C-14 is an important radionuclide for safety assessment studies associated with operational discharges as well as radioactive waste disposal. As C-14 has almost identical chemical characteristics to stable carbon, which is a fundamental component of organic molecules, C-14 requires special consideration when assessing potential consequences of releases to the biosphere. Over the past fifteen years, a sequence of BIOPROTA workshops, model-data and model-model comparison exercises have contributed to both improvements to, and helping to build confidence in, the representation of C-14 in assessments covering both short and long-term releases to the biosphere. This study will address the transport and distribution of C-14 in terrestrial, freshwater and marine environments following its discharge into those environments either in effluents from operating facilities or, primarily, because of releases from geological disposal facilities for solid radioactive wastes.
Following discharge, C-14 is transported through the environment by a wide variety of aeolian, fluvial and biotic processes, and becomes integrated into the biogeochemical cycle of stable carbon. This results in the various carbon ‘pools’ in the environment exhibiting time-dependent changes in the specific activity (or C-14:C-12 ratio) of their contents. However, in many assessment studies, this complex pattern of changes is simplified to a model in which the specific activity of all environmental media of relevance is assumed to be the same (or related through fixed ratios) and independent of time. This study, which began in 2021 and will conclude in 2022, aims to investigate the adequacy of this approach and identify situations in which it does not provide an adequate basis for radiological impact assessment and provide proposals for alternative modelling approaches that are as simple and transparent as possible, but not to the degree that potentially important processes are either not represented or are represented unduly simplistically.
The work programme includes: