卷 81, 编号 7 (2018)

The strategic line of development of a nuclear power system based on fission and fusion reactors which ensures electricity generation on a specified scale, solves the fuel problem for a long-term outlook, and secures the lowest risk of environmental contamination is presented. A contemporary view of prospects of developing the nuclear power industry on the basis of replacement of thermal reactors in the future by fast reactors, owing to a long duration of this process and the necessity of additional resources of natural uranium, forces us to consider the possibility of implementation of this strategy as unlikely. In addition, the fuel cycle of fast reactors requires the quick reprocessing of the highly active spent fuel, and because of this, the fuel cycle will have a high risk of a negative radioactive effect on the environment. The transition of the nuclear power industry to fast reactors will lead to a full change of the infrastructure related to reactor construction and operation. In the development of a nuclear power system with fusion and fission reactors, the demands for natural uranium will correspond to current estimates of economically effective stockpiles, the risk of radioactive contamination of the environment associated with the spent fuel reprocessing will be the lowest, and the contemporary infrastructure of the nuclear power industry will be maintained, i.e., the prevalence of generating capacities based on thermal neutron reactors. Thus, the integration of nuclear power production by fusion and fission reactions into a unified system creates a significant synergetic effect, in which the deficiencies of each technology are compensated by another technology of nuclear power production.

Realization of steady-state operation of a fusion reactor requires the development of essentially new designs and materials for plasma facing elements (PFE). The most promising solution in this field is the concept of capillary-porous systems (CPS) with liquid metal (first of all, lithium) that provide PFE surface self-renewal, closed circulation of their corrosion products, and plasma performance improvement and promote achievement of almost stationary modes of plasma burning. Furthermore, the problem of power exhaust with high specific density (20–30 МW/m²) and maintaining a reasonable temperature level on the PFE surface can be solved by the introduction of a special heat removal system. The survey covers the experience in the development, manufacture, and experimental study of liquid metal CPS based on the tests of PFE element models with thermal stabilization systems in steady-state conditions for the T-11М, Т-10, FTU, and КТМ tokamaks and different aspects of liquid metal application.

The effect of deuterium plasma on tungsten with high levels of radiation damage was studied experimentally. Tungsten was examined as a candidate plasma-facing material for a fusion reactor. The effect of damage accumulation in a material irradiated with fusion neutrons was simulated using high-energy ions. Primary radiation defects of 1–100 dpa were produced in tungsten irradiated with He²⁺ and C³⁺ ions accelerated to 3–10 MeV in the cyclotron at the Kurchatov Institute with a fluence of 10¹⁷–10¹⁹ ion/cm². The irradiated material was exposed to deuterium plasma at the LENTA linear plasma facility operated in the continuous regime and providing a plasma flux of 10²¹–10²² D/cm². The erosion dynamics, the development of surface microstructure, and the accumulation of deuterium in tungsten were studied. Enhanced retention of deuterium was observed in the samples damaged both by helium and carbon ions at room temperature (ERDA). The effect of deuterium retention was suppressed in the damaged tungsten samples processed at a temperature of 500°C.

The 2/1 tearing mode instability during the plateau phase of the plasma current time evolution has been observed since the start of the Globus-M spherical tokamak operation. Because of a small amount of shots in a database, the poloidal beta dependence of the instability growth rate had been investigated with an insufficient accuracy. In this work, a more detailed analysis has been produced that proves the fact that the observed modes can be treated as neoclassical. The saturated island width as a function of poloidal beta has been obtained; a time evolution of the magnetic island has been calculated from the Mirnov magnetic coil signals and compared to the modified Rutherford theory, and the critical magnetic island width has been found for the neoclassical tearing mode (NTM) of the Globus-M tokamak.

The results of numerical modeling of impurity concentration profiles of tungsten ions for discharges with ohmic heating (OH) on the T-10 tokamak with W limiter (for Z_eff ≈ 1) are described. It is shown that in OH discharges the maximum values of relative concentrations for each tungsten ion state are located on their radii of coronal equilibrium. Fulfillment of coronal equilibrium on the T-10 tokamak makes it possible to determine the full radiation intensity from the total concentration of tungsten ions. The results show that modeling of the P_rad(r) profile for tungsten using currently accepted scaling of anomalous transport coefficients of light and moderate impurities for T-10 plasma does not make it possible to obtain complete alignment with the experimental data. The dependences of tungsten radiation intensity profiles on different published data on excitation, ionization, recombination rates, and anomalous transport coefficients are shown in the paper. A conclusion about the value of the anomalous diffusion coefficient and its radial distribution for heavy impurity (tungsten) in OH discharges at the T-10 tokamak is made.

