Uranium Isotope Separation Research Articles

Scientific search under the pressure of high responsibility: development of the technology of electromagnetic isotope separation in the framework of the USSR Atomic project

One of the ways to obtain nuclear explosives for the manufacture of the first atomic bombs was the separation of uranium isotopes by electromagnetic (mass spectrographic) method. The theoretical justification and experimental separation of uranium isotopes by this method was carried out by L. A. Artsimovich in the Laboratory No. 2 of the USSR Academy of Sciences. By the middle of 1945, L. A. Artsimovich had obtained results at the experimental facility indicating the possibility of stable enrichment of uranium with the U-235 isotope using this method. Having the results of the experiments, the Design Bureau at the “Electrosila” plant (D. V. Efremov), with the participation of the Research Vacuum Institute (S. A. Vekshinsky) and the “A” Institute (M. Ardenne), developed a project of an industrial multi-chamber installation for electromagnetic separation of uranium isotopes SU-20. Such an installation was manufactured and put into operation at the newly created plant in the Urals, which allowed in 1951 to obtain the necessary amount of uranium-235 for the RDS-3 atomic bomb. After 1952, the technology of electromagnetic separation was no more used for the separation of uranium isotopes due to the improvement of more productive equipment for gas-diffusion separation of isotopes. The equipment of the electromagnetic isotope separation plant built in the Urals was used to produce lithium-6, needed to equip the first thermonuclear charge, which was successfully tested in 1953. In the next years, the electromagnetic isotope separation plant was involved in the manufacture of isotope products for scientific, technical and medical applications at wide range of utilization in Russia and abroad.

Modeling and Simulation of Flow and Uranium Isotopes Separation in Gas Centrifuges Using Implicit Coupled Density-Based Solver in OpenFOAM

The performance of a gas centrifuge that is used for isotopes separation is dependent on the gas flow inside it. In this study, for modeling the UF6 gas flow, an Implicit Coupled Density-Based (ICDB) solver, was developed in OpenFOAM. To validate the ICDB solver, the gas flow within the rotor in total reflux state was compared with the analytical solution obtained by Onsager model and the numerical solution obtained by the Fluent software. The results showed that the ICDB solver had acceptable accuracy and validity. Also the computational efficiency of Roe, AUSM (Advection Upstream Splitting Method) and AUSM+ up schemes were compared. The results showed AUSM+ up scheme is efficient. Then, the uranium isotopes separation in a gas centrifuge was simulated. It was revealed that all gas flow characteristics including velocity, pressure, temperature and axial mass flux, as well as uranium isotope separation parameters including separation power and separation coefficients could well be predicted.

New results for laser isotope separation using low-energy methods

Today, research aimed at the development of low-energy methods of molecular laser isotope separation (MLIS) is relevant and in demand. The main goal of these studies is to find efficient and cost-effective methods that can be used as the basis for the technology of laser separation of uranium isotopes, as well as other elements. To date, a number of approaches to the implementation of low-energy methods of MLIS using infrared (IR) lasers have been proposed. Many of these approaches are not well understood and/or are difficult to put into practice. Some of them are considered to be promising and require further study. These include the method of isotope-selective suppression of the clustering of molecules using IR lasers during gas-dynamic expansion at a nozzle exit and the method of isotope-selective IR dissociation of small molecular van der Waals clusters. A review of recent results obtained using these two methods is presented. The experimental facilities and research methods are briefly described, and the choice of the objects of study is substantiated. Results obtained with model SF6 and CF3Br molecules are analyzed with reference to studying the process of isotope-selective suppression of the clustering of molecules among themselves and with atoms of an argon carrier gas, as well as the process of isotope-selective IR dissociation of small homogeneous and mixed clusters of (SF6)mArn and (CF3Br) m Arn (where m = 1 – 2 and 0 ⩽ n ⩽ 5 are the numbers of molecules and atoms in the clusters, respectively). The results presented suggest that these methods can be used for the separation of isotopes in molecules containing isotopes of heavy elements, which have a slight isotopic shift in the IR absorption spectra.

