LIETDOS-BIO assessment approach to the environment non-human biota exposure by ionizing radiation

The increasing public concern over environmental hazards has led to the emergence of a variety of national and international legal commitments for the environment protection. The LIETDOS-BIO assessment approach to Environment protection from ionizing radiation is being developed to address contamination issues associated with nuclear power production and radioactive waste disposal in Lithuania. The LIETDOS-BIO was designed to be consistent with MCNPX code and Crystal Ball software for uncertainty analysis. The modelling of radionuclide migration through the components of a hypothetical waste disposal system (hypothetical Stabatiskes waste disposal contaminated zone, unsaturated zone, aquifer, and recharge to Lake Druksiai) has been performed using the computer code RESRAD-OFFSITE and a number of site-specific parameters together with distributions. Submerged hydrophytes were selected as biota exposure indicators because they represent the largest biomass in Lake Druksiai and have comparatively high radionuclide activity concentrations. The presented data demonstrate that submerged hydrophyte exposure is determined mainly by natural background radionuclides with predominance of (226)Ra ionizing radiation in the case of external exposure and internally incorporated a-emitters. (238)U is the major contributor in the case of internal exposure. The LIETDOS-BIO code for non-human biota dose rate calculations was assessed during IAEA EMRAS BWG scientific program performance, and modelled-to-measured activity concentration predictions were found to be acceptable with the absolute value of Z-score between 0 and 2 derived from the Z-score intercomparison. The preliminary data presented here make it possible to investigate the relevance of Lake Druksiai as a cooling pond for the progression of nuclear energetics in Lithuania. A final decision on acceptability of this option awaits further review.