The local measurements of electron density and temperature by Thomson scattering (TS) diagnostics are essential for research of energy confinement, plasma heating, and control at nuclear fusion devices. This paper presents a digital filter polychromator designed for TS spectrum registration. A distinguishing feature of such a digital polychromator is the use of an analog-to-digital converter (ADC) having analog memory with discretization frequency of 5 GHz and 12-bit sampling. The low heat dissipation and compact design of the ADC allow us to integrate the recording and data handling systems in the spectral unit to obtain a standalone device that is totally isolated from other systems and equipment in the voltaic sense. The scattered laser radiation received from the plasma comes to the entrance of the polychromator through a fiber-optic cable, and the processed scattering signals and calculated electron density and temperature are available on a digital interface. The polychromator was tested within the Thomson scattering system at the Globus-M tokamak using two probing lasers: Nd:YAG 1064 nm and Nd:Glass 1055 nm operating with pulse energy up to 2J and FWHM of 4 and 40 ns, respectively. The employed ADCs allowed us to perform superfast signal digitizing in the oscilloscope mode and to demonstrate the possibility of stray signal time separation despite the modest size (~1 m) of the vacuum chamber. The results of measurements performed during the plasma experiment at the Globus-M tokamak are presented, and their comparative analysis with the data obtained at the operating TS system is made.

The hydrodynamics and heat transfer at downward and upward flows of liquid metal in the rectangular duct with the height-to-width aspect ratio of ~3/1 in a coplanar magnetic field were studied. The problem simulates the flow in head-transfer ducts of the liquid metal test module of the blanket of a fusion reactor of tokamak type. The experiments were conducted on the basis of the mercury magnetohydrodynamic test bench. The probe technique was used for measurements in the flow. The averaged profiles of velocity, temperatures, temperature oscillations of flow, and duct wall temperatures were measured in the duct cross section located far from the beginning of heating in the region of uniform magnetic field. The magnetic field suppresses the turbulent transfer owing to the decrease in the heat transfer coefficients and the increase in the wall temperature. However, under the conditions of downward flow, a significant influence of the counter thermogravitational convection (TGC) on the flow was discovered. The interaction of TGC with an external magnetic field in a number of modes leads to the appearance and development of secondary flows. The largescale vortex structures of TGC generate low-frequency temperature oscillations of very high intensity. In this case, the heat emission is improved.

A considerable attention has recently been focused on the issue of large target fabrication for inertial confinement fusion (ICF) research on MJ-class laser facilities. The targets require a condensed uniform layer of hydrogen fuel on the inside of a spherical shell. The fusion fuel inside the targets must have such a structure, which supports the fuel layer survivability under target injection and transport through the reactor chamber. Over the last two decades, the Lebedev Physical Institute (LPI), has been devising the structuresensitive methods of forming high-quality hydrogen fuel with an isotropic structure (ultra-fine type of solid layers) to meet the requirements of implosion physics. A considerable anisotropy of HCP-phases of H₂ and D₂ (single crystal or coarse-grained crystalline layers) results in the layer degrading due to roughening of the layer surface before the target reaches the chamber center, or can result in the spherical-shock velocity dependence on the grain orientation. On the contrary, the ultra-fine solid layers have enhanced mechanical strength and thermal stability which is of critical importance for target fabrication, acceleration and injection. To meet the goal of ultra-fine solid layers formation, the LPI has constructed a piezo-vibration module, in which the couple “membrane & target” is driven by an input signal generated due to inverse piezoelectric effect during fuel cooling via the heat conductivity within vibrating targets. It allows one to modify the key experimental parameters (mechanical and thermal) for influencing the fuel microstructure and intensifying the creation of ultimate disordered structures with a large defect density, i.e., isotropic medium. In this report, the modeling results of the processes of cryogenic layer fabrication in the conditions of high-frequency mechanical influence are presented. The investigation is carried out to gain insight into the relation between the microstructure and bulk properties of the fusion fuel, and to fabricate this fuel with a given microstructure within ICF targets.