Physics of Atomic Nuclei最新文献

A 1350-00 nickel alloy powder coating has been deposited on thin-walled 12Kh18N10T stainless steel tubes by high-speed laser cladding. Cladding has been performed using cw radiation from a 10-kW ytterbium fiber laser on a robotic complex. The shapes of the gas–powder jet for Fraunhofer nozzles have been determined. The influence of the laser radiation power and the amount of supplied powder on the structure of the coatings obtained has been evaluated. Metallographic studies of the obtained samples have been carried out. It has been shown that laser cladding under optimal conditions provides an almost nonporous coating with minimal penetration of the base material, ensuring metallurgical fusion. According to the X-ray spectral microanalysis, the chemical composition of the deposited coating hardly differs from the chemical composition of the used powder. The thickness of the deposited layer is adjusted within 100–300 µm in one pass, depending on the deposition modes. The fusion line is identical in structure, which shows a high uniformity of heat input during cladding. The size of the region of thermal influence in the substrate material varies within 50–200 µm, depending on the deposition modes.

The process of laser hardening of 42KhN2MA steel samples using continuous radiation and transverse beam vibrations at a frequency of 223 Hz has been considered. The influence of processing modes on the response parameters of the system and the depth and width of the laser quenching regions has been determined. It has been shown that the use of transverse beam vibrations increases the microhardness, the area of the hardened layer, and its uniformity and preserves the geometric shape of the slot profile compared to processing with a defocused beam. The wear resistance of the laser-hardened regions is significantly higher than the base material.

This work is devoted to the determination of the tissue optical properties of the organs of the human gastrointestinal tract in the spectral range of 400–620 nm. The diffuse reflection and transmission spectra were measured using a Hitachi U-3400 integrating sphere spectrophotometer. The absorption and reduced scattering coefficients were determined using the inverse adding-doubling method. The obtained results of optical properties were compared with the available literature data.

The authors consider the creation of scientific and technical programs for conversion of nuclear research reactors at the decommissioning stage in terms of extending the designated service life of all operating nuclear research reactors (RRs) in Russia. To solve this problem, a methodology is proposed that includes an information model and a description of the necessary step-by-step actions, along with a set of appendices in the form of documents describing the best ways of creating a project for managing the quality of RR conversion in relation to special conditions of the life cycles of specific nuclear reactors. The methodology is described in the form of principles and means of construction and structure. An example of applying this methodology to the conversion of the Hydra salt solution pulse nuclear research reactor at the stage of decommissioning is presented. The reason for converting the Hydra reactor is to extend the designated service life by replacing nonrepairable equipment (the vessel). The main criteria for confirming the remaining service life of the vessel are formulated. They include the safety margin of the vessel’s material with allowance for the fluence accumulated on the more vulnerable areas and confirming the integrity and tightness of the vessel. For clarity, the conceptual information model of the methodology for confirming the safety of replacing the Hydra reactor vessel is given in the form of an Ishikawa diagram. The methodology consists of a number of consecutive scientific and technical activities, studies, and a finite number of actions in order to achieve the ultimate goal of extending the service life. The stages of the methodology for confirming the safety of replacing the Hydra reactor vessel are described. These include clarifying the initial data, performing computational studies and laboratory experiments, clarifying the requirements of methodological documentation, creating a working plan, and preparing license documents of operation.

The relevance of this work is determined by the need to predict the operation of seal assemblies for localizing safety system (LSS) elements of  WWER power units, which include penetrations, hatches, airlocks, doors, and other elements of the sealed enclosure (SE) in operating modes. Operating modes are understood as normal operation modes, abnormal conditions, and emergency situations. During the manufacture and operation of LSS elements, the problem arises of uneven protrusion of a two-row rubber gasket from the grooves in the LSS element web, which leads to the need to clarify the integral compression force of the seal as a whole for this element. The problem is caused by the imperfection of the technology for manufacturing large webs for LSS elements (doors, hatches, and airlocks: the perimeter of the seals can reach 10–20 m, the web diameter is 2–6 m) and the need to maintain strict technological requirements for flatness, parallelism, and tolerance extremes in linear and angular dimensions. The manufacture of large structures is complicated by the presence of welded joints, heat treatment, and the complexity of metalworking. The compression force of the PNAE-7-002-86 rubber gasket is not regulated; therefore, for the reliable design of seal compression mechanisms, the magnitude of this force is determined. Based on the results of rubber gasket tests for tightness and cyclic loading, an assessment of the tightness of the used rubber gaskets has been performed and calculations of the rubber gasket deformations have been performed using the FEM software package. Recommendations have been developed to increase the reliability of seal assemblies for LSS elements of WWER power units in operating modes and to select the compression for the required force to provide tightness at the commencement of operation and after 5000 open/close cycles.

