Topaz-II is a space nuclear reactor which developed in the Former Soviet Union. It is a thermal-neutron reactor which used UO2 ceramics as fuel. It generates electricity based on the principle of thermoelectric conversion. The reactivity is controlled by several groups control drums. Its lifetime can be three years and it has different reactivity feedback characteristics and dynamic characteristics in different lifetime. Its positive reactivity feedback characteristics and different dynamic characteristics in different lifetime make it difficult to design a suitable control system for Topaz-II.All-coefficient adaptive control is a single-input single-output adaptive control method applied to a parameter unknown, linear time invariant or slowly changing object. In some specific conditions, it is also suitable for the non-linear systems. In this method, the model where the sum of coefficients is equal to one is built based on the original model. All coefficients in this model can be identified easily. Therefore, it is possible to realize the optimal control.Firstly, the model of Topaz-II nuclear reactor system is built. It includes point-reactor kinetics model with six groups delayed neutrons, a one-dimensional lumped transient thermal model of the nuclear fuel element and the moderator, a thermionic model of the converters, a simple control drums drive model and two main types of reactivity feedback. Based on the model, the dynamic characteristics and positive reactivity feedback characteristics are analyzed.Then, based on the nonlinear model of Topaz-II nuclear reactor system, the transfer functions are gained and analyzed. Based on the transfer functions, the model where the sum of coefficients is equal to one is built by using the all-coefficient adaptive control method. And after dealing with the parameter and analyzing the error, the all-coefficient adaptive control systems are designed.To evaluate the performance of the control systems, power maneuvering events including a 30%FP (Full Power) step change and a ramp change with a rate of 10%FP/min are simulated. The important control parameters varying with time are evaluated and compared. The conclusions can be drawn from the simulation analyses of the control performance. The all-coefficient adaptive control system has a better performance in settling time and overshoot compared with those with PID controller.

All-Coefficient Adaptive Control System Design for a Space Nuclear Reactor

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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