Estimation of the poisons reactivity in the P.W.R Nuclear Reactors using modified higher order sliding mode observer based on the multi-point nuclear reactor model

Reactor power control is one of the most important problems in a nuclear power plant. Considering the importance of the negative feedback reactivity from neutron absorber poisons such as xenon and samarium in the design of the nuclear reactor control system and regarding the limitations of the xenon and samarium reactivity measurement, in this paper, for the first time, a modified higher-order sliding mode observer is presented to estimate the xenon and samarium reactivity in the P.W.R Nuclear Reactors. The reactor core is simulated based on the multi-point nuclear reactor model (neutronic and Thermal-hydraulic) and three delayed neutrons groups. Traditional sliding mode technique has intrinsic problem of chattering. To cope with this problem, Higher Order Sliding Mode (HOSM) is used. The employed method is easy to implement in practical applications and moreover, the higher order sliding mode control exhibits the desired dynamic behavior during the entire output-tracking process. Simulation results are presented to demonstrate the effectiveness of the proposed observer in terms of performance, robustness and stability and show that the HOSM observer follows the actual system variables accurately and is satisfactory in the presence of the parameters uncertainties and disturbances.