Preliminary Investigations of the Contribution of Scatter Radiation During Calibration of TLD-100 Using a Cs-137 Panoramic Source

Studies were carried out to determine the contribution of secondary photons to the calibration set-up of a Secondary Standard Dosimetry Laboratory. In these studies the response of LiF:Mg TLD-100 to known exposures using Cs-137 panoramic-source were investigated. Each TLD chip showed a linear dose response to radiation, demonstrating a typical characteristic of LiF:Mg chips. Whilst TLDs showed an acceptable response range for radiation protection purposes, the percentage differences observed were higher. The relative response values ranged from 0.91 to 1.52. These values indicated the presence of scatter contributing to the exposures. While a contribution of 28.1% was contributed to an exposure of 1 mSv and 48.3% being added to an exposure of 2 mSv, the integrity of the calibration TLDs used for personnel monitoring may not be justified. The set-up may be used for calibrating dosimeters with correction for scattered photons and collimating the beam from the Cs-137 source.