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Neptunium-235 has 142 neutrons and a half-life of 396.1 days. This isotope decays by: Alpha emission: the decay energy is 5.2 MeV and the decay product is protactinium-231. Electron capture: the decay energy is 0.125 MeV and the decay product is uranium-235; This isotope of neptunium has a weight of 235.044 063 3 u.
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.
This element also has at least four meta states, with the most stable being 236m Np with a half-life of 22.5 hours. [27] The isotopes of neptunium range in atomic weight from 219.032 u (219 Np) to 244.068 u (244 Np), though 221 Np has not yet been reported. [5]
Thus they again take their places in the chain: plutonium-239, used in nuclear weapons, is the major example, decaying to uranium-235 via alpha emission with a half-life 24,500 years. There has also been large-scale production of neptunium-237, which has resurrected the hitherto extinct fourth chain. [7]
At least 3,300 nuclides have been experimentally characterized [1] (see List of radioactive nuclides by half-life for the nuclides with decay half-lives less than one hour). A nuclide is defined conventionally as an experimentally examined bound collection of protons and neutrons that either is stable or has an observed decay mode .
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For such use, the concentration of fissile isotopes uranium-235 and plutonium-239 in the element used must be sufficiently high. Uranium from natural sources is enriched by isotope separation , and plutonium is produced in a suitable nuclear reactor .
SOURCE: Integrated Postsecondary Education Data System, University of Missouri-Columbia (2014, 2013, 2012, 2011, 2010).Read our methodology here.. HuffPost and The Chronicle examined 201 public D-I schools from 2010-2014.