Analytical redundancy for CANDU nuclear power plants using a modified dedicated observer

Due to competition from other methods of electricity production, as well as social and political scrutiny, nuclear power plants (NPPs) have to find new ways to improve safety and efficiency. An instrument fault detection and isolation (IFDI) scheme that incorporates analytical redundancy can be one of ways to achieve these goals. Such a system could augment some of the hardware redundancy employed in the existing NPPs. This paper presents a unique approach to the concept of fault detection in applications that involve slowly varying processes and may also have limited flexible computer resources, such as the systems in an NPP. The method is based on a modified dedicated observer scheme (MDOS) that addresses some of the shortfalls of the original DOS. Modifications include the incorporation of adaptive thresholds as well as a fault value estimation and replacement algorithm. The MDOS is tested using a simple model in a CANDU reactor process and established fault scenarios from a CANDU simulator. The test results have shown that the MDOS is promising as an IFDI algorithm for NPPs. (authors)