The paper analyzes a possibility for large-scale production of high-purity plutonium suitable for radioisotope thermo-electrical generators (RITEG) of spacecrafts in a light-water power reactor with supercritical coolant parameters. Neptunium and americium fractions of minor actinides from trans-uranium radioactive wastes were used as the starting materials. The starting materials were placed in central fuel assembly (FA) of the reactor core. It was shown that significant plutonium amounts with low content of ²³⁶Pu (below 2 ppm) and high content of ²³⁸Pu (above 80%) could be produced in central (Np,Am)-FA surrounded by the assemblies filled up with natural or radiogenic lead. These assemblies play a role of a protective barrier against high-energy fission neutrons emitted by the neighboring UO₂–FA which are able to increase content of ²³⁶Pu through threshold ²³⁷Np(n,2n)²³⁶Pu reaction. The paper presents numerical evaluations for production rates of the RITEG-suitable plutonium in central (Np,Am)-FA surrounded by such protective lead-containing assemblies.

The work describes a comparison of the laser-assisted quadrupole mass spectrometry for two laser pulses: 15 ns and 80 ps for W−D films and Ti−V alloys with D. A technique is presented for samples production with high concentrations of the trapped deuterium, which allows to obtain a good signal repeatability on a quadrupole mass spectrometer for several laser shots, which can be used to align a diagnostic’s laser system. An experimental dependence of the deuterium release from the materials on the energy density is obtained. A high sensitivity of the technique is demonstrated, as well as a weak dependence on the duration of the laser pulse. A significant change in the deuterium concentration in the near-surface layer of the tungsten film during contact with the atmosphere is noted.

The effect of the thermal motion of ions on the spectra of multicharged ions in dense plasma is investigated. An analytical expression is obtained for the frequency of jumps in the amplitude of the ion micropole. A modification of the Frequency Fluctuation Model technique is proposed, which allows taking into account the dependence of the frequency of jumps of the ion microfield on the energy shift. A new approach to the diagnosis of plasma density by the area of the dip in the center of spectral lines is presented. Calculations of the spectra of argon impurity in deuterium plasma are given.

To date, a multitude of methods have been developed for numerical solution of problems based on ordinary differential equations (ODEs) and partial differential equations (PDEs). The most common of these are finite-difference method, the finite-element method, and the finite-volume method. In this study, an alternative numerical approach is implemented, based on the approximation of functions by feedforward neural networks. The solution obtained using this approach is a differentiable analytical expression; in this respect it differs significantly from other methods that offer either discrete solutions or solutions with limited differentiability. In this study, we examine the influence of neural-network parameters (such as activation functions and weights in the error function) on the rate of convergence and accuracy of the obtained approximation of the solution for three types of differential equations: ordinary differential equations, integrable partial differential equations, and non-integrable partial differential equations. As model equations, we consider Korteweg–de Vries and Kudryashov–Sinelshchikov partial differential equations and second-order ordinary differential equations. In each case described above, the optimal ratios of the weight coefficients are found. The activation functions most efficient for each problem are determined.

The processes of plastic shear localization in DU-0.75Ti alloy samples subjected to high-speed shear are considered. A mathematical model describing this process in the 1D and 2D cases is formulated. A numerical algorithm for the mathematical modeling of the processes under consideration is proposed. A series of computational experiments on high-speed loading of DU samples is carried out. The localization process dynamics depending on the initial rate of plastic shear is investigated. The values of the temperature, velocity, stress, and shear fields are obtained. The influence of the problem dimension on some of the most important characteristics of the localization process is investigated.

Results of calculations of the electrodynamic characteristics of short five-gap accelerating cavities of the IH type are presented. The cavities are designed for a linear accelerator of protons and light ions with a charge-to-mass ratio A/Z ranging from 1 to 3.5. Developed at National Research Nuclear University MEPhI, this accelerator, which is designed as a source of charged particles with a beam energy of 7.5MeV/nucleon, is intended for basic and applied research. The issues of the complex influence of the geometry of the drift tubes and the geometry of the drift tube support on the magnitude of the field strength on the surface of the resonators, the power losses in the walls of the resonators, and the distribution of the accelerating field on the axis are considered, taking into account the influence of the accuracy of segmenting in simulation.

A compact modified thermionic electron source was developed for the 6 MeV medical accelerator. This gun features significantly reduced size, due to a change in the power supply feeder scheme. In this work, the penetration of the magnetic field into the cathode electrode was studied depending on the radius of the holes for pumping and their number, as well as the possibility of subsequent capture of electrons by it.

