Atomic Energy最新文献

The article examines a mechanism that significantly influences the operation of radioelectronic equipment when it is located in close proximity to an electron accelerator. In particular, the effect of accumulation of an opposite sign charge and the appearance of micro-breakdown effects are considered in terms of this mechanism. A calculation model explaining these phenomena is described. The model is based on measuring the path of positrons and electrons in substances, as well as the characteristic dependence of the transmission coefficient for electrons and positrons on the path length.

The paper presents a justification, setting, and results of experiments on the determination of the liquidus temperature for a molten salt comprised of 73LiF–27BeF₂ with plutonium trifluoride, considered as the fuel circuit salt of a liquid-salt reactor for burning Np, Am, Cm. The liquidus temperature of the melt was determined using a differential scanning calorimetry method; the plutonium concentration in the samples was controlled by recording the γ‑radiation of plutonium isotopes. According to the results of the studies, the liquidus temperature comprised 600–680 °C across a range of plutonium trifluoride concentrations from 0.1–3 mol.%. According to the performed calculations, in order to transmute 250 kg/year of Np, Am, Cm in an MSR‑T reactor, this restriction on the concentration of actinide fluorides in the fuel salt at its operating temperature in the reactor of 650–750 °C requires 550–660 kg/year of plutonium.

The RITM-200N reactor represents a modification of a RITM-200 icebreaker reactor, which is designed on the basis of proven ship reactor construction technologies. The reactor plant is being developed for a ground-based SNPP power unit to be constructed on the territory of the Republic of Sakha (Yakutia). The article reflects the main results of developing the technical design of the RITM-200N reactor and completing a part of R&D in support of technical solutions.

Abstract

A total number of 18 experimental fuel assemblies (FAs), containing mixed nitride fuel rods with claddings of various geometry, were irradiated in an BN-600 core. By the end of 2022, JSC SSC NIIAR had completed the post-reactor studies of 16 ETVS BN-600 nitride fuel rods, 4 fuel rods with a gas sublayer irradiated in the composition of OU‑1 and OU‑2 collapsible irradiation devices, and 3 OU‑4 BOR-60 fuel rods with a liquid metal sublayer. Post-reactor studies of nitride fuel rods were preceded by pre-test calculations of their stress-strain and temperature states, taking into account the actual irradiation parameters. The results of the studies were compared with the calculated data. Fuel radiation swelling represents one of the most important factors that determine the degree of thermomechanical interaction between the fuel and the cladding, thus limiting the performance of nitride fuel rods. The present article summarizes and analyzes the currently obtained data on the swelling and its rate for mixed uranium-plutonium nitride fuel in fuel rods with a gas sublayer.

According to the strategy for the development of the nuclear power industry in Russia for the first half of the 21st century, the nuclear power industry complex should undergo the initial stage in the formation of a two-component nuclear power system and a closed nuclear fuel cycle (NFC) infrastructure. All elements of such a nuclear power system, including NPPs, facilities for the fabrication of uranium and uranium-plutonium fuel, processing of spent nuclear fuel, and radioactive waste management, must be organically linked for producing competitive electricity in both domestic and foreign markets. The present article demonstrates the systemic benefits from a large-scale introduction of fast reactors for the Russian nuclear power industry in terms of a sustainable resource provision and a solution to the key problems of the final NFC stage, which is associated with the accumulation of spent fuel and transuranic actinides. The study proposes an optimum NFC closure scenario, in which the described problems can be solved without increasing the high parameters of the BR in a fast reactor and using special burners.

The present paper considers a typical scenario for the development of a design-basis loss-of-coolant accident (LOCA) in a VVER-1000 reactor. Processes occurring in the fuel and cladding at each stage of the accident are described. The main directions of the development of fuel and fuel claddings for water-water thermal reactors are reviewed. The advantages and disadvantages of various fuel composition types (fuel + cladding) from the perspective of their behavior in design-basis LOCAs are analyzed. Results of preliminary modeling design-basis and beyond design-basis LOCAs for VVER-1000 and PWR reactors with various fuel compositions are presented.

In an electrochemical cell comprising an equilibrium metal felt anode based on a sorption filter, as well as a highly polarized cathode having a significantly smaller surface area, hydroxonium cations and hydroxide anions form a double electric layer in a viscous sublayer of the aqueous coolant near the cathode surface. If the cathode electric potential allows for an electron exchange between these ions, then the double layer becomes a powerful source of hydroxyl radicals, which are chemically active outside the cathode. Then, when the aqueous coolant flows through this cell, trace radionuclide impurities will be extracted from it by the adsorption on a renewable surface of a metal felt, continuously oxidized by hydroxyl radicals.

The article considers factors contributing to the increased interest in the development of medium and small nuclear power plants (SNPPs) based on small modular reactors (SMR) in terms of a high-tech mass product within the contemporary electric power industry. Conditions for reducing SNPP costs are determined taking into account the modularity and mass production of equipment. The systemic effects of integrating SNPPs into electric power systems and possibilities for their development in the Unified Energy System (UES) of Russia, including as combined heat and power sources (nuclear cogeneration heat plants, CHP) are investigated along with the conditions and requirements for their active application in areas where there is a decentralized power supply.

The paper presents the results of modeling an L4 experiment using an ACE test facility (USA) on the interaction of the melt with concrete. The study aims to validate previously developed models of interaction between the melt and concretes of two particular types used in the construction of VVER-1000 NPPs. The experimental and calculation results were compared according to the movement of the concrete erosion boundary, the integral yield of hydrogen, carbon monoxide, and vapors of structural materials, as well as simulators of melt fission products. A satisfactory agreement was obtained according to all characteristics. The scatter of the results at the variation of main calculation parameters was estimated along with the degree of their influence on the concrete penetration depth.

The paper presents the experimental assessment for the characteristics of a fast neutron spectrometer based on a diamond sensor detector. The presented characteristics include the energy range of detected neutrons, energy resolution, the effect of associated radiation (γ-quants and scattered neutrons) on the measurement results, as well as the range of the measured neutron flux density. Some effects typical to diamond-based detectors, e.g., the effect of polarization on the measurement results, are considered. The possibility of performing spectrometry of neutrons with an energy of 14 MeV at a resolution of less than 1% is demonstrated, including the influence of electronics, as well as the absence of a polarization effect on the detector operation during measurement at points where the fast neutron flux density is up to 10⁷ s⁻¹ ∙ cm⁻².