Induced nuclear reactions: processes – systems – and elements – Nuclear transmutation – By charged particle bombardment
Patent
1996-04-24
1998-06-30
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Nuclear transmutation
By charged particle bombardment
376181, 376171, 376194, 376355, 376381, G21C 130
Patent
active
057745145
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing energy from a nuclear fuel material. The invention is also directed to an energy amplifier for implementing such method, and to an energy production installation incorporating such energy amplifier.
Nuclear Reactors are of widespread use for the production of thermal or electrical power. Numerous Reactor designs have been developed, leading to extensive technological studies. However, conventional Reactors are not without problems. Control of the operation is generally delicate, as dramatically demonstrated by some accidents. For most Reactor designs, preparation of the fuel material involves isotopic separation, a complex and costly process which gives rise to proliferation risks. Proliferation risks also result from the fact that conventional nuclear Reactors generally produce fissile Plutonium. Energy recovery from such Plutonium, for instance by means of a fast neutron breeder Reactor, has raised many difficulties and is only marginally employed. Moreover, Plutonium and other actinides produced in non-negligible amounts in conventional Reactors are radiologically toxic, and are not easily disposed of. Geological storage of such actinides, together with fission fragments, is used, but clearly is not a satisfying solution.
Today's nuclear energy is based primarily on fissions of natural U.sup.235, which constitutes however only about 0.7% of ordinary Uranium. Early in the development of nuclear energy, one realised the importance of breeding artificial fuels from more abundant nuclear species with the help of neutron captures. In particular, starting from the dominant U.sup.238 one can breed Pu.sup.239 and from natural Thorium (pure isotope Th.sup.232) readily fissionable U.sup.233. While U.sup.238 --Pu.sup.239 breeding has led to the extensive but controversial development of the (fast) breeder Reactors, so far relatively little progress has been made on the Th.sup.232 --U.sup.233 breeding chain.
In "Nuclear energy generation and waste transmutation using an accelerator-driven intense thermal neutron source" (Nuclear Instruments and Methods in Physics Research, 1992, Vol. A320, pages 336-367), C. D. Bowman et al contemplate using a proton accelerator for incinerating actinide wastes produced by a light-water Reactor (see also U.S. Pat. No. 5,160,696). The installation is also expected to be capable of producing energy from the thorium cycle. However, the thermal neutron flux in the installation core needs to be very high (in the 10.sup.16 cm.sup.-2.s.sup.-1 range) in order to achieve the transmutation of Neptunium and Americium. Under these conditions, the energy producing breeding and fission process (i.e. capture of a neutron by Th.sup.232 leading to Pa.sup.233, .beta.decay of Pa.sup.233 into U.sup.233, and n-fission of U.sup.233) cannot be performed in situ, but instead necessitates continuous extraction of Pa.sup.233 away from the neutron flux to allow for .beta.decay of Pa.sup.233 into U.sup.233 outside the core while limiting neutron captures by Pa.sup.233, which would plague the neutron balance and lead to producing additional actinides (at about 10.sup.16 cm .sup.-2 .s .sup.-1 the probabilities of forming Pa.sup.234 and U.sup.233 from Pa.sup.233 are comparable) . Moreover, abundant fission products must be continuously extracted from the installation core and chemically processed. Such extractions and chemical processing are complicated manipulations which would make the installation virtually unsuitable for commercial energy production applications. Also, the accumulation of Pa.sup.233 out of the installation core is undesirable because it would decay, after about 27 days, into highly proliferative U.sup.233.
To summarize the prior art, practical nuclear energy Reactors and fast breeders rely on a critical chain reaction which is generally carried out inside a sealed enclosure, but still raise many problems despite several decades of extensive developments. And the above proposition of an accelerator-driven thermal neutron scheme is present
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Bowman et al, Nuclear Instuments and Methods in Physics Research vol. A320, No. 1-2, pp. 336-367, Aug. 15. 1992.
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