This paper presents the results of thermohydraulic modeling of a lead-cooled reactor, which is based on the design scheme for the ATHLET code, obtained on the basis of open information on the BREST-OD-300 reactor plant. The main goal of the work is to show the influence of detailed modeling of the installation and various models of hydrodynamics in a system of parallel channels on the distribution of coolant parameters in space. The task of this stage of work was to show a step-by-step modeling of one of the options for dividing the in-reactor space into a system of hydraulic channels. The subdivision of the in-core space is based on the type and number of various elements of the core such as: fuel assemblies with fuel, fuel assemblies with regulating devices, reflector unit, etc. This way of modeling the core allows you to see changes in different parts of the reactor plant when calculating transients. Also for this model, two schemes for modeling parallel channels without cross-links between channels and with cross-links have been created. In early works, studies were carried out on the effect of the splitting method on the parameters of the coolant when simulating transients, but the effect of cross-links has not yet been investigated. These schemes will make it possible to carry out the necessary studies and draw a conclusion about the best way to simulate the reactor core in a given partition of the in-reactor space. Earlier results obtained on simpler models showed the efficiency of dividing the inreactor space into a system of hydraulic channels in transient modes. As a result, the partitioning of the incore space allows, in fact, to perform model calculations in 3D representation. These models will make it possible to carry out a number of calculations with various transient modes and justify the use or not use of crosslinks for this type of modeling of reactors with a liquid metal coolant. The main results of the work show the need for further research in the direction of 3D modeling and hydraulics of the in-reactor space for reactors with a liquid metal coolant.

This article presents the results of the development of one-dimensional thermal-hydraulics model of the reactor core with a supercritical steam coolant (SCPS-600 type), intended for the analysis of thermal-hydraulic stability. To create it, an approach was chosen that involves the use of a modified semi-implicit algorithm based on SIMPLE. The algorithm was implemented using C ++ software. The object of the study was a single channel with a circular cross-section with the fuel assemblies of a hexagonal shape in it. A calculation was carried out that simulates the process of starting the reactor and its reaching the steady state mode. The calculation was carried out in two stages: at the first stage, the ascending flow was established in the unheated channel; at the moment of time 0.2 s, the heating of the system began, which led to a rearrangement of the velocity, pressure and temperature fields. The model included the conservation of momentum, and the energy of the coolant in the core, presented as finite differences. All the properties of the supercritical steam coolant required for the calculation were obtained using the IAPWS-IF97 library. The algorithm assumes solution of the basic equations of thermal-hydraulics with continuity check twice at one time step. Based on the results of the calculation, a picture of the fields of velocity, pressure and temperature was obtained. With the help of the heat balance, a conclusion was made about the correct operation of the model and the possibility of its application for the analysis of the stability of a reactor with a supercritical steam coolant.

The paper analyzes the results of modeling one of the types of fuel assemblies used in the IR-8 research reactor. The article is a continuation of the work in which the analysis of hydraulic tests of the eight- and six-tube fuel assemblies IRT-3M was carried out and the nature of the change in the velocity field of the coolant in the cross-section of a standard six-tube fuel assembly, without taking into account the energy release in the fuel elements, was revealed. The calculation was carried out using the program for thermohydraulic calculation ATHLET. This paper presents the results of a connected thermohydraulic and neutron-physical calculation of IRT-3M fuel assemblies. For neutron-physical calculations, the MCU-PTR program was used. The multiphysics approach makes it possible to take into account the effect on the calculation results of changes in the physical properties of the core materials. The paper presents the results of mathematical modeling of stationary operation of a standard IRT-3M fuel assembly with power rate of 600 kW. The coupled work of the neutron-physical and thermal-hydraulic calculation codes has been debugged. The main thermophysical parameters of fuel assemblies are obtained: temperatures of the coolant, cladding, and fuel, and the margin to surface boiling are determined. Using a multiphysics approach, these thermohydraulic parameters were refined. The data obtained can be useful for further calculations of such fuel assemblies using the central channel of the fuel assembly for installing experimental irradiation devices. In addition, the indicated temperature distributions can serve as boundary conditions for design models of irradiation devices used in 3-D CFD codes. The results of this work can be used to determine the permissible power of research reactors of the IRT type: IR-8 at NRC KI (Moscow), IRT-MEPhI at NRNU MEPhI (Moscow), IRT-T at TPU (Tomsk) and WWRSM at INP (Tashkent).

