The basic principles for performing analysis and the systems requirements for large-scale nuclear power in our country are formulated. The problems of modern nuclear power are examined and ways for modern nuclear power to transition to innovative development while satisfying these systems requirements for fuel use, handling spent fuel and wastes, and nonproliferation are indicated. The basic scenario of innovative development in the near term (up to 2030) is based on using predominantly 235 U as fuel and water-moderated water-cooled reactors, which have been well mastered, for increasing nuclear capacities with limited introduction of fast reactors for solving the problem of spent fuel from thermal reactors. In the long term , a transition to 238 U as the primary raw material with fast reactors predominating and complete closure of the nuclear power fuel cycle will be made.Nuclear physicists understood from the very beginning of work on peaceful uses of atomic energy (1948)(1949) that the mankind's energy needs can be met on a large scale and in the long term only by mastering the technologies which extensively breed nuclear fuel. Even back then, our ingenious predecessors and teachers studied, together with the questions of obtaining energy from "fissile" 235 U, the possibilities of converting "non-fissile" 238 U and 232 Th into fissile 239 Pu and 233 U. The physical principles for fast reactors, which make possible the technological implementation of the idea of expanded breeding of fuel, were formulated at the same time.Nonetheless, after the first nuclear power plant in the world was put into operation (1954, Obninsk), nuclear power in our country, just as in other nuclear countries, developed mainly along the most obvious, under conditions at that time, low-consumption path of using already existing exact knowledge and industrial experience -nuclear power started to develop on the basis of technologies which were developed within the framework of strictly military technologies. Even now, it is based on enriching technologies for supplying fuel and thermal reactors based on 235 U in an open nuclear fuel cycle with the accumulation of spent nuclear fuel.At the same time, scientific research on improving existing and developing new, advanced, nuclear power technologies, including closed nuclear fuel cycle technologies with fast reactors, was being conducted in our and other industrially
The results of investigations of the interaction of oxide melt with steel, which were performed following the international OECD program Masca, are presented. The experimental conditions simulated the high-temperature stage of a serious accident in a VVER-1000 vessel. It is determined that the temperature range 2500-2600°C oxide and metallic phases which are immiscible in the fused state form as a result of the interaction of underoxidized melts C-32-C-70 (U/Zr = 1.2). Fused iron is saturated with uranium, zirconium, and oxygen. The density of the metallic phase becomes greater than the density of the oxide melt, which causes the metallic phase to move to the bottom of the pool. The compositions of the coexisting oxide and metallic phases are determined. This can serve as a basis for constructing thermodynamic models of melts in the U-Zr-O-Fe system.In a serious accident in a water cooled and moderated power reactor with loss of cooling of the fuel elements, the core becomes heated, which causes the core to melt and a high temperature melt to form. The melt interacts with the in-vessel structural components and control rods, whose melting temperature is lower. As a result, a complicated multiphase fused system is formed; its main components are uranium, zirconium, oxygen, iron, chromium, nickel, boron, carbon, and fission products. Special theoretical and experimental investigations were performed as part of the OECD program Masca to determine the structure of this multicomponent system. The objectives of the experiments were to determine the characteristics of the interaction of melt and iron and to determine the equilibrium concentration of the elements in the coexisting oxide and metallic phases as a function of time, the degree of oxidation, and the iron-melt mass ratio. The experimental conditions were formulated so as to obtain an experimental basis for constructing an adequate thermodynamic model of melt in the system U-Zr-O-Fe [1, 2]. Experimental Part. Uranium oxide UO 2 , zirconium oxide ZrO 2 , and zirconium hydride ZrH 2 were used as the initial materials to obtain a melt with the required composition. Spectral analysis showed that the mass fraction of the initial materials was at least (%): 99.95 UO 2 , 99.83 ZrO 2 , 99.5 ZrH 2 . The oxygen ratio of uranium oxide was 2.126 ± 0.005. To eliminate acidification of metallic zirconium, its hydride was used in an amount equivalent to the required amount of metal. The powders of the initial materials were carefully mixed, pressed, placed in protective tantalum containers, and sintered in a purified argon atmosphere for 1 h at 1900°C in furnaces with metallic heaters. Disks with diameter 30-31 mm and height
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