Determination of transmission curves through barite-based mortars using the Monte Carlo method

Purpose To determine workload-weighted primary and secondary X-ray transmission curves and Archer parameters for different barite-based mortars, and to assess the influence of chemical composition on their attenuation properties. Methods Primary transmission curves for X-ray spectra with tube potentials of 50, 70, 100, 125, and 150 kVp were determined using the Monte Carlo code PENELOPE and then weighted with different workload spectra. Secondary transmission curves were obtained by the mathematical formulation established in NCRP Report No. 147. The geometric model employed multiple shielding layers to optimise the air kerma computation. Three barite-based mortars with different barium contents were investigated: white, cream, and purple barite. The methodology was validated by reproducing primary and secondary transmission data from NCRP 147 for different materials. Results Good agreement with NCRP 147 was achieved, with most differences remaining below 10%. To achieve the same transmission factor, the mortars with higher and lower barium contents showed average relative differences of 67.5% and 41.1% for the primary and secondary curves, respectively. For the primary curves, the differences in the half-value layers at high and low attenuation reached 21.5% and 121.7%, respectively. In addition, differences of up to 49.3% were found between primary and secondary curves for the same transmission factor. Conclusion Accurate shielding design requires knowledge of both primary and secondary transmission curves. The discrepancies observed highlight the importance of accounting for material composition and secondary radiation in shielding assessments. The proposed methodology provides a reliable framework for evaluating existing and emerging shielding materials and can be extended to other radiological modalities, such as mammography.