Patent Number: 
Section: claims

1. A control rod motion monitoring system for a reactor comprising:a plurality of neutron detector assemblies arranged in a radial direction of the core, each assembly including a plurality of neutron detectors, wherein the neutron detectors of each of the different neutron detector assemblies are located at a plurality of predetermined heights in the axial direction of the core, the plurality of predetermined heights being substantially the same for each of the different neutron detector assemblies and including a first predetermined height and a plurality of other predetermined heights;a signal processing device which calculates average values of neutron fluxes continuously measured by the neutron detectors for each of the plurality of predetermined heights; andan arithmetic device which outputs a signal based on the average values calculated by the signal processing device,whereinthe arithmetic device calculates deviations of the calculated average values between the first predetermined height and the plurality of other predetermined heights and outputs the signal when a maximum value of the deviations exceeds a predetermined set point, andthe signal processing device monitors all of the neutron detector assemblies in the core and constantly monitors control rod insertion throughout the core to detect abnormalities. 2. The control rod motion monitoring system according to claim 1, whereinthe arithmetic device is configured to transmit the signal when the average values calculated by the signal processing device exceed another predetermined set point. 3. The control rod motion monitoring system according to claim 1, whereina signal from a neutron detector assembly, of the plurality of neutron detector assemblies, at an outermost peripheral portion of the core is excluded from the average values calculated by the signal processing device. 4. A control rod motion monitoring system for a reactor comprising:a plurality of neutron detector assemblies arranged in a radial direction of the core, each assembly including a plurality of neutron detectors, wherein the neutron detectors of each of the different neutron detector assemblies are located at a plurality of predetermined heights in the axial direction of the core, the plurality of predetermined heights being substantially the same height for each of the different neutron detector assemblies and including a first predetermined height and a plurality of other predetermined heights;a signal processing device which calculates average values of neutron fluxes continuously measured by the neutron detectors for each of the plurality of predetermined heights; andan arithmetic device which outputs a signal based on the average values calculated by the signal processing device, whereinthe arithmetic device calculates a ratio between the calculated average value for the first predetermined height relative to the calculated average values for the plurality of other predetermined heights and outputs the signal when the ratio exceeds a predetermined set point, andthe signal processing device monitors all of the neutron detector assemblies in the core and constantly monitors control rod insertion throughout the core to detect abnormalities. 5. The control rod motion monitoring system according to claim 4, wherein the arithmetic device is configured to transmit the signal when the average values calculated by the signal processing device exceed another predetermined set point. 6. The control rod motion monitoring system according to claim 4, whereina signal from a neutron detector assembly, of the plurality of neutron detector assemblies, at an outermost peripheral portion of the core is excluded from the average values calculated by the signal processing device.