My career 238
August 20, 2022
Uranium 238 (238U or U-238) is the most common isotope of uranium found in nature, accounting for about 99.284% of the mass of uranium. There are two parent isotopes of uranium 238, 242Pu and 238Pa. The parent isotope 242Pu, when α decays, produces a daughter isotope 238U. And the parent isotope 238Pa when decaying β- also produces 238U. Uranium 238 has 146 neutrons and 92 protons. Its isotope mass is 238.05078826 u. Unlike uranium-235, it is not fissile, which means it cannot sustain a chain reaction in a thermal neutron reactor. However, it is fissionable by fast neutrons, and is fertile, meaning it can be converted to fissile plutonium-239.238 U cannot support a chain reaction because of inelastic scattering. Recovery reduces neutron energy below the range where rapid fission of one or more next-generation nuclei can occur. Doppler expansion of U-238's neutron absorption resonance, which increases absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control. Approximately 99.286% of the mass of natural uranium is uranium-238, which has a half-life of 1.41 × 10 17 seconds (4.468 × 10 9 years, or 4.468 billion years). Due to its natural abundance and half-life compared to other radioactive elements, 238 U produces ~40% of the radioactive heat generated in the Earth. The 238U decay contributes 6 antineutrino electrons per decay (1 beta decay), resulting in a large geoneutrino signal that can be detected as decay occurs within the Earth. >The decay of 238 U isotopes to near isotopes is widely used in radiometric dating, especially for material older than ~1 million years. Depleted uranium has a higher concentration of the 238 U isotope, and even depleted uranium (LEU), while having a higher proportion of the uranium-235 isotope (compared to depleted uranium), is still mostly 238 U. Recycled uranium is also mainly 238 U, with uranium-235 equivalents to natural uranium, in proportions comparable to uranium-236 and small amounts of other uranium isotopes such as uranium-234, uranium-233 and uranium-233. uranium-232.