Том 81, № 10 (2018)

Partially ionized and weakly magnetized plasma (typical for MHD generators) flows along the outer spherical chamber, and is placed around the inner chamber where an field reversed configuration (FRC) is injected. Inside the outer chamber, the azimuthal E_r × B drift induces a paramagnetic field B_p, with an intensity of tens of Teslas. The intensity of the B_p field is controlled by the inwardly directed radial electric field E_r. Inside the inner chamber the B_p field becomes anti-parallel to the external magnetic field B_em. After establishing the magnetic mirror configuration of magnetic field intensity B_p ~ 20T (in the mid-plane), the FRC (target plasma) is injected into the magnetic mirror with the help of a magnetic wave generator. Inside the magnetic mirror (inner chamber), the rotating magnetic field (RMF) induces the azimuthal current j_ω inside the FRC. This current gives the magnetic field B_j an intensity of dozens of Teslas. This field is antiparallel to the B_p field. Interaction between magnetic fields, B_p and B_j, causes radial compression of the injected FRC. As a result of the magnetic compression, the product of density and the energy confinement time amounts to 1.72 × 10¹⁹ s/m³, which is close to the level expected for the working reactor (~10²⁰ s/m³). Detailed analyses reveal that the compressed plasma (compact toroid) is very stable, the kinetic stability condition is fulfilled (S*/ε≅0.28), and the ratio α is very low: (~8.6×10^-2). This makes the most destructive rotational modes, n=1 and n=2, harmless.

Improvement of computational methods used for the uncertainty analysis of critical experiments allows the accuracy of the results to be more realistically estimated, which is important for further improvement of computational codes and cross section libraries used to justify nuclear safety of the research on uses of nuclear energy. Standard uncertainty estimation methods (Monte Carlo, sensitivity analysis, etc.) have disadvantages arising from considerably growing needs for computational resources to be used for nonlinear problems with a lot of measured parameters that contribute to the total uncertainty of a critical experiment. This has provoked increasing interest in spectral methods for uncertainty analysis, in particular, the polynomial chaos method. In this work, the necessity of the regression analysis is substantiated for approximations of random variables by the polynomial chaos method to estimate uncertainties and confidence levels of the results of critical experiments.

The WWR-K is a multipurpose research reactor in the Republic of Kazakhstan. The WWR-K reactor was started up for the first time on October 30, 1967, under the direction of B.T. Dubovsky, V.N. Okolovicha, G.A. Batyrbekova, L.A. Yurovsky, and A.I. Maslova. The WWR-K research reactor is a water-water reactor of a heterogeneous type with a thermal neutron spectrum, a rated capacity of 10 MW, and a 36% enrichment of uranium-235. The reactor operated without any accidents until 1988. After the Chernobyl accident, the USSR Gospromatomnadzor decided to suspend the operation of the WWR-K reactor in October 1988 until the requirements for ensuring safe operation of the reactor under high seismicity conditions were met. Specialists at the Institute of Nuclear Physics endeavored to increase the seismic safety of the reactor and to provide for its safe operation in conditions of high seismicity. In 1998, the operation of the WWRK reactor was resumed with the permitted power of 6 MW. Prior to the collapse of the USSR, the main purposes of the WWR-K reactor were testing the thermionic reactor-converter elements, neutron activation analysis, studies of ultracold neutrons, studies of inert gas plasma parameters, and studies of the electroionization of CO₂ and CO lasers. In 2003, a feasibility study was begun for the conversion of the reactor to lowenriched fuel with preservation of operational and experimental capabilities. As a result, a new fuel assembly, WWR-KN, was designed on its basis—a compact core, which allows improving the characteristics of the reactor. During the period from 2011 to 2013, the life-cycle tests of three test assemblies were conducted; on the basis of the test results, the WWR-KN FA was recommended for the conversion of the WWR-K reactor. In the first half of 2016, successful physical and power startups of the WWR-K reactor with low-enriched fuel were carried out. As a result of the conversion, the thermal neutron flux in the center of the core was doubled. The main current purposes of the WWR-K reactor are the following

• testing fuel and structural materials of reactors of the fourth generation;

• testing fusion reactor materials;

• producing radioisotopes for medicine and industry;

• neutron activation analysis.

The inverse beta decay is the most important reaction for registration of an electronic antineutrino.

\({\tilde v_e} + p = {e^ + }n\begin{array}{*{20}{c}} { \nearrow n + p \to d + \gamma \left( {2.2MeV} \right)} \\ { \searrow n{ + ^{157}}GD + \gamma \left( {8MeV} \right)} \end{array}\)

The detector of electronic antineutrinos consists of a target and a gamma-ray detector. Sorbent C100 with the applied gadolinium is supposed to be used as a target for the detector to register the products of reaction ṽ_e + p= e⁺ + n. According to the Boyd model [1], the sorption on ion-exchange resins is a complicated and multistage process that includes mechanisms of external (film) diffusion and internal (gel) diffusion. The mechanism of chemical reaction also influences the sorption process. Diffusion mechanisms are sequential stages of the sorption process, so that the slowest of them is the limiting stage of the process. The sorption kinetics was examined by the finite volume method. The main purpose was to reveal the limiting stage in each phase of the sorption process [2] in system Gd³⁺–C100 in H⁺ form. It was necessary to find out how the acid concentration and temperature influence the sorbent sorption properties.

