Uranium Isotopic Enrichment
The operation of pressurized light water reactors (PWR) adopted by
Many of the enrichment processes were developed in laboratory, but only two of them operate in large scale: gas diffusion or ultracentrifugation. The companies who own gaseous diffusion plants, due to technical and economic reasons, started their deactivation at the same time in which they programmed the implantation of ultracentrifugation industrial unities.
The physical process of ultracentrifugation splits uranium isotopes 235 and 238 increasing the concentration of fissile uranium isotope 235 from 0.7%, as occurs in nature, to 4%.
The gas ultracentrifuge (in this case UF6) is a vertical and thin cylinder that spins at an extremely high speed inside a carcass with vacuum. An ultracentrifuge force field generated inside the rotating cylinder (rotor) splits the different isotopes along radial direction.
An axial countercurrent flow is established to increase the isotope splitting. In practice, ultracentrifuge gas efficiency depends on the peripheral speed and rotor length, recirculation axial ratio and feeding machine ratio.
Since big quantities of enrichment materials are needed for the supply of Likewise, as the split effect in each stage is little, the increment percentage of enrichment from enriched flow is small, so there is a necessity of interlacing the stages in series, forming the configuration called “cascade”. Therefore, to obtain products with the desirable percentages in an industrial scale, an enrichment plant comprehends several cascades made of isotopic split elements interlaced in series and parallel by tubes according to uranium feeding flows and withdrawal of enriched and poor uranium, as the diagram bellow shows:
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