The article describes the factors under the influence of which the formation of thermohydraulic characteristics occurs in the fuel assemblies of the core of fast reactors with liquid metal cooling. It is shown that one of the most important factors is a complex multiply connected geometry of a stochastic nature, subject to deformation during the campaign under the influence of temperature irregularities and radiation effects. The paper presents and analyzes the results of experimental and computational studies of the velocity field and shear stress, the microstructure of turbulence, momentum transfer in the central and peripheral regions of fuel assemblies without and with displacers, as well as in the case of deformation of the lattice of rods. The intensification of turbulent momentum transfer in the channels in the azimuthal direction in the area of the gaps between the rods is demonstrated. The anisotropy coefficient of turbulent momentum transfer reaches 30-40 units. The performed analysis indicated a significant difference in the calculated in the framework of semi-empirical models of turbulent transfer and experimental dependences of the coefficients of turbulent transfer of momentum in the radial and azimuthal directions and the coefficients of anisotropy of turbulent transfer of momentum in rod bundles. The results of an open benchmark on the thermohydraulics of fuel assemblies showed that common commercial computational thermohydraulic codes only approximately describe the experimental data. It is shown that the intensification of turbulent momentum transfer in the channels of rod assemblies is due to the appearance of large-scale turbulent momentum transfer (secondary flows). The contribution of large-scale turbulent momentum transfer to the kinetic energy of turbulent pulsations, azimuthal turbulent shear stresses, and turbulent momentum transfer coefficients in rod assemblies is calculated. An empirical dependence of the coefficient of interchannel turbulent impulse exchange in bundles of smooth rods is obtained, on the basis of a semi-empirical model, data on interchannel turbulent impulse exchange in assemblies of smooth rods are generalized, and the intensification of interchannel turbulent exchange in close lattices of rods is explained. Data on hydraulic resistance in bundles of smooth rods are analyzed. The tasks of further research are discussed.
Abstract. The intensity of the hydrogen sources arriving from the third contour of installation in second in comparison with the hydrogen sources on NPP BN-600 increases by two -three order at using of high-temperature nuclear power plants with the sodium coolant (HT-NPP) for drawing of hydrogen and other innovative applications (gasification and a liquefaction of coal, profound oil refining, transformation of biomass to liquid fuel, in the chemical industry, metallurgy, the food-processing industry etc.). For these conditions basic new technological solutions are offered. The main condition of their implementation is raise of hydrogen concentration in the sodium coolant on two -three order in comparison with the modern NPP, in a combination to hydrogen removal from sodium and its pumping out through membranes from vanadium or niobium. The researches with use diffusive model have shown possibility to expel a casium inflow in sodium through a leakproof shell of fuel rods if vary such parameters as a material of fuel rods shell, its thickness and maintenance time at design of fuel rods for high-temperature NPP. However maintenance of high-temperature NPP in the presence of casium in sodium is inevitable at loss of leakproof of a fuel rods shell. In these conditions for minimisation of casium diffusion in structural materials it is necessary to provide deep clearing of sodium from cesium. ВведениеThe future of hydrogen power engineering will depend to a considerable degree on the efficiency of technological hydrogen production processes. As a rule, these processes use high-grade heat, the generation of which requires considerable energy resources. The same applies to efficient petroleum products refinery processes. Gas and petroleum products rather than renewable sources of energy are presently used for obtaining such heat.However, this method does not hold much promise [1], because it involves additional depletion of resources, the natural reserves of which are far from being unlimited, and the possibility of using nuclear energy for these purposes is being discussed. A sodium-cooled fast-neutron nuclear reactor may become one of possible sources producing high-grade energy [2][3][4].The using of traditional sodium technology, central to which is removal of hydrogen from sodium by means of cold traps only, does not hold promise for development of high-temperature nuclear power installations (NPPs): the intensity of hydrogen flows from the tertiary to the secondary coolant circuit in a high-temperature NPP increases by several tens of times as compared with that in the BN-600 reactor. This is attributed to the following two main factors. First, this is the kinetics relating to the physicochemical processes in the liquid metal system: in accordance with the Arrhenius equation, the constants determining this kinetics are exponential functions of temperature (as the temperature increases by a few hundreds of degrees, the values of these constants grow by several orders of magnitude). And second, the pressure of hydrog...
As a result sixty years of experience in the development of alkaline liquid metals - sodium, eutectic alloys of sodium-potassium, lithium, cesium, the scientific bases of their application in nuclear power were created, the thermohydraulic parameters and highly efficient technological processes were substantiated, devices and systems were developed and implemented that ensured the successful operation of fundamentally new NPPs. The main areas of research were: thermal hydraulics, mechanisms of turbulent heat exchange, boiling and condensation of liquid metals, physical chemistry and liquid metal coolant technology, thermophysical properties of materials of the reactor, coolants, analysis and generalization of thermophysical data, bases of the experimental data, heat pipes, thermophysics of thermionic converters, high-temperature space nuclear power units and thermonuclear installations. The results investigations of hydrodynamics and heat transfer in channels of complex shape were studied, both under normal operating conditions and deformation of a fuel cell grid. The justified reduction of collector hydraulic irregularities in reactors, heat exchangers and steam generators. A channel-by-channel method of thermal-hydraulic calculation of fuel assemblies of the core of fast reactors for nominal and non-nominal operating regimes was developed. A theory of anisotropic porous body has been developed as applied to calculations of complex flows in reactors, heat exchangers and steam generator. Experimental investigations of the circulation and heat transfer in the reactor tank during forced circulation, in transitional and accident regimes with natural circulation showed a stratification and temperature pulsations in the upper mixing chamber and other regimes of the reactor installation. The boiling processes in a large volume, tubes and bundles of rods, the condensation of liquid metals, the occurrence of accident processes during sodium leaks in steam generators and sodium circuits have been experimentally investigated. The tasks of further research are formulated.
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