Hydraulic stability monitor for reactor

Purpose: To provide a hydraulic stability monitor for a BWR reactor, which permits confirmation of the presence or absence of a hydraulically instable phenomenon taking place in the reactor core. Constitution: A local neutron detector tube is provided between adjacent fuel assemblies, and it has local neutron detectors provided at four positions in its axial direction. The output of each of the neutron detectors is coupled together with the output of a band-pass filter unit to an operational unit for deriving relative amplitude values. After the operational unit is provided a divider for deriving ratios of relative amplitude values in axial positions. The ratio of the relative amplitude values and a preset value of a presetter are compared in a comparator, which produces a pulse signal when the ratio exceeds the preset value. The signal thus produced is detected by an OR circuit, whereby the occurrence of a hydraulically instable phenomenon is indicated by means of a lamp. (Seki, T.)