| 摘要 |
PURPOSE: To exactly measure variousγ-ray and more exactly calculate the burnup of spent fuel by checking the integrated count value of all energy channel output from a pulse height analyzer and controlling the insertion and withdrawal of absorber as to measure in optimum range of theγ-ray detector. CONSTITUTION: In the opening of a collimator 3, an absorber 9a and an absorber 9b having a larger shield attenuation rate are provided free of insertion and withdrawal. A controller 10 for controlling the insertion and withdrawal of each absorber 9a, 9b is provided. At the momentγ-ray of spent fuel 2 is measured, the integrated count value of all energy channel output from a pulse height analyzer 5 is checked and based on the result, the insertion and withdrawal of each absorber 9a, 9b is controlled 10. Thus, even in a high doseγ-ray field wherein a plurality ofγ-ray species exist and in the case theγ-ray energy difference of the measuring object is large, theγ-ray from fuel 2 can be exactly detected in optimum range of aγ-ray detector 4 without miscounts.
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