Atomic Energy最新文献

Aspects of separation potentials for a multicomponent mixture of isotopes are considered. In order to separate isotopes of reprocessed uranium and germanium in cascades with high separation factors corresponding to gas centrifuges, a computational experiment was carried out. The application of potentials for calculating the separation power of elements, stages, and cascades is analyzed. Potentials that provide a satisfactory assessment of the actual separation power for the stages and the cascade, thus determining the costs of the separation work, are established. This characteristic, along with the separation power of the element, is virtually independent of the used potential type.

The paper presents the results of a calculation study connected with the composition of RBMK-1000 fuel having a reduced erbium content. The computational studies were carried out using SADCO software systems (developed by JSC “NIKIET”) and MCU-RBMK (developed by NRC “Kurchatov Institute”). The studies include calculations of a fuel cell with various compositions of uranium-erbium fuel and a RBMK-1000 reactor under fuel-loading conditions involving a reduced erbium content. The conversion of RBMK-1000 to a fuel having a reduced erbium content ensures the neutron-physical characteristics and volumes of accumulating commercial ⁶⁰Co to be maintained within operational limits under conditions of extending the reactor service life for more than 50 years.

The paper presents the results of critical, correlation, and spectral precision experiments carried out at the FKBN‑2 assembly machine using a cylindrical multiplying system made of low-background α‑phase plutonium. In the experiments, the critical state of the multiplying system was determined, the characteristics of non-stationary prompt neutron processes were investigated, and the number of nuclear reactions in the detectors was measured at a controlled power level of the multiplying system. After constructing a benchmark model for the multiplying system, a computational simulation of integral experiments was carried out. Based on the experimental results, the average lifetime of prompt neutrons and the effective fraction of delayed neutrons for the multiplying system were determined. The obtained results can be used to verify the codes of neutron-physics and refine neutron constants.

The paper addresses the development of prototype large-scale purified inert atmosphere cells for testing equipment used in the pyrochemical treatment of spent nuclear fuel from fast neutron reactors. In addition, design peculiarities of the cells are discussed along with a presentation of preliminary results of tests on the generation and maintenance of an inert atmosphere of required quality in them.

The BN-800 reactor with a hybrid core has been in commercial operation in Russia since 2016. During the initial period, the layout of the hybrid core was constantly changed, including variations in the ratios of fuel assemblies with uranium and mixed oxide fuel, as well as the number of fuel assemblies in medium and high enrichment zones. In 2021, the transition of the BN-800 core to full mixed oxide fuel loading began. The transition was carried out in stages: during the reloading period, fuel assemblies with mixed oxide fuel (one third of the total amount of fuel assemblies in the core) was loaded into the core. In 2022, the reactor was brought to its minimum controlled power level at full mixed oxide fuel loading. During BN-800 operation, a large amount of experimental data on the main neutron-physical characteristics of the core has been accumulated. The adequacy of the computational prediction of the BN-800 neutron-physical characteristics was confirmed by comparing the neutron-physical values. The experimental results were evaluated using a set of critical BFS assemblies for modeling the reactor core. A comparative analysis of calculated values between the neutron-physical characteristics, which were obtained by various calculation codes within the framework of a reactor operation support, and the experimental data, was carried out.

This study evaluates the impact of accident-tolerant fuel compositions on the nuclear power plant (NPP) electricity cost associated with the fuel component across a broad spectrum of fuel cycle parameters. The cost of electricity is influenced by changes in burnup, fuel enrichment, thermal stress, reactor campaign, as well as market prices for natural uranium, its conversion, enrichment, fabrication of fuel assemblies, and the cost of spent fuel treatment. From derived analytical expressions that depict the relation between fuel burnup and various reactor operation parameters, grid diagrams were developed. By adhering to specified limitations on burnup and the fuel-related component of NPP electricity cost, these diagrams facilitate the selection of the fuel cycle.

In the present study, data for converting the pulse-height spectra of an airborne gamma-ray spectrometer with a NaI (31 × 31 mm) detector to the dose rate values were obtained using the mathematical simulation. The results were tested using model tasks for determining pulse-height spectra at heights from 15 to 75 m. A point isotropic source of ⁶⁰Co and the infinite contamination of the soil surface with ¹³⁷Cs were considered as sources of gamma-radiation. The simulation was carried out using the Monte Carlo method. As a result, uncertainties of obtained conversion coefficients for dose rate estimations were evaluated.

The paper discusses issues connected with the enhancement of nuclear safety and productivity of integral critical experiments by means of applied digitalization and robotics in technological solutions. Experiments performed at a FKBN compact assembly machine must be precise and informative. The concept of robotics in hazardous nuclear operations is discussed in terms of its potential advantages. The basic requirements for mechanics and artificial intelligence are outlined.

During their initial development, passive autocatalytic hydrogen recombiners (PARs) were presumed to operate in a flameless mode. However, a series of independent experiments conducted in the 1990s observed hydrogen-air gas mixtures igniting as a result of PAR operation. This ignition was due to overheating of the catalyst, leading to the thermal ignition of hydrogen-air mixtures (termed “internal ignition”). Additionally, individual particles may become detached from the catalyst substrate and swept up by the gas stream to subsequently ignite the gas mixture outside the recombiner housing, a phenomenon known as “external ignition.” This article delves into the experimental findings concerning two mechanisms of hydrogen-air mixture ignition. Direct evidence for recombiner-induced external ignition was captured using the Schlieren method. It was confirmed that the concentration limits for external ignition differ from those for internal ignition. In order to ensure nuclear power plant safety, the development of a testing methodology for the technology used in manufacturing catalysts is essential.

The present work aims to study the influence of the feed solution flow rate on uranium refining in a cascade of extraction columns. Numerical studies of uranium extraction refining in a column cascade using a nonequilibrium mathematical model of liquid extraction are presented. The model describes the main physical and chemical processes in the column, including the longitudinal mixing of liquid phases, convective mass transfer, as well as the mass exchange between the water and organic phases. The model used a uranium extraction isotherm based on the data of the interaction between an aqueous solution of uranyl nitrate, nitric acid, and a tributyl phosphate solution in a hydrocarbon diluent. The operation of the extraction column cascade with various flow rates of the water phase at the inlet was simulated. Based on the calculations, the maximum flow rate of the feed aqueous solution was established ensuring the maximum cascade productivity and isolation of uranium from the water-tail solution.