'Radiotoxicity Index': An Inappropriate Discriminator for Advanced Fuel Cycle Technology Selection - 12276
A radiotoxicity index (RI) is often used as a figure of merit for evaluating for evaluating the attractiveness of employing an advanced fuel cycle (i.e., a fuel cycle that uses some combination of separations and other reactor technologies, such as fast reactors), rather than continued use of the current 'once-through' fuel cycle. The RI is calculated by multiplying the amount of every radionuclide found in a waste form for some unit amount of waste times the drinking water dose conversion factor, DCF, for each radionuclide, then summing these together. Some argue that if the RI for an advanced fuel cycle is lower than the RI for a once-through fuel cycle, then implementation of the particular advanced fuel cycle has merit because it reduces the radiotoxicity of the waste. Use of an RI for justifying separations technologies and other components of advanced fuel cycles is not only inappropriate, but can be misleading with respect to judging benefits of advance fuel cycle options. The disposal system, through its use of multiple engineered and natural barriers to migration, eliminates most of the radionuclides contributing to the RI such that additional separations technologies will make little difference to peak dose rates. What must also be considered is the health/dose risk caused to workers and the public by the construction and operation of the separations facility itself. Thus, use of RI may lead to selection of separations technologies that may have a negligible effect on lowering the potential health risks associated with disposal, but will increase real worker and public health risks in the near term. The use of the radiotoxicity index (RI) as a figure of merit for justifying advanced fuel cycles involving separations technologies is not only inappropriate, but can be misleading with respect to judging benefits of advance fuel cycle options. The disposal system, through its use of multiple engineered and natural barriers to migration, eliminates most of the radionuclides contributing to the RI such that additional separations technologies will make little difference to peak dose rates. What must also be considered is the health/dose risk caused to workers and the public by the construction and operation of the separations facility itself. Thus, use of RI may lead to selection of separations technologies that may have a negligible effect on lowering the potential health risks associated with disposal, but will increase real worker and public health risks in the near term. (authors)