Development of carbon-based metabolic models for estimation of doses of organically bound tritium ingested in humans

Abstract

The tritium dose coefficient is an important parameter for assessment of the radiation safety of nuclear facilities such as fusion reactors. The dose coefficient for dietarily derived organically bound tritium (OBT) for members of the public is recommended by the International Commission on Radiological Protection (ICRP), which makes some assumptions regarding the human metabolism in calculating this value, because metabolic data for tritium is limited. The objective of this study is to develop biokinetic models for OBT based on metabolic data to validate the current ICRP-recommended dose coefficient for OBT. In contrast to the ICRP model, by modifying biokinetic models for 14C developed in a previous study, the models described in this study consider OBT activity in a range of nutrient molecules. The dose coefficient estimated using these OBT models ((2.4 ± 0.1) × 10−11 Sv Bq-1) was smaller than the value recommended by the ICRP (4.2 × 10−11 Sv Bq-1), suggesting that human metabolic data support its recommendations. However, the conservative estimation considering uncertainties in metabolic data was significantly larger ((9.7 ± 3.5) × 10−11 Sv Bq-1) than the ICRP recommended value; therefore, further studies to reduce the uncertainties are required.