Development of the MCNPX model for the portable HPGe detector

• Inner structure of the HPGe detector is determined.
• An MCNPX model of the detector is developed.
• The model is verified using different sources for two measurement geometries.

The portable HPGe coaxial detector Canberra Big MAC is used in LVR-15 research reactor for spectrometric measurement of spent nuclear fuel. The fuel is measured in the dedicated system located in the spent fuel pool situated near the reactor. For the purpose of the spectrometric system calibration, the detector was precisely modeled with the MCNPX code. This model was constructed with the data acquired from the technical specification provided by the manufacturer and from the data obtained by the radiography of the crystal. The detector model was verified on the experimental data measured with available standard radionuclide sources and on-site prepared 110mAg source.