Control rod operation monitoring method and control rod operation monitoring system

A control rod operation monitoring method of monitoring a plurality of control rods inserted into a core,

• wherein a plurality of neutron detector assemblies, each including a plurality of neutron detectors arranged in an axial direction of the core, are disposed adjacent to each of the control rods, including insertion selection control rods selected from the plurality of control rods for insertion into the core,
• wherein first neutron detectors, of the plurality of neutron detectors, are respectively arranged at first positions in each said neutron detector assembly and a plurality of second detectors, of the plurality of neutron detectors, are respectively arranged at second positions in each said neutron detector assembly,
• wherein each said first position in each said neutron detector assembly is closest to a control rod insertion end of the core, and
• wherein each said second position in each said neutron detector assembly is different in the axial position from the first position, the method comprising:
• for each one of the plurality of insertion selection control rods, calculating a first average neutron flux of neutron fluxes measured from each of said first neutron detectors in each of said neutron detector assemblies disposed adjacent to the one insertion selection control rod;
• for each one of the plurality of insertion selection control rods, calculating a second average neutron flux of neutron fluxes measured from each of said second neutron detectors in each of said neutron detector assemblies disposed adjacent to the one insertion selection control rod;
• for each one of the plurality of insertion selection control rods, calculating a first neutron flux ratio, each said first neutron flux ratio being a ratio of the second average neutron flux with respect to said first average neutron flux;
• and
• upon determining the first neutron flux ratio of one of the insertion selection control rods exceeds a predetermined neutron flux ratio, generating a rod insertion block signal for the one insertion selection control rod.