Gas Centrifuge Research Articles

Molybdenum Isotope Separation in a Cascade with a Specified Number of Gas Centrifuges in Stages

A method of calculating and optimizing a multi-flow cascade with a specified number of gas centrifuges in stages on cuts of their partial flows were developed. A special feature of the method is an iterative fitting of the separation coefficients of the gas centrifuges that depend on the feed flow and the division factor of the flow. A computational experiment was conducted on the separation of molybdenum hexafluoride and concentration of the isotopes 98Mo in an additional product and 100Mo in the waste of the cascade. The basic factors that affect the efficiency in concentrating the components and are associated with the cascade feed and the types of stages in terms of the number of gas centrifuges are determined. It is shown that the feed flows and the separation coefficients of the stages of such cascades differ significantly from those of rectangular and rectangular-sectioned cascades.

General and Particular Separation Potentials for Multicomponent Mixtures

The definition of the separation potential for multicomponent separation is analyzed. The possibility of introducing a particular separation potential together with the general separation potential for concrete setups is examined. An expression is obtained for the particular separation potential of a gas centrifuge.

Nano-Structured Crystals of Zirconium Dioxide for Extreme Applications

The paper discusses application possibilities of nanostructured crystals of partly stabilized zirconium dioxide in greaseless running of plain bearings in order to support normal operation of friction joints at high temperatures and in aggressive conditions. This issue is a burning one in different industries, e.g. circulating pumps in nuclear power engineering, mixing units of crystal synthesizing lines in chemical engineering; motors in space-based targets, rotors of guide blades in axial compressors of airplane engines, supports of high-speed gas centrifuges. Micro-hardness was investigated, and friction surfaces were explored using methods of X-ray, electron-microscopic and element analysis to find a wear mechanism for crystals ZrO2- Y2O3. The paper reports on tribological properties of partly stabilized zirconium dioxide crystals and prospects of their industrial usage.

Influence of Separating-Cascade Streams on the Duration of a Transient Process

A study has been made of the transient process with the example of obtaining germanium enriched with a 72Ge isotope to 50% in a cascade of gas centrifuges. The influence of the values of outgoing cascade streams on the dynamics of the concentration of isotopes and the duration of the transient process has been shown. Conditions for the change in the values of outgoing cascade streams have been established, with which the minimum duration of the transient process is attained and the efficiency of operation of the cascade rises.

Self-balancing of high-rate two-section gas centrifuge for uranium processing

Self-balancing of high-rate two-section gas centrifuge for uranium processing

Prediction of the compression ratio of a Holweck-type molecular pump with the presence of multi-component gases using a modified Sickafus method for high-speed rotors

Analyzing behavior inside a gas centrifuge machine can be divided into two parts: modeling and simulating spaces inside and outside of a rotor. Examining the mass percentage of the gas used in the Holweck-type pump is essential in approaching the desired compression ratio. Due to the contact between outside and inside spaces of a rotor with each other, after flow equilibrium, it is possible to predict the gas components outside the rotor by examining the concentration of gas components at the axis of the rotor. For this purpose, Multi Component Concentration-Direct Simulation Monte Carlo (MCC-DSMC) solver has been developed in this paper. By this solver, variations in concentration inside a rotor for a different combination of light gas with heavy gases were examined. Based on the mass percentages of the components formed in the rotor axis, the gas was selected to simulate the Holweck-type molecular pump by the modified Sickafus method in different geometries. The results show that the compression ratios of the modified Sickafus method are in good agreement with the experimental results. Also, the presence of small percentages of a light gas inside the rotor has a significant influence on the compression ratio made by a molecular pump.

Modeling and simulating of feed flow in a gas centrifuge using the Monte Carlo method to calculate the maximum separation power.

Most of the gas enters into a small portion of the rotating cylinder by increasing the rotational speed in a rotating cylinder. Navier-Stokes equations were used to evaluate gas behavior in this area. In this paper, the mass source calculated by the DSMC method at the boundary of the two regions has been used in the Onsager-Pancake equation and finite difference method was used to solve this equation. One of the assumed flow functions taking into account the effects of the scoop and thermal driving is the Olander's flow function. By combining the flow function that resulted from the Onsager-Pancake equation and the Olander's flow function, a new flow function is suggested, that in addition to applying the effect of thermal and mechanical driving, the feed driving added to it with the DSMC method. The results obtained using this new flow function in the modified diffusion equation by Onsager-Cohen, showing the resulted optimal separation power from that in comparison to the Olander's function occurs in a state where thermal driving is insignificant and scoop driving has increased. The effects of scoop drive have increased by increasing the feed value with the new flow function. Furthermore, the diffusion equations have been solved for 235UF6 and 238UF6 using the new flow function and it has been calculated the separation parameters.

