Implicit Assumptions in Radiotoxicity Plots for High-Level Nuclear Waste: Reference Values and Choice of Dose Coefficients

Plots showing the radiotoxicity of different nuclide groups of HLW are often used to argue for Partitioning and Transmutation (P&T) as a nuclear waste management option. Apart from the limited value of using radiotoxicity to assess the impact of P&T on a repository, these representations are based on assumptions that are usually not explicitly stated. Using a model spent fuel inventory, this paper examines two aspects: the reference level against which spent fuel radiotoxicity is compared, and the dose conversion coefficients used to calculate radiotoxicity.

The reference level for radiotoxicity is usually referred to as "uranium ore". It is argued that no special precautions need to be taken below this level because uranium ore occurs naturally. However, uranium ore is found in various compositions and concentrations throughout the world. Different "reference levels" are often calculated based on different assumptions about how much uranium is actually needed for fuel. The impact of these assumptions on the conclusions drawn from the radiotoxicity plot is discussed.

In recent years, gender-specific effects of ionizing radiation have become an increasingly important area of research. Re-evaluation of data from the bombings of Hiroshima and Nagasaki has shown that women and children are disproportionately affected by the effects of ionizing radiation. The reasons for this are not fully understood. Nevertheless, for many types of radiation assessment and radiation protection analysis, the default is still to use dose conversion coefficients for males - the group least susceptible to harm from ionizing radiation. The dose conversion coefficients for children published by the International Commission on Radiological Protection (ICRP) are used to calculate the radiotoxicity of spent fuel for different age groups. Again, the focus is on how this adjustment in assumptions changes the conclusions that can be drawn from the figure.