New methods and approaches to development of nuclear power plant unit imitation models development. An imitation model is proposed for nuclear power plant unit developed on the basis of oriented graph applied to unit flow diagram description logic-numerical operators for calculation of parameters and characteristics determining its operation efficiency, reliability and safety. Automatic system is described developed on the basis of imitation model for decision-making support, applied to analysis of VVER nuclear power plant unit operation efficiency with due consideration of equipment operation reliability and safety indices.

The designing of NPP steam generators, which are complex technical systems, requires a large number of variant calculations, as result of which must be obtained both optimal integral characteristics of steam generators (total heat transfer surface, metal capacity, hydraulic circuits, etc.) and many of their local characteristics (distributions heat flux densities and temperatures, possible amplitudes of their pulsations and others). The complexity of NPP steam generators as technical systems is determined by their multi-parameter, the presence of a complex logical and functional relationship between the parameters, the presence of various restrictions on the change of parameters, the stochastic change of parameters during exploitation. The article presents methods of mathematical modeling of thermal and hydraulic processes in NPP steam generators and modular programs of their calculations in one-dimensional formulation on the example of a steam generator with countercurrent (direct current) mutual motion of the coolant and the working substance. Logical and structural schemes of computer programs of thermal and hydraulic calculations of NPP steam generators are presented.

АНОТАЦІЯ

The strength condition of the cylindrical parts of pressure vessels (water drums, collectors, heating surfaces, etc.) of steam-generating systems, which takes into account stresses due to the internal pressure and thermal stresses. Stresses due to internal pressure and temperature stresses are obtained using all-known results of the theory of elasticity for infinite cylinders. It is assumed that the strength of the cylindrical parts of pressure vessels of steam-generating systems is limited due to the formation of the plastic deformation in one point at least. The theory of maximum shear stress is used to formulate the strength condition. A geometric interpretation of the formulated strength condition is considered. The strength conditions for cylindrical parts of pressure vessels is reduced to the inequality that under given structural material properties restricts the possible values of the internal pressure and temperature drop across the wall thickness. The geometrical interpretation of the strength condition proposed for the cylindrical parts of pressure vessels in the base of the graphical representing of the solution of the inequality, corresponded to the strength condition. Graphical solution of the pressure vessels strength condition was presented on a coordinate plane the internal pressure-the temperature drop across the wall thickness. It is shown that the allowable by the strength condition the values of the internal pressure and temperature drop across the wall thickness in the coordinate plane occupies the limited area in the form of the right triangle. Proposed geometric interpretation allows us to determine the optimum value of the relationship between the inner and outer radii for the strength of cylindrical parts of pressure vessels of steam-generating systems.

The results of studies of parameters, characteristics and performance of NPP units by mathematical modeling methods using computer-integrated technologies for their implementation, which allow to simulate many functional states of systems and equipment of NPP units during the simulation experiment are presented. The general structure of interaction of blocks of software complex for analysis of efficiency of work and parametric diagnostics of NPP units with WWER is developed. The structure of the block of programs of parametric diagnostics of equipment of NPP units is presented. The essence of methods and approaches of parametric diagnostics of power unit equipment is considered.