Investigation on the effect of holdup and cascade shape in NFSW cascades

No Feed and Single Withdrawal (NFSW) cascades are of non-conventional gas centrifuge cascades. The present study has been conducted to investigate the effect of holdup of pipes and stages as well as the shape of cascade in separating the multi-component isotopes in NFSW cascades. These cascades are optimized by the Particle Swarm Optimization (PSO) algorithm with an advanced objective function to evaluate the effect of the cascade shape. Moreover, we take into account the holdup term in the equations to study the effect of the holdup of pipes and stages. By investigating the effect of the Holdup of pipes and stages, we found that as the holdup increases, the amount of flow concentration changes. We also compare the optimal tapered structure with the square shape of the NFSW cascade. The results showed that the optimal tapered shape is superior over the square shape in separating the middle component of Xenon.

Rotor Length Dependence of the Separative Power of a Gas Centrifuge

An analytical expression is obtained for the dependence of the maximum separative power of a centrifuge on the rotor length taking the feed flow into account. It is shown that the maximum separative power of a centrifuge is a nonlinear function of the rotor length.

Change of the External Flows of a Separating Cascade to Shorten the Duration of a Transient Process

A transient process is studied for the example of obtaining in a cascade of gas centrifuges germanium enriched in 72Ge to 50%. The nature of the effect of the cascade flows on the concentration dynamics of the isotopes and duration of the transient process is determined. The conditions under which the accumulation of the desired isotope in the cascade is accelerated and the duration of the transient process is decreased are shown.

Разделение многокомпонентной изотопной смеси в процессе заполнения каскада газовых центрифуг

Разделение многокомпонентной изотопной смеси в процессе заполнения каскада газовых центрифуг

A finite element solution to the generalized Onsager model of fluid flow in a countercurrent gas centrifuge

ABSTRACT Based on the Onsager Equation, a linearized sixth-order partial differential equation describing the flow in the volume of the rotor of a gas centrifuge is solved using a finite element algorithm employed by the CurvSOL code. The results are compared to those from Pancake, an existing code that uses eigenfunction expansion to solve the Onsager equation. Excellent agreement is demonstrated between the solutions of the wall temperature gradient and scoop drive mechanisms for both the Rome and Iguaçu centrifuge designs. Results suggest rotor speed and radius play key roles in the influence of wall curvature on the flow solution.

Separation of Nickel Isotopes during the Filling of a Cascade of Gas Centrifuges with Different Numbers of Stages

The results of our study of the filling of a cascade of gas centrifuges with different numbers of stages for separation of nickel isotopes used in nuclear physical research and production of radioactive isotopes are presented. During the filling of the cascade, the natural mixture of nickel isotopes is separated, and the isotopes are concentrated in different cascade stages. The concentrations of nickel isotopes in the stages and flows of light and heavy fractions after the filling of the cascade were shown to depend on the number of stages in the cascade.

Waves in strong centrifugal field: dissipative gas

In the fast rotating gas (with the velocity typical for Iguassu gas centrifuge), three families of linear waves exist with different polarizations and law of dispersion. The energy of the waves is basically concentrated at the axis of rotation in the rarefied region. Therefore, these waves decay on the distance comparable with the wavelength. There is only one type of waves propagating strictly along the axis of rotation with the law of dispersion similar to ordinary acoustic waves. These waves are interested for the physics of gas centrifuges. The energy density of these waves concentrates at the wall of the rotor. These waves have weak damping due to the molecular viscosity and heat conductivity. The damping coefficient is determined for this type of waves by numerical calculations. Analytical approximations for the damping coefficient are defined as well. At the parameters typical for the Iguassu centrifuge, the damping is defined by interaction of the waves with the rotor wall.

Method for Enriching Reprocessed Uranium in a Cascade of Gas Centrifuges with Simultaneous Decrease in the 232,234,236U Content

It is shown that reprocessed uranium can be enriched with simultaneous dilution of 232,234,236U isotopes in a cascade of gas centrifuges that has three feed flows (depleted uranium, low-enriched uranium, reprocessed uranium). Computational experiments are carried out for different 235U content of the lowenriched uranium. It is demonstrated that the chosen combination of diluents can simultaneously reduce the cost of the separation procedure and the consumption of natural uranium, which in turn ensures cost reduction relative to not only the earlier used multiflow cascades but also the standard cascade for enrichment of natural uranium.

