Noun
the commonest isotope of uranium; it is not fissionable but when irradiated with neutrons it produces fissionable plutonium 239
Source: WordNeturanium-238
233 U has a much higher fission efficiency by low-energy (thermal) neutrons, compared e.g. with 235 U. Most uranium chemistry studies were carried out on uranium-238 owing to its long half-life of 4.4 years. Source: Internet
Further work found that the far more common uranium-238 isotope can be transmuted into plutonium, which, like uranium-235, is also fissile by thermal neutrons. Source: Internet
Emsley, pp. 345-347 In particular, 239 Np and 237 Np are the most common of these isotopes; they are directly formed from neutron capture by uranium-238 atoms. Source: Internet
Only minute traces of technetium occur naturally in the Earth's crust—as a spontaneous fission product of uranium-238 or by neutron capture in molybdenum ores—but technetium is present naturally in red giant stars. Source: Internet
Examples of these are radium -226 (decay product of uranium-238) and radon-222 (a decay product of radium -226). Source: Internet
Initially, two major types of fission bombs were built: a relatively simple device that uses uranium-235 and a more complicated mechanism that uses plutonium-239 derived from uranium-238. Source: Internet