A Design and Implementation of a Fault-Tolerant Rod Control System for Nuclear Power Plants

The design and implementation of a fault-tolerant control rod control system for nuclear power plants is described. High reliability and safety are necessary for the instrumentation and control systems for safety-critical plants such as nuclear power plants. For a control rod control system that controls the nuclear reactivity inside the reactor by inserting or withdrawing the rods into or from the reactor, the reliability is more critical than the safety since its malfunction directly results in an unexpected shutdown of the power plant. This paper deals with a design and implementation practice to enhance the reliability of the control system. The reliability enhancement is basically achieved by adopting hardware redundancy in its structure. The reliability is evaluated quantitatively to check if the designed and implemented system is reliable enough to be applied to commercial plants. The ability of fault detection realized in the system is expected to give a further reliability enhancement by means of software. The bumpless control problem that can be arisen from adopting hardware redundancy is discussed here. Also a new algorithm for the rod movement detection is briefly introduced and demonstrated with a test result