U.S. department of energy's graded approach for evaluating radiation doses to aquatic and terrestrial biota

The United States Department of Energy (DOE) has been active in the development of requirements, methods and guidance for protection of the environment (biota and ecosystems) from the effects of ionising radiation since the late 1980's. This oral presentation provided an overview of: (1) DOE's requirements and strategic objectives for the evaluation of doses to biota at DOE sites and facilities; (2) a practical screening tool provided within DOE's graded approach to biota dose evaluation; (3) lessons learned from the first year of the graded approach methodology's implementation at DOE sites; and (4) thoughts for International Commission on Radiological Protection (ICRP) activities on radiological protection of the environment. Practical and cost-effective methods are needed for demonstrating protection of biota. Through its Biota Dose Assessment Committee (BDAC), the DOE has developed screening methods, models, and guidance within a graded approach for evaluating radiation impacts to biota (Figure 1). DOE's graded approach is described in the DOE Technical Standard, 'A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota'. A series of electronic spread-sheets for conducting an evaluation are contained in a 'RAD-BCG Calculator'.' A practical screening methodology provides limiting concentrations of radionuclides, termed Biota Concentration Guides (BCGs), for use in screening water, sediment, and soil media to determine if dose limits for biota might be exceeded. Methods and models for site-specific screening and detailed analysis, if needed, are also provided (Table 1). Four reference organisms were selected as the basis for methods development. Internal and external exposure assumptions and default parameters used provide for conservative screening values. Users can modify the biota dose limits and parameter values to account for site-specific receptors and exposure scenarios. DOE's proactive outreach and co-ordination with other U.S. agencies (through the Interagency Steering Committee on Radiation Standards) and with international organisations has resulted in opportunities for partnerships and methods advancement. DOE's approach for evaluating radiation doses to biota is proving useful as a sensible and cost-effective tool that could be employed within an overall framework for protection of the environment from the effects of ionising radiation. (author)