Relationships between protection and operational dosimetric quantities for external exposure to natural background radiation.

Abstract

Protection and operational dosimetric quantities for human external exposure have been compared for situations of outdoor exposure to natural background radiation represented by gamma radiation of primordial and cosmogenic radionuclides and by radiations produced by the galactic cosmic rays in the Earth atmosphere. Calculations were performed using the data from publications of the International Commission on Radiation Units and Measurements CRU (ICRU Report 43: Determination of dose equivalents from external radiation sources-part 2. J ICRU os-22(2), 1988), ICRU (Operational quantities for external radiation exposure. ICRU Report 95. J ICRU 20(1), 2020) and the International Commission on Radiological Protection for global geographical grid of marine and terrestrial locations. Using modelled fluence spectra of natural cosmogenic and terrestrial background radiation, the ratios of the protection to operational quantities were calculated, demonstrating the effect of high-LET neutron component on the ratios of effective dose to absorbed dose, air kerma and the operational quantities. The influence of the neutron component was found to be stronger for high-altitude terrestrial locations and for terrestrial and marine locations at higher geographic latitudes. The computed ratios can be used for interpretation of the measured ambient dose rate data and calculation of effective doses in radiological protection tasks or assessment of public exposure to natural and anthropogenic sources of radiation.