New Method Applied for the HPGe Detector

Gamma ray spectrometry is a passive non destructive assay most commonly used to identify and quantify the radionuclides present in complex objects such as nuclear waste packages. The treatment of spectra from the measurement of nuclear waste is performed in two steps: the first step is to extract the raw data from the spectra (energies and net photoelectric absorption peaks areas) and the second step is to determine the detection efficiency of the measured scene. The establishment by numerical modelling of the detection efficiency of the measured scene requires numerical modelling of the detector (HPGe detector) and of the measured object. HPGe detector characterization must have a spatial response equivalent to the real HPGe detector. This HPGe detector characterization by numerical modelling is essential for the quantification of complex irreproducible huge objects for which the detection efficiency cannot be determined empirically. We have developed a new methodology for characterizing HPGe detector. The methodology has been tested experimentally with a real detector available in the laboratory (Ptype planar detector). The characterization of the HPGe detector obtained with this methodology is similar to a real HPGe detector with an uncertainty approaching 5 percents. Characterization obtained in the laboratory with this real HPGe detector is valid for a distance ranging from 10 cm to 150 cm, an angle ranging from 0 to 90 degrees and energy range from 53 kev to 1112 keV. The energy range is obtained with a source of Barium133 and a source of Europium152. The continuity of the detection efficiency curve is checked between the two sources with an uncertainty less than 2 percents. In addition, this methodology can be extrapolated to any type of detector crystal geometry (planar, well…).