Patent Number: 055552790
Section: abstract

A computer-based power oscillation detection system and method for detecting, monitoring and indicating thermal-hydraulic stability margin in a nuclear reactor is provided. A group of neutron flux detectors is distributed throughout the reactor core, in contiguous relation to the reactor fuel assemblies, with each flux detector providing an output signal indicative of the power density of the portion of the core adjacent to the detector. A computer-based system processes the detector output signals utilizing a period based algorithm that employs an oscillation detection counting function wherein a count corresponding to the level of periodicity of the signal is determined. Since a representative oscillation count for each reactor stability state usually only occurs on the order of several minutes for a single detector signal, a unique simulated decay ratio algorithm reduces the time required to obtain a representative count by processing the group of detector signals spread throughout the core. The highest count for any detector in the group is utilized by the simulated decay ratio algorithm to provide a simulated decay ratio signal that corresponds to the reactor thermal-hydraulic stability. To overcome statistical variations in successive oscillation period counts, a spike rejection function and a smoothing function may be employed to provide improved simulated decay ratio signal performance. A corrective signal issues when the simulated decay ratio signal reaches a predetermined level which may be used to take corrective action, activate an alarm, provide a visual indication of decay ratio, or to initiate an automatic reactor suppression function.