Achievement of Quality Control Parameters for NIS Personal Thermoluminescence Dosimeter (TLD) System

This work intend to identify and follow up quality control parameters to improve thermoluminescence dosemeter (TLD) system used for personal dosimetry in ionizing radiation metrology laboratory (IRML). Characterization of personal dosimetry system has presented in terms of the stability of reader calibration factors, linearity of response for Cs as reference radiation source, energy and angular dependence. In this study the TLD cards type GN-6770 with holder type 8806 manufactured by Harshaw which contained three TLDs detectors were used as personal dosimeter. Radiation characteristics and calibration methods were given in terms of personal dose equivalents (Hp (10)) incident on the ISO calibration phantom (water slab phantom). The distribution of the element correction coefficients (ECC) for the total population of cards, stability of the average reader calibration factors (RCF), and linearity of the response to dosimeter were studied. It was observed that the distribution of ECC for total cards population follows a Gaussian shaped curve and that the uncertainty associated to the ECC of the field cards is 10.3%. Over the 5 years period, the annual RCF varied 1.3% which indicates reliability and stability of the reading system. The angular dependence of the dosimeter was determined, using X-ray, γ-rays from Cs and Co sources [ISO 4037], at the angles of 0◦, ±30◦ and ±60◦. Further studies should be conducted in order to implement correction factors for supralinearity and different energies measurement. A correction factor needs to be implemented or the dosimeter modified (changes in holder filtration or another sensitive element) to meet the national requirement in the field of neutron dosimetry.