| 摘要 |
PURPOSE:To make quantitative determination of radioactivity of a storage vessel by the first radioactivity measurement per cross section by finding an energy spectrum of radiation from an inspected object which is made incident through a collimator set at the front of a radiation detector. CONSTITUTION:In order to find the radiation of gamma ray release nuclide of the inside of a drum can from gamma ray strength measured in the circumfer ence of the drum can, measured gamma ray strength is corrected on the basis of the detected efficiency of a measuring system dependent on radioactivity distribution and the density distribution of the content of the drum can. The setting of the measuring system composed of the drum can 1, collimaters 4, 5 and a radiation detector 2 is performed at least once before a series of the radiation of the drum can are determined. The correction of radioactivity distri bution in the major axis direction of the drum can and density distribution of contents thereof sets the opening width of the vertical collimator 4 so that a detector 2 anticipates only a cross section in the major axis direction of the drum can and the whole cross section of the drum can 1 can be measured as the drum can 1 is ascended or decreased in the major axis direction of the drum can.
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