Oleg I. Rebrin’s research while affiliated with Ural Federal University and other places

The magnesiothermic reduction of zirconium from its tetrachloride is a promising method for producing a nuclear-purity zirconium sponge. High-purity zirconium tetrachloride can be produced by extractive rectification. This method of zirconium and hafnium separation is based on the difference in the vapor pressures of zirconium and hafnium chlorides over a molten mixture of aluminum and potassium chlorides that is used as a liquid salt extractant. The separation of zirconium and hafnium tetrachlorides is carried out at controlled pressure in direct contact with a low-melting solvent, which is represented by a chloroalu-minate melt. One of the main criteria for the suitability of molten potassium and aluminum chlorides for the separation of zirconium and hafnium is the molar ratio AlCl 3 /KCl. A technique for determining the chemical and phase compositions of frozen chloroaluminate melts, including zirconium tetrachloride containing salts, is developed in this work using the results obtained with a set of modern methods and specific approaches. INTRODUCTION Zirconium and zirconium-based alloys have proven themselves to be reliable structural materials for the needs of nuclear energy due to their nuclear physical characteristics and good mechanical and corrosion properties. The principal quality of structural materials for use in peaceful nuclear technologies is the small thermal neutron capture cross section of alloy. The one of the main problems of nuclear-purity zirconium is its separation from hafnium impurities (presence of 1.5 wt % hafnium increases the neutron capture cross section of a material by twenty times). Reduction melting is a widely used method for producing metals in a compact form. The method is characterized by high purity of the produced metal, high productivity, and relative simplicity of the technological process. In the modification of magnesiothermic reduction of zirconium chlorides, the metallothermal method attracted the attention of researchers for investigation of zirconium chloride propertieis and the methods of ZrCl 4 and HfCl 4 separation. The most promising approaches to the separation of zirconium and hafnium tetrachlorides are based on the difference

Two contact masses were obtained and analyzed for their catalytic properties in the production of hydrophobic coatings. These masses are based on the silicon-copper system and consist of 25%Cu-75%Si and 50%Cu-50%Si compositions. A standard method of copper(I) chloride reduction was optimized to obtain finely dispersed copper particles with high catalytic activity. It is shown that reduction is possible directly in contact with silicon, the resulting average diameter of copper particles is 5-10 microns in both contact masses (25%Cu-75%Si and 50%Cu-50%Si). A metallographic analysis revealed a loose morphology of the silicon-copper phase interfaces, which is necessary to enhance the catalytic activity of the contact masses. Local chemical analysis by scanning electron microscopy has established the ratio of the particle size of the initial polycrystals of copper chloride(I) and the resulting copper particles as a result of reduction on silicon. The process of deep reduction makes it possible to obtain particles up to 5 microns in size. These results provide useful insights into the formulation of coatings containing organosilicon compounds to reduce friction in hydrocarbon transport.

Link for citation: Nikitin D.I., Polovov I.B., Rebrin O.I. Possibility of uranium extraction from spent nuclear fuel in fused electrolytes containing rare elements . Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 210-218. In Rus. The relevance of the research is caused by the plans of using electrolytic separation of metalized spent nuclear fuel as a stage in pyrochemical reprocessing of mixed nitride uranium-plutonium fuel. The main aim is to determine the parameters of uranium electrolytic separation from an alloy with simulators of fission products (precious metals and rare earth elements) simulating spent nuclear fuel in salt mixtures based on 3LiCl–2KCl with additives of rare earth element chlorides. Objects: model spent nuclear fuel – uranium alloy with simulators of fission product (precious metals and rare earth elements) with a mass compound of Pd:Ru:Ag:Rh=25:1:3:3, Nd:Ce:La:Pr:Sm:Y=15:10:5:5:5:1). Methods: electrorefining, X-ray fluorescence and X-ray diffraction method of analysis, inductively coupled plasma mass spectrometry, assessment of distribution of components in the system. Results. The data obtained showed that uranium deposits have dendrite formations of alpha-uranium at 550 °C in orthorhombic crystal system toward needle cathode current density. The resulting cathode deposits are free from impurities of ruthenium, rhodium, molybdenum, praseodymium and yttrium. The purification coefficient for palladium reaches 3000, and for silver 1700. Noble metals accumulate in the anode sludge, and even with the complete depletion of the anode material. The concentration of noble metals in the cathode deposit does not exceed 0,0015 wt %. Despite the high concentration of rare-earth chlorides in the electrolyte, which simulates the accumulation of rare-earth ions during repeated reprocessing of spent nuclear fuel, the concentration of rare-earth metals in the cathode product did not exceed 0,007 wt %. During uranium electrowinning from a model spent nuclear fuel in the 3LiCl–2KCl–UCl3 electrolyte (10,1 wt %) with REE chlorides, which imitate their accumulation in the electrolyte during repeated processing, at 550 °C, as well as the initial cathode current density of 0,2 A/cm2, the specific amount of electricity is 1,0 A∙h/cm2. A cathode uranium deposit is released with a current efficiency exceeding 90 % with all anode mass depletion, and purification coefficient 1800 for the sum of precious metals and for the sum of rare earth metals.