Development of control rod position indicator by using a reed switch in a System-integrated Modular Advanced Reactor

The reliability and accuracy of the information on a control rod position are essential for the reactor safety and the design of the core protection system. A survey on the RSPT (Reed Switch Position Transmitter) type control rod position indicator (CRPI) system and its actual implementation in the existing nuclear power plants in Korea was performed at first. A CRPI with a high performance for SMART was developed on the basis of the RSPT technology identified through the survey. The arrangement of the permanent magnet and the reed switches is one of the important procedures in the design of a CRPI. The hysteresis of the reed switches is also one of the important factors for a repeat accuracy of a CRPI. This paper investigates the efficiency of the magnetic field concentrator and the hysteresis by using FEM and those of the experiment. As a result, it is shown that the characteristics of the prototype CRPI have a good agreement with the results of the FEM.