Radiological risk assessment in the terrestrial ecosystem: comparative study of two software tools used for dose rate calculations.

Abstract

In this study, two software tools, namely the ERICA Assessment Tool and the RESRAD-BIOTA code, are used for the calculation of the radiological exposure of non-human organisms. For the purposes of the analysis, data retrieved from field studies are used. The site-specific measurements were performed on organisms (mammals-sheep and goats of Bovidae spp.) collected from free-ranged grazing regions in Greece. Plants (grass) of Poaceae spp. and soil samples were also collected from these regions. Natural radionuclides (226Ra, 228Ra, and 228Th) of lithogenic origin and 137Cs, resulted from human activities (Chernobyl and Fukushima nuclear power plant accidents and global fallout), were detected in all samples. The measured activity concentrations were used as input to the two software tools, the ERICA Assessment Tool and the RESRAD-BIOTA code. The results of the simulations provided the external, internal, and total dose rates received by the organisms due to the exposure to the radionuclides. The assessments indicated that out of all detected radionuclides, 228Th is the main contributor to the external dose and 226Ra and 228Ra are the main contributors to the internal dose. The comparative analysis of the two tools revealed significant differences in the calculated doses. In fact, external and internal doses calculated by RESRAD-BIOTA are higher than the values calculated by the ERICA Tool, due to the dose conversion coefficients (DCCs) used for the dose calculation. RESRAD-BIOTA provides more conservative values, but ERICA Tool provides lower uncertainty due to the higher flexibility in the design of the phantom organism. On a risk assessment basis, there is no significant impact, due to organisms' exposure to radioactivity. However, further consideration of the exposure levels is required due to the potential effects of protracted low-level ionizing radiation on the various levels of life's organization.