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Nuclear Power Information: Fuel Preparation.Nuclear Power Information: Uranium ore deposits consist mainly of the stable isotope Uranium 238, which is shortened to U-238. with less than 1% of the Uranium being of the fissile, or splittable, isotope U-235. The fuel rods used in nuclear reactors need about 5% U-235, so the basic ore that is mined needs to be refined. The Uranium is converted into Uranium Hexafluoride (UF6) which can then be separated into its U-235 and U-238 components by passing the compound through a series of filters. The U-235 hexafluoride is lighter and therefore travels slightly faster allowing it to be purified out of the U-238 to an acceptable degree. The U-238 that is left over from the refining process, or that is left over after the fuel rods in the nuclear reactor are used up, is not wasted. It is put through a process called enrichment where it is converted into a different fissile material, Plutonium. Nuclear Power Information: Uranium Enrichment When bombarded with neutrons, U-238 captures one of these into its nucleus and becomes the heavier U-239 isotope. Uranium 239 is element 92, meaning it has 92 protons and 147 neutrons.
This undergoes two successive decays, both of which emit an electron from the nucleus (this is called beta decay). This happens when a neutron, which has no overall charge, splits into a proton (+) and an electron (-) with additional energy also being lost. In short, beta decay is illustrated to the right.If we apply this to one of the neutrons in the core of U-239 turns into a proton; the electron is lost. This means that while the number of particles in the nucleus does not change, the number of protons has gone up by one and the number of neutrons has gone down by one. Since the resulting nucleus now has 93 protons, it is a different element, Neptunium-239. This process of beta decay is repeated again with the Neptunium to give Plutonium-239. This product is fissile and so is ideal for use in either nuclear reactors or weapons. It produces the same kind of chain reaction as does U-235.
Plutonium sourced through this process is usually contaminated with another Plutonium isotope, Pt-240. This is highly unstable and so difficult to control. The higher the grade of Plutonium, the more Pt-239 and the less Pt-240 it has. Lower grades can be used in electricity generation, but the higher grades are best suited to nuclear weapon use. This is why Plutonium enrichment equipment is seen by the International Atomic Energy Agency as a possible indicator of nuclear weapon production. Nuclear Power Information: Fuel Preparation. Return from Nuclear Power Information: Fuel Preparation to Fossil Fuels or return to the Green Planet home page for more Solar Power Facts
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