Method and apparatus for continuous on-line monitoring of power distribution in a nuclear reactor core

摘要

On-line, real time monitoring of core-wide and local power in an advanced pressurized water reactor is provided by a system having four channel sets of fixed incore nuclear detector strings distributed in fuel assemblies across the core in a pattern which produces a uniquely identifiable detector response to rod movement even with one channel set out of service. Separate signal processors for each channel generate totally independent core-wide overpower protection signals and exchange detector responses through fiber optic data links for local power monitoring. The local power density at each detector level for any desired point across the core is determined by fitting a surface spline function to the detector responses adjusted to eliminate the local effects of rod movement from a reference condition, interpolation of the fitting function, and factoring back in the local effects of rod movement. If local power in the X-Y plane approaches but does not exceed trip criteria, a pointwise axial power distribution is generated to determine if a local overpower condition exists between detector levels. Misalignment of rods from the positions indicated by the position indicators is detected by a pattern recognition procedure for finding a fit between the effects of successive assumptions of misaligned rods and the detector responses adjusted for known rod movement.