Calculation of Skin Dose Rate Conversion Factors Due to Surface Contamination from Frequently used Radionuclides in Local Nuclear and Medical Facilities.

Abstract

The use of nonsealed radioactive sources can lead to skin contamination due to radiological accidents and staff oversight. This contamination has been shown to contribute considerably to the total skin dose received by nuclear medicine technicians and can easily exceed the limit of 500 mSv/year established by the current regulations. To assess the severity of contamination, it is necessary to estimate the skin dose through the use of suitable skin dose rate conversion factors. To determine the appropriate factors, it is important to study the influence of the contamination area, the epidermal thickness, and the percutaneous absorption on them. Monte Carlo simulations using the code PHITS 3.02 were carried out to study and quantify the dosimetry conversion factors of 15 frequently used radionuclides (11C, 18F, 36Cl, 54Mn, 60Co, 90Sr, 99 mTc, 123I, 131I, 137Cs, 153Sm, 177 Lu, 223Ra, 226Ra, and 241Am). The absorbed dose to the skin is significantly influenced by epidermal thickness and percutaneous absorptions and can differ by up to two orders of magnitude with respect to the operational magnitude H'(0.07,0°). Skin dosimetry after a contamination incident may be complex because the absorbed dose delivered to the basal layer is influenced by the contamination area, the epidermal thickness, and the percutaneous absorption. Therefore, when an accident occurs, the dose should be quantified taking into account these parameters, especially the epidermal thickness, and the possible percutaneous absorption should be evaluated in cases where the contamination involves a dose approximately equivalent to the established limits.