Khomiak E. A method for assessing the quality of parameters of a fuel element of a nuclear power plant unit

The object of the research - is the process of assessing the quality of control of fuel element shell parameters. The subject of the research - is the method of controlling the parameters of the fuel element. The purpose of the study is to assess the quality of control of the fuel element parameters by developing a method of automated non-destructive testing using the theory of fractal-cluster geometry. The study was performed using the provisions of fractal-cluster theory, mathematical modeling, numerical methods of analysis, modern information technology and methods of mathematical statistics for processing experimental data. Scientific novelty of the obtained results. – For the first time, a mathematical model for calculating the shape change of the geometry of the fuel element was developed, which, unlike the known ones, allows to take into account structural and phase changes and fractal properties in the volume of the cladding material when exposed to damage to its outer and inner surface, based on the application of the theory of fractal geometry; – For the first time, a fractal model of the damaged fuel element cladding was developed, which, unlike the known ones, allows to determine the appearance and dynamics of the through crack growth in the structure of the fuel element cladding material, based on the calculation of the time and speed of formation of a common cluster of helium gas molecules in the through crack using the fractal cluster geometry computing apparatus; – For the first time, an experimental method of non-destructive automated control of the tightness of the shell of the fuel element was developed, which, unlike the known ones, allows you to determine the location, type and dimensions of the defect on the outer and inner surface of the shell, without removing the fuel element from the fuel assembly, based on further development of analytical expressions of the improved model of damage and deformation of the shell of the fuel element and determination of the criterion for assessing the degree of depressurization in the form of a quantitative value of fractal dimension on axial segments along the height of the fuel element; by determining the depth of the skin layer in the thickness of the shell, based on measurements of electrical resistance and power, depending on the applied frequency when using the skin effect.