Validating the application of the revised ICRP’s biokinetic models for organic ¹⁴C and organically bound tritium to members of the public

In 2016, the International Commission on Radiological Protection (ICRP) has revised the biokinetic models for carbon and tritium in Publication 134 to calculate the dose coefficients of these radionuclides for workers. The following publication for members of the public is now in the process of revising by the ICRP. According to the draft manuscript published for consultation in 2023, the same models will be adopted for members of the public, although the parameters in these models are not corroborated by the metabolic data of radionuclides in foods. Dose coefficients for adult were estimated using modified models developed in this study to validate the application of the revised ICRP models to members of the public. In the modified models, several parameters were replaced based on the metabolic data of these nuclides in foods and compartments of radio-insensitive tissues were introduced. For these estimations, we utilised an inhouse program for internal-dose calculation developed by the Japan Atomic Energy Agency. The estimated dose coefficient values for ingestion of organic¹⁴C and organically bound tritium (OBT) ranged from 3.2 × 10^-11-7.6 × 10^-11Sv Bq^-1and from 3.5 × 10^-11-5.4 × 10^-11Sv Bq^-1, respectively. We concluded that the dose coefficient value of 1.6 × 10^-10Sv Bq^-1obtained by the revised ICRP's carbon model was conservative for members of the public, while the value of 5.1 × 10^-11Sv Bq^-1for OBT was appropriate.