| 摘要 |
PROBLEM TO BE SOLVED: To easily, positively, and safely determine end of decontamination, by detecting radiation included in a circulating decontamination liquid and obtaining a radiation concentration, and judging the decontamination end timing of equipment to be decontaminated based on the value of the radiation concentration. SOLUTION: When a pump 5 is driven while switching valves 6a, 6b, and 6c are closed and switching valves 6c and 6d are open on decontamination, a decontamination liquid in a tank 2 flows into equipment 1 to be decontaminated via pipes (d) and 1b and returns to the tank 2. This circulation process is repeated. The circulation decontaminates a radioactive material in the equipment 1 to be decontaminated and decontaminates a decontamination liquid. At this time,γrays discharged from the decontamination liquid are detected by a radiation detector 8, a wave-height distribution corresponding toγ-ray energy is obtained by a wave-height analysis device 11, and a desired nuclide radiation concentration in the decontamination liquid is obtained by an operation device 12 based on the wave-height distribution and its size is monitored. When the radiation concentration gradually increases and reaches a balanced state at a preset concentration, it is judged that the end timing of decontamination has been reached and an output device 13 reports the end timing of decontamination to a person in charge.
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