From <i>H</i> p(10) to <i>H</i> p: impact of implementing ICRU/ICRP report 95 personal dose quantity on CaSO4:Dy-based TLD dosemeters – a Monte Carlo study

The International Commission on Radiation Units and Measurements (ICRU), in collaboration with the International Commission on Radiological Protection (ICRP), has introduced new operational quantities in ICRU Report 95. Among these, the personal dose Hp addresses the significant limitations of the currently used Hp (10), which can overestimate the effective dose by up to a factor of 5.5 at photon energies below 70 keV. These changes necessitate a re-estimation of dosemeter response to evaluate potential modifications in dose algorithms and detector design. In this study, the performance of CaSO4:Dy thermoluminescent dosemeter (TLD) badges was investigated for the new operational quantity Hp and compared with the existing Hp (10). The badge response was simulated over photon energy range 12.3-1250 keV using the Monte Carlo Simulation code FLUKA and benchmarked against experimental validation. To correct for energy-dependent overestimation at lower photon energies, a new dose evaluation algorithm for Hp was developed based on disc dose ratio (R12). The disc dose ratio (R12) refers to the ratio of absorbed doses measured in CaSO₄:Dy TL discs D1 and D2 positioned under different filtration conditions within the badge and serves as an energy-sensitive parameter for correcting the over-response of the dosemeter in terms of Hp. The proposed algorithm demonstrated strong compliance with IEC 62387:2020 performance criteria (acceptance range 0.71-1.67), with 95% of estimated Hp values lying within 0.9-1.3 of the delivered dose. These results confirm that CaSO4:Dy TLD badges, when combined with the improved algorithm, are fully compatible with the new operational quantities recommended in ICRU Report 95, ensuring reliable application in personnel dosimetry.