Vol 81, No 11 (2018)

The paper analyzes a principal capability to transmute neptunium, the main component of transuranium radiowastes (TRW), in lead-cooled fast BREST-type reactor. High-energy neutron spectrum of the BREST-type fast reactor makes it possible either to eliminate neptunium in fission reactions or convert neptunium to plutonium with large fraction of ²³⁸Pu in radiative neutron capture reactions. According to the IAEA regulatory documents, plutonium containing above 80% ²³⁸Pu is regarded as an unsuitable material for manufacturing of nuclear explosive devices. Besides, good neutron-multiplying properties of ²³⁸Pu and ²³⁹Pu can prolong substantially the reactor core lifetime. Thus, introduction of neptunium into fresh fuel composition can eliminate the largest TRW fraction, strengthen regime of nuclear non-proliferation, produce some additional amount of thermal energy and prolong the reactor core lifetime.

The optical diagnostics of an inductively coupled RF discharge in a magnetic field is considered. The radiative processes in the plasma are described by an extended corona equilibrium model. The temperature distribution of plasma electrons over the radius of the separator chamber is obtained using the line-ratio method for argon spectral lines (763.5/811.5, 451.1/811.5, 425.9/811.5 nm) and taking into account the excitation of levels from both the ground and metastable states. The results are compared with the data obtained by the electrostatic probe method.

The trapping of helium in tungsten irradiated with He⁺ ions with an energy of 3 keV and fluence of 10¹⁹–10²² He/m² at room temperature was studied by thermal desorption spectroscopy and scanning electron microscopy. Both as-prepared and recrystallized (at 2000 K for 30 min prior to irradiation) tungsten foils with a thickness of 50 μm were used. It was found that the initial structure of tungsten affects both the dynamics of helium accumulation and the size of defects formed in the process of irradiation and subsequent heating. At low irradiation fluences, helium desorption proceeds primarily at 2000–2500 K in recrystallized tungsten and at 1100–1900 K in as-prepared tungsten samples. At high fluences (higher than 10²¹ He/m²), a considerable amount of helium is released at low temperatures (starting from 400 K), but a significant fraction of it remains in the samples even after heating to maximum temperatures. Analysis of cross-section of the samples performed after thermal desorption revealed pores 10–75 nm in diameter. The largest pores were formed in the samples that were recrystallized prior to irradiation.

The regularities of ion-induced corrugation of a VMN-4 carbon-fiber shell of the KUP-VM unidirectional composite under high-fluence irradiation with Ar⁺ ions at energies of 20 and 30 keV have been experimentally studied in the range from room temperature to 600°C. A developed submicron corrugated structure of the carbon fiber surface at an ion path length of 20–40 nm in graphite is registered starting from temperatures around 200°C. The corrugation period is a few hundred nanometers, weakly depends on the temperature of the irradiated carbon fiber, and decreases with a decrease in the ion energy or an increase in the incidence angle of the ion beam on the cylindrical fiber surface. The temperature of an irradiated fiber has a strong effect on the geometry and the fraction of corrugations in the fiber surface part irradiated with ions at normal incidence. For an ion energy of 20 keV in the temperature range of 350–500°C, the apical part of the fiber is similar to the initial surface. A stronger effect of corrugation reduction for an argon-ion beam energy of 20 keV in comparison with an irradiation energy of 30 keV is explained by the competition between the processes of ion-induced corrugation under plastic deformation of the modified layer and the surface erosion at sputtering, which leads to the smoothing of the surface.

