Health test of components in nuclear reactor instrument systems using process identification

A process identification technique using an auto regressive model has been applied to measurements at Ringhals 4, a PWR in Sweden. The purpose of the present work is to develop a method for testing the dynamics of sensors and signal conditioning circuits in safety systems as well as the regulator parameters during normal operation of the reactor. The noise analysis was performed for a coolant temperature safety system and a pressure regulator in a loop for control of boron concentration in the reactor. The results show convincingly that filter characteristics as well as temperature sensor response time can be estimated with good accuracy. Therefore the present method enables us to evaluate integral performance of instrumentation chains in a safety system during reactor operation. The same conclusion holds for the analysis of the controller. On-line application of the present method to test components in the reactor safety system would increase the system reliability. It also results in reduction of manpower by replacing the component test, performed manually, by automated on-line tests during the reactor operation. (author)