Atomic Energy最新文献

A review of literature sources demonstrates the relevance of improving the accuracy of liquid flow measurements. To solve this problem, a neural-network model for liquid flow determination was developed and tested. The optimum structure and training parameters of an artificial neural network, such as the activation function, transfer function of the output layer, number of hidden layers and neurons in them, were selected. The training sample was generated using empirical expressions of GOST 8.586.1–2005 (ISO 5167–1:2022). The developed neural-network predictive model, which provides an uncertainty of calculations no greater than 0.32%, is intended for use as part of a software and hardware system for improving the accuracy of liquid flow measurements at nuclear industry enterprises.

Since 2021, a comprehensive program comprising five projects has been implemented by the Rosatom State Corporation in the Russian Federation. Of these, the project entitled “Development of controlled fusion and innovative plasma technologies” is scientifically supervised by NRC Kurchatov Institute. The program envisages a development of the concept of a hybrid reactor plant that combines fusion and fission technologies. As well as presenting an overview of the feasibility, functions, and parameters of planned fusion neutron sources, the paper outlines the development concept of the hybrid system and prospects for its implementation as a means of expanding the fuel base and recycling high-level wastes. An analysis of target indicators is provided.

The paper considers the processes involved in leaking fuel elements during the shutdown and preparation of a reactor for refueling in the case of a defect located at the bottom, in the middle, or at the top of the fuel column. The volume and activity of gaseous fission products released during fuel cladding failure detection were evaluated using the mast sipping system of the refueling machine. It is demonstrated that the sensitivity of the beta-radiometer, which starts at 37 kBq/m³, provides for the detection of leaking fuel elements at any power density located at various locations of the defect along its height. Neglecting to wash all fuel elements in the FA with bubble air may result in a failure to detect leaking fuel elements.

The concept of slowing down the kinetics of a fast reactor, according to which a rapid reactivity insertion is used to reduce the development rate of transients at initial events, is aimed at achieving a higher level of reactor self-protection. The paper presents a set of studies on the engineering and technical implementation of this concept on the example of a high-power fast lead-cooled reactor. Considering a hypothetical initial event with a rapid insertion of a complete reactivity margin, the stability of the reactor with the slowed down kinetics in relation to such an event was analyzed. An updated physical-mathematical apparatus is proposed for evaluating the slowed-down kinetics and calculating the dynamics of transient processes. The basic principles for the formation of a reflector for such a reactor based on formulated criteria for slowing down the kinetics include the use of ²⁰⁸Pb and weakly neutron-absorbing materials, as well as the optimum location of various structural elements in the reflector. The theoretical possibility of achieving a slowed-down kinetics in layouts that meet the developed principles is demonstrated.

Considering present opportunities for modernizing accelerated preventive protection (APP) for VVER-1200 reactors, a methodology for selecting two APP groups is presented. Using the described methodology and selection criteria, two APP groups (APP1 and APP2) are selected for modes of disabled RCPSs and two electric feeding pumps during operation at a rated power level. The study represents an important stage in the modernization of the safety algorithm, i.e., accelerated preventive protection of the reactor. The results presented in the article are relevant for research and development purposes, as well as for safety analysis.

The paper analyzes a nano-scale atomic-molecular model for filling a cable gland with sealant. The dependence of the NPP cable gland state assessment on the parameters of the sealant movement model is demonstrated. The simulation gives a satisfactory convergence with the known experimental and theoretical results.

Given the assumption of normal distribution, the determination of the calculation error for the correlation of the initial reference data is considered. In this case, it is proposed to use the maximum likelihood method with a non-diagonal covariance matrix. The relationship of calculation deviations from the reference data is assumed to be described by known correlation coefficients. Techniques for constructing the average value, error variance, and distribution of its probability are described. The determination of the correlation coefficient for k_eff is considered using two consecutive campaigns of the PIK reactor. Possible directions for future modification of the methodology are discussed.

The paper presents the results of neutron-physical calculations for determining the optimum configuration of materials for use as a cryogenic moderator in a DARIA university-grade compact neutron source. It is shown that a cryogenic moderator based on a solid frozen mesitylene of a certain configuration may represent the optimum source of cold neutrons for studying the structure and properties of substances by neutron-physical methods in the DARIA neutron source.

The paper considers features of purification the reprocessed uranium hexafluoride from ^{232, 234, 236}U in two cascades of gas centrifuges with additional feeding streams of waste uranium hexafluoride to the product stages of the cascades. The effective purification from ²³⁶U in the first cascade is carried out at a ²³⁵U concentration of less than 20% in long cascades having a large number of stages. The parameters of the second cascade that significantly reduce the concentration of ^{232, 234}U in the wastes were determined. As a result of the reduction with waste uranium hexafluoride, this stream ensures a commercial low-enriched product to meet the requirements of the ASTM C996-20 specification established for enriched industrial uranium hexafluoride.

The article presents a comparative analysis of the consequences of accidents at Chernobyl and Fukushima Daiichi NPPs. Both accidents are demonstrated to have had severe effects for agriculture and natural environment. The consequences of radiation accidents are shown to have been significantly impacted by the composition of the radionuclide release during the accident, the season of the year, and the natural features of the contaminated regions.