Accumulation of organically bound tritium in Arabidopsis thaliana cultivated in soil containing tritiated water

Tritium is essential for generating D-T reactions in a fusion reactor, which is expected to be used as a next power generation technology. If tritium is released into the environment due to unexpected accidents, it may transfer to human body through plants eventually. Therefore, it is needed to understand the behavior of tritium in plants from the viewpoint of radiation protection. In this study, an airtight plant cultivation system was constructed and Arabidopsis thaliana was cultivated in the humus supplied with tritiated water. Then, the amount of tritium accumulated in the collected samples was investigated by water immersion, drying, isotope exchange and combustion. It was suggested that the mass transfer rate of exchangeable organically bound tritium to tissue free water by the isotope exchange reaction was faster than the mass transfer rate of tissue free water tritium to the surrounding water. The percentage of non-exchangeable organically bound tritium was in the range from 2.5 to 9.0 % to the total amount of tritium accumulated.