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Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series, which starts with the primordial isotope uranium-235; the equilibrium concentration in uranium ore is 46.55 231 Pa per million 235 U.
However, small amounts exist as spontaneous fission products in uranium ores. A kilogram of uranium contains an estimated 1 nanogram (10 −9 g) equivalent to ten trillion atoms of technetium. [21] [61] [62] Some red giant stars with the spectral types S-, M-, and N display a spectral absorption line indicating the presence of technetium.
In a fission nuclear reactor, uranium-238 can be used to generate plutonium-239, which itself can be used in a nuclear weapon or as a nuclear-reactor fuel supply. In a typical nuclear reactor, up to one-third of the generated power comes from the fission of 239 Pu, which is not supplied as a fuel to the reactor, but rather, produced from 238 U. [5] A certain amount of production of 239
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified in natural samples (tellurium-128, barium-130). There are 35 of these (see these nuclides), of which 25 have half-lives longer than 10 13 years. With most of these 25, decay is difficult to observe and for ...
a photopeak (full energy peak) at an energy of 662 keV The Compton distribution is a continuous distribution that is present up to channel 150 in Figure 1. The distribution arises because of primary gamma rays undergoing Compton scattering within the crystal: Depending on the scattering angle, the Compton electrons have different energies and ...
Actinium-227 (half-life 21.77 years) occurs in all uranium ores, but in small quantities. One gram of uranium (in radioactive equilibrium) contains only 2 × 10 −10 gram of 227 Ac. [30] [57] Actinium-228 is a member of the radioactive thorium series formed by the decay of 228 Ra; [60] it is a β − emitter with a half-life of 6.15 hours.
One barn is 10 −28 square metres, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, when the uranium nucleus was described, and the phrases "big as a barn" and "hit a barn door" were used. Barn are typically used for cross sections in nuclear and particle physics.