| 摘要 |
PURPOSE:To exclude the missing of measurement immediately after the change of a flow paths by sampling the measured values of the flow rates during the transition period of a flowmeter at a short period over the specified time period immediately after the switching of the flow path of sampling gas into a sampling line. CONSTITUTION:A control device 2 imparts the opening command into a sampling valve 4 and imparts the closing command into a bypass valve 5. Thus, the flow path of the sampling gas from a pipe 1 is switched to a sampling line 2 from a bypass line 3. When the flow path is changed, the sampling gas is introduced into a collecting container 6. Dust is collected into filter paper 7 when the sampling gas passes the container 6. The radiation discharged from the radioactive nuclear species in the dust is counted in a detector 8. The counted value is sent into a data processing device 22. At this time, the measured values of the flow rates in the transition period of a flowmeter 10 are sampled in a short period over the specified time period immediately after the switching of the flow path. The concentration of the radioactivity is obtained in the processing device 22 based on the sampled average value of the flow rate and the detected signal value of the radiation.
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