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Документ Modeling the distribution of emergency release productsat a nuclear power plant unit(Національний технічний університет "Харківський політехнічний інститут", 2024) Biliaieva, Viktoriia; Levchenko, Larysa; Myshchenko, Iryna; Tykhenko, Oksana; Kozachyna, VitaliiDespite the fact that much attention is paid to the safe operation of nuclear power plants, there is a possibility of an accident with the release of radionuclides. This is especially true in Ukraine, where there is a threat of the damage to nuclear reactors as a result of military operations. It is impossible to research the distribution of products emergency releases radioactive substances in laboratory conditions. Therefore, the only tool for the development predicting of an accident is the modeling the spread of a radionuclides cloud. Thepurpose of the researchis a modeling the distribution of emergency release products in a nuclear power plant unit, suitable for the operative assessment of a development an accident. Results of the research: The mathematical model of the distribution emission products of a nuclear power plant has been developed, which takes into account the value of the initial activity of emission products, the rate of the settling radioactive particles, the wind speed components, the intensity changes radionuclide emission over time. The technique for solving the boundary value problem of modeling in conditions of a complex shape of the computational domain, taking into account the presence of obstacles to the spread of emission products has been developed. The use of the velocity potential equation in evolutionary form allows us to speed up the calculation process. The chosen splitting scheme of an alternating-triangular method allows to find the speed potential according to the explicit form at each splitting step. This allowed software implementation of the CFD model. The visualized models of the emission cloud distribution allow to determine the radiation situation in any place of the emission product distribution zone. The developed model makes it possible to quickly predict the development of an accident in space and time, which makes it possible to take measures to protect people from exposure in the shortest possibletime. Conclusions: The obtained emission cloud propagation models and their visualization make it possible to determine the state of environmental pollution under various initial conditions during the development of the accident. Не дивлячись на те, що безпечній експлуатації ядерних енергетичних установок приділяється багато уваги, існує ймовірність аварії з викидом радіонуклідів. Особливо це актуально в Україні, де існує загроза ушкодження ядерних реакторів внаслідок бойових дій. Дослідження розповсюдження продуктів аварійних викидів радіоактивних речовин у лабораторних умовах неможливо. Тому єдиним інструментом прогнозування розвитку аварії є моделювання розповсюдження хмари радіонуклідів. Метою дослідження є моделювання поширення продуктів аварійного викиду на енергоблоці атомної електростанції, придатного для оперативного оцінювання розвитку аварії. Результати дослідження: Розроблено математичну модель поширення продуктів викиду. Енергоблоку атомної електростанції, яка враховує значення початкової активності продуктів викиду, швидкість осіданняр адіоактивних часток, компоненти швидкості вітру, зміни інтенсивності викиду радіонуклідів з часом. Розроблено методику розв’язку крайової задачі моделювання в умовах складної форми розрахункової області, яка враховує наявність перешкод розповсюдженню продуктів викиду. Застосування рівняння потенціалу швидкості у еволюційному вигляді дозволяє пришвидшити процес розрахунків. Обрана схема розщеплення поперемінно-трикутного методу дозволяє на кожному кроці розщеплення знаходити потенціал швидкості за явною формою. Це дозволило здійснити програмну реалізацію CFD моделі. Візуалізовані моделі поширення хмари викиду дозволяють визначити радіаційну обстановку у будь-якому місці зони розповсюдження продуктів викиду. Висновки: розроблена модель дозволяє оперативно прогнозувати розвиток аварії у просторі і часі, що надає можливість у мінімальні терміни вжити заходи із захисту людей від опромінення. Ключові слова: моделювання; ядерна аварія; радіонукліди; прогнозування.Документ Modeling of the external magnetic field of electric machines(Національний технічний університет "Харківський політехнічний інститут", 2024) Levchenko, Larysa; Ausheva, Nataliia; Karaieva, Nataliia; Glyva, Valentyn; Burdeina, NataliiaThe goal of the work. Proposals for methods of solving systems of linear homogeneous and nonhomogeneous differential equations with constant and variable coefficients that defined in interval form and intended for modeling exchange processes in multicomponent environments. Research subject: systems of linear homogeneous and nonhomogeneous differential equations with constant and variable coefficients defined in interval form. Powerful electric machines – such as electric generators, electric motors generate a magnetic field of great tension. These fields negatively effect on personnel and can to violate the stability of electronic equipment. To determine safe areas for workers, laying communication cables and placing sensitive electronic equipment, it is advisable to model the propagation of magnetic fields of electrical machines. This will make it possible to rationalize the placing of electrical equipment at design stages. The most common high-power electrical machines are four-pole electrical machines with a dipole-quadrupole structure of the external magnetic field. The purpose of the research is a development of models of the propagation of the external magnetic field generated by alternating current electric machines. Results of the research: it is substantiated that to simulate the propagation of the magnetic field of electric