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Abstract: 32-1

32-1

Combining 3D Printing with OSL Dosemeters for Extremity Monitoring for ICRU 95 Operational Quantities

Authors:
Gabriel Henrique Rocha Barreto de França (DEN/UFPE - Nuclear Energy Department, Federal University of Pernambuco) ; Helen Jamil Khoury (DEN/UFPE - Nuclear Energy Department, Federal University of Pernambuco) ; Viviane Khoury Asfora (DEN/UFPE - Nuclear Energy Department, Federal University of Pernambuco) ; Vinícius Saito Monteiro de Barros (DEN/UFPE - Nuclear Energy Department, Federal University of Pernambuco)

Abstract:

The International Commission on Radiation Unites and Measurements (ICRU) recently proposed (ICRU Report 95[1]) a new set of operational quantities for personal and area monitoring. The formalism behind defining these operational quantities is greatly simplified by adopting the same anthropomorphic phantom used to calculate the protection quantities. However, since the conversion factors between protection and operational quantities changed, personal dosemeters must be re-evaluated or even redesigned due to eventual changings into their energy dependence response.  This work then demonstrates the viability of using stereolithography (SLA) technique to produce a new wrist-type dosemeter casing, for photon radiation, with a commercial beryllium oxide (BeO) crystal as its detector. Such system must meet the applicable current international criteria[2] for the new ICRU 95 operational quantity. The casing was designed using SolidWorks® CAD software and the parts were printed with a FormLabs® Form2 printer. During the design, the detector’s window thickness was meant to be as thin as achievable, and also, besides that, a thin layer of aluminium foil was applied to the window’s inner surface for reaching light-proofness. Tests for evaluating energy and angle dependence were carried in the Radiation Metrology Laboratory (LMRI-DEN/UFPE). In these, the casings were put three by three on an ICRU/ISO Pillar Phantom and a dose of 1.0 mSv for Hp(0.07) was used for both dependences, with three repetitions for each angle and quality. Then, it is possible to obtain the energy response in the new operational quantity by multiplying the equivalence ratio of new/old conversion factors. The energy range evaluated was from 23 to 164 keV (ISO-N30 to N200), for X-rays and S-Cs-137 (662 keV); angular dependence, in turn, was evaluated ranging from 0° to 60°. Since calibration is usually made with ISO S-Cs-137 quality, a correction factor, fE,A, of 1.20 was calculated as a single-element correction algorithm that shifts energy dependence upwards, reducing deviations at lower energies. This kind of procedure is a standard practice in single-element dosimetry, as the energy to which a user is exposed in field is not known. As result, maximum deviation for 23-662 keV range is below 30%, which is within the acceptable range established by current IEC standards.

Keywords:
 Extremity Dosimetry, Personal Monitoring, ICRU 95, OSL