HPGe efficiency calibration using GEANT4-GAMOS code for study environmental materials: radioactivity transfer study nearby the phosphate area in southern Tunisia

ABSTRACT

HPGe efficiency calibration requires the use of a standard source with similar characteristics as the studied sample. However, these standards are difficult to supply due to their high cost and extensive effort needed. Monte Carlo codes allow the efficiency calibration of the HPGe detector by the simulation of the photon’s interaction emitted by the source within the detector crystal. For this purpose, a Monte Carlo model using GEANT4-GAMOS code was developed. This simulated model was carefully validated by comparing efficiency values obtained from experiments with those from simulations, using a standard radioactive source mixed with a soil matrix covering an energy range from 59.54 to 1836.12 keV. The shift values between the experimental and the simulated efficiencies are less than 8% for all measurement configurations. The results show a maximum deviation amount to 8% for the ²⁴¹Am radionuclide. In the case of high gamma energies, significant deviations of 7% and 8% are observed too for the radionuclides ⁸⁸Y and ⁶⁰Co, respectively, resulting from the coincidence summing effect. After validation, the model was employed to determine efficiency values for environmental materials. The Monte Carlo results were successfully applied to estimate the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in Gafsa and Gabes matrices. All the activity concentrations were below the worldwide limit in all the samples except the ⁴⁰K which reached a value of 909.13 Bq.kg⁻¹ in the plant sample.

KEYWORDS:

• HPGe detector efficiency
• GEANT4-GAMOS code
• phosphate contamination
• natural radionuclides
• environmental materials
• transfer factor

Acknowledgments

The authors sincerely acknowledge the members of the PN2P Laboratory at Carthage University and the members of Laboratory Soil, of DATN, CRNA for their help.

Author contributions

All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

Disclosure statement

No potential conflict of interest was reported by the author(s).