ORGANICALLY BOUND TRITIUM FORMATION AND TRANSLOCATION IN CROP PLANTS - MODELING AND EXPERIMENTAL RESULTS

For estimations of the ingestion dose of tritium the dynamic behaviour of organically bound tritium (OBT) is studied in the framework of saf ety considerations for the nuclear fusion technology. In diet relevant plants, such as wheat, the formation of OBT and the subsequent transl ocation into the seeds till the time of harvest have been investigated in chamber experiments. Sets of field data on photosynthesis transcri ption and stomatal resistances at individual plants during several veg etation periods have been collected by gas exchange measurements. Thes e data were used to test the recently developed model 'Plant-OBT'. The paper analyses the results of comparsions between calculated and obse rved tritium concentrations in wheat plants after short-term exposures to atmospheric tritated water (HTO). While the final OBT concentratio ns in the grains can be simulated sufficiently the modelling of the OB T formation and turnover processes in the leaves seems unsatisfactory so far. The unsolved problems in the recent OBT modelling approach are discussed.