Study Of Separation Of Isotopic Mixtures By Non-Conventional Centrifugal Cascades

The demand of enriched uranium, as well as stable isotopes, is large at present inthe world, which leads to different separation objects. It is beneficial to the separationstudy and various productions of stable isotopes to have a cascade with a simplestructure and a good separation performance that is able to carry out the separation ofdifferent target components without changing the structure of the cascade.Pulse cascade are designed and analyzed. A pulse cascade, whose shape isdetermined by the pipe holdups, can obtain very high concentrations of targetcomponents with a short cascade length, through alternating operations of the open andthe closed phases, based on the property of centrifuges that the separation factorincreases with the decrease of the feed. The total number of stages, the centrifugeholdup, the pipe holdup, the feed and the feed position have great influences on thetransient process, the concentration distribution at steady state, the separation power andthe separation efficiency of pulse cascades, and are the most important parameters forpulse cascades. These parameters should be appropriately chosen in order to gain a goodseparation performance. The operation manner of a pulse cascade is improved by usinga method to allowing the isotopic mixtures to flow into the head and tail pipes veryslowly and without recirculating. Because there is only one phase in a pulse, the pulsecascade after the improvement has a much shorter pulse period, less concentrationmixing, a higher separation efficiency, as well as easier implementation in engineering.For different shapes of cascades, in both binary and multicomponent separation, a pulsecascade is always shorter than a conventional cascade to obtain the same concentrationsin the product and waste, but its transient time is longer. If a pulse cascade and aconventional cascase are equiped with the same number of centrifuges, the formeryields a higher concentration in the product.Net cascades, that are able to realize no-mixing at all in the cascades, are presented.Given the condition that two key components are symmetrically separated at all thestages in a net cascade, no mixings is achieved for all the components at confluentpoints for multicomponent separation. Three different structures of net cascades, idealnet cascade, matched abundance ratio net cascade (MAR net cascade), and ordinary net cascade, are constructed through different setups of the withdrawals and the recircultingflows at stages in the last layer. There are no mixings for all the components at allconfluent points in an ideal net cascade, but in an MAR net cascade only the abundanceratio of the key components is not mixed at confluent points. Of the three kinds of netcascades, an ordinary net cascade has the largest mixing. To achieve the sameconcentration in the product of a target component, an MAR net cascade is of the sametotal flow, separation power and separation efficiency with a conventional MARC. If anet cascade and a conventional cascade with the same total flows and the samewithdrawal flows are utilized, an ordinary net cascade gives a higher concentration ofthe target component, and, therefore, has a larger separation power and a higherseparation efficiency, and makes more effective use of the separation properties of gascentrifuges.