Digital Controller for a Nuclear Reactor

This paper presents the development and implementation of a digital control system in an operating nuclear reactor. The control system incorporates on-line detection and isolation of faulty equipment, sensor calibration, measurement estimation, and information display in a given controller structure. It is tolerant of process disturbances, certain equipment failures, and sensor degradation and noise. Rather than relying on signals from single sensors, each feedback/feedforward signal that is sent to the controller under this approach is a digitally processed, weighted average of several valid measurements of the appropriate process variable. The weights are not à priori fixed but depend on the à posteriori probabilities of failure of individual sensors and are computed on the basis of past and current observations. Thus, for a gradually degrading measurement, its weight is smoothly reduced and eventual isolation of the fault does not cause an abrupt change in the estimate, i.e. the controller action remains bumpless.