This is the basis of objection from some quarters to reprocessing and separation of any plutonium from used fuel. However, safeguards arrangements assume that both kinds of plutonium could conceivably be used for weapons, particularly weapons designed for terror rather than military use. Design and construction of nuclear explosives based on normal reactor-grade plutonium would be difficult, dangerous and unreliable, and has not so far been done 4. Nuclear weapons (can be recycled as fuel in fast neutron reactor or as ingredient of MOX)ĭue to the spontaneous fission of Pu-240, only a very low level of it is tolerable in material for making weapons. 5%-7%) of MOX fuel for normal reactor (can also be used as fuel in fast neutron reactor)įrom military “production” reactors specifically designed and operated for production of low burnup Pu Pu-241 (half-life 13 years) is the source, by beta decay, of americium-241, the vital ingredient in most household smoke detectors.ĥ5%-60% Pu-239, >19% Pu-240, typically about 30% non-fissileĬomprises about 1% of spent fuel from normal operation of civil nuclear reactors used for electricity generationĪs ingredient (c. The main peaceful use of Pu-239 is as nuclear reactor fuel. Pu-240 has been used in similar applications. Plutonium power enabled the Voyager spacecraft to send back pictures of distant planets. The decay heat of Pu-238 (0.56 W/g) enables its use as an energy source in the thermoelectric generators of some cardiac pacemakers, space satellites, navigation beacons and so on. Providing protection from this alpha radioactivity involves sealing the plutonium from physical contact, such as in a plastic bag. It also emits neutrons from spontaneous fission disintegrations, as does Pu-238 (half-life 86 years). Its half-life is 6600 years, therefore it has a higher level of radioactivity than Pu-239. Pu-240 emits alpha particles as it decays to U-236 (another non-fissile isotope). Its half-life is 24,390 years, therefore it has a low level of radioactivity. Pu-239 emits alpha particles to decay to U-235 (see Appendix 2). (Pu-240 is fissionable in a fast neutron reactor.) Pu-240 is not fissile in a thermal reactor, but can become fissile Pu-241 by further neutron capture. The amount of Pu-240 increases with the time that fuel elements remain in the reactor (see Figure 21). It remains locked up in highly radioactive spent fuel unless reprocessed (see Figure 16). After fuel has been irradiated in the reactor for a couple of years, Pu-239 burns almost as fast as it forms, whereas Pu-240 accumulates steadily.Ī very small amount of Pu-238 is formed from U-235 by neutron capture.Ī 1000 MWe reactor produces about 250 kg of plutonium (especially Pu-239) each year. Pu-241 and Pu-242 are formed by successive neutron capture in the reactor fuel. On average, one in four neutron absorptions by Pu-239 results in the formation of Pu-240 rather than in fission.
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