Validating the application of the revised ICRP's biokinetic models for organic C and organically bound tritium to members of the public

Masuda, Tsuyoshi*; Manabe, Kentaro   

If organic compound containing tritium or C-14 is taken into the body, it is metabolised into inorganic matter at a certain rate and excreted quickly. On the other hand, tritium and C-14 that remain in the organic form have a longer biological half-life than inorganic forms, and therefore contribute more to the radiation dose. For this reason, the metabolic ratio of organic matter is important for dose assessment. However, the International Commission on Radiological Protection (ICRP) sets the metabolic ratio based on animal experiments or carbon mass balance. Therefore, we conducted a dose assessment by referring to the results of measuring the metabolic ratio by orally administering organic matter labelled with deuterium or C-13 to humans. As a result, it was found that the ICRP dose coefficient was appropriate for organic matter containing tritium, but that it was about twice as conservative for organic matter containing C-14.