| 摘要 |
PURPOSE:To obtain an accurate measured value by setting the sensitivity of an arbitrary radiation detector calculated by performing the averaging processing of a detection signal outputted from the radiation detector as reference, and performing sensitivity correction setting the difference of a counting rate with that of another radiation detector as a calibration constant. CONSTITUTION:Plural gamma ray detectors 2(A1,A2)-(F1,F2) forming pairs in a depth direction are arranged on an inner wall forming cylindrical space. A used fuel rod 4 supported with a handling mechanism 3 is inserted from an aperture at the upper terminal of the cylindrical space to the space at an inspection board 1. The fuel rod 4 is inserted to the inspection board 1 while stepping at each of stopping positions A-F by the mechanism 3 in this configuration. When the tip of the fuel rod 4 arrives at the positions A-F, a signal detected by a detector 2 is inputted to a statistical processing circuit 6. The averaging processing is applied to a statistical processing result outputted from the circuit 6 at an averaging processing circuit 7. At a sensitive correction part 9, the sensitivity correction is performed setting the difference of the counting rate as the relative sensitivity calibration constant of each correspondent detector by setting, for example, a certain gamma ray detector as reference, and finding the difference between the counting rate of the gamma ray detector set as reference and that of another gamma ray detector.
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