Diagnosis of steam generator by estimating an unobserved important state variable

In this study, a technique has been developed for diagnosing in on-line the state of the steam generator of the fast-breeder reactor (FBR) “Monju” by estimating an unobserved important state variable from observed data. The secondary coolant of liquid sodium faces to water/steam across a thin metal tube wall in the steam generator. Therefore, it is very important to detect a small anomaly of the wall of heat transfer tubes at an early stage. The aim of this study is to develop a technique for diagnosing in on-line a state of the steam generator by estimating an overall heat transfer coefficient, which is an unobserved important state variable, from observed data. This study shows simplified mathematical models of superheater and evaporator to estimate the overall heat transfer coefficient. The applicability of the technique is confirmed by configuring state observer with the mathematical model and noise filter and estimating using simulated data. As the results of the estimations, relative errors of the overall heat transfer coefficient of the superheater and the evaporator are less than ±0.5%.