![]() ![]() Because the fuel in a reactor is only three to four percent U-235, the reactor cannot explode like a nuclear bomb. However, to produce a large explosion, the uranium needs to be enriched to more than 50 percent U-235. This is the basics behind a nuclear weapon. If enough U-235 nuclei are close together, the process can accelerate, producing a lot of energy in a short time. Therefore, if a single U-235 nucleus fissions, the emitted neutrons can induce a fission in two or more U-235 nuclei, which each in turn can produce two or more, etc. However, U-235 can fission if a neutron hits it. The rate of U-235 spontaneous fission is very slow, too slow to be of any use in a nuclear reactor. In fact, radioactive decay of fission products produces about 7% of the heat in a nuclear reactor that has been operating for several months. Because the radiation has energy, it is also a source of heat in a nuclear reactor. Collectively, the beta particle and gamma rays are called radiation and this radiation has energy. In addition, when a fission product decays, the nucleus emits one or more gamma rays. A radioactive nucleus changes (decays) to another nucleus by emitting a particle for fission products, this is a beta particle, which is just a high speed electron. One aspect of the fission products, which was a major factor in the TMI accident, is that the fission products are radioactive. To have U-235 fission efficiently, the uranium fuel in a reactor is enriched the uranium goes through a process to increase the content of U-235 from 0.7% to 3 to 4%. The fission products and the neutrons have energy, which is the source of heat. The most important difference is that U-235 spontaneously splits, or fissions, producing two smaller nuclei (called fission products) plus two to five neutrons. Even though both U-238 and U-235 are uranium, they have different characteristics. However, not all uranium atoms have 146 neutrons 0.7% have 143, and these are called U-235. We call this number the mass number, and refer to these atoms as uranium-238, or just U-238. Most uranium atoms (99.3%) have a nucleus with 146 uncharged neutrons and 92 positively charged protons, for a total of 238 neutrons and protons. The fuel for a nuclear reactor is uranium, but not just any uranium. ![]() Although the basic process is simple, making it work is rather complicated.įirst, let’s look at the process of how nuclear fuel produces heat. In a nuclear plant the source of heat is a nuclear reactor. In fossil fuel plants the source of heat is burning coal, oil, or gas. The steam then turns a turbine, the turbine turns an electrical generator, and the generator produces electricity. To produce electricity, a power plant needs a source of heat to boil water which becomes steam. The only purpose of a nuclear power plant is to produce electricity.
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