Advanced mechanical properties of ODS steels are mainly due to the high number density of homogeneously distributed oxide inclusions. It is well known that some alloying elements like Ti, V, Zr, … play important role in oxide/nanocluster formation and influence on number density and size of these inclusions. In this work, we studied an ODS steel contained both vanadium and titanium. The ODS 12Cr-1.1W-0.2V-0.3Ti steel was characterized with TEM and APT. Different types of oxides inclusions were revealed in the steel: large (>70 nm) Ti₂O₃ oxides, small (~ 2–15 nm) Y-Ti-O oxides, and nanoclusters (2–5 nm). It was shown that the number density of these nanoclusters was considerably high than the one of the oxides and nanoclusters are enriched in Y, O, Cr, Ti, and V. Moreover, in spite of the fact that V and Ti are present in the material in approximately close value, clusters are predominantly enriched in Ti. APT samples of this material were irradiated with Fe ions up to ~ 8 dpa at room temperature. APT analysis of the irradiated material revealed decreasing of nanocluster number density with increasing their sizes. Changing in nanocluster composition was detected after the irradiation, but the decrease of Ti concentration in clusters was considerably less than the one for V. However, the Y/Ti, Y/(Ti + V), and (Ti + V + Y)/O composition ratios of nanoclusters remained stable under Fe ion irradiation to 8 dpa at room temperature.

The influence of the shock-wave action of plasma on the structure and properties of coatings of magnesium and boron on various ductile metals (copper, aluminum, tin) was studied in this work. Experiments were performed to investigate the capabilities of МgВ₂ synthesis from the powder mixture of Mg and B in a metal covering with optimization of the impact conditions. The constitution, the structure, and the properties of the prepared samples were studied. As a result, a sharp decrease in voltage was established at temperatures of 30–40 K across the Cu-Nb-MgB wire.

The acceleration of a flyer by a magnetic field allows studying the dynamic characteristics of matter in submicrosecond processes. At the Angara-5-1 facility, pressure is created by a magnetic field of the current with the linear current density of up to 5 MA/cm. The velocity of up to 10 km/s was obtained in the first experiments on acceleration of a duralumin flyer 1 mm thick. Two methods are used for registration of the flyer velocity: laser shadow photography and VISAR interferometric method. This paper presents the results of experiments on determining the velocity of a flyer by the VISAR method. Particular attention is paid to the problem of suppression of spurious signals in the VISAR registration system. The first problem was electromagnetic interference emerging when the Angara-5-1 facility is activated, when megavolt voltages and megaampere currents are generated within a hundred nanoseconds. The second problem was bremstrahlung radiation emerging when magnetic self-isolation is established in vacuum transmission lines. This radiation affects the optics, fiber optic cables, and photomultipliers. The suppression of these two sources of interference ensured the reliable registration of the VISAR signals. The results obtained by the two laser methods—shadow photography and VISAR—coincide with each other and with the results of numerical simulation of flyer acceleration. The experimental results and simulation results are compared.

The behavior of hydrogen in metals and their alloys is of great interest, since hydrogen–metal systems are used in practice for absorption of nuclear radiation, in neutron sources, and for hydrogen storage. This study is focused on simulation of the behavior of hydrogen in titanium hydrides at ultrahigh concentrations of H in TiH_{2 + x}. Numerical methods of continuum mechanics are used. The structure of the hydrogen sublattice of titanium hydride is taken into account in the model of diffusion and thermal desorption of H. This makes it possible to model the thermal desorption of hydrogen under irradiation with a beam of hydrogen ions.

Multifunctional software-controlled systems for monitoring the physical parameters of nuclear research reactor radiation has been developed at the All-Russian Research Institute of Experimental Physics (VNIIEF). The paper discusses approaches to designing and principles of building such systems as a combination of software and hardware tools using techniques for the diagnosis of radiation fields developed at the VNIIEF.

The propagation of relativistic electrons and muons within multilayer structures is considered. The Geant4 model of X-ray transition radiation (the yield of photons, their angular and spectral distributions, and the spectrum absorbed by a gas detector) is compared to experimental and RADIATOR data. It is demonstrated that the Geant4 spectral and, even more so, angular distributions differ from the experimental ones.

