Modelling and Spatial Control of 540 MWe Pressurized Heavy Water Reactor

The paper presents the Mathematical Model of 540 MWe Pressurized Heavy Water Reactor (PHWR), which from neutronic viewpoint, is a large reactor. In it, the neutron flux in different parts of the core may experience nonuniform variations with time and to account for such effects, the reactor core is considered to be divided into 14 zones. In each zone, power, delayed neutron precursors’ concentration and xenon and iodine concentrations are represented by their respective volume averaged values in the zone. Neutron diffusion among different zones is modelled through coupling coefficients. This leads to a large number of nonlinear equations characterizing the behaviour of the reactor core. Owing again to the large core size, the reactor is provided with a large number of measuring and reactivity control devices. For complete characterization of the system behaviour, these measuring and control devices have also been modelled. Thus, a very high order model characterized by 132 continuous-time and 75 discrete-time state variables, 14 inputs, 29 direct measurement signals and 15 estimated signals has been obtained for the 540 MWe PHWR. The model has been linearized around steady-state operating point and represented in a standard state space form. The control of the 540 MWe PHWR involves control of both the total power and core power distribution. Each of the fourteen zones of the reactor has been provided with a liquid Zone Control Compartment (ZCC) in which water level can be independently manoeuvred to exercise total power and power distribution control. The water level in each ZCC is also required to be controlled to avoid any instances of flooding or draining. To accomplish these tasks, an output feedback controller has been designed so as to achieve stability and good transient response characteristics. Simulation of typical operational scenarios has been carried out and results thus obtained have been reported.