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Документ Analysis of finite-difference approximation of code "FLOW" in performing design calculations of parameters in the primary and secondary circuits of VVER reactor plant(Національний технічний університет "Харківський політехнічний інститут", 2024) Lys, Stepan; Yurasova, Oksana; Galyanchuk, IgorIn code package “FLOW” energy and coolant hydrodynamics equations, neutron kinetics equations and equations of heat conduction in metalwork and fuel rods are solved together. Processes described by these equations are characterized by different time constants and during calculation different degree of time and space discretization is required. The objective of the work was demonstration of stability of numerical schemes used in “FLOW" program and its modules, assessment of error of numerical solution for nodalization. Initial differential equations in partial derivative of the law of conservation of mass, energy and momentum are reduced to the system of usual differential equations on the basis of spatial approximation with the use of integro-interpolation method. Approximation was performed by integrating the initial differential equations in partial derivatives within the limits of each elemental volume of division by spatial coordinate. The usage of integro-interpolation method provides fulfilment of laws of conservation on computational mesh as a whole and the second order of approximation by spatial coordinate. The usage of integro-interpolation method provides fulfilment of laws of conservation on computational mesh as a whole (conservatism of approximation method) and the second order of approximation by spatial coordinate. Effect of limiting error of integration in “FLOW” code on pressure values at the core outlet and mass discharge from the leak is not practically distinguished. Effect of these errors on the values of coolant flow rates at the core inlet and outlet becomes more noticeable. Still, maximum value of these differences doesn’t exceed 7 % for flow rate at the core inlet. More substantial differences (of the order of 10–15 %) are observed in the course of calculated temperature of fuel rod cladding.Документ Construction of the software and technical complex of control basic parameters of reactor installation(Національний технічний університет "Харківський політехнічний інститут", 2022) Koba, Kostyantyn; Lys, Stepan; Kravets, Taras; Yurasova, Oksana; Galyanchuk, IgorThe main problem associated with the operation of nuclear power plants is the problem of correct and timely diagnosis of failure or violation. The mistakes of technologists can lead to severe damage to nuclear power plants, or simply to a reduction in the utilization rate of installed capacity. The personnel make the main mistakes in the conditions of time shortage and being in a stressful situation during the development of an accident, when assessing changes in emergency parameters is not always possible, which leads to incorrect diagnosis of initial events (IE). Any IE leads to the deviation of the monitored parameters from normal values (values that are inherent to normal operation). The operator-technologist needs as soon as possible to determine the parameter (or parameters) for which the change occurs and, by performing a certain sequence of actions, bring their values to the norm. For information support of the operator-technologist is the information computing system (ICS). In the ICS, it is possible to control all parameters affecting the safe operation of the equipment, for each of which there are certain values, the deviation from which may lead to an accident. The paper considers the issues of the need to separate the measured parameters of NPP into separate groups that uniquely characterize the state of the critical security features. In particular, the necessity of consideration as the most important mass parameter of the primary coolant is shown. The issues of level measurement problems in the pressure compensator are discussed as the most important from the point of view of determining the mass of the primary coolant. Methods are proposed for determining the operability of sensors, the method of calculating a reliable level in the volume compensator. Estimates of the computational efficiency of the proposed methods are given.