Methods for calculating the heat and neutron transport in structural elements of nuclear and fusion power devices are considered in the framework of statistical modeling and physical neutron kinetics based on the cross sections of interaction of neutrons with matter. Statistical modeling makes it possible to establish the nature of the neutron transport and energy in matter. In the extreme cases, within the framework of this approach, the diffusion and ballistic regimes are realized. In the calculation of heat transfer, the heat release associated with gamma quanta is also taken into account. The possibilities of these methods for estimation of the joint thermal effects of these factors are shown.

Experimental data on the interactions of charged particles with light nuclei have been compiled at the Institute of Nuclear and Radiation Physics of the Russian Federal Nuclear Center—All-Russian Research Institute of Experimental Physics (RFNC-VNIIEF) since 1973. Currently, this work is carried out by the staff of the Center of Nuclear Physics Data (CNPD), which was established in 1997 [1]. The paper presents the main directions of the activities of the CNPD, describes its contribution to the development of the EXFOR international library of experimental nuclear data, and gives a detailed overview of the EXFOR-Editor software package for entering, editing, and writing data on nuclear reactions in the EXFOR format [2].

The basic properties of the plasma of capillary discharges are discussed. A mathematical simulation of the interaction of pulsed plasma jets generated by a capillary discharge at atmospheric pressure is presented.

The article reviews thermal neutron detector developments in the Department of the IBR-2 Spectrometer Complex of the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research (FLNP JINR). A variety of detector types are considered: neutron monitors, ring detectors, position-sensitive detectors (PSD), and scintillation detectors. The experience of exploitation of these detectors at the research facilities of the FLNP JINR is presented.

In this paper, we aimed to establish the similarity of dispersion of various metals at high-intensity loading. Characteristics of the dispersing products and the cascade of arising dissipative structures (the inner surface roughness of the destruction centers, the cascade of the slip bands of the crystal lattice, the cascade of destruction centers, and the roughness of the destruction surface) were quantified on the basis of fractal geometry using the interactive image analysis system (IIAS) package. We numerically simulated destruction in loaded samples using the TIM 3D Lagrangian technique.

Conversion electron Mössbauer spectroscopy was used to study the thin films obtained by co-precipitation of coatings from two sources: magnetron sputtering of a metal tantalum target and thermovacuum evaporation of metallic iron enriched in the ⁵⁷Fe isotope. The films of required thickness were formed by alternating exposure to a magnetron-generated tantalum flow and a flow of iron vapor from a thermal evaporator. The analysis of the Mössbauer spectra showed that co-precipitation of iron atoms transferred to the vapor state by heating and tantalum atoms from the magnetron plasma forms a solid solution of iron in tantalum. The film structure is mainly a metastable β-modification of tantalum of the tetragonal crystal system. Annealing of the samples at 1100°С led to the transition of the β-tantalum structure into the body-centered cubic structure of the α-modification of tantalum. It is found that magnetron sputtering creates favorable conditions for formation of solid solutions of two metals at temperatures far from the melting temperatures of their components.

The results of estimating the activity of the aerosol form and gaseous compounds of iodine isotopes in the ventilation system of the IVV-2M reactor facility are presented. The contribution of aerosol and gaseous forms of iodine to the total volumetric activity was simultaneously determined. Criteria of homogeneity of sorbed iodine compounds are determined on the basis of analysis of the dependence of the activity distribution in the layers of a multilayer filter. The study made it possible to determine the form in which radioactive iodine enters the space above the surface of the coolant of the water-moderated water-cooled pool-type research reactor. It is shown that the volumetric iodine activity in the air of the ventilation system of the reactor facility is generally determined by hardly sorbed gaseous compounds.

Characteristic X-ray spectra of materials containing heavy-metal components irradiated with gamma rays are measured. The samples are irradiated with photons with energies of 122.06 keV (85.5%) and 136.47 keV (10.7%) emitted by a cobalt-57 source and include tungsten, lead, and bismuth plates and a sample of a radiation-protective composite material. The characteristic radiation from the samples and incident photons passing through the samples are detected with a low-background gamma spectrometer based on a highpurity germanium (HPGe) detector. The measured intensity of the characteristic X-ray radiation from the protective material amounts to 10% of that of the primary radiation. The elemental composition of the radiation- protective material is determined by peak positions in the spectra of the characteristic X-rays from the samples of W, Pb, and Bi. The analyzed composite material features Pb as the dominant heavy component, whereby the primary photon radiation from the source is attenuated by a factor of 3.7. The density of the lead component in the protective material was determined.

In this review, the problems of the development of radiopharmaceuticals (RPs) based on alphaemitting radionuclides are discussed. The prospects of application of the radionuclides ²²⁷Th, ²²⁵Ac, ²²³Ra, ²¹³Bi, ²¹²Pb/²¹²Bi, ²¹²Bi, ²¹¹At, and ¹⁴⁹Tb are estimated in the aspect of their physicochemical properties, such as half-life, properties of daughter radionuclides, and complexing ability. The methods used for the production of radionuclides and their industrial availability are considered. Some examples of radionuclide complexes with ligands and nanoparticles for targeted delivery are presented. The results of medical trials for RPs based on alpha emitters are given.