On the sequential separation and quantification of 237Np, 241Am, thorium, plutonium, and uranium isotopes in environmental and urine samples

The implementation of the one-pass-through separation technique using two stacked chromatography columns of TEVA – TRU resins for the separation of 237Np, 241Am, thorium, plutonium and uranium from environmental and urine samples was investigated. The sequential separation technique proved to be successful and gave similar results to those obtained when using individual separations. The analysis time was considerably improved. The amount of chemical waste was also reduced by 50% and the use of HClO4 was avoided. The technique of ICP-MS was also investigated as a complementary technique to alpha-spectrometry.

An experimental study on high-purity uranium refining by passing in succession through pulsed extraction, washing, and stripping columns

Nuclear-purity uranium was refined by passing a solution of uranyl nitrate in 3–5 M HNO3 in succession through pulsed extraction, washing, and stripping columns for feeding into the U(III)–U(IV) chemical exchange system for uranium isotope separation. The extractant (tri-n-butyl phosphate, TBP), the diluent (kerosene), nitric acid, ammonium carbonate, sodium nitrate, and water were preliminarily refined to chemical purity. The diameter and height of pulsed columns for uranium purification was 25 and 1500 mm, respectively, and the pulse frequency was 1 s–1. The content of transition metals (Fe, Co, Ni, Cu, Ag) and Pb, which can catalyze the U(III) oxidation in acidic aqueous solutions, was reduced to the level lower than 1 ppm (10–4%). The total purification factor was higher than 103. The purification required 3–4 theoretical plates with HETP of the columns of 35–40 cm.

Waves in a gas centrifuge

Impact of the pulsed braking force on the axial gas circulation and gas content in centrifuges for uranium isotope separation was investigated by the method of numerical simulation. Pulsed brake of the rotating gas by the momentum source results into generation of the waves which propagate along the rotor of the centrifuge. The waves almost doubles the axial circulation flux in the working camera in compare with the case of the steady state breaking force with the same average power in the model under the consideration. Flux through the hole in the bottom baffle on 15% exceeds the flux in the stationary case for the same pressure and temperature in the model. We argue that the waves reduce the pressure in the GC on the same 15%.

Sequential separation and determination of uranium and thorium isotopes in soil samples with Microthene-TOPO chromatographic column and alpha-spectrometry

In the method, soil was fused together with Na2CO3 and Na2O2 at 600 °C, uranium and thorium were leached out with HCl, HNO3 and HF, and HClO4 was used to eliminate the residual HF through evaporation. The leaching solution (2 M HNO3) was passed through a Microthene-TOPO column to adsorb uranium and thorium. Thorium was first eluted with 2 M HCl and electrodeposited in 0.025 M H2C2O4 + 0.15 M HNO3 on a stainless steel disc. Uranium was eluted with a 0.025 M ammonium oxalate solution and also electrodeposited. Both thorium and uranium isotopes on the discs were measured separately by α-spectrometry.

A Proliferation Assessment of Third Generation Laser Uranium Enrichment Technology

ABSTRACTLong-standing efforts to develop a commercially viable laser-based process for uranium enrichment, initially with atomic and later molecular isotope separation, have had limited success. This article discusses a model for a third generation of laser enrichment technology where CO2 laser light is Raman scattered to generate 16 μm photons that excite a vibrational mode in uranium-235 hexafluoride molecules within an adiabatically expanding free carrier gas jet, allowing for the partial separation of uranium isotopes by condensation repression. The SILEX (Separation of Isotopes by Laser Excitation) process being developed as part of the Global Laser Enrichment project may be one example of this separation technique. An ideal, asymmetric cascade for enriching uranium to weapon-grade levels is presented, and an analysis of the minimum laser performance requirements is included. Optimal running parameters, physical space constraints, and energy efficiency estimates are discussed. An assessment of the technical skills required is also provided. Finally, material available in an online supplement discusses possible lasers that may be utilized in such a process, and offers an introduction to dimer formation, a laser-based enrichment cascade, and a model for estimating the enrichment factor.

