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Growing electricity requirement and the serious pollution caused by burning petroleum and coal give the current rebirth of nuclear energy industry. State observation is one of the key and basic technologies of system monitoring which is very necessary to the safe and effective operation of today's nuclear reactors. Since nuclear reactors are complex and nonlinear systems, it is quite necessary to design a nonlinear state-observer with high-performance for nuclear reactors. A dissipation-based high gain filter (DHGF) is presented for nonlinear systems in this paper, and robustness analysis is also given. The DHGF is then applied to the state-observation for a nuclear heating reactor (NHR), and simulation results show the feasibility of the DHGF.

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Due to the existing serious climate and environment problems caused by burning fossil fuels, nuclear energy is now under rapid development. As a crucial technology in the field of nuclear energy, power-level control for nuclear power plants is significant for not only regular operating but also safety issues. A nonlinear controller based on feedback dissipation and backstepping (FDBC) is presented in this paper. This new controller can guarantee not only globally closed-loop asymptotic stability but also robustness to the uncertainties of the control rod dynamics. Numerical simulation results show the high performance of this controller. Moreover, this newly built controller is simplified to a proportional power-level controller under the assumption of no modeling error in control rod dynamics. The characteristics of these two power-level controllers are given by theoretic analysis and numerical simulation.

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The NHR200-II is a full-power range natural circulation small modular heating reactor characterized with inherent safety. The significant difference between NHR200-II and a general pressurized water reactor is that the load of NHR200-II is relatively smaller, and it could vary rapidly in a wider range under different operation conditions. The control system of NHR200-II is required to sustain the stability of reactor operating parameters and make sure the reactor follows the load change in time. Anomaly conditions may occur during the operation of NHR200-II. They may not induce safety-related accidents that gravely impair the reactor core or lead to the release of large-scale radioactivity, but they will fluctuate the power output. Therefore, it is practically valuable to detect abnormal working conditions in time. Furthermore, the detected information of anomaly is helpful for operators to conduct the reactor operation. A model-based anomaly detection method to diagnose abnormal conditions of circulation pump sensor in NHR200-II is investigated in this paper and verified with the NHR200-II model. The simulation results show that the circulation pump sensor fault will cause the variation of running parameters, including inlet and outlet temperature of the coolant inside the reactor core, nuclear power, and output steam flowrate from the steam generator. The variation of parameters will lead to system deviation from expected operating conditions and system stability degradation. When the proposed anomaly detection method is applied, the circulation pump sensor fault could be successfully diagnosed and detected, and a fault-tolerant control strategy is deployed to correct the deviations and stabilize the operation of the NHR200-II reactor.