RU2500461C2 - Method of isotope separation - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to isotope separation and can be used for enrichment of stable and radioactive isotopes to required concentrations. Proposed method exploits separation cascade including three-component separation steps for single-shot separation of multicomponent mix into three parts. Said cascade has flows of components isolation and one or several feed flows. Arbitrary component isolation flow of separation step gets to step feed with quantity of enrichments unity larger at equal enrichments in other components. Note here that at three sequential enrichment events for different components, starting from arbitrary separation step, the last isolation flow feed this step.

EFFECT: higher efficiency of separation and lower costs.

6 cl, 5 dwg

Description

The invention relates to the nuclear, medical and other industries and can be used to obtain the required isotopes extracted from a multicomponent mixture, to solve problems of enriching various stable and radioactive isotopes, to solve problems of upgrading the regenerated fuel of nuclear power plants, as well as to obtain rare and expensive isotopes necessary for nuclear medicine, etc.

Most modern methods of isotope separation and the development of multicomponent separation cascades associated with them are reduced to standard schemes and methods that use three-stream separation elements with one input - power and two outputs - selection enriched in the target component and a blade depleted in the target component. Their combination into countercurrent cascades using a common feed, dump and selection allows you to get a separation scheme of a multicomponent mixture, where at the different ends of the cascade enrichment of the extreme components by molecular weight is obtained. However, separation cascades built on such elements require several cascade separation cycles to isolate isotopes with an intermediate molecular weight.

A known method of isotope separation (Cohen K. The Theory of Isotope Separation as Applied to the Large Scale Production of U235. New York: McGraw-Hill, 1951. 165 p.), Which proposed ideal (without mixing flows with different concentrations at the inputs in steps) and rectangular cascades for the separation of binary isotopic mixtures. However, the known method is not suitable for the separation of multicomponent isotopic mixtures.

A known method of separating isotopes (De la Garza A., Garret GA, Murphy JE Multicomponent Isotope Separation in cascades. Chem.Eng.Sci.:1961, v.15, p. 188-209) using a new type of separation cascade ("R cascade "), which is characterized by non-mixing of streams with different relative concentrations of the selected components. However, this method has a significant drawback, since the "R-cascades" do not have the optimality property - they do not provide a minimum total power supply flow of the steps. In the known method, it is also impossible to isolate all isotopic components in a single separation cycle, since the "R-cascades" are built on three-stream elements.

A known method of separation of isotopes (Sazykin AA Thermodynamic approach to the separation of isotopes. "Isotopes: properties, preparation, application." Edited by V.Yu. Baranov. M .: IzdAT, 2000. S. 72-108), in which multicomponent quasi-ideal cascades generalizing “R-cascades” are proposed. The separation cascade based on this separation method provides the same sections of the partial flows of components across all stages. However, such a cascade does not provide a minimum total power supply to the stages. In this method, it is also impossible to isolate all isotopic components in a single separation cycle, since the proposed cascade is built on three-stream elements.

A known method for the separation of isotopes (Pat. No. 2331463 of the Russian Federation. The method of separation of isotopes. V. G. Afanasyev, V. V. Vodolazskikh, P. M. Gavrilov, V. A. Zhurin, A. L. Kalashnikov, A. I. Kolesnikov , VM Korotkevich IPC B01D 59/00, 59/20, claimed September 25, 2006; published August 20, 2008) using intermediate selection in the cascade. This method involves the use of centrifugation as a separation method, which makes it dependent on the type of working substance and the extracted isotope.

A known method for the separation of isotopes and a separation cascade based on it (Palkin V.A., Sbitnev N.A., Frolov E.S. Calculation of the optimal parameters of the cascade for the separation of a multicomponent mixture of isotopes. "Atomic energy", 2002, T.92 , issue 2, p.130-133), which are intended for the separation of multicomponent mixtures, providing a minimum total power flow of steps for given external concentrations of the target isotope. However, the known method and the separation cascade based on it do not have the ability to isolate all isotopic components in a single separation cycle, since they use three-stream separation elements to build the cascade.

Closest to the claimed invention is a method of separation of a three-component mixture of isotopes (Aleksandrov O.E. Construction of a three-component separation cascade. Collection of reports, 14th International Scientific Conference “Physicochemical Processes in the Selection of Atoms and Molecules.” Promising materials, special issue No. 10. Zvenigorod, Russia, February, 2011, pp. 61-64), which proposed a separation cascade circuit based on four-flow separation elements with one input and three outputs, each of which yields ogaschenie one component.

