Procedure for Characterization and Validation of Commercial Clearance Monitors Using Monte Carlo Simulations

The goal of the present work is to propose and validate a numerical model for the calibration of clearance monitors, aimed at determining conversion factors between the measured count rates and the activity for non-standard radionuclides and geometries. For this, Monte Carlo simulations were carried out using the multipurpose code FLUKA in combination with an offline optimization of the model parameters used to correct the simulation results. Parameter optimization was performed by comparing experimental measurements of point sources in an empty chamber of a clearance monitor with the simulation results, whereas for model validation, the simulation results were compared to measurements of the sources in different geometries. The maximum relative discrepancy between the calculated and measured efficiencies in the validation was <10%. This procedure is relevant for the calibration of clearance monitors used in particle accelerator and nuclear facilities, where a variety of radionuclides, materials and geometries need to be measured and released from regulatory control.