| 摘要 |
PURPOSE:To enable an activity to be monitored with a detecting sensitivity for a low concentration by subtracting the activity detected by second detecting means from the activity detected by a first detecting means, thereby removing the effect of a natural backgroud. CONSTITUTION:First detecting means 2 detects an activity from within a liquid that has passed an area wherein a radioactive unclide is present other than a natural radioactive unclide. Second detecting means 3 detects the activity from within the liquid that has passed the area wherein only the natural radioactive unclide is substantially present. A high speed arithmetic processing unit 4 is inputted with the data outputted from the means 2 and 3 and calculates the activity of the dust collected by first and second dust samplers 6 and 10, respectively. Then, the activity detected by the means 3 is subtracted from the activity detected by the means 2 to calculate the activity of a handled radioactive unclear material and the activity is compared with a set alarm activity inputted to storing means in advance by discriminating means 4b. Output means 5 display a result and, when the set activity is exceeded, emit an alarm by a buzzer or the like.
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