| 摘要 |
PURPOSE: To measure the volumetric activity of a radioactive element in circulating liquid by discriminating multiple events and performing mathematical simulation by a substituting method in consideration of probabilistic variable properties of a phenomenon to be measured, and comparing the simulation result with a measurement result. CONSTITUTION: A detecting device 30 has a probe 20 for measurement and a probe 22 for background gamma-ray correction and is arranged in a shield 16 connected to a pipe by a piping system 18. Further, a spectrometry chain consists of the main body part 38 of the device 30 composed of the probes 20 and 22 and a main body part 40 which performs electronic processing, and the main body part 40 consists of two subordinate main body parts of the same constitution relating to the probes 20 and 22 and consists of plural circuits, i.e., a pulse height selector 48 having an energy window, a recording device 50, etc. Then a microcomputer 56 periodically makes an inquiry to the device 50 to receive pieces of information from respective selectors 48 connected to the probes 20 and 22, subtracts a correction gamma-ray dosage corresponding to the probe 22 from the measurement signal of the probe 20 by windows to obtain a probabilistic variable, and determines the volumetric activity of a radioactive isotope circulated in the pipe in a last certain time at fixed time in consideration of the variable.
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