Features of light-water reactor fuel made of reprocessed uranium in terms of IAEA safeguards implementation

One of the main priorities of nuclear power development is Non-Proliferation of Nuclear Weapons. So, the possibility of nuclear materials illicit diversion must be ruled out. This study aims to assess the chance of producing significant quantity of Highly enriched uranium (HEU) in case of covert diversion of fresh fuel. Analysis is carried out on the assumption that stolen reactor-grade Low enriched uranium (LEU) fuel was made of reprocessed uranium and got to be enriched to 90% 235U in gas centrifuges. As its isotopic composition contains a set of even-numbered minors 232,234,236U, such operation for producing the main component of nuclear explosive device is harder comparing to one when fuel was made of natural uranium. Despite the higher proliferation resistance of reused fuel, there is a chance that it could be used in undeclared nuclear weapons programs. So, we are highlighting the importance of timely detection of nuclear materials diversion, especially for the LEU, which is the most sensitive to proliferation. Fortunately, due to unique physical properties of reprocessed uranium, such detection is possible with a quick NDA test even in case of a single fuel rod replacement.

High-flux lead reactors with average neutron energies up to 1 MeV

The paper is devoted to the physics and technology of special nuclear reactor operating on hard neutrons. As is known, a fast neutron spectrum is realized in sodium fast reactors (SFR) at neutron flux densities up to 8⋅1015 neutrons / cm2⋅ s. In SFRs the coolant and fuel limit the average neutron energy by a value of not more than 0.5 MeV, with a relatively small fraction,15%, of hard neutrons, En>0.8 MeV. Future high-flux reactors on hard neutrons, with an average neutron energy up to 1 MeV and neutron flux densities on the order of (3-5)⋅1015 neutrons / cm2⋅s, may be constructed and claimed in the medium term as multipurpose reactors that combine the functions of reactors - transmutators of minor actinides (MA), as well as isotope and research reactors. The requirements for obtaining a hard neutron spectrum in the core of the reactor lead to the need to use nuclear fuel and a coolant that slow moderate neutrons. Metallic fuel should be used as a fuel, and as a coolant - natural lead, whose isotopic composition accounts for the fraction of the slow-moderating 208Pb isotope a value of 52.3%. An even more harder neutron spectrum can be obtained in the case of using a coolant based on enriched at gas centrifuges 208Pb or radiogenic 208Pb extracted from lead-rich thorium ores. The next condition leading to a hard neutron spectrum is the small dimensions of core, D × H ≈ 0.5 × 0.5 meters, in which the initial neutron fission spectra of 235U, 239 Pu, 241Pu are not strongly changed. This requirement means that reactors on hard neutrons should be classified as small power or research reactors, within which their thermal capacity does not exceed a value of the order of 200-300 MW.

On the scoop heating effect of a gas centrifuge in numerical simulation

The withdrawal scoops in a gas centrifuge generate heat due to frictions and shock waves from the interaction between the scoops and the gas at a high speed motion. The heat changes the flow field in the centrifuge and influences the separation performance, giving rise to the heating effect. In the study of the flow field in a gas centrifuge with the two-dimensional axisymmetric approximation, the effects of a scoops are modelled by momentum and energy sources/sinks, or by a rotating disk with an angular speed different from that of the centrifuge rotor. The scoop-gas interaction is very complicated, and it is important to ensure to have the heating effect appropriately considered. Numerical simulation shows that, if the heating effect is not properly taken into account, the gas temperature around the scoops decreases, which is inconsistent with the real physical process. Some approaches dealing with the heating effect are discussed to avoid making incorrect modelling. Simulation results reveal that the scoop heating effect has a significant influence on the separation performances of the gas centrifuge.

Analytical equation for the damping coefficient of the acoustic wave in the strong centrifugal field

In the fast rotating gas (for example, in the gas centrifuge) three families of linear waves exist with different polarizations and law of dispersion. Analytical equation for the damping coefficient of the wave with the weakest damping is determined. This wave propagates strictly along the axis of rotation and the energy density of this wave concentrates at the wall of the rotor.

Optimization of cascades with variable overall separation factors by various efficiency criteria

Construction and operation of separation facilities require considerable investments. That is why the special attention in the theory of isotope separation in cascades is paid to their optimization. The installation allowing obtaining the required quantity of a commercial isotope product by a minimum unit cost it is customary to call as the optimum cascade. However, the use of such the criterion in theoretical calculations is inconvenient, in view of the fact that the cost coefficients are generally inaccessible and can vary depending on external factors. Therefore, theoretically the minimum possible number of separation unit or elements, for instance, gas centrifuges, is often used as the optimization criterion, since its value directly indicates the unit costs. In addition, such criteria as the minimum of the total cascade separation capacity or the minimum of the deviation sums of the maximum possible separation capabilities are also applied in the optimization calculation. In this connection for the case of the cascade with a variable from stage to stage overall separation factor of a centrifuge, the parameters of the cascades optimized by means of various optimization criteria may differ largely. In this paper, we compare the parameters of cascades with the same external conditions, which are optimized by the above criteria. As the criterion to compare all cascades under investigation is chosen the minimum number of separation elements in the installation. The chosen approach allows us to estimate the deviation in the number of gas centrifuge in a case of optimization of a separation plant by different efficiency criteria.