The disadvantage of this prototype method is that in the separation cascade based on it in the separation stages, there is a large mixing of flows with different concentrations of enriched components, which leads to loss of separation work and, as a result, to a decrease in cascade performance.

The objective of the invention is to develop a method for the separation of isotopes of a three-component mixture, which involves the use of a separation cascade based on four-stream elements and, in contrast to the prototype method, has a higher productivity for obtaining the required concentrations of isotopes, and, accordingly, lower cost of isotope products, due to a more rational scheme connection of steps to a cascade suitable for various types of separation methods used and types of extracted isotope.

The separation element of the separation cascade is the smallest part of the separation installation, in which the mixture feeding this element is divided into three “enriched fractions”, in each of which the enrichment of the corresponding concentrate component is obtained, when the other two components are depleted. Several dividing elements connected in parallel form a dividing stage (a single dividing element can also be a dividing stage). In all elements of one stage, the feed mixture is characterized by the same isotopic composition, and this is also true for any “enriched fraction”. The required concentration of emitted isotopes can be achieved by sequentially connecting several stages; in this case, the set of steps forms a dividing cascade.

The problem in the claimed invention is solved due to the fact that in the method of isotope separation using a separation cascade containing separation stages, capable of dividing a multicomponent mixture into three parts in one separation act, having selection flows of emitted components and one or more supply flows of the separation cascade, the selection stream for an arbitrary component of the separation stage of the separation cascade (conventionally designated - the selection stream "G") is supplied to the power of the stage having the number of enrichments in the corresponding selection stream “G” component is one more, with equal enrichments in other components, and, in the cascade, three successive acts of enrichment for different components are implemented sequentially, starting from an arbitrary dividing stage (symbolically designated “A” stage), the last the selection stream is fed to this stage “A”.

In this case, the selection stream for some component (conditionally designated - component "K") of an extreme arbitrary dividing stage (conditionally designated - stage "B"), which is not a cascade selection stream and is not connected in series with another stage, is sent to the power of the separation stage ( conditionally designated - stage "C"), the selection flow of which according to another component (conditionally designated - component "L") is supplied to the power of stage "B".

In this case, the selection flow for some component (conditionally designated - the selection flow "G1") of the extreme arbitrary dividing stage "B", which is not a cascade selection flow and is not connected in series with another stage, can be directed to the power of the dividing stage (conventionally designated - stage “D”), the selection stream of which for another component (conditionally designated as the selection stream “G2”), which is not a cascade selection stream and is not connected in series with another stage, has the same number of enrichments for any th component as stream selection «G1», wherein the stream selection «G2» is directed to "B" stage power.

Moreover, if it is impossible to find the separation stage “D” for the selection flow for a certain component “G1” of the extreme arbitrary dividing stage “B”, the selection flow of which for the other component has the same amount of enrichment for any of the components as the selection flow “ G1 ", then the selection flow" G1 "is directed to the power of the separation stage (conditionally designated - stage" E "), the selection flow of which through another component is supplied to the power of stage" B ".

In this case, the selection flow of an arbitrary dividing stage (conditionally designated - stage "F"), can be fully or partially directed to the power of this stage "F".

In this case, the flow of selection of the separation cascade for an arbitrary component (conditionally designated - component "M") can be directed to the power of an additional separation stage (conditionally designated - stage "N"), which becomes the extreme separation stage and acquires all their properties and connection principles, the selection stream for component “M” of the additional separation stage “N” becomes the selection stream for the separation stage for component “M”.

The dividing stage of the dividing cascade, all the selection flows of which are fed to the stages having the amount of enrichment in the corresponding component selection stream by one more, with equal enrichments in other components, is conventionally called the dividing stage inside the cascade. The dividing stage, for which it is not performed for at least one selection stream, is conventionally called the extreme dividing stage of the cascade or the dividing stage on the "edge" of the cascade.