In the paper, we present the development of the powerful multiple-beam klystron amplifier with the peak output power of 3.2 MW and operating frequency of 5712 MHz. We show the capability of suppressing the high-voltage breakdowns in the collector area and increasing the efficiency of the multiple-beam klystron owing to alignment of the electric fields in the output cascade.

At the present time, the Dubna gas-filled separator is the world’s leading physical facility in the field of synthesis of superheavy elements. This is the device where new elements with Z = 114–118 (Fl, Mc, Lv, Ts, Og) were synthesized. The original tools and methods considered in this paper are applied in reactions of complete fusion of actinide target + ⁴⁸Ca → SHN + xn type. Modification of the active correlation method is planned after the launch of new DC-280 cyclotron developed at the Flerov Laboratory of Nuclear Reactions in 2019.

A study of samples of metal-ceramic beryllium using atomic force microscopy and nuclear scanning probe microscopy is carried out. Images of the surface at different scale levels are obtained (5 × 5 μm, 10 × 10 μm, 30 × 30 μm, and 90 × 90 μm); structural analysis of the samples is performed. By example of processing RBS spectra of beryllium samples, a fragment of studies on the implementation of the algorithm for obtaining two-dimensional maps and 3D images at different scale levels for one set of experimental data is presented. A multilevel approach to the evaluation of the material structure is demonstrated by example of beryllium as a modern dispersion-strengthened alloy.

Work on the conceptual design of a dedicated fourth-generation fourth-generation Specialized Synchrotron Radiation Source (SSRS-4) is in progress at the Kurchatov Institute, Moscow. The project is being developed in collaboration with the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. In this paper, the initial results of our work on this project are reported, major directions of current research are presented, and possible areas of application of the SSRS-4 are outlined. The key element of the currently discussed design is a 6-GeV storage synchrotron with an orbit length of ~1300 m and the magnetic lattice that should provide a horizontal transverse emission of 70–100 pm rad. Further optimization may allow for reducing the emittance to 20–40 pm rad. Of the injection schemes under discussion, one features a full-scale booster synchrotron deployed in the same tunnel as the main storage ring, and the second is a topup linac. The latter can also be used as an electron-beam driver for a free-electron laser.

Studies on the radiation treatment of fish products using an electron accelerator with an energy of 1 MeV were carried out. Here, we report the results of the effect of the beams of accelerated electrons with an energy of 1 MeV at the doses of 100 Gy, 1 kGy, and 5 kGy on the viability of bacteria in trout meat. Escherichia coli bacteria present in the fish homogenate were shown to be more resistant to the effect of ionizing radiation than the bacteria which were without a nutrient medium.

The diversity of carbon materials has allowed them to be used for fundamental and applied research to date. The newest modifications of carbon, such as nanodiamonds, graphene, fullerenes, and nanotubes, are of particular interest owing to their outstanding physical and chemical properties, as well as to prospects of their practical application in various fields of industry, from medicine to nanoelectronics. At the same time, one-dimensional forms of carbon, predicted in the 1960s, were underestimated because of imperfection of experimental tools [1–3].

The results of calculating the thermal electromotive force for a crystalline state and a model lattice of nanoclusters of noble transition metals Ag, Au, and Pd are presented. The electron structure was calculated by the method of density functional theory (DFT) with the plane-wave pseudopotential and the generalized gradient approximation of the density functional with consideration for relativistic effects and noncollinear magnetism. The electron transport coefficients were found by analyzing the electron structure with the use of the semiclassic solution of the kinetic Boltzmann equation in the constant relaxation time approximation. The obtained results on the temperature dependence of the thermal electromotive force demonstrated quantitative coincidence with the tabular values within a temperature range of 200–500 K for crystalline Au and 200–400 K for Ag and Pd. At 300 K, the precision of calculated results attained 4% for Au. For the simplified model of the nanostructured material representing lattices of Me₁₃ nanoclusters, the thermal electromotive force was revealed to grow by an order of magnitude in comparison with the crystalline state.