Patent Number: 054815754
Section: abstract

A method and a device for detecting oscillations in the core of a boiling-water nuclear reactor (BWR) comprising a plurality of neutron detectors, wherein instability is detected based on oscillations in the output signals of the neutron detectors. For each one of a number of selected neutron detectors, oscillations in the output signals of the neutron detectors are detected. The oscillations are detected on the basis of an oscillation signal (SS) which indicates that an oscillation criterion is fulfilled. An alarm signal for remaining oscillations Ka is generated if the oscillation signal (SS) remains during one delay interval (T3). A first alarm signal (LR) is generated if the oscillation signal (SS) indicates that the oscillation criterion is fulfilled at least once, during each of a predetermined number of consecutive alarm intervals (T1). An alarm signal for intermittent oscillations (Ra) is generated by blocking the first alarm signal (LR) when the alarm signal for remaining oscillations (Ka) is present. (FIG. 5)