Nuclear fission uranium fuel

Economic Aspects. The principal market for deuterium has been as a moderator for nuclear fission reactors fueled by unenriched uranium. The decline in nuclear reactor constmetion has sharply reduced the demand for heavy water. The United States has stopped large-scale production of D2O, and Canada is the only suppHer of heavy water at this time. Heavy water is priced as a fine chemical, and its price is not subject to market forces. 

In summary, a heavy-water-moderated nuclear fission reactor fueled with UO3 or U3O8 can be operated with natural uranium that is produced by means of a standard uranium wet chemistry solvent extraction purification process. Additionally, given the neutronic properties of other elements, it is expected that similar reactors can be operated with uranium carbide, uranium tetrafluoride, and uranium-beryllium alloys. 

Uranium is converted by CIF, BiF, and BrP to UF. The recovery of uranium from irradiated fuels has been the subject of numerous and extensive investigations sponsored by atomic energy agencies in a number of countries (55—63). The fluorides of the nuclear fission products are nonvolatile hence the volatile UF can be removed by distiUation (see Nuclearreactors Uraniumand uranium compounds). 

The only large-scale use of deuterium in industry is as a moderator, in the form of D2O, for nuclear reactors. Because of its favorable slowing-down properties and its small capture cross section for neutrons, deuterium moderation permits the use of uranium containing the natural abundance of uranium-235, thus avoiding an isotope enrichment step in the preparation of reactor fuel. Heavy water-moderated thermal neutron reactors fueled with uranium-233 and surrounded with a natural thorium blanket offer the prospect of successful fuel breeding, ie, production of greater amounts of (by neutron capture in thorium) than are consumed by nuclear fission in the operation of the reactor. The advantages of heavy water-moderated reactors are difficult to assess. 

Nuclear fission is also involved in nuclear weapons. To create a bomb, the concentration of the isotope uranium-235 must be increased to at least 85 percent from its natural concenti ation of only 0.7 percent. This increase ot concentration is difficult and expensive. In a typical nuclear reactor the uranium-235 concentration in the fuel is only 3 to 4 percent, and hence a nuclear reactor cannot explode like a bomb. In a nuclear bomb... 

Canada, are examples. These reactors do not use ordinai y water for the moderator. Most nuclear fission reactors use ordinaiy water for a moderator which requires that the fuel he about 3 percent and about 97 percent U. Achieving this enrichment requires that the solid uranium compounds in the yellow cake be converted to gaseous uranium hexafluoride (UF,). Following enrichment, gaseous UF is converted to solid uranium oxide (UO,) for fabrication of fuel elements for a nuclear reactor. 

Induced nuclear fission is fission caused by bombarding a heavy nucleus with neutrons (Fig. 17.23). The nucleus breaks into two fragments when struck by a projectile. Nuclei that can undergo induced fission are called fissionable. For most nuclei, fission takes place only if the impinging neutrons travel so rapidly that they can smash into the nucleus and drive it apart with the shock of impact uranium-238 undergoes fission in this way. Fissile nuclei, however, are nuclei that can be nudged into breaking apart even by slow neutrons. They include uranium-235, uranium-233, and plutonium-239—the fuels of nuclear power plants. 

Fluidized-bed CVD was developed in the late 1950s for a specific application the coating of nuclear-fuel particles for high temperature gas-cooled reactors. PI The particles are uranium-thorium carbide coated with pyrolytic carbon and silicon carbide for the purpose of containing the products of nuclear fission. The carbon is obtained from the decomposition of propane (C3H8) or propylene... 

Nuclear fission power plants were at one time thought to be the answer to diminishing fossil fuels. Although the enriched uranium fuel was also limited, an advanced nuclear reactor called breeders would be able to produce more radioactive fuel, in the form of plutonium, than consumed. This would make plutonium fuel renewable. Although plutonium has been called one of the most toxic elements known, it is similar to other radioactive materials and requires careful handling since it can remain radioactive for thousands of years. 

Fissile materials are defined as materials that are fissionable by nentrons with zero kinetic energy. In nuclear engineering, a fissile material is one that is capable of snstaining a chain reaction of nuclear fission Nuclear power reactors are mainly fueled with manium, the heaviest element that occurs in natnre in more than trace qnantities. The principal nuclear energy soiuces are maninm-235, plutonium-239, uranium-233 and thorium. 

The lanthanide elements are very difficult to separate because of their highly similar chemistry, but the earlier actinide elements have sufficiently different redox chemistry to allow easy chemical separations. This is important in the nuclear power industry, where separations have to be made of the elements produced in fuel rods of nuclear power stations as fission products, and of the products Np and Pu, which arise from the neutron bombardment of the uranium fuel. 

Deriving electrical energy from nuclear fission produces almost no atmospheric pollutants, such as carbon dioxide, sulfur oxides, nitrogen oxides, heavy metals, and airborne particulates. Although not discussed in the text, there is also an abundant supply of fuel for nuclear fission reactors in the form of plutonium-239, which can be manufactured from uranium-238. Use the keyword Breeder Reactor on your Internet search engine to learn about how this is so. 

No The worst-case scenario for a nuclear power plant is the meltdown, which occurs as an uncooled nuclear reactor gets so hot that it melts to the floor of the containment building. Nuclear fuel is enriched with fissionable uranium-235 to at most 4 percent. The remainder of the fuel is nonfissionable uranium-238. As discussed in Chapter 4, to build a nuclear bomb, uranium-235 must be enriched to over 90 percent. 

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