| Abstract: | Monte Carlo calculations were performed to estimate the effective doses E for external photons based on the recent proposals in the ICRP 1990 Recommendations. Twelve photon energies between 17 keV and 8.5 MeV and eleven irradiation geometries were selected to be applicable to many exposure conditions encountered in the working and living environment. A MIRD-based unisex phantom was used in conjunction with the Monte Carlo transport code MORSE-CG. The results were presented as a form of dose conversion coefficients transforming the air kerma or fluence in free air to the effective dose. These coefficients were given in graphical and tabular forms. Analyses of organs' fractional contribution to E showed that the gonadal exposure has generally a great contribution for all the geometries except the incidence from above. A comparison of conversion coefficients with other results gave a reasonably satisfactory agreement. Finally, the ambient dose equivalent H *(10), one of the operational quantities proposed by the ICRU, was found to give conservative estimates of E for most of the irradiation geometries considered, but it gives a considerable overestimate of E at the incidences from above and below. |
