3/16/2023 0 Comments Nuclear fission uranium bombReflector: a material such as beryllium that bounces neutrons back into the core to increase fission.Ĭore: made of metallic plutonium-239 or uranium-235, the most widely used “fissile” isotopes, so-called because of their natural property to split, or fission, when struck by a low energy (or “thermal”) neutron. Tamper: a dense metal such as natural uranium that holds the core together by inertia. High explosive: shaped charges made from materials such as HMX, RDX, and TATB. Implosion design Figure 1 – A schematic diagram of an implosion bomb similar to the one designed by Iraqįiring Set: a wiring system that sends a large electrical impulse to set off the detonators.ĭetonators: devices used to ignite the high explosive section of the weapon. Table 2 - Five psi radii for various yield nuclear weaponsġ. Table 1 - Effective lethal radii for nuclear weapons Underwater uranium, however, would be extremely costly to exploit.Learn about the steps and materials needed to make a nuclear weapon, a description of weapon designs, and a history of nuclear weapon tests. Uranium reserves which exist under the oceans are about a thousand times more abundant than the reserves found in high quality minerals on land. Plutonium 239 is highly fissile and can also be used as a nuclear fuel or an atomic explosive. After a few days, uranium 239 has transformed into plutonium 239, a radioisotope with a half-life of 24,000 years. What happens more frequently is that a neutron capture causes the nucleus to become unstable. Fission occurs comparatively rarely, and even under bombardment with energetic neutrons the probability of fission remains very low. The more abundant uranium 238 is sometimes called fertile. Highly sought-after, it can be used as a fuel in nuclear reactors and as an explosive in atomic bombs. IN2P3 Uranium 235 is the only natural nucleus that can easily undergo fission. The boundary between the uranium meant for civilian uses (LEU or low-enriched uranium) and that uranium meant for military use (HEU or highly-enriched uranium) is generally fixed at 20%. In order to have an atomic bomb, the uranium has to be enriched to above 90%. These reactors are powered by uranium which is enriched to have anywhere between 3 and 4% of uranium 235. It must be enriched before it can be used as a fuel in any commercial reactor. Natural uranium is poor in the fissile isotope, containing as it does only 0.70% of uranium 235. Certain uranium compounds (hexavalent ones) are highly soluble whereas others (tetravalent) are not.Īs a particularly heavy element, uranium isotopes are primarily alpha emitters, though these radiations are sometimes accompanied by gamma rays. Uranium can be found in the Earth crust at 3 parts per million, particularly in granite and volcanic rocks. PHILIPPE LESAGE/COGEMA From a chemical point of view, uranium belongs to the actinide family, a group of atoms whose properties are similar to those of actinium, the 89th element in Mendeleyev’s periodic table. The photograph above shows the ‘yellow cake’ on a filter at a treatment plant in Jouac (Haute-Vienne) at Limousin, France. This high concentration makes it much easier to transport the uranium from the mine to the factory. The concentrated uranium they are handling, also known as ‘Yellow Cake’, takes the form of a bright yellow powder containing about 750kg of uranium per tonne. The radioactivity of uranium is low, and so no particularly high standards of radioprotection are needed: as can be seen with the above workmen. They were all formed billions of years ago by the explosion of heavy stars (supernovae). The nuclei of uranium 235 and 238 are, along with those of thorium 232, the heaviest present in nature. Though both isotopes were at the time of Earth formation equally abundant, natural uranium today consists today of 99.3% uranium 238 and only 0.70% uranium 235. The half-life of uranium 238 is of 4.5 billion years, while uranium 235 has a half-life of ‘only’ 700 million years. HARRY GRUYAERT /MAGNUM /AREVAAll isotopes of uranium are unstable and radioactive, but uranium 238 and uranium 235 have half-lives which are sufficiently long to have allowed them to still be present in the Solar System and indeed on Earth. This high abundance, taken in conjunction with the difficult geological conditions and the harsh climate have made the extraction process an almost entirely automated one. Western Canada is particularly rich in uranium, with anywhere between 28 to 210 kilograms of uranium per tonne as opposed to the usual 3 grams per tonne found elsewhere. Athabasca plateau in Saskatchewan province, Canada.
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