We have applied the self-consistent local pseudopotential method to study the electronic structure of Si, Ge and e&. The calculated band structures and valence charge densities agree well with experiment. The momentum-space formalism of Ihm, Zunger and Cohen, based on the self-consistent local pseudopotential method, is used to calculate the total energy of these crystals. The results are in good agreement with experiment.

A model is presented on nuclear sodium alumina phosphate (NAP) glass aqueous corrosion accounting for dissolution of radioactive glass and formation of corrosion products surface layer on the glass contacting ground water of a disposal environment. Modelling is used to process available experimental data demonstrating the generic inhibiting role of corrosion products on the NAP glass surface.

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Rydberg matter is a condensed excited state made of highly excited atoms. State of art of research in the field of Rydberg matter is briefly reviewed. Special attention is focused on the contribution of Russian and Swedish scientists' groups to the analysis ofthis problem. Most attention is concentrated on physical principles ofpseudopotential method and density functional theory used to describe the Rydberg matter. The description of Rydberg matter as an excited state becomes viable after the formal replacement of excited atoms by ground state pseudoatoms. This procedure has been used to find parameters of Rydberg matter made of highly excited cesium atoms. Theoretical estimations conform to experimental data available.

According to the multibarrier concept adopted in this country for the burial of high-level wastes, the main barriers of the burial system which isolate the system from man are the matrix which contains the radionuclides and the geological formation in which the burial site is located. The packing of the wastes, the driving complex of the burial site, and so on are viewed as additional engineering barriers. The properties of each component of the system must meet certain requirements and, on the whole, they must be coordinated with one another so that the radionuclides are reliably isolated from the biosphere until they decay to a safe level.The first step in assessing the reliability of the burial site is to characterize the properties of the solidified highlevel wastes which are included in different matrices. Phosphate, borosilicate, and aluminosilicate glasslike and minerallike materials were considered as matrices. The composition of these materials is given in Table 1.To choose the optimal composition, the properties of the wastes determining the conditions of temporary storage and burial are investigated: the chemical stability of the materials in de-ionized water and water of the corresponding geological formations, the thermal stability, the mechanical strength, the radiation resistance, and the thermophysical characteristics (linear expansion coefficient, thermal conductivity, and heat capacity).The assessment of the properties of the solidified wastes starts with the hydrolytic stability, which determines the main possible escape of radionuclides from the matrix during storage. According to GOST-211-91, the chemical stability of the materials is determined by the rate of leaching of the radionuclides (Table 2).To assess the behavior of the solidified wastes during storage in geological formations, the escape of nuclides from solidified wastes in simulators of formation waters of different formations in the temperature range 20-150~ was studied. It was shown that the true behavior of the solidified wastes during geological storage will depend not only on the temperature but also on the rate of the diffusion of water, the ratio of the flow volume of the soil water to the contact surface area with the solidified material, the composition of the ground waters (salt content and pH), and other factors that must be taken into account for the specific conditions of a geological storage site. For example, at high temperatures (100~ and higher) separate components of the formation water (for example, calcium and iron) can interact with the products of leaching of separate components of the solidified wastes with formation of insoluble compounds at the surface of the solidified waste. The "secondary" layer of insoluble compounds that forms screens the surface of the materials and slows down to some degree the escape of leached nuclides in the contact waters. The thickness and composition of the secondary layer depend on the composition of the solidified material and the contact water (Table 3) and the interaction ...

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