Figure 1 presents a diagram of a possible variant of the separation cascade based on the proposed method for the separation of isotopes. Figure 2 shows the principle of connection between a three-component separation stages inside the separation cascade. Figure 3 explains the various options for connecting the extreme dividing steps of the dividing cascade, in accordance with the claims. Figure 4 presents the known connection diagrams: at the top is a cascade connection diagram based on the prototype, at the bottom is a cascade connection diagram under the code name "star". Figure 5 presents tables of the results of comparison of various circuits of separation cascades.

The main elements in figure 1 - figure 4 are separation stages, capable of dividing a multicomponent mixture into three parts in one act of separation. The dividing steps in the figures are conventionally shown in the form of triangles. They are interconnected by selection flows enriched in the corresponding component, which are indicated in the diagrams (here and below, that the choice of the component number is arbitrary) by arrows as follows:

- arrow with a solid line - the selection flow of the 1st component;

- arrow with a dashed line - stream of selection of the 2nd component;

- arrow with a line in the form of dots - selection stream of the 3rd component;

- arrow with a bold line - the flow of the "swirl" (redirection of flows from the extreme dividing steps to others).

Each dividing stage of the dividing cascade will be assigned its own “number” (i, j, k), where i is the number of enrichments for the 1st component, j is the number of enrichments for the 2nd component, k is the number of enrichments for the 3rd component (Fig .one). The calculation shows that in a cascade with steps connected according to the scheme, as in FIG. 1, the conditions for non-mixing of flows with different concentrations can be approximately satisfied. This means that the relative concentrations of the components R _N (i, j, k) (N = 1,2,3 - component number) in the power supply stream (ij, k) -u of the separation stage can be represented as:

$$\{\begin{array}{c}{R}_{\mathrm{one}}(i,j,k)={\alpha }_{\mathrm{eleven}}^i\cdot {\alpha }_{21}^j\cdot {\alpha }_{31}^k\cdot R_{\mathrm{one}}(\mathrm{0,0,0}),\\ R_2(i,j,k)={\alpha }_{12}^i\cdot {\alpha }_{22}^j\cdot {\alpha }_{32}^k\cdot R_2(\mathrm{0,0,0}),\\ R_3(i,j,k)={\alpha }_{13}^i\cdot {\alpha }_{23}^j\cdot {\alpha }_{33}^k\cdot R_3(\mathrm{0,0,0}),\end{array}\left(\mathrm{one}\right)$$

.where R ₁ (0,0,0), R ₂ (0,0,0), R ₃ (0,0,0) are the relative concentrations of the components in the feed stream of the separation cascade, which can be expressed through mass concentrations according to the known formula $$R=\frac{c}{\mathrm{one}-c}$$

.

The cascade power flow is supplied to the (0,0,0) -stage. Can also be implemented additional power flows in stages with a concentration corresponding to the concentration of the additional power flow.

Values α _MN are the enrichment / depletion coefficients for the Nth component in the Mth selection stream, which are conveniently written in the form of a matrix A _MN :

$$A_{MN}=\left(\begin{array}{ccc}{\alpha }_{\mathrm{eleven}}& {\alpha }_{12}& {\alpha }_{13}\\ {\alpha }_{21}& {\alpha }_{22}& {\alpha }_{23}\\ {\alpha }_{31}& {\alpha }_{32}& {\alpha }_{33}\end{array}\right).\left(2\right)$$

In the matrix A _MN along the main diagonal are the enrichment coefficients of the components in the flows of the same name. All other elements are component depletion coefficients (by definition, enrichment coefficients are greater than one, depletion coefficients are less than unity).

The necessary conditions imposed on these coefficients and ensuring the fulfillment of the non-mixing conditions are relations of the form:

$${\alpha }_{\mathrm{one}N}{\alpha }_{2N}{\alpha }_{3N}=\mathrm{one,}i=\overline{1.3}.\left(3\right)$$

In the simplest case, the claimed separation method involves the use of steps with the same enrichment coefficients α _MM , that is, α ₁₁ = α ₂₂ = α ₃₃ = α. Moreover, the depletion coefficients are taken equal to α ₁₂ = α ₂₃ = α ₃₁ = β ₁ and α ₁₃ = α ₂₁ = α ₃₂ = β ₂ . From here, condition (3) becomes the equality:

$$\alpha \cdot {\beta }_{\mathrm{one}}\cdot {\mathrm{<figure-callout\; id="2"\; label="\beta "\; filenames="00000011.png,00000013.png"\; state="\{\{state\}\}">\beta </figure-callout>}}_2=\mathrm{one}\left(\mathrm{four}\right)$$

or in the case β ₁ = β ₂ = β:

$$\alpha \cdot {\mathrm{<figure-callout\; id="2"\; label="\beta "\; filenames="00000011.png,00000013.png"\; state="\{\{state\}\}">\beta </figure-callout>}}^2=\mathrm{one.}\left(5\right)$$