The DC-140 cyclotron complex now under construction at the Flerov Laboratory of Nuclear Reactions (FLNR) is designed for wide range of applied research using accelerated heavy ion beams, e.g., studying the radiation physics of solids, the development and production of track membranes (nuclear filters), and the radiation resistance of electronic components. To perform experiments, the accelerator must provide accelerated ion beams with two fixed energies: 2.1 MeV/nucleon and 4.8 MeV/nucleon in the mass range of Ne to Bi, with intensities of up to 10¹² particles/s (for Xe ions) on the target. In accordance with the working diagram of DC-140 cyclotron, the ion source must provide ion beams with mass-to-charge ratios in the range A/Z = 5–8 (Ne⁴⁺–Bi³⁸⁺).

Heavy ion beam probing (HIBP) is a unique diagnostic technique that enables independent and simultaneous measurement of the plasma electric potential (varphi ) and its fluctuations (tilde {varphi }), as well as the electron density fluctuations ({{tilde {n}}_{e}}) and poloidal magnetic field ({{tilde {B}}_{{{text{pol}}}}}) in the hot plasma region. A method for calculating the spatial resolution of the designed HIBP diagnostics for the T-15MD tokamak has been presented. The dependence of the size of the measurement area point on the width of the input slits in the energy analyzer has been studied.

The high-temperature interaction of triuranium disilicide U₃Si₂ with BeO, Y₂O₃, Al₂O₃, ZrO₂, Mo, and Ta has been considered. The formation of eutectics in these systems has been analyzed theoretically, and experiments on heating samples of triuranium disilicide located on substrates of appropriate materials in vacuum to a temperature of 1500°С have been carried out. The result shows the absence of interaction between U₃Si₂ with BeO, Y₂O₃, ZrO₂, and Mo. The formation of eutectic in the U₃Si₂–Al₂O₃ system has been experimentally confirmed. In addition, the strong interaction of U₃Si₂ with Ta with the formation of diffusion layers has been revealed. The possibility of using the materials under study in contact with triuranium disilicide at high temperatures is concluded.

A method for calculating the absorption and emission characteristics of CO₂ in the range from 3200 to 5400 cm^–1 with allowance for the effect of thermal nonequilibrium has been presented. A series of calculations using line-by-line (LBL) and statistical narrow-band (SNB) models has been performed at various pressures, spectral regions, layer thicknesses, temperatures, and molar fractions of CO₂. The developed method shows good agreement between the LBL and SNB models and satisfactorily agrees with experimental data when calculating the transmission capacity. In the considered range, the nonequilibrium in rotational temperature has virtually no effect on the radiative characteristics, unlike translational and vibrational temperatures, which have a significant effect on the nonequilibrium Planck function. The resulting methodology can be used for calculations when studying the problem of global warming.

This paper presents theoretical and experimental data determining the effect of acoustic perturbation on the readings of a γ-detector with high-pressure xenon gas as a working medium (XGS) operating in the field of IR. For this purpose, a chain of events is considered: an acoustic wave falls on the surface of the XGS, passes through and produces a perturbation in the gas which forms a nonuniform pressure distribution in the working medium. Exposure to IR leads to the formation of positive ions in the gas, the mobility of which is much lower than the mobility of free electrons, which are the main carriers in XGS. The experiments are carried out using an unmanned BDK dosimetric complex with a carrier in the form of a helicopter-type UAV on which dosimetric equipment used for radiation control of the environment in conditions of its radioactive contamination is attached. Theoretical results obtained by solving the wave equation of sound wave passage in xenon filling the XGS are presented in the form of xenon density. These data allow us to obtain the radial distribution of the current density at different moments of the harmonic acoustic oscillation period. Experimental data demonstrated frequency characteristics of acoustic load and their amplitudes in different modes of UAV operation. The results of the research determine the recommendations that should be taken into account when using UAVs as carriers of dosimetric equipment in radiation monitoring of the environment.