V. D. Borisevich

CASCADES FOR SEPARATION OF MULTICOMPONENT ISOTOPE MIXTURES

This article reviews and analyzes the state-of-the art on separation of multicomponent isotope mixtures in cascades. Different methods, which are applied to calculate the cascade configurations and designs as well as those used to describe some transient processes in cascades when separating multicomponent isotope mixtures are discussed and analyzed in detail. The main directions for the further development of isotopes fractionation using cascades are formulated.

The separation power and thermodynamic work of separation for a three-flow unit during the equilibrium separation of a binary gas mixture

Equations for calculating the separation power and thermodynamic work of a three-flow separation element and cascade for the separation of a binary gas mixture are discussed.

On a Criterion Efficiency for Multi-Isotope Mixtures Separation

The criterion for efficiency for separation of binary isotopic mixtures is the well-known value function. However, in the case of multi-isotope separation, this value function does not exist. In this paper we develop a criterion to define the efficiency for separation of multi-isotope mixtures. It is based on the concept of the match-abundance ratio cascade (MARC) originally introduced by De La Garza for a ternary isotope mixture. The criterion has the property that, when applied to binary mixtures, it is the same as the value function. This approach has demonstrated that for obtaining the optimal parameters of a single stage in the cascade it is necessary to minimize the linear combination of the inverse values of “partial separative powers” for all mixture components. A numerical example using this efficiency criterion is presented using the separation of chromium isotopes by a single gas centrifuge.

STUDY OF ISOTOPE SEPARATION OF SOME CHEMICAL ELEMENTS IN A GAS CENTRIFUGE

Abstract The procedure of the numerical technique adjustment on the selected type of the gas centrifuge is considered. A satisfactory agreement is shown between theoretical and experimental results for enrichment of sulfur or tellurium isotopes in a single gas centrifuge.

Comparative Study of the Model and Optimum Cascades for Multicomponent Isotope Separation

The possibility of estimating the minimum total flow in a cascade with concentrations of a target component given in the product and waste flows by means of a model match abundance ratio cascade (MARC) is studied. The parameters required to describe MARC characteristics are the total number of separation stages, the feed flow location, and the M* parameter, which is equal to a half-sum of mass numbers of the target and the supporting components. Specific research carried out independently in two scientific labs in China and Russia has demonstrated that the integral parameters of the MARC, optimized by the M* parameter, are very close to that of the optimum by the minimum total flow cascade found by means of numerical optimization. The calculation is performed for separation of krypton isotopes when the end component 78Kr and the intermediate component 83Kr are considered to be the targets. It paves the way to use the optimized MARC parameters for two purposes: first, for fast and easy evaluation of the real cascade parameters and second, as an initial guess in its further direct numerical optimization, thereby allowing significant savings in computation time.

Quasi-ideal cascades with an additional flow for separation of multicomponent isotope mixtures

The theory of the R-cascade is generalized to a cascade with an additional external flow, which can be either one more feed flow to the cascade or an additional product flow from the separator at arbitrary degrees of enrichment in the stages of the cascade. Calculations are performed for the enrichment of recycled fuel in the R-cascade to a necessary concentration, provided that the effect of the isotope 236U is compensated and the concentration of the isotope 232U is decreased. It is demonstrated that the theory of the R-cascade with an additional product flow from an intermediate section of the cascade with the maximal component concentration and an intermediate mass number can be used to calculate the optimal conditions in simultaneous separation of several enriched isotopes in the cascade.

On a Formula to Evaluate the Separative Power of Long Gas Centrifuges

We discuss the possibility of applying the semi-empirical formula derived for evaluating the separative power of the Russian-type optimized gas centrifuge, with a rotor length about 1 m, to centrifugal machines of arbitrary length. It is demonstrated that the formula can adequately describe the dependence of a single gas centrifuges performance on rotor peripheral rotation, length, and diameter for machines with lengths of up to 5 m. The comparison of the calculated values for separative power, obtained by numerical simulations of flow and diffusion in gas centrifuges with that of the URENCO machines, demonstrates satisfactory agreement.

Verification of software codes for simulation of unsteady flows in a gas centrifuge

A simple semi-analytical solution is proposed for the problem of an unsteady gas flow in a gas centrifuge. The circulation in the centrifuge is driven by a source/sink of energy and by an external force (deceleration/acceleration of the gas rotation) acting on the gas at a given frequency. In the semi-analytical solution, the rotor is infinite, while the given forces vary harmonically with a given wave-length along the axial coordinate. As a result, the unsteady flow problem is reduced to a system of ordinary differential equations, which can be quickly solved to any prescribed accuracy. This problem is proposed for verifying numerical codes designed for the simulation of unsteady processes in gas centrifuges. A similar unsteady problem is solved numerically, in which case the cylinder is finite with the rotor length equal to the wavelength of the external force along the axis of rotation. The periodicity of the solution is set at end faces of the cylinder. As an example, the semi-analytical solution is compared with the numerical one obtained with these boundary conditions. The comparison confirms that the problem formulations are equivalent in both cases.

The Q-Cascade Explanation

The physical meaning of a continuous profile cascade, which is frequently used in the study of multicomponent isotope separation and named as the Q-cascade is explained. It is found that the parameter Q for a component at a stage is nothing but the relative increase of the concentration of the component, and is constant at all cascade stages. The Q-cascade is classified as the quasi-ideal cascade playing an importantrole for fast evaluation of the separation cascade parameters for multi-isotope mixture separation.

Numerical investigation of the separation of sulfur isotopes in a single gas centrifuge

ConclusionsThe method developed was used to analyze the separation of stable chromium isotopes (in the form CrO2F2) as well as some other elements in the type of centrifuge studied. It was determined that the efficiency as a function of the parameter studied in the present work is similar. Moreover, the results made it possible to determine the dependence of the separation capability on the molecular mass and physical properties of the working gases.