Control rod monitoring system and control rod monitoring method

A control rod monitoring system having provided therein: a relationship model database storing pressure container internal sensor known relationship models indicating the mutual relationships between output values for individual neutron ray measurement sensor means, for a plurality of neutron ray measurement sensor means provided inside a nuclear reactor pressure container; and a relationship verification means that compares the pressure container internal sensor known relationship models stored in the relationship model database and a relationship model found from measurement values, being the monitoring target, obtained from the plurality of neutron ray measurement sensor means, monitors relationship collapse using the number of relationship mismatch locations as a reference therefor, and extracts a prescribed number of relationship collapses as notification events.