Monitor inspection device

The device of the present invention reliably conducts monitoring by radiation monitors in a nuclear power plant thereby contributing to save the number of radiation operators and reduction of radiation exposure. Namely, radiation monitors continuously measure a plurality of γ-ray levels. A branched simultaneously counting circuit receives these signals. The output of the branched simultaneously counting circuit is inputted to a differentiation means. The differentiation means calculates a variation coefficient for each of the radiation monitoring values, namely, equivalent dose rates, and records and monitors change with time of the equivalent dose rates. With such procedures, the results of the monitoring of γ-ray levels can be judged objectively corresponding to the increase of the equivalent dose rates. As a result, the number of radiation operators can be saves and radiation exposure of the radiation operators can be reduced. (I.S.)