Small power engineering is a new direction of development of the nuclear industry. In this paper, the design of the integrated low-power reactor project “MODEST” is considered. The results of calculations of the main technical characteristics of the power installation are presented. Natural circulation of the coolant is carried out in the module to increase the safety of the project. Natural heat removal from active core prevents accidents associated with loss of power supply. In the design, there is a more efficient helical coil steam generator, compared to straight-tube ones. Such a reactor can be used for power generation, hydrogen production and water desalination.

In article the problem of reconstructing the true physical value distribution from measured one (distorted by instrumental effects) is cosidered. This problem is known as deconvolution (unfolding). There are several common ways to solve it: bayesian algorithm, singular value decomposition approach and TUnfold method, based on regularisation. We are discussing terms of use, how to choose optimal parameters for different methods, and comparing the reconstruction quality. The object of analysis was choosen the cosmic rays energetical spectrum simulated by Monte-Carlo method and measured by PAMELA magnetic spectrometer. We focused on the analysis of spectrum reconstruction quality for different algorithm parameters and the comparative analysis of methods results depend on spectrum discretisation features. The main result is the approach to optimal regularisation parameter choice for SVD method and iterations number for bayesian method.

Kurchatov Institute has a critical ASTRA stand, where experiments are carried out to study the neutron-physical characteristics of VTGR-type reactors. Information on the evaluated experiments currently exists only for stationary experiments and is absent for non-stationary ones; moreover the calculation analysis for most part of non-stationary experiments has not been carried out yet. The last task demands the calculation by neutronic code to be able to solve time-dependent problems in accordance to space distribution of neutron field. When considering the complex neutron-physical systems with the number of calculation points than 1 million, the calculation time can be an hour or more, and in case of non-stationary process with the small step of time, the waiting can be a month. ASTRA is a complex system with about 1 million calculated points. Parallel technologies can be used to speed up the non-stationary calculation. The aim of the study is to imply efficient methods of stationary computational modeling using parallelization technology into a module for calculating non-stationary processes. A parallelization scheme with height decomposition has been developed. The calculation of non-stationary experiments using parallel technologies is carried out.

The work is devoted to reproduction of the 27-day variations of the galactic cosmic rays (GCR) flux, observed in the PAMELA experiment, by simulating the propagation of GCR in the heliosphere. The map of the interplanetary electromagnetic field has been constructed in accordance with the Parker model and measurements of the ACE spacecraft. We have created an algorithm, which numerically solves the motion equation of cosmic rays in that field and reconstructs their trajectory. Charged particles are generated on the edge of the heliosphere, then the particles are traced with help of the numerical algorithm. The initial characteristics of the particles correspond to the uniform and isotropic distribution. As a result of calculations we have obtained the time dependencies of the GCR flux in the near-Earth space for energy 1 GeV.

The paper predicts the Bose–Einstein condensation of light in the resonant optical microcavities (pores) of a photonic crystal makes essential the inelastic photon-photon interaction resulting to the two photons coupling into a graviton-like biphoton (paraphoton). The estimates demonstrate the observability of the effect both by a standard gravitational-wave routine as well as by the indirect spectral method registering the extra peak in the optical and Raman spectra of the photonic crystal.

The article presents the energy dependence of the cross section for the inelastic interaction of light nuclei (protons, helium, lithium) with energies of several hundred megaelectronvolts with tungsten nuclei, obtained using the data of the PAMELA space experiment. The PAMELA instrument is intended for precision measurements of cosmic ray fluxes of various natures and included a set of detector systems for reliable determination of particle characteristics (type and energy). In this work, the particles were identified using a track system in a magnetic field, a time-of-flight system, and an anti-coincidence system. A position-sensitive calorimeter with a tungsten absorber, in turn, makes it possible to study the characteristics of the interaction of particles inside it, in particular, to calculate the cross section of their inelastic interaction.

The design of a station for recording the tracks of charged particles is presented. The station is assembled from two mutually orthogonal chambers; each chamber contains three layers of tightly packed drift tubes made of Mylar. The layer consists of 24 tubes 810 mm long and 30 mm in diameter. Track stations are used in experiments on the setup for detection of particles with large transverse momenta of accelerator of NRC ”Kurchatov Institute” — IHEP. The procedure for checking drift tube chambers is described. The results of testing chambers using cosmic muons and proton beams are presented.