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or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233.
Neptunium-236 has 143 neutrons and a half-life of 154,000 years. It can decay by the following methods: Electron capture: the decay energy is 0.93 MeV and the decay product is uranium-236. This usually decays (with a half-life of 23 million years) to thorium-232. Beta emission: the decay energy is 0.48 MeV and the decay product is plutonium-236.
The two types of beta decay are known as beta minus and beta plus.In beta minus (β −) decay, a neutron is converted to a proton, and the process creates an electron and an electron antineutrino; while in beta plus (β +) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino. β + decay is also known as positron emission.
In nuclear physics, a beta decay transition is the change in state of an atomic nucleus undergoing beta decay. When undergoing beta decay, a nucleus emits a beta particle and a corresponding neutrino, transforming the original nuclide into one with the same mass number but differing atomic number (nuclear charge). There are several types of ...
The decay scheme of a radioactive substance is a graphical presentation of all the transitions occurring in a decay, and of their relationships. Examples are shown below. It is useful to think of the decay scheme as placed in a coordinate system, where the vertical axis is energy, increasing from bottom to top, and the horizontal axis is the proton number, increasing from left to right.
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]
Trace amounts of the neptunium isotopes neptunium-237 and -239 are found naturally as decay products from transmutation reactions in uranium ores. [ 7 ] [ 34 ] 239 Np and 237 Np are the most common of these isotopes; they are directly formed from neutron capture by uranium-238 atoms.
Uranium-239 is usually produced by exposing 238 U to neutron radiation in a nuclear reactor. 239 U has a half-life of about 23.45 minutes and beta decays into neptunium-239 , with a total decay energy of about 1.29 MeV. [ 33 ]