SUPERCRITICAL FLUID EXTRACTION OF MOLYBDENUM COMPLEXES AND ITS ISOTOPES WITH CARBON DIOXIDE

Separation of molybdenum complexes and its isotopes by supercritical fluid extraction (SFE) with carbon dioxide was experimentally investigated. The type of modifier, which provides increasing the efficiency of the metal and its isotopes separation, was determined. Extraction of molybdenum isotope complexes was carried out in the updated SFE-U unit at a constant value of the initial pressure P = 20 MPa and constant temperatures of the upper (T1 = 35 ⁰C) and bottom (T2 = 45 ⁰C) flanges of the extraction chamber. The exposure time of the extract and the level along the extraction chamber height, from which the eluent was sampled, were set in the experiments. It is shown, that at a certain sampling height and at certain exposure times, change in the natural content of Mo isotopes in the extracts takes place.

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.