Instrument failure detection and reconstruction methodology in space-time nuclear reactor dynamic systems with fixed in-core detectors

The detection and isolation of instrument failures in nuclear reactors equipped with fixed in-core detectors were studied in order to improve reliability and safety. This was done by representing the reactor as a linear stochastic distributed parameter system. A bank of detection observers based on the Kalman filter concept was constructed in order to isolate component failures via robust observation. Each observer was sensitive to only one specified component failure. This was done to minimize the covariance matrix error. However, because observed deviations may be attributed to changes in system behavior, failure decisions are confirmed by a multiple consecutive miscomparison (MCM) counter. Following failure detection, the failed sensor´s output is replaced with an estimate from the failure-free filter. Various simulations were performed to verify this failure detection method as applied to reactor instrument failures. It was demonstrated that the method can detect both single- and common-mode failures. Also, without hardware redundancy, it can describe the system dynamics in the event of failures