Method and device for monitoring exposure of reactor core

Purpose: To prevent beforehand a serious accident or the like by monitoring the malfunction of a reactor water level meter due to an accident in a reactor system and the degree of the reactor core exposure due to the decrease in the water level. Method: Signals from a local power region monitor (LPRM), an intermediate region monitor (IRM), a neutron source region monitor (SRM), a traversing incor probe (TIP) and so forth as neutron detectors or signals from a plurality of gamma-ray detectors installed out of a reactor pressure vessel as inserted into the reactor core are processed to calculate the dispersion values. These dispersion values are compared with a predetermined reference value, and when this ratio exceeds a thershold value, it is decided that the reactor is exposed. (Aizawa, K.)