![]() ![]() Through beta disintegration, Xenon-133 and the like, which are nuclear fission products, disintegrate into Cesium-133, and Cesium-133 then turns into Cesium-134 as decelerated neutrons are trapped.Īs long as the reactor is working properly, these products remain in nuclear fuel rods and do not leak out of the reactor. When Uranium-238 is bombarded with neutrons, Plutonium-239 is created.Ĭesium-134 is not created directly from the nuclear fission of Uranium-235. ![]() Radioactive nuclear fission products such as Iodine-131, Cesium-137, and Strontium-90 are created in this process. Bombarding enriched uranium fuel (Uranium-235: 3-5% Uranium-238: 95-97%) with neutrons results in nuclear fission. In contrast, a coal power station of equivalent size requires more than two and a half million tonnes of coal to produce as much electricity.The light-water nuclear reactor is currently the most widely used type of reactor around the world (also used at Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi NPS). Nuclear fuel in its powder and pellet form (Image: Urenco)Ībout 27 tonnes of uranium – around 18 million fuel pellets housed in over 50,000 fuel rods – is required each year for a 1000 MWe pressurized water reactor. Once loaded, the fuel normally stays in the reactor core for several years. The number of fuel rods used to make each fuel assembly ranges from around 90 to well over 200, depending on the type of reactor. The pellets are subsequently inserted into thin tubes known as fuel rods, which are then grouped together to form fuel assemblies. This powder is then pressed to form small fuel pellets and heated to make a hard ceramic material. The enriched uranium is transported to a fuel fabrication plant where it is converted to uranium dioxide powder. The centrifuges separate the uranium into two streams: one stream is enriched in uranium-235 the other consists of ‘tails’ containing a lower concentration of uranium-235, and known as depleted uranium (DU).Ī bank of centrifuges at an enrichment plant (Image: Urenco) The making of nuclear fuel The uranium hexafluoride is fed into centrifuges, with thousands of rapidly-spinning vertical tubes that separate uranium-235 from the slightly heavier uranium-238 isotope. This is achieved through a process called conversion, where uranium oxide is converted to a different compound (uranium hexafluoride) which is a gas at relatively low temperatures. The enrichment process requires the uranium to be in a gaseous form. This increases the uranium-235 concentration from 0.7% to between 3% and 5%, which is the level used in most reactors.Ī small number of reactors, most notably the CANDU reactors from Canada, are fuelled with natural uranium, which does not have to be enriched. The vast majority of nuclear power reactors use the isotope uranium-235 as fuel however, it only makes up 0.7% of the natural uranium mined and must therefore be increased through a process called enrichment. ‘Yellowcake’ – one of the first steps towards making nuclear fuel (Image: Kazatomprom) Enrichment The uranium solution from the mines is then separated, filtered and dried to produce uranium oxide concentrate, often referred to as ‘yellowcake’. The uranium solution is then pumped to the surface. Water injected with oxygen (or an alkali, acid or other oxidizing solution) is circulated through the uranium ore, extracting the uranium. However, over half of the world's uranium mines now use a method called in-situ leaching, where the mining is accomplished without any major ground disturbance. The slurry is leached with sulfuric acid or an alkaline solution to dissolve the uranium, leaving the remaining rock and other minerals undissolved. After mining, the ore is crushed in a mill, where water is added to produce a slurry of fine ore particles and other materials. open pit or underground) were the main source of uranium. ![]() Uranium mines operate in many countries, but more than 85% of uranium is produced in six countries: Kazakhstan, Canada, Australia, Namibia, Niger, and Russia. Uranium is found in small amounts in most rocks, and even in seawater. Nuclear fuel pellets, with each pellet – not much larger than a sugar cube – contains as much energy as a tonne of coal (Image: Kazatomprom) The mining of uranium In order to make the fuel, uranium is mined and goes through refining and enrichment before being loaded into a nuclear reactor. Uranium is the main fuel for nuclear reactors, and it can be found in many places around the world. ![]()
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