Nuclear reactor power monitor

A nuclear reactor power monitor, comprising:

• a first calculation unit configured to calculate a first stability index of the reactor core based on time series data which indicate a power oscillation in nuclear instrumentation signals outputted from a plurality of nuclear instrumentation detectors which detect neutrons in a reactor core;
• a first determination unit configured to compare the first stability index and a first reference value and determine whether nuclear thermal hydraulic stability of the reactor core is stable or deteriorated;
• a second calculation unit configured to calculate a second stability index of the reactor core based on the time series data when the nuclear thermal hydraulic stability is determined to be deteriorated in the first determination unit;
• and
• a second determination unit configured to compare the second stability index and a second reference value and determine whether to perform suppressing operation of the power oscillation, further comprising
• a third determination unit configured to execute the power oscillation suppression operation if it is determined that the first stability index satisfies a third reference value which is set more severely than the first reference value even when the power oscillation suppression operation has been determined to be unnecessary based on the second stability index.