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Plutonium-241 is fissile, but beta decays with a half-life of 14 years to americium-241. Plutonium-242 is not fissile, nor very fertile (requiring 3 more neutron captures to become fissile); and has a low neutron capture cross section, and a longer half-life than any of the lighter isotopes. Plutonium-244 is the most stable isotope of plutonium ...
Plutonium-241 (241 Pu or Pu-241) is an isotope of plutonium formed when plutonium-240 captures a neutron. Like some other plutonium isotopes (especially 239 Pu), 241 Pu is fissile , with a neutron absorption cross section about one-third greater than that of 239 Pu, and a similar probability of fissioning on neutron absorption, around 73%.
The main decay mode for isotopes heavier than 244 Pu, along with 241 Pu and 243 Pu, is beta emission, forming americium isotopes (95 protons). Plutonium-241 is the parent isotope of the neptunium series, decaying to americium-241 via beta emission. [9] [24] Plutonium-238 and 239 are the most widely synthesized isotopes.
Only fissile isotopes of certain elements have the potential for use in nuclear weapons. 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.
When the isotope 240 Pu captures a neutron, it is about 4500 times more likely to become plutonium-241 than to fission. In general, isotopes of odd mass numbers are more likely to absorb a neutron, and can undergo fission upon neutron absorption more easily than isotopes of even mass number. Thus, even mass isotopes tend to accumulate ...
A critical mass is a mass of fissile material that self-sustains a fission chain reaction. In this case, known as criticality, k = 1. A steady rate of spontaneous fission causes a proportionally steady level of neutron activity. A supercritical mass is a mass which, once fission has started, will proceed at an increasing rate. [1]
Plutonium-241, commonly comprising about 0.5% of weapon-grade plutonium, decays to americium-241, which is a powerful gamma radiation emitter. After several years, americium builds up in the plutonium metal, leading to increased gamma activity that poses an occupational hazard for workers.
Transmutation flow in LWR. Plutonium-242 is produced by successive neutron capture on 239 Pu, 240 Pu, and 241 Pu.The odd-mass isotopes 239 Pu and 241 Pu have about a 3/4 chance of undergoing fission on capture of a thermal neutron and about a 1/4 chance of retaining the neutron and becoming the following isotope.