The fulfillment of conditions (3) - (5) in determining the relative concentrations according to formulas (1), which also assumes a small difference between the coefficients α _MN and unity, allows us to write down the non-mixing conditions as:

$$\begin{array}{c}{R}_{\mathrm{one}}{(i,j+\mathrm{one,}k+\mathrm{one})}_{\mathrm{one}}=R_{\mathrm{one}}{(i+\mathrm{one,}j,k+\mathrm{one})}_2=R_{\mathrm{one}}{(i+\mathrm{one,}j+\mathrm{one,}k)}_3=R_{\mathrm{one}}(i,j,k),\\ R_2{(i,j+\mathrm{one,}k+\mathrm{one})}_{\mathrm{one}}=R_2{(i+\mathrm{one,}j,k+\mathrm{one})}_2=R_2{(i+\mathrm{one,}j+\mathrm{one,}k)}_3=R_2(i,j,k),\\ R_3{(i,j+\mathrm{one,}k+\mathrm{one})}_{\mathrm{one}}=R_3{(i+\mathrm{one,}j,k+\mathrm{one})}_2=R_3{(i+\mathrm{one,}j+\mathrm{one,}k)}_3=R_3(i,j,k),\end{array}\left(6\right)$$

where R _N (i, j, k) _M is the relative concentration of the Nth component in the _Mth stream of selection of an arbitrary stage.

From (3) - (5) it follows that R _N (i + 1, j + 1, k + 1) = R _N (i, j, k) and that if any of the numbers i, j or k less than the other two of them, for example, j <i, j <k, then R _N (i, j, k) = R _N (ij, 0, kj). In fact, this means that these are identical steps: (i, j, k) -, (i + 1, j + 1, k + 1) - and (ij, 0, kj) - steps. Therefore, it is possible to number the steps in a cascade as shown in FIG. 1.

- суммарный поток в каскаде и $${\alpha }^q=\frac{R_n}{R_0}$$

- коэффициент разделения каскада относительно точки питания, где R_n - относительная концентрация выбранного компонента в потоке отбора каскада, R₀ - относительная концентрация выбранного компонента в потоке питания каскада, q - число обогащений в ступени на которой идет отбор выбранного компонента в каскаде (на Фиг.1 данное число указано в номере ступени - к примеру (n-1,0,0)-ая ступень, т.е. для приведенной схемы q=n-1).Let us analyze the operation of the separation cascade circuit based on the proposed separation method (Figure 1). With an increase in the number of dividing steps, the influence of the “swirl” flows will be practically absent inside the cascade, and only a small effect will remain at the “edges” of the cascade. Compare the given circuit of the separation cascade with the prototype and the circuit, under the code name "star", in which the separation elements are connected so that, starting from the supply stage, the selection of the selected component goes only in one direction; the remaining selection flows are returned to the power of the previous stage (Figure 4). To compare the schemes, we set the characteristics of the separation stage in stages: the division coefficients of the stage flows are 1/3, the enrichment coefficients α = 1.01, and the depletion coefficients β ₁ = β ₂ = 0.995. The absolute concentrations of each of the components in the cascade power flows are equal to each other and equal to 1/3. The comparison results are presented in the form of two tables in Figure 5. The criteria for comparison are: $${\displaystyle \sum _i{G}_i}$$

- total flow in cascade and $${\alpha }^q=\frac{{\mathrm{<figure-callout\; id="0"\; label="R\; n\; R"\; filenames="00000012.png"\; state="\{\{state\}\}">R\; </figure-callout>}}_n}{R_{}}$$

is the separation coefficient of the cascade relative to the feed point, where R _n is the relative concentration of the selected component in the cascade feed stream, R ₀ is the relative concentration of the selected component in the cascade feed stream, q is the number of enrichments in the stage at which the selected component is selected in the cascade (in Fig. .1 this number is indicated in the stage number - for example, the (n-1,0,0) -th stage, i.e. for the given scheme q = n-1).

