemical properties, which makes this type of separation impractical, except for separation of deuterium.
Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238, uranium-235, and uranium-234. 235U is the only nuclide existing in nature that is fissile with thermal neutrons.
Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
Yellowcake is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before fuel fabrication or uranium enrichment. Yellowcake concentrates are prepared by various extraction and refining methods, depending on the types of ores. Typically, yellowcakes are obtained through the milling and chemical processing of uranium ore, forming a coarse powder that has a pungent odor, is insoluble in water, and contains about 80% uranium oxide, which melts at approximately 2880 °C.
The vortex tube, also known as the Ranque-Hilsch vortex tube, is a mechanical device that separates a compressed gas into hot and cold streams. The gas emerging from the hot end can reach temperatures of 200 °C (390 °F), and the gas emerging from the cold end can reach −50 °C (−60 °F). It has no moving parts and is considered an environmentally friendly technology because it can work solely on compressed air and does not use Freon.
A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centrifugal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of uranium-235 (235U) from uranium-238 (238U). The gas centrifuge was developed to replace the gaseous diffusion method of uranium-235 extraction. High degrees of separation of these isotopes relies on using many individual centrifuges arranged in series, that achieve successively higher concentrations. This process yields higher concentrations of uranium-235 while using significantly less energy compared to the gaseous diffusion process.
Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride (UF6) through semipermeable membranes. This produces a slight separation between the molecules containing uranium-235 (235U) and uranium-238 (238U). By use of a large cascade of many stages, high separations can be achieved. It was the first process to be developed that was capable of producing enriched uranium in industrially useful quantities, but is nowadays considered obsolete, having been superseded by the more-efficient gas centrifuge process.
A calutron is a mass spectrometer originally designed and used for separating the isotopes of uranium. It was developed by Ernest Lawrence during the Manhattan Project and was based on his earlier invention, the cyclotron. Its name was derived from California University Cyclotron, in tribute to Lawrence's institution, the University of California, where it was invented. Calutrons were used in the industrial-scale Y-12 uranium enrichment plant at the Clinton Engineer Works in Oak Ridge, Tennessee. The enriched uranium produced was used in the Little Boy atomic bomb that was detonated over Hiroshima on 6 August 1945.
Atomic vapor laser isotope separation, or AVLIS, is a method by which specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions. A similar technology, using molecules instead of atoms, is molecular laser isotope separation (MLIS).
From the 1960s to the 1990s, South Africa pursued research into weapons of mass destruction, including nuclear, biological, and chemical weapons under the apartheid government. Six nuclear weapons were assembled. South African strategy was, if political and military instability in Southern Africa became unmanageable, to conduct a nuclear weapon test in a location such as the Kalahari desert, where an underground testing site had been prepared, to demonstrate its capability and resolve—and thereby highlight the peril of intensified conflict in the region—and then invite a larger power such as the United States to intervene.
An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from other rotating compressors such as centrifugal compressor, axi-centrifugal compressors and mixed-flow compressors where the fluid flow will include a "radial component" through the compressor. The energy level of the fluid increases as it flows through the compressor due to the action of the rotor blades which exert a torque on the fluid. The stationary blades slow the fluid, converting the circumferential component of flow into pressure. Compressors are typically driven by an electric motor or a steam or a gas turbine.
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233. Plutonium-239 has a half-life of 24,110 years.
Molecular laser isotope separation (MLIS) is a method of isotope separation, where specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions of uranium hexafluoride molecules. It is similar to AVLIS. Its main advantage over AVLIS is low energy consumption and use of uranium hexafluoride instead of vaporized uranium.
Separation of isotopes by laser excitation (SILEX) is a process for isotope separation that is used to produce enriched uranium using lasers. It was developed in the 1990s, based on earlier technologies.
The South African Nuclear Energy Corporation (Necsa) was established as a public company by the Republic of South Africa Nuclear Energy Act in 1999 and is wholly owned by the State. The name is correctly indicated above, although the sequence of letters in the acronym may be taken as suggesting that the name should be the "Nuclear Energy Corporation of South Africa".
The Valindaba site, also known as Pelindaba East or Y-plant, was an experimental uranium enrichment plant, located 35 km west of Pretoria, Gauteng province, South Africa. Valindaba is a Zulu word that means "about this we do not speak at all". The plant's name is consistent with the South African government's policy of official secrecy that concealed the plant's role in nuclear weapons production.
A radial turbine is a turbine in which the flow of the working fluid is radial to the shaft. The difference between axial and radial turbines consists in the way the fluid flows through the components. Whereas for an axial turbine the rotor is 'impacted' by the fluid flow, for a radial turbine, the flow is smoothly orientated perpendicular to the rotation axis, and it drives the turbine in the same way water drives a watermill. The result is less mechanical stress which enables a radial turbine to be simpler, more robust, and more efficient when compared to axial turbines. When it comes to high power ranges the radial turbine is no longer competitive and the efficiency becomes similar to that of the axial turbines.
The Zippe-type centrifuge is a gas centrifuge designed to enrich the rare fissile isotope uranium-235 (235U) from the mixture of isotopes found in naturally occurring uranium compounds. The isotopic separation is based on the slight difference in mass of the isotopes. The Zippe design was originally developed in the Soviet Union by a team led by 60 Austrian and German scientists and engineers captured after World War II, working in detention. In the West the type is known by the name of the man who recreated the technology after his return to the West in 1956, based on his recollection of his work in the Soviet program, Gernot Zippe. To the extent that it might be referred to in Soviet/Russian usage by any one person's name, it was known as a Kamenev centrifuge.
Project-706, also known as Project-786 was the codename of a research and development program to develop Pakistan's first nuclear weapons. The program was initiated by Prime Minister Zulfiqar Ali Bhutto in 1974 in response to the Indian nuclear tests conducted in May 1974. During the course of this program, Pakistani nuclear scientists and engineers developed the requisite nuclear infrastructure and gained expertise in the extraction, refining, processing and handling of fissile material with the ultimate goal of designing a nuclear device. These objectives were achieved by the early 1980s with the first successful cold test of a Pakistani nuclear device in 1983. The two institutions responsible for the execution of the program were the Pakistan Atomic Energy Commission and the Kahuta Research Laboratories, led by Munir Ahmed Khan and Abdul Qadeer Khan respectively. In 1976 an organization called Special Development Works (SDW) was created within the Pakistan Army, directly under the Chief of the Army Staff (Pakistan) (COAS). This organization worked closely with PAEC and KRL to secretly prepare the nuclear test sites in Baluchistan and other required civil infrastructure.
The Siberian Chemical Combine was established in 1953 in Tomsk-7 now known as Seversk, in the Tomsk Region as a single complex of the nuclear technological cycle for the creation of nuclear weapons components based on fissile materials. It is a subsidiary of TVEL.
References
- ↑ Farmelo, Graham (2009). The Strangest Man: The Hidden Life of Paul Dirac . New York: Basic Books. pp. 248-9, 307, 311, 313–4, 321, 431. ISBN 978-0-465-02210-6.
- ↑ de Villiers, J. W.; Jardine, Roger; Reiss, Mitchell (1993). "Why South Africa Gave up the Bomb". Foreign Affairs. 72 (5): 98–109. doi:10.2307/20045817. ISSN 0015-7120. JSTOR 20045817.