Determination of uranium concentrations and 234U/238U activity ratio in some granitic rock samples by alpha spectrometry: Application of a radiochemical procedure

The present study is an application of a radiochemical procedure using alpha spectrometry technique for determination of uranium isotopes 238 U,234 U, and 235 U on 13 granitic samples. These samples were collected from Gabal Gattar area, Northeastern Desert, Egypt. The collected samples were digested using microwave technique with aqua regia and spiked with 232 U for chemical yield and activity calculation. Separation of uranium isotopes from the samples was done by Dowex 1 × 4 (50–100 mesh) resin followed by source preparation using microprecipitation technique. The concentrations of 238 U were ranged between 28.9 ± 0.9 and 134.8 ± 1.8 Bq/g, and the 234 U concentrations were between 24 ± 0.6 and 147.7 ± 2.2 Bq/g. For the 235 U, the activity concentrations were between 1.3 ± 0.2 and 6.7 ± 1.2 Bq/g. The activity ratio of 234 U/238 U was calculated and varied from 0.80 to 1.30.

Rapid quantitation of uranium from mixed fission product samples

Chemical similarities between uranium(VI) and molybdenum(VI) create challenges for separation and quantitation of uranium isotopes from a mixed fission product sample. The purpose of this work was to demonstrate an improved chemical separation for the detection of 235U using gamma spectroscopy. The optimized method, which included extraction and anion exchange chromatography, demonstrated a consistent chemical yield of 74 ± 3 % for uranium. Using a fresh fission product sample the minimum detectable activity for 235U, 237U, and 238U was reduced by a factor of two. The chemical isolation of uranium was achieved in less than 4 h, with a separation factor of 1.41 × 105 from molybdenum.

Impact of the pulsed braking force on the axial circulation in a gas centrifuge

Impact of the pulsed braking force on the axial gas circulation in centrifuges for a uranium isotope separation was investigated by the method of numerical simulation. Two camera model has been explored. The pulsed braking of the rotating gas results into generation of waves which propagate along all length of the rotor of the centrifuge. The wavelength appears in accordance with predictions of our analytic theory. Pulsations almost doubles the axial circulation flux in the working camera in comparison with the case of the steady state breaking force with the same average power.

Uranium Isotopes Separation Technique

This work describes the atomic laser isotope separation (LIS). The (LIS) plant means calculating the values of a large number of parameters in order to optimize some objective function. Here we use simple model to describe the elementary physical processes: evaporation, vapor expansion, interaction between photons and atoms, ion extraction etc...concentrated on theoretical and empirical bases. An optimization process for the separation of Uranium isotopes is described and discussed.

Uranium Isotopes Separation Technique

This work describes the atomic laser isotope separation (LIS). The (LIS) plant means calculating the values of a large number of parameters in order to optimize some objective function. Here we use simple model to describe the elementary physical processes: evaporation, vapor expansion, interaction between photons and atoms, ion extraction etc...concentrated on theoretical and empirical bases. An optimization process for the separation of Uranium isotopes is described and discussed.

Waves in strong centrifugal fields: dissipationless gas

Linear waves are investigated in a rotating gas under the condition of strong centrifugal acceleration of the order $10^6 g$ realized in gas centrifuges for separation of uranium isotopes. Sound waves splits into three families of the waves under these conditions. Dispersion equations are obtained. The characteristics of the waves strongly differ from the conventional sound waves on polarisation, velocity of propagation and distribution of energy of the waves in space for two families having frequencies above and below the frequency of the conventional sound waves. The energy of these waves is localized in rarefied region of the gas. The waves of the third family were not specified before. They propagate exactly along the rotational axis with the conventional sound velocity. These waves are polarized only along the rotational axis. Radial and azimuthal motions are not excited. Energy of the waves is concentrated near the wall of the rotor where the density of the gas is largest.