As can be seen from the first table, the proposed separation method in comparison with the prototype is characterized by a higher separation coefficient and a lower total flow (an increase in the number of steps in the prototype increases the effect of mixing flows, reducing the separation coefficient) with a smaller number of enrichments in the selection. When comparing the separation cascade circuit based on the proposed separation method and the "star" circuit, a larger separation coefficient and a lower total flow are also observed. With an increase in the number of steps, a larger value of the separation coefficient is also observed, compared with the known schemes, with a significant decrease in the total flow. This confirms the efficiency and high performance of the proposed separation method.

This example of the connection of the separation stages in the separation cascade does not exhaust all the possibilities of the proposed method of separation. When using other options, there is also a high separation efficiency.

Depending on the purpose, the selection of the components of the initial mixture can be carried out not at the points of selection of the cascade, but at other stages, or additional selections from arbitrary stages can also be implemented.

The main distinguishing features of the proposed method for the separation of isotopes using a separation cascade are the above-described principle of interconnecting the separation steps within the separation cascade (Figure 2) and methods for connecting the extreme separation steps of the separation cascade (Figure 3). These features provide an increase in the productivity of separation production and a decrease in the cost of the resulting isotope products.

The proposed method for the separation of isotopes using a separation cascade is suitable for various separation methods, and, for example, can be implemented when the method of electromagnetic separation of isotopes is used as technology for the separation elements.

The proposed method for the separation of isotopes using a separation cascade provides the following technical effect: an increase in the productivity of separation production (due to the separation of a mixture of isotopes in three components at once) and, as a result, a decrease in the cost of the resulting isotope products.

Claims (6)

1. The method of separation of isotopes of a multicomponent mixture using a separation cascade containing three-component separation steps, capable of dividing a multicomponent mixture into three parts in one separation act, having the selection flows of the components to be separated and one or more supply flows of the separation cascade, characterized in that the selection flow is to an arbitrary component of the separation stage of the separation cascade — the selection flow “G” - is supplied to the power of the stage having the number of enrichments according to there is one more component for the existing “G” selection flow, with equal enrichments for other components, and, in the cascade, three successive acts of enrichment for different components are implemented sequentially, starting from an arbitrary dividing stage - “A” stage, the last selection stream is supplied to this stage "BUT". 2. The method for separating isotopes of a multicomponent mixture according to claim 1, characterized in that the selection stream for some component - component "K" - of an extreme arbitrary dividing stage - stage "B", which is not a cascade selection stream and is not connected in series with another stage , direct to the power of the separation stage - stage "C", the selection flow of which according to another component - component "L" - is fed to the power of stage "B". 3. The method for separating isotopes of a multicomponent mixture according to claim 1, characterized in that the sampling stream for some component is a sampling stream "G1" - an extreme arbitrary separation stage - stage "B", which is not a cascade selection stream and is not connected in series with another stage, they are directed to the power of the separation stage - stage "D", the selection stream of which for another component - the selection stream "G2", which is not a selection stream of the cascade and is not connected in series with another stage, has the same number of enrichments about any of the components, as well as the selection flow "G1", while the selection flow "G2" is directed to the power supply of stage "B". 4. The method for separating isotopes of a multicomponent mixture according to claim 3, characterized in that if it is impossible to find a separation stage “D” for the selection stream for some component “G1” of an extreme arbitrary separation stage “B”, the selection stream of which for another component has such the same amount of enrichment for any of the components, as well as the selection flow “G1”, the selection flow “G1” is directed to the power of the separation stage - stage “E”, the selection flow of which through the other component is supplied to the power of stage “B”. 5. The method of isotope separation of a multicomponent mixture according to claim 1, characterized in that the selection stream of an arbitrary separation stage - stage "F" is fully or partially directed to the power of this stage "F". 6. A method for separating isotopes of a multicomponent mixture according to any one of claims 1 to 5, characterized in that the flow of selection of the separation cascade by an arbitrary component - component "M" - is directed to the power of an additional separation stage - stage "H", which becomes the final separation stage and acquires all their properties and connection principles, the selection stream for component “M” of the additional separation stage “H” becomes the selection stream for the separation stage for component “M”.

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