Plutonium processing Uranium fuel cycle

The use of a simplified PUREX process with low decontamination factor the use of a process flowchart with no separation of uranium and plutonium at any fuel cycle stage (RMWR). 

In a typical fast breeder nuclear reactor, most of the fuel is 238U (90 to 93%). The remainder of the fuel is in the form of fissile isotopes, which sustain the fission process. The majority of these fissile isotopes are in the form of 239Pu and 241Pu, although a small portion of 235U can also be present. Because the fast breeder converts die fertile isotope 238 U into the fissile isotope 239Pu, no enrichment plant is necessary. The fast breeder serves as its own enrichment plant. The need for electricity for supplemental uses in the fuel cycle process is thus reduced. Several of the early hquid-metal-cooled fast reactors used plutonium fuels. The reactor Clementine, first operated in the Unired States in 1949. utilized plutonium metal, as did the BR-1 and BR.-2 reactors in the former Soviet Union in 1955 and 1956, respectively. The BR-5 in the former Soviet Union, put into operation in 1959. utilized plutonium oxide and carbide. The reactor Rapsodie first operated in France in 1967 utilized uranium and plutonium oxides. 

Plutonium-239. Plutonium-239 represents a fortuitous phenomenon. Whereas U-235 is the only significant fissile nuclide in nature, its major isotope, U-238, captures a neutron to produce another fissile nuclide, plutonium-239. A substantial amount of the energy produced during the life of uranium fuel is produced by the conversion of U-238 to Pu-239 which subsequently fissions. This process provides the basis for the nuclear breeding cycle. 

Of special interest in the mass spectrometric determination of transuranium elements is the characterization of microparticles stemming from different radioactivity release scenarios. Such microparticles bearing radionuchdes, in particular uranium, plutonium, neptunium and americium, can enter the environment and therefore the human food chain through different processes which can be related to the nuclear fuel cycle as well as to clandestine nuclear activities. In addition, nuclear safeguards programmes seek to determine the uranium isotope abundances of individual p,m sized particles. Anomalous amounts of or may indicate that artificial isotope enrichment... 

The processes involved in weapon production as related to the nuclear fuel cycle are presented schematically in Fig. 8.7. It should be kept in mind that a significant quantity of the material needed for a single, relatively simple nuclear device is plutonium 5-8 kg enriched uranium 25 kg... 

At the end of irradiation in such reactors, fuel consists of a mixture of thorium, uranium containing fissile isotopes, and fission products. Figure 3.33 showed a fuel-cycle flow sheet for an HTGR. The Thorex process has been developed for recovering the uranium and thorium from such fuel cycles, freeing them from fission products and separating them from each other. The Thorex process will be described in this section. When the fuel being irradiated contains appreciable the plutonium thus formed requires that a combination of the Thorex and Purex processes be used. 

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

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