Mathematical Model and Method for Automated Power Control of a Nuclear Power Plant

Abstract

The creation of methods for automated power control of power units is an urgent task, for which it is advisable to use the capacities of nuclear power plants. A mathematical model of a nuclear power plant (NPP) as a control object is proposed, which includes a multi-zone model of the active zone with distributed parameters, which makes it possible to take into account its internal properties (including transitional processes for xenon). This makes it possible to reduce the error in modeling the static and dynamic properties of nuclear power plants. A method for automated control of NPP power change using three control loops has been developed: one maintains a scheduled change in reactor power by controlling the concentration of boric acid in the coolant, the second maintains the required value of the axial offset by changing the position of the adjustment rods, and the third supports the temperature regime of heat transfer. Due to the adjustment of the position of the main valves of the turbogenerator, the developed method makes it possible to improve the stability of the energy release in the core with a change in its power under normal operating conditions of the reactor. K e y w o r d s: nuclear power plant, axial offset, pressurized water reactor.In Ukraine, nuclear power plants are used to cover the base load of the country's Unified Energy System (UES). For satisfactory coverage of peak and semi-peak loads of UES, there is a share of electricity generation at hydroelectric power plants of about 20%, but today this share is only 5%. Since today the share of electricity generation at the country's nuclear power plants has reached 60%, in order to solve the problem of insufficiency of maneuvering capacities in the UES, it is advisable to use nuclear power plants, which will bring electricity consumption and generation into line. Therefore, the task of adapting the existing nuclear power units of Ukraine to maneuverable operating conditions by creating methods for automated control of changes in the power of power units is relevant.

Structure of a Multi-Zone Model of a Pressurized Water Reactor

“…Figure 1 shows a simplified diagram of the structure of the distributed model of the reactor core. Each zone structurally includes a point model of reactor kinetics that relates the neutron flux density to reactivity, a model of energy release in the fissile material that determines the amount of energy released as a result of fuel fission reactions depending on the neutron flux density, a coolant heating model, a model of heat transfer inside fuel rods that relates fuel temperature with the amount of energy released, a model of the reactivity effect from xenon poisoning, a model of the temperature effect of reactivity, a model of the power effect of reactivity , a model of the reactivity effect of the control group of reactor control and protection system, and a model of the reactivity effect of boron regulation [3,4]. The multi-zone structure of the reactor model divides the reactor core in order to reduce the modeling error resulting from the linearization of a nonlinear object and enable implementation in a simulation environment [5].…”