Core power control analysis and design for triga nuclear reactor

Abstract

An efficient nuclear core power control is essential in providing a safe and reliable nuclear power generation system. It is technically challenging to ensure that the core power output is always stable and operating within acceptable error bands. The core power control in TRIGA PUSPATI Reactor (RTP) Malaysia is designed based on the Feedback Control Algorithm (FCA), which includes the Proportional- Integral controller, Control Rod Selection Algorithm (CRSA), Control Rod Velocity Design (CRVD), and Power Change Rate Constraint (PCRC). However, the current setting generally produces an unsmooth transient response and a long settling time. The conventional CRSA suffers during transient and fine-tuning conditions due to the rod selection process only considers the rod position and ignores the rod worth value. The conventional PCRC has a constant gain, incapable of providing a sufficient amount of penalty and sensitivity effects on control rod velocity under all operating conditions. Thus, a new strategy for each component in the FCA is investigated to further improve overall core power tracking performance. To address the current CRSA problems, a novel CRSA called Single Control Absorbing Rod (SCAR) is designed based on the rod worth value and operational condition-based activation. The SCAR is not only reducing the complexity of the CRSA process but also reduces the time required for rod selection. In addition, a new saturation model and velocity value are studied for CRVD. On top of that, a fuzzy-based PCRC is proposed to produce a fast-tracking power response. Finally, a hybrid controller based on the integration of Model Predictive Control and Proportional controller is developed to exploit the benefits of both controllers via a switching control mechanism. In the present study, the RTP model is derived based on equations of neutronic, thermal-hydraulic, reactivity, and dynamic rod position. Both analytical and system identification models are considered. In the proposed design strategy, all of the safety design requirements based on the Final Safety Analysis Report are taken into account, ensuring that the outcome of the study is practical and reliable. The proposed strategy is designed via simulation with MATLAB Simulink and experimentation with actual hardware at the RTP. A stability analysis based on Lyapunov is derived to numerically guarantee the stability of the new power controller. An extensive comparison to the existing FCA is presented to demonstrate the compatibility and effectiveness of the proposed strategies in nuclear reactor environments. Overall, the results show that the response from hybrid Model Predictive Control-Proportional (MPC-P) offers better results than the FCA, in which reduces the rise time by up to 73 %, the settling time by up to 70 %, and the workload by up to 42 %. The hybrid MPC-P with multiple-component constraints is able to solve the unsmooth transient response and a long settling time tracking performance at the RTP and offers improvements in terms of fuel economic aspect in the long run and extending the lifetime of the plant operation.