Uncertainty Budget for Measurement of Personal Dose Equivalent Hp(10) and Skin Dose Equivalent Hp(0.07) Using TL Dosemeters

The uncertainty budget for measurements of personal dose equivalent Hp(10) and skin dose equivalent Hp(0.07) was performed on the ThermoFisher Scientific (Harshaw) system (model 6600 reader and thermoluminescent dosemeters (TLD) LiF: Mg,Ti), according to the 'Guide to the expression of uncertainty in measurement' (GUM) guidelines. This paper gives an overview of components which enter into the calculation of the so-called fish-bone approach for uncertainty evaluation. For purposes of the uncertainty budget, the type testing against the requirements of HRN IEC 61066:2007 was made. Measurements itself, as well as the calculation of measurement uncertainty, were performed for the personal dose equivalent Hp(10) as well as for the skin dose equivalent Hp(0.07). The type test includes tests for linearity, energy and angular dependence, additivity and signal fading. Results are expressed as an expanded uncertainty with confidence of 95 % (a factor overlay of 1.96), which is obtained by combining two types of uncertainty, type A and type B. Measurements were carried out for 20 months, and for the purposes of testing more than 500 TL dosemeters were used. Dosemeters were irradiated in the Secondary Standard Dosimetry Laboratory (SSDL) at the Ruder Boskovic Institute, Zagreb, Croatia with an energy range from 33 keV to 1.33 MeV. The highest contribution to the overall uncertainty gives energy and angular dependence; the lowest gives self-irradiation and correction factors of individual detectors (ECC). Overall uncertainty of described TL system could be reduced by reanalysis of electromagnetic, environmental and mechanical effects. The total expanded uncertainty of this system does not deviate from the uncertainty reported by the majority of technical services in Europe.(author)