Enhancement of Identity in the Hydraulic Characteristics of a Gas Centrifuge for Isotope Separation

The problem of non-identity in characteristics of the GCs for uranium isotope separation grows up with increase of a rotor speed of rotation. It may lead to noticeable decrease of the separative power of the centrifugal machines. The carried out assessments allowed to get the dependence of the relative separation performance losses on the non-identity in the hydraulic characteristics of the GCs connected in parallel. The results of calculation are compared with that of obtained in experiments.

Effect of Bellows on the Separation of Uranium Isotopes in a Supercritical Gas Centrifuge

The effect of bellows in a supercritical gas centrifuge on the separative power is studied experimentally. It is found that the separative power of a gas centrifuge with bellows placed in the rotor is lower than that of a centrifuge with a smooth rotor and the difference increases with increasing number of bellows in the rotor. It is shown that the reduction of the separative power can be compensated to a large extent by increasing the temperature component of the circulation flow.

Rapid determination of actinides in asphalt samples

A new rapid method for the determination of actinides in asphalt samples has been developed that can be used in emergency response situations or for routine analysis. If a radiological dispersive device, improvised nuclear device or a nuclear accident such as the accident at the Fukushima Nuclear Power Plant in March, 2011 occurs, there will be an urgent need for rapid analyses of many different environmental matrices, including asphalt materials, to support dose mitigation and environmental clean-up. The new method for the determination of actinides in asphalt utilizes a rapid furnace step to destroy bitumen and organics present in the asphalt and sodium hydroxide fusion to digest the remaining sample. Sample preconcentration steps are used to collect the actinides and a new stacked TRU Resin + DGA Resin column method is employed to separate the actinide isotopes in the asphalt samples. The TRU Resin plus DGA Resin separation approach, which allows sequential separation of plutonium, uranium, americium and curium isotopes in asphalt samples, can be applied to soil samples as well.

Methods of Extracting a Small Quantity of Impurities during Rectification of Uranium Hexafluoride in Fluoride Gas Reprocessing of Spent Nuclear Fuel

Methods for concentrating and extracting a small quantity of volatile impurities of the fluorides of fission products in the rectification method of reprocessing uranium hexafluoride are discussed. Such methods are shown to be efficacious during the operation of experimental and commercial facilities for sublimate and radiochemical operations and in uranium isotope separation plants.

HOW THE UNITED STATES HELPED IRAN BUILD A LASER ENRICHMENT LABORATORY

In the spring of 1975, Iran became one of the first states to begin comprehensive research into using lasers for uranium isotope separation. As part of that research, the government sought the expertise of Jeff Eerkens, a leading American specialist in the field. This investigative article tells the story of their relationship: how it began, how it developed, and how it ended, drawing extensively from the authors' personal interviews with Eerkens as well as numerous publications and other interviews.

Generation of tunable 16 μm radiation from CO2 by cascade lasing

In this paper we propose a scheme to generate tunable 16 μm radiation from CO2 molecules by cascade lasing. The stimulating 9.5 μm radiation is generated internally by the fast rotating mirror Q-switching technique. The optical scheme proposed by us uses an intracavity prism to separate the 9.5 μm and the 16 μm beams. This facilitates independent tuning of the two beams if required. In the present configuration, only the 16 μm cavity is dispersive. The 9.5 μm beam grows spontaneously in a stable semiconfocal resonator. We have developed a theoretical model to simulate the proposed scheme. The model predicts the energy and power of 16 μm radiation. The calculated values are much higher than the previously obtained experimental values. The results point out the feasibility of developing a laser system based on the theoretical design parameters presented in this paper. Such laser systems can find application in uranium isotope separation studies.