Estimation of permanent magnet aging and output signal error in control rod position indicator

The integral type reactor currently under development at the Korea Atomic Energy Research Institute is being designed with a soluble boron free operation and the use of nuclear heating for the reactor start-up. These design features require a Control Element Drive Mechanism (CEDM) for the Integral reactor to have a fine-step movement capability as well as a high reliability for a fine reactivity control. Also the reliability and accuracy of the information for the control rod position is very important to the reactor safety as well as the design of the core protection system. The position indicator is classified as a Class 1E component because the rod position signal of the position indicator is used in the safety related systems. In this paper, the estimation of permanent magnet aging in the upper pressure housing and the signal error due to the resistors error in the voltage divider circuit was performed. These estimation results were considered in the design of the control rod position indicator