Kwan S. Kwok

Design and Experimental Evaluation of a "Fuzzy" System for the Control of Reactor Power

A rule-based, digital controller that incorporates fuzzy logic has been designed and experimentally demonstrated on the 5 MWt MIT Research Reactor. The potential value of fuzzy logic to the control of reactor power was assessed by comparing the performance of the fuzzy controller to that of one of identical structure that did not rely upon fuzzy logic. The fuzzy system perfomed better under degraded conditions, was less sensitive to noise, and required less movement of the actuator mechanism. Additional tests showed that the fuzzy controller adjusted the reactor power smoothly and without overshoot in response to changes in setpoint. Also, it functioned properly in the presence of externally-induced disturbances. Sensitivity experisents were conducted to identify the structural and design features responsible for the performance of the fuzzy system. Finally, the possible role of fuzzy logic in the control of industrial processes was explored.

Autonomous Control Of Spacecraft Nuclear Reactors

Recent theoretical and experimental progress towards the achievement of an autonomous control system for spacecraft nuclear reactors is reported. A controller having a multitiered structure with the capability for both supervisory and predictive control as well as automated reasoning is proposed. Such a system would establish bounds for permitted operation (supervisory control), facilitate the inference of system response (predictive control), and provide a means for assessing its own performance (automated reasoning). Recent developments concerning specific features of this controller are reported including the use of energy constraints for supervisory control, the performance of automated reactor startups using the MIT-SNL Period-Generated Minimum Time Laws, and considerations relevant to the use of pattern recognition, expert systems, and causal analysis for the on-line assessment of controller performance. Also, an overview is given of the MIT program on reactor control.

Experimental demonstration of automated reactor startup with on‐line reactivity estimation

A generic method for performing automated startups of nuclear reactors described by space‐independent kinetics under conditions of closed‐loop digital control was developed, implemented, and tested on the 5‐MWt MIT Research Reactor. The technique entails first obtaining a reliable estimate of the reactor’s initial degree of subcriticality and then substituting that estimate into a model‐based control law so as to permit a power increase from subcritical on a demanded trajectory. The estimation of subcriticality is accomplished by application of the ‘Perturbed Reactivity Method’ which was developed in the course of this research. The shutdown reactor is perturbed by the insertion of reactivity at a known rate. Observation of the resulting period permits determination of the initial degree of subcriticality. A major advantage to this method is that repeated estimates are obtained of the same quantity. Hence, statistical methods can be applied to improve the quality of the calculation. In addition to describ...