Experimental study on the conversion factor between ambient dose equivalent and air kerma for external photon radiations

In accordance with the recommendations of the International Commission on Radiation Units and Measurements, operational quantities should be used in environmental or individual monitoring for external photon radiations. Therefore, the conversion factor between ambient dose equivalent, H*(10), and air kerma, Ka, was studied. A sphere made of polyethylene with 30 cm diameter was chosen as a substitute of ICRU sphere. The absorbed doses on the surface and at a depth 10 mm of the sphere measured by thermoluminescence dosemeters were converted to the dose value in ICRU sphere with necessary corrections. The measurement of H*(10), Ka was performed for ISO-4037 narrow X rays and for gamma rays from 137Cs and 60Co. the source and value of uncertainty were analyzed and the total uncertainty was 3.2%. Comparisons were made between authors' results and other published values. The results obtained are in agreement with the theoretical studies within uncertainties, and they can be used for the calibration of environmental monitors or individual dosemeters