Turbulent convective heat transfer in an inclined tube filled with sodium

Turbulent free convection of liquid sodium in a straight thermally insulated tube with a length equal to 20 diameters and with end heat exchangers ensuring a fixed temperature drop is investigated experimentally. The experiments are performed for a fixed Rayleigh number Ra = 2.4 × 10⁶ and various angles of inclination of the tube relative to the vertical. A strong dependence of the power transferred along the tube on the angle of inclination is revealed: the Nusselt number in the angular range under investigation changes by an order of magnitude with a maximum at the angle of 65° with the vertical. The characteristics of large-scale circulation and turbulent temperature pulsations show that convective heat transfer is mainly determined by the velocity of large-scale circulation of sodium. Turbulent pulsations are maximal for small angles of inclination (α = 20°–30°) and reduce the heat flux along the channel, although in the limit of small angles (vertical tube), there is no large-scale circulation, and the convective heat flux, which is an order of magnitude larger than the molecular heat flux, is ensured only by small scale (turbulent) flow.     

Nanostructure Evolution of Oxide Dispersion Strengthened Steels under Fe Ion Irradiation at 350°C

Physics of Atomic Nuclei - Improved mechanical properties of oxide dispersion strengthened (ODS) steels, the advanced materials for the reactor core, are due to the high density of uniformly...     

Phase competition in late stages of diffusive decomposition

The late stages of diffusive decomposition of a supersaturated solid solution into phases consisting of multicomponent stoichiometric compounds with a common element are investigated. It is shown that a competition is possible between phases for the common component, as a result of which only one of these phases survives. Fiz. Tverd. Tela (St. Petersburg) 40, 655–657 (April 1998)     

Optimization of Mass Reconstruction Algorithm for Atom Probe Tomography Analysis

Physics of Atomic Nuclei - Atom probe tomography (ATP) is a technique that has actively been developed in recent years. This method allows one to investigate three-dimensional distributions of...     

Optimization of Material Analysis Conditions for Laser-Assisted Atom Probe Tomography Characterization

Atom probe tomography (APT) analysis with a femtosecond laser is one of the most promising techniques to characterize local variations of chemical distribution in materials with subnanometer spatial resolution. In this study, the effect of APT analysis conditions on the accuracy of data recovery for chromium steels and Fe-Cr alloys is investigated. Dependences of mass resolving power and the detected composition of chromium as a function of laser power, specimen geometry, and evaporation rate are presented.     

Atom Probe Tomography Analysis of Materials using Femtosecond-Laser Assisted Evaporation

We study the possibilities of the chemical analysis of materials with determination of the positions of individual atoms of various chemical elements in a sample using an APPLE-3D atom probe tomograph with femtosecond-laser assisted evaporation, developed at the Institute of Theoretical and Experimental Physics of the National Research Center “Kurchatov Institute.” The results of investigations of ferritic-martensitic steels and an aluminum alloy are presented; the characterization and visualization of features with a size on the order of 10 nm are demonstrated.     

Kinetics of impurity segregation at grain boundaries in polycrystals. II. Concentrated solution

The isothermal impurity segregation from a finite-size grain into an intergrain boundary region or at an external free surface is investigated when the impurity concentration in the boundary region is not small. Simple algebraic equations are obtained that describe the impurity concentration for the case of several competing and interacting impurities. The process of segregation of two impurities is discussed in detail, and it is shown that the concentration of one of them can have a maximum as a function of time. Fiz. Tverd. Tela (St. Petersburg) 40, 251–253 (February 1998)     

Simulation of Ion Paths in the Target Material for the Injection Complex of the BELA Facility

To realize the simulation experiments with the use of two ion beams at the injection complex of the BELA accelerator (Based on ECR ion source Linear Accelerator), it is necessary to determine the energy and irradiation angle of the beam of light ions which will be implanted into the region of radiation damage induced by heavy-ion beam. The depth of light-ion implantation is determined by the energy and kind of particles initiating the damage, as well as by their incidence angle. It is supposed that the incidence direction of heavy ions will coincide with the normal to the specimen surface. In our work, the necessary implantation zone for the iron ion beam with an energy of 3.2 MeV is located at depths of 300–800 nm. The simulation of the hydrogen and helium ion paths in the material of the iron target in the energy range from 150 to 600 keV at the angle to the normal from 0° to 65° is performed. The range of energies and irradiation angles for the hydrogen and helium ions are determined for the implantation into the radiation-induced defect-formation zone.     

Atom Probe Tomography of High-Entropy Alloy AlCoCrFeNi

Physics of Atomic Nuclei - In this paper, the results of study of the AlCoCrFeNi high-entropy alloy by means of atom probe tomography are presented. Two phases were found, one enriched in Fe and Cr...     

Analysis of Mechanical Properties and Nanostructure Changes of VVER-440 Reactor Pressure Vessel Metal after Annealing

Physics of Atomic Nuclei - Analysis of mechanical testing and microstructural investigations of the irradiated VVER-440 reactor pressure vessel (RPV) metal before and after annealing carried out in...