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Google sheets offline mac12/9/2023 ![]() ![]() ![]() ![]() The larger portion of the total explosive yield in this design comes from the final fission stage fueled by uranium-238, producing enormous amounts of radioactive fission products. Such weapons are referred to as fission-fusion-fission weapons after the three consecutive stages of the explosion. In the case of a thermonuclear weapon uranium-238Ĭan be used to encase the fusion fuel, the high flux of very energetic neutrons from the resulting fusion reaction causes the uranium-238 to fission and adds energy to the yield of the weapon. As such, it increases the efficiency of the weapon and reduces the amount of critical mass required. A tamper which surrounds a fissile core works to reflect neutrons and add inertia to the compression of the plutonium charge. Most modern nuclear weapons utilize uranium-238 as a "tamper" material (see nuclear weapon design). This dilution, also called downblending, means that any nation or group that acquired the finished fuel would have to repeat the very expensive and complex enrichment and separation processes before assembling a weapon. Uranium-238 from depleted uranium and natural uranium is also used with recycled plutonium from weapons stockpiles for making mixed oxide fuel (MOX) which is now being redirected to become reactor fuel. Surplus highly-enriched uranium can be downblended with depleted uranium or natural uranium to turn it into low enriched uranium suitable for use in commercial nuclear fuel. The opposite of enriching is downblending. Uranium is about five times better as a gamma ray shield than lead, so a shield with the same effectivity can be packed into a thinner layer.ĭUCRETE, a concrete made with uranium dioxide aggregate instead of gravel, is being investigated as a material for dry cask storage systems to store radioactive waste. Both metallic depleted uranium and depleted uranium dioxide are being used as materials for radiation shielding. However, it is not as effective as ordinary water for stopping fast neutrons. Uranium-238 is also used as a radiation shield - its alpha radiation is easily stopped by the non- radioactive casing of the shielding and the uranium's high atomic weight and high number of electrons is highly effective in absorbing gamma rays and x-rays. This design is still in the early stages of development. The Clean And Environmentally Safe Advanced Reactor (CAESAR), a nuclear reactor concept that would use steam as a moderator to control delayed neutrons, will potentially be able to burn uranium-238 as fuel once the reactor is started with LEU fuel. Also, Japan's Monju breeder reactor is planned for restart, having been shut down since 1995, and both China and India have announced intentions to build breeder reactors. Russia has planned to build another unit, BN-800, at Beloyarsk nuclear power plant. Īs of December 2005, the only breeder reactor producing power is the 600-megawatt BN-600 reactor at the Beloyarsk Nuclear Power Station in Russia. ![]() Breeder technology has been used in several reactors. It has been estimated that there is anywhere from 10,000 to five billion years worth of uranium-238 for use in these power plants. Breeder reactors carry out such a process of transmutation to convert fertile isotopes such as uranium-238 into fissile plutonium. Uranium-238 is not usable directly as nuclear fuel however, it can be used as a source material for creating the element plutonium. In fact, in a typical nuclear reactor, up to a third of the generated power does come from the fission of plutonium-239, which is not supplied as a fuel to the reactor, but transmuted from uranium-238. In a nuclear reactor, uranium-238 can be used to breed plutonium-239, which itself can be used in a nuclear weapon or as a reactor fuel source. Reprocessed uranium is also mainly U-238, but contains significant quantities of uranium-236, and in fact all the isotopes of uranium between uranium-232 and uranium-238 except uranium-237. Depleted uranium consists mainly of the 238 isotope, and enriched uranium has a higher-than-natural quantity of the uranium-235 isotope. When hit by a neutron, it becomes uranium-239 (U-239), an unstable element which decays into neptunium-239 (Np-239), which then itself decays, with a half-life of 2.355 days, into plutonium-239 (Pu-239).Īround 99.284% of natural uranium is uranium-238, which has a half-life of 1.41 × 10 17 seconds (4.46 × 10 9 years, or 4.46 billion years). Uranium-238 (U-238), is the most common isotope of uranium found in nature. ![]()
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