[en] The radiation and weather monitoring system (KRS system) of nuclear power plants is used to monitor whether there are abnormal changes of the environmental gamma dose rate in the plant and its surroundings. From the time and frequency of occurrence, and the trend of fluctuations, through analysis and experimental verification, we confirmed that dose rate data fluctuations of the AS4 sub-sites of the KRS system in a nuclear power plant are caused by radiographic inspection activities in 3MX and 4MX workshops. (authors)