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Neutron radiation is a form of ionizing radiation that presents as free neutrons.Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides—which, in turn, may trigger further neutron radiation.
237 Np is the product of alpha decay of 241 Am, which is produced through neutron irradiation of uranium-238. [28] Heavier isotopes of neptunium decay quickly, and lighter isotopes of neptunium cannot be produced by neutron capture, so chemical separation of neptunium from cooled spent nuclear fuel gives nearly pure 237 Np. [28]
On May 27, Edwin McMillan and Philip Abelson publish the discovery of neptunium at the Berkeley Radiation Laboratory. They use the 60-inch cyclotron produce a small sample of neptunium-239 via neutron bombardment of uranium-238. They also correctly assume its beta decay to the alpha-emitting plutonium-239, but are unable to isolate it. [23]
Even neutrons without significant kinetic energy are indirectly ionizing, and are thus a significant radiation hazard. Not all materials are capable of neutron activation; in water, for example, the most common isotopes of both types atoms present (hydrogen and oxygen) capture neutrons and become heavier but remain stable forms of those atoms.
Neutronium (or neutrium, [1] neutrite, [2] or element zero) is a hypothetical substance made purely of neutrons.The word was coined by scientist Andreas von Antropoff in 1926 (before the 1932 discovery of the neutron) for the hypothetical "element of atomic number zero" (with no protons in its nucleus) that he placed at the head of the periodic table (denoted by -).
Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation and in neutron scattering experiments. A free neutron spontaneously decays to a proton, an electron, and an antineutrino, with a mean lifetime of about 15 minutes.
is the only neptunium isotope produced in significant quantity in the nuclear fuel cycle, both by successive neutron capture by uranium-235 (which fissions most but not all of the time) and uranium-236, or (n,2n) reactions where a fast neutron occasionally knocks a neutron loose from uranium-238 or isotopes of plutonium. Over the long term, 237 Np
Values of k larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self-sustaining chain reaction. A mass of fissile material large enough (and in a suitable configuration) to induce a self-sustaining chain reaction is called a critical mass .