NEW DATA CONCERNING THE EFFICIENCY CALIBRATION OF A DRUM WASTE ASSAY SYSTEM. PART I: EXPERIMENTAL CALIBRATION

摘要

The study is focused on the efficiency calibration of the gamma spectroscopy system used in the NIPNE drum waste assay facility. The measurement of a radioactive drum waste is generally difficult because of its high volume, the complex and usually unknown distribution of the waste in the drum and its high self-attenuation. To solve these problems, a complex calibration of the system is required. For this purpose, a calibration drum filled with Portland cement and provided with seven tubes, placed at different distances from its center was used. For the efficiency calibration appropriate for a uniformly distributed source, the shell method, using a linear source of ~(152)Eu, was applied. The linear calibration source was introduced successively in the seven tubes, the gamma-spectra were collected while the drum was translated and simultaneously rotated. Using the GENIE-PC software, the gamma-spectra were analyzed and the detection efficiencies were obtained. For the efficiency calibration in the case of a non-homogeneous source, supplemental measurements in the following geometries were made. First with a point source of ~(152)Eu placed in front of the detector, measured in all seven tubes, the dram being only rotated. Second with the linear source of ~(152)Eu placed in front of the detector, measured in all seven tubes, the drum being only rotated. For each case the gamma spectra were recorded and the detection efficiency was calculated.