Within the framework of the BELA project (Based on ECR ion source Linear Accelerator), designed to solve various problems, an injection complex based on several ion sources is being created. One of the tasks is multibeam irradiation of structural materials of nuclear and thermonuclear power plants to analyze their radiation resistance. Heavy (Fe) and light (H2/He) ion beams will irradiate the target in the same chamber simultaneously. To generate beams of light ions, a compact ion source based on electron cyclotron resonance (ECR source) is being developed. The paper contains description of the studies of the dependences of the operation of an ECR source of light ions with a resonant discharge chamber on the pressure of the working gas, the magnitude and distribution of the magnetic field, as well as the mass-charge spectrum of a helium-ion beam.

The results of the Oxygen 5⁺ beam dynamics simulation in the regular section of a 7.5 MeV/u linear accelerator are presented. Linear accelerator LU-1 consists of several ion sources, RFQ section (Radio Frequency Quadrupole) and two groups of identical IH (Interdigital H-type) cavities. Beam transport between the accelerating sections is done via low energy (LEBT) line, two medium energy MEBT-1 and MEBT-2 lines, and high energy (HEBT) line that transfers the beam to the booster synchrotron or a beam dump. This paper contains the results on Oxygen 5⁺A/Z = 3.2 beam dynamics end-to-end simulation in the LU-1 sections (LEBT, RFQ, MEBT-1, MEBT-2 beam transport lines and both groups of IH cavities).

The problem of recognition and classification of loads at the output of generating and transmitting distributed parameter lines (DPL) in devices of high-power pulse technology (HPPT) by the amplitude and shape of the output signal using mathematical models based on machine learning methods and neural networks has been considered. A web application that recognizes parasitic parameters occurring in the devices based on DPL has been developed.

The paper investigates the trapping and desorption of hydrogen isotopes under irradiation of zirconium alloy E110 with ions of deuterium plasma. It is established that under the irradiation, hydrogen exchange between the alloy and the gaseous ambient occurs: part of deuterium from the irradiation flux is trapped by the alloy, and at the same time hydrogen initially contained in the alloy is partially desorbed. In general, hydrogen exchange results in an increase in the content of hydrogen isotopes in the sample. Addition of 30 at. % oxygen to the plasma-forming gas, as well as increasing the sample temperature from T = 450 K to T = 600 K, slows down deuterium trapping and accelerates hydrogen desorption, leading to a decrease in the content of hydrogen isotopes in the sample. Increasing the dose of irradiation of E110 alloy with deuterium plasma ions intensifies both deuterium trapping and hydrogen desorption. Based on the experimental results, the mechanism of hydrogen exchange between zirconium alloy and gaseous ambient under the ion irradiation is proposed. The process includes three stages: reactions on the oxidized surface of zirconium alloy (hydroxylation of surface oxide and formation of water molecules); reactions on the metal-oxide boundary; and transport of hydrogen isotopes through the surface oxide layer in both directions. Surface reactions initiated by irradiation trigger the hydrogen exchange process.

A new method of X-ray photoelectron spectra processing based on a target model with a stochastic surface layer is suggested. On the base of this model, X-ray photoelectron spectra of multilayer multicomponent metallic targets with an inhomogeneous surface layer are obtained for various probing angles considering surface shading effects. A layer-by-layer phase profile of metallic samples is obtained using the advanced method of surface analysis based on angle-resolved X-ray photoelectron spectroscopy. The results are approved be atomic force microscopy.

Our recent work on multiple locations of boron atoms in the exohedral and endohedral C₆₀ fullerene [1], carried out within the Hartree-Fock method with the second order Møller-Plesset perturbation theory MP2 (HF-MP2), prompted recently a comment from Xu and Hou [2], who have performed several density functional theory (DFT) calculations using DFT functionals of different complexity. In three out of five cases considered in our work, DFT calculations give the same ground state confirmations whereas in two cases optimal configurations have turned out to be different. However, depending on the choice of the exchange-correlation functional, the geometry optimization within DFT can also result in different ground state confirmations. The energy balance between nearest confirmations in these molecular complexes is subtle, and various methods can give different ground state structures. We therefore argue that the presented DFT calculations are not benchmark, and their results should be compared with ours (HF-MP2) on equal ground. We also present additional HF geometry optimizations with the 6-31G* basis set, which confirm the ground state confirmations obtained at the HF/6-31G level.