Current trend of researches on 14C transfer modelling in human and livestock

Safety of nuclear energy is one of the major tasks in the debate nowadays on future energy resources in the context of climate change and resource vulnerability. There are needed robust dosimetric models for humans as well as reliable predictions of radionuclide dynamics in farm animals and crops and wild species. 14C and 3H need special consideration in the context of waste safety, heavy water reactors and the proposed fusion reactor, as well as fuel reprocessing plants. 14C is unusual, in that it is isotope of macro-elements which form the basis of animal tissues and feed. There are few published values describing the transfer of 14C from feed to animal derived food products under steady state conditions. We recommend that the concentration ratio between feed and animal product activity concentrations can be used as it is less variable than the transfer coefficient. As a result of the close biological and chemical link between OBT and organic carbon, the biological half-times of 14C and 3H in organic forms are likely to be the same and models for 3H and 14C share common parameters. We have recently shown that the currently used single organic compartment models, as used in the ICRP approach, are not appropriate to describe the dynamics of 14C and 3H in mammals as they underestimate long term retention considerably. After an overview of present models in literature, we concentrate on the new developed metabolic model for mammals and test examples (no calibration) are presented for rat, sheep and cow milk. The dosimetric implication of the model will be investigated for further model extension. (author)