Approaches to the definition of potentially exposed groups and potentially exposed populations of biota in the context of solid radioactive waste

Abstract

A methodology for addressing the biosphere in safety assessments for solid radioactive waste disposal was developed through theme 1 of the IAEA coordinated research project on BIOsphere Modelling and ASSessment (BIOMASS) that ran from 1996 to 2001. This methodology provided guidance on how the biosphere can be addressed in safety assessments for disposal of solid radioactive waste. Since the methodology was developed, it has proven useful and has been widely referenced in assessments in a diversity of contexts encompassing both near-surface and deep geological disposal of solid radioactive waste. The principles that could be adopted for defining potentially exposed groups (PEGs) were an important aspect in the original BIOMASS methodology as the endpoint of an assessment usually includes the evaluation of individual dose or risk to human health. Identification of PEGs and definition of their characteristics are usually made to be consistent with the biosphere system description being developed, acknowledging that due to inherent uncertainties in projecting future human behaviour, the biosphere models adopted for assessing safety of a disposal system can only be illustrative. Since the publication of the original BIOMASS methodology, consideration has been extended to include potentially exposed populations of biota (PEPs), in the context of dose assessment and protection of the environment. Considering the need for the development of transfer pathways from a source term to an end point (for either PEGs or PEPs), the exposure modes that may occur and those to be assessed quantitatively should be identified. Within an expert working group (WG6) of the second phase of the IAEA coordinated project Modelling and Data for Radiological Impact Assessments (MODARIA II), the experience of participating organisations has been collected on topics associated with the definition of PEGs and PEPs using a questionnaire. The objective of the questionnaire was to review the current status and on-going discussions on the handling of issues related to definitions of PEGs and PEPs as an input to the development of biosphere models for assessing radiological impacts on human health and the environment. The answers received to the questionnaire provided a clear overview of the progress that has been made since the original BIOMASS methodology was published, together with the lessons learned from the application of that methodology in the development of safety cases. This paper summarises the questionnaire responses in five subject areas: (1) environment of the PEGs and its evolution; (2) linking the choice of PEGs to these environments; (3) food habits and consumption rates; (4) populations of non-human biota (PEPs) and (5) national and international regulations and guidance. We illustrate how the results of the questionnaire have been used to enhance the original BIOMASS methodology (IAEA Enhanced BIOMASS Methodology Report in press).

A research and development roadmap to support applications of the enhanced BIOMASS methodology

“…Finally, societal assumptions will condition both the types of land use adopted for the purpose of assessment modelling and the potentially exposed groups (PEGs) that are assumed to make use of those environments. The issue of how land use and PEGs may be selected is the topic of another paper in this special issue (Griffault et al 2021) and is not discussed further here.…”

Demonstrating the use of a framework for risk-informed decisions with stakeholder engagement through case studies for NORM and nuclear legacy sites

“…For a particular environmental system, a variety of radionuclide transport and transfer processes take place leading to specific exposure conditions. Moreover, in accordance with the radiation protection principle of optimization of protection and safety, the risk assessment (RA) and management need to take into account a much wider range of socio-economic, land use, environmental policy and other issues in addition to those related to human health (IAEA 2014, 2022, Yankovich et al 2022. There is also a general need in many societies to engage stakeholders in the decision-making and remediation process and consult with them throughout the process.…”

“…In recent years, decision-making regarding radioactivity on NORM and nuclear legacy sites has been moving towards using a risk-informed, performance-based approach (e.g. National Research Council 2014, IAEA 2019, 2022. The term, 'risk-informed decision-making' , pertains to the assessment of human health and the ecological risk to support a decision-making process, as appropriate.…”

“…The term, 'risk-informed decision-making' , pertains to the assessment of human health and the ecological risk to support a decision-making process, as appropriate. However, there are many other contributing factors or objectives that inform a more complete decision analysis, such as worker safety, economic (cost) constraints, financing and insurance, economic health and employment of local communities, stakeholder expectations and preferences, environmental justice, and others (IAEA 2002, 2022, NUREG 17572006. Considerations such as these are increasingly being considered when addressing decommissioning, remediation, and waste management issues in a holistic manner that accommodates other relevant objectives in addition to regulatory compliance (IAEA 2002).…”