Keywords:CFD IFMIF Free surface Liquid metal Thermal hydraulics Boiling point CFD (Computational fluid dynamics) calculation turns out to be a good approximation to the real behavior of the lithium (Li) flow of the target of the international fusion materials irradiation facility (IFMIF). A three-dimensional (3D) modelling of the IFMIF design Li target assembly, made with the CFD commercial code ANSYS-FLUENT has been carried out. The simulation by a structural mesh is focused on the thermalhydraulic analysis inside the Li jet flow. For, this purpose, the two deuteron beams energy deposition profile is modelled as an energy source term inside the volume of liquid affected. Turbulence is estimated using the RNG k-s model, and a surface-tracking technique applied to a fixed Eulerian mesh called volume of fluid (VOF) is used to determine the position of the free surface. Calculations varying the jet velocity from a range of 10-20 m/s, show that maximum calculated temperatures are still below the lithium's boiling point, due to the increase of the pressure induced by centrifugal force.
Investigations of processes associated with the disruption of cooling of the reactor core and possible subsequent destruction and melting of the core have become of paramount importance in connection with the stricter safety requirements for operational and planned nuclear power plants. It is necessary to know how to correctly describe the scenario of the development of accident situations, to characterize quantitatively accident processes, to predict the probable consequences of accidents, and to develop methods and technical means for decreasing undesirable consequences.Boiling of liquid-metal coolant in the fuel assemblies of a fast reactor is one of the uncalculated operating regimes of a reactor and can arise as a result of a decrease of the coolant flow rate, increase of power production, and other reasons. Overheating of the coolant in the fuel assembly (and, as a consequence, boiling of the coolant) is also possible after accidental reactor shutdown, when the core is cooled. In the process, the power released corresponds to the residual energy release, and the coolant either stops moving or it moves as a result of natural convection.Boiling of the coolant as an accident situation, characterized by a large difference of the specific volume of the vapor and the liquid, is a strong perturbative factor, which gives rise to a sharp restructuring of the hydrodynamics of the entire flow. as a result of which the flow becomes unstable. The character of boiling of a liquid metal (sodium) in the core of a fast reactor and. primarily, the propagation velocity of the steam phase determine the rate of increase of the positive reactivity in the reactor core. Further development of the accident process depends on the amount of energy released as a result of the increase of reactivity because of the boiling of the hquid metal.In some countries (Japan, Germany. USA, France, and Great Britain) long-term programs of experimental and computational thermal-hydraulic investigations of the development and consequence of accident situations in a liquid-metalcooled reactor core have been conducted since the 1970s. Attention was focused mainly on the investigation of the dynamics of the development of the vapor phase m a fuel assembly, the character of the cooling during boiling of the coolant in the region behind the blockage in the fuel assembly, and so on. For example, staged investigations of accident processes accompanied by boiling of a liquid-metal coolant in ring-shaped channels and multirod assemblies with a duration of not more than 10 sec (power increase, decrease of the flow rate, blockage) were conducted in Japan [1][2][3][4][5]. In Germany nonstationary processes associated with the study of a loss of coolant accident and blocking of part of the flow section of the fuel assembly were investigated [6, 7]. In France investigations of boiling of the coolant in a fuel assembly under stationary conditions, during slow transient processes with a decrease of the flow rate, natural convection, fast processes with an increase...
Приведены результаты экспериментов получения многокомпонентных покрытий, обладающих более широким спектром свойств по сравнению с однокомпонентными. Изучены процессы формирования покрытий на основе многокомпонентного сплава Co(18…20 %)-Cr(5…7 %)-Al(0,3…0,4 %)-Y(0,2…0,5). Исследован химический состав покрытия, его толщина, состояние переходной зоны. Приведены результаты рентгенофлюоресцентного и рентгеноспектрального микроанализа получаемых покрытий. Показано, что характер микрорельефа поверхности определяется условиями формирования покрытий, набор химических элементов в покрытии на каждом из образцов аналогичный, концентрация их зависит от условий процесса осаждения, распределение химических элементов по толщине на образцах постоянно, зона диффузии материалов покрытия и подложки практически отсутствует. Выявлено наличие в сформированном покрытии незначительного процентного содержания материала подложки. По мере роста толщины покрытия процентное содержание материала подложки резко уменьшалось.
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