Evaluation of the potential hazard of secondary radioactive contamination of underground water by sewage works

The time dependence of the distribution of the volume activity of radionuclides over ground layers is calculated under chemically equilibrium and hydraulically stationary condition sand under conditions of continuous operation of radioactively hazardous units of sewage works. As initial information, a set of data on the hydrogeological characteristics and physicochemical properties of the sewage-water sediments (SWSs) found at the sewage works of Chechersk and Slavgorod is used. The results of the calculations performed are analyzed, and the data on the egress of radiocesium from the SWSs found in the sludge areas and filtration fields with different bases into underground water are presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 557–560, March–April, 2000.     

Calcium Production by the Electrolysis of Molten CaCl2—Part I. Interaction of Calcium and Copper-Calcium Alloy with Electrolyte

This paper describes the interaction between calcium and molten CaCl₂ and the solubility of calcium in this melt, depending on the calcium content in the copper-calcium alloy that comes in contact with the molten CaCl₂. The negative influence of the dissolved calcium on the current efficiency was verified. The negative effects of moisture and CaO impurities on the calcium current efficiency were demonstrated. The dependence of the current efficiency and the purity of the metal obtained by the electrolysis conditions were studied in a laboratory electrolyzer (20 to 80 A).     

Electronic and Magnetic Properties of Superconducting Sr4V2Fe2As2O6 Versus Sr4Sc2Fe2As2O6

First principles of FLAPW-GGA calculations have been performed with the purpose to understand the peculiarities of band structure and Fermi surface topology for recently discovered 37 K superconductor: Sr₄V₂Fe₂As₂O₆—in comparison with isostructural phase Sr₄Sc₂Fe₂As₂O₆. Our main finding is that the replacement of Sc with V leads to drastic transformation of electronic, magnetic and conductive properties of these materials: as against non-magnetic Sr₄Sc₂Fe₂As₂O₆ which is formed from non-magnetic conducting [Fe₂As₂] and insulating [Sr₄Sc₂O₆] blocks, Sr₄V₂Fe₂As₂O₆ consists of non-magnetic conducting [Fe₂As₂] blocks and [Sr₄V₂O₆] blocks which exhibit magnetic half-metallic properties.     

Estimate of the solubility of titanium in beryllium oxide based on quantum-chemical calculations

The maximum solubility of titanium in BeO is estimated on the basis of calculations of the formation enthalpy of beryllium oxide, doped with titanium, performed using quantum-chemical calculations within the framework of the DFT theory. Amethod for estimating numerically the maximum solubility of impurities in crystals is examined for beryllium oxide doped with titanium. The method is based on using the results of nonempirical quantum-chemical calculations. The method can be used to estimate the maximum solubility of diverse impurities in inorganic compounds and ceramic materials based on these compounds.     

Composition of beryllium oxide ceramics

The physicochemical and electrophysical properties of ceramics based on BeO without impregnation and after impregnation with an aqueous solution of sodium carbonate Na₂CO₃ are studied. It is established that impregnation leads to preparation of ceramic specimens with a white color, which develop increased porosity, lower amount of impurities and smaller average microcrystal size, although it has little effect on their electrophysical properties. In order to improve these properties considerably it is necessary to increase ceramic density by increasing its sintering temperature by 20 – 40 K. Values of electrical permittivity δ and dielectric loss tangent tg δ are determined for a series of BeO ceramic specimens (732 pieces), having identical geometric dimensions, but prepared from original BeO powder of different batches. Studies show considerable scatter in the distribution of these parameters, which points to a requirement for further improvement of BeO-ceramic preparation technology.     

Ab initio Probing of Magnetic and Electronic Properties of Monoclinic ε-WO3 Doped with 3d Transition Metals Within GGA and GGA+U

Based on ab initio band structure calculations, we have systematically examined the monoclinic tungsten trioxide doped with all 3d metals (M=Sc,Ti,…,Ni,Cu) focusing on the effects of these impurities on the electronic and magnetic properties of ε-WO₃. We found that all of the 3d impurity atoms can be divided into two main groups. The first group includes the atoms of the beginning of the 3d row, and for these systems (for example, ε-WO₃:Ti) the highest magnetic moments and the peculiarities of the near-Fermi states are due to the atoms of the oxygen lattice of trioxides. On the contrary, the impurity atoms of the end of the 3d row play a dominant role in the formation of magnetic and electronic properties. These results are fair for calculations within both GGA and GGA+U approximations. Finally, there are so-called “border” systems (for example, ε-WO₃:Cr), where the Coulomb interactions have a critical influence on the electronic and magnetic parameters.     

Synthesis and Application of Transparent Beryllium Ceramics

The physicochemical properties of beryllium ceramics and its application in different fields of technology and special instrument making are considered. Transparent BeO ceramics designed for use in laser technology and ionizing radiation dosimetry is prepared by hot pressing with the use of different modifying additives at temperatures up to 1520 K.