Events involving unnoticed power oscillations have occurred at different boiling water reactors (BWRs) in the past, and have led to the implementation of interim corrective actions to avoid their repetition. Despite these measures, power oscillations continue to occur. In response to this situation, a great deal of research and analytical activities have been undertaken to improve the knowledge of the underlying phenomenology, and to define final solutions to handle this type of event.
An OECD/NEA expert group has carried out studies in which the predictive capability of the codes and models for stability analysis are compared. This report provides the results of a specific study investigating the possibility of determining the main stability parameters from the neutronic signals time series with sufficient reliability and accuracy. It is based on a series of six complex cases derived from measurements carried out at the Forsmark nuclear power plant in Sweden.