machines, it is advisable to use the Gauss equation for the magnetic scalar potential. This will make it possible to take into account the required number of spatial harmonics of the magnetic field to ensure an acceptable calculation error. An electric machine is considered in a spherical approximation. Calculations were carried out in spherical coordinates. The distances were determined in relative radii of the electric machine – the ratio of the radius of the machine to the definition of field strength. The calculations were made for two planes of spherical coordinates and a three-dimensional image was obtained. As a result of the simulation, it is possible to determine the magnetic field strength of a four-pole electric machine at selected distances and directions around the electric machine with the required accuracy. It has been established that there are points of zero external magnetic field strength around electrical machines. Verification of the simulation results was carried out using the method of full-scale measurements of the magnetic field strength around a real four-pole machine. The measurement results showed acceptable agreement with the calculated data. Conclusions: the chosen approach and the results of modeling the propagation of the external magnetic field of electrical machines can be used to design the placement of electrical equipment, taking into account the requirements for electromagnetic safety and electromagnetic compatibility of technical equipment.Документ Methodology for modeling the spread of radioactive substances in case of an emergency release at a nuclear power plant(Національний технічний університет "Харківський політехнічний інститут", 2023) Levchenko, Larysa; Biliaiev, Mykola; Biliaieva, Viktoriia; Ausheva, Nataliia; Tykhenko, OksanaThe methodology for modeling the propagation of accidental releases of radionuclides from a power unit of a nuclear power plant has been developed. The calculation method takes into account the most critical factors propagation cloud ─ wind direction and speed, the intensity of the release radionuclides change: semi-continuous release, long-term release, instantaneous release. Diffuse processes and the presence of interference in the form of buildings were also taken into account. To solve the modeling equation of the aerodynamic model, the velocity potential equation is solved. The use of this equation instead of the traditional Novier-Stokes equation makes it possible to rationalize the calculation process in terms of the speed obtaining simulated data. To build a numerical model, a rectangular difference grid is used. The velocity potential and the quantities values of volumetric activity are determined at the centers of difference cells. The value of the airflow velocity vector component is determined on the sides of the difference cells. A finite-difference splitting scheme is used for numerical integration of the equation convective-diffusion transfer radionuclides. A computer code was developed on the basis of the constructed numerical model, the programming language Fortran was used. The approach used makes it possible to reduce the time for obtaining one scenario of an accident development. The cloud propagation dynamics determining is carried out almost in real time. This allows you to quickly respond to changing situations and make adequate decisions.Документ Mathematical apparatus for modeling of the propagation the magnetic field electric machines with a given accuracy(Національний технічний університет "Харківський політехнічний інститут", 2022) Levchenko, Larysa; Glyva, Valentyn; Burdeina, NataliiaThe problem of modeling the propagation local magnetic fields and spatially dispersed sources is large errors compared to field measurements. An important aspect of dequate modeling is the use of the correct mathematical apparatus. It is shown that in order to obtain reliable models of the propagation magnetic fields around electrical machines (generators, electric motors of different power, geometric dimensions and poles), it is advisable to apply the Gauss equation for a scalar potential. The solution of the equation in polar coordinates makes it possible to take into account not only the fundamental, but also other harmonics of the magnetic field (dipole, quadrupole, octupole). This allows, depending on the number of spatial harmo nics taken into account, to obtain a model with the required accuracy (error) for predicting the magnetic field strength at any point around the machine. It is considered in the paper that an electronic machine is an object of base radius R0. The present ed approach makes it possible to nambiguously determine the location of zero field points at a distance from the source (for a quadrupole source and zero field lines, for an octupole source). The results of modeling and their verification by full - scale me asurements for the most common four - pole machines (quadrupole source) are presented. The main task of modeling the propagation the magnetic field of such sources is to ensure the required accuracy based on the goals of modeling. It is shown that the modeling accuracy and the presence of zero field points are due to different field levels near the electrical machine housing for different harmonics. The dipole harmonic at the cabinet is 20% of its own harmonic. But it falls more slowly with distance. This necessitates taking into account a different number of harmonics depending on the value of the ratio R0/R, R is the distance to the point of determining the field strength from the source. Therefore, with the ratio R0/R=2/3, the eighth harmonic is essential. At R0/R=1/5, already the fourth spatial harmonic can be neglected. Such data allow you to choose a rational number of harmonics. This reduces the amount of calculations and simplifies the process of odeling the propagation of the magnetic field around the source.