Application of Interval Analysis for Improving Reliability of Estimation of Hardness Value Spread 
For Nuclear Structural Materials

The analysis of the influence of changes in the parameters of steam superheater separators SHS-1000 of nuclear power plant units with the capacity of 1000 MW on the efficiency and safety of their operation, including the temperature characteristics at the nominal and partial operating modes of power units, has been carried out. Based on the experimental data of the thermal tests of the power unit, the temperature characteristic of the second stage of the SHS-1000 has been constructed in the form of the dependence of the temperature change of the heated steam at the second stage of the SHS on the change in the operating mode of the power unit. To create a correct mathematical model of this dependence, taking into account the limited amount of experimental data and the uncertainty of information about the structure and the probabilistic nature of measurement error during testing, the use of numerical methods of interval analysis has been proposed. Interval analysis has allowed to obtain an interval model that describes the receiver, which contains all possible values of the dependence of temperature change of the heated steam at the second stage of SHS on the unit operating mode (the electrical load). It has been shown that in conditions of limited initial data and uncertainty of information about it, numerical methods of interval analysis allow to create interval models of operational (energy) characteristics technological processes and equipment of NPP units with the maximum possible correspondence to real processes and objects, which is important to ensure high efficiency and safe operation of power units.

Section: Results and Their Discussionmentioning

confidence: 99%

Section: Initial Data and Statement Of The Problemmentioning

confidence: 99%

Interval Models of Temperature Characteristics of Superheater Separators in Nuclear Power Plant Units With the Capacity of 1000 Mw

Yefimov¹,

Potanina²,

Kavertsev³

et al. 2022

“…The velocity of the steam-water mixture is the speed that water would have in a given cross-section if it passed through it with a mass flow rate equal to the flow rate of the steam-water mixture. These parameters are calculated by the following ratios: (7) where and -respectively, the specific volumes of steam and water at saturation temperature s t , m 3 /kg; f -the cross-sectional area of the steam-generating channel, m 2 .…”

Section: Scheme Of the Steam Generating Channelmentioning

confidence: 99%

“…The cross-sectional mean velocities of the liquid and vapor phases of the flow are not equal to each other, and the difference in the velocities of the phases in the steadystate mode of motion of the two-phase flow depends on the mass flow rate of the steam-water mixture, its pressure, direction of flow, heating intensity, and other indicators. All this complicates experimental studies and calculations of parameters and hydrodynamic (gasdynamic) characteristics of two-phase flows of a steamwater mixture of a working substance in reactors and steam generators of nuclear power plants [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

MATHEMATICAL RELATIONSHIPS OF MODELS OF TWO-PHASE FLOWS IN CHANNELS OF REACTORS AND STEAM GENERATORS OF NPP’s FOR CALCULATION OF THEIR HYDRODYNAMIC CHARACTERISTICS

Yefimov¹,

Pylypenko²,

Kavertsev³

et al. 2022

Two-phase flows of the working substance in the steam-generating channels of reactors of single-circuit NPP’s and steam generators of two- and three-circuit NPP’s represent the joint movement of liquid (feed water) and steam in the form of a steam-water mixture. The forms of movement of two-phase flows are much more diverse, and the laws of their movement are much more complicated than flows of single-phase media, and they are characterized by a large number of parameters. This is due to the fact that when the flow of the steam-water mixture moves in the steam-generating channels, mass exchange processes occur between the liquid and vapor phases of the mixture, in which the volumes of the phases change; the interfaces between the phases of the mixture vary along the length of the channel and often do not have a distinct character. The cross-sectional mean velocities of the liquid and vapor phases of the flow are not equal to each other, and the difference in the velocities of the phases in the steady-state mode of motion of the two-phase flow depends on the mass flow rate of the steam-water mixture, its pressure, direction of flow, heating intensity, and other indicators. All this complicates experimental studies and calculations of parameters and hydrodynamic (gas-dynamic) characteristics of two-phase flows of a steam-water mixture of a working substance in reactors and steam generators of nuclear power plants. The article discusses mathematical relationships for calculating the hydraulic characteristics of two-phase flows of different structures during the movement of a steam-water mixture in the steam-generating channels of reactors and steam generators of nuclear power plants, namely bubble, slug, rod, dispersed. The ratios are given for various designs of the channels of reactors and steam generators.

“…. (12) Dependencies that determine the limits of heat transfer modes from the feed water and steam in the steam-generating channel:…”

Section: Introductionmentioning

confidence: 99%

Computer Simulation of Thermal and Hydraulic Processes in NPP Steam Generator Channels on the Basis of Interval-Iterative Method

Yefimov¹,

Pylypenko²,

Potanina³

et al. 2022

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.