Abstract: One new detailed biokinetic model for systemic iodine has been published in the International Commission on Radiological Protection (ICRP) Publication No. 137, which will lead to the calculation results of retention and excretion based on the new model that differs from the old iodine model. This paper aims to quantitatively analyze the difference in the calculation results of the old and new iodine system models, to provide a reference for the accurate assessment of radioactive iodine-induced internal exposure in China. In this paper, the matrix algorithm was used to build a calculation model of radioactive iodine based on ICRP publications, and the retention of radioactive iodine (including I-125, I-129, I-131) in thyroid and daily urine after intake through different ways (inhalation, ingestion and intravenous injection) was systematically analyzed. In addition, considering that the new model divides the liver and kidney parts that were not in the old model, the retention of radioactive iodine in these organs is also calculated and analyzed in this paper. The results showed that there were significant differences in the calculation results of radioactive iodine in the thyroid gland and daily urination calculated by the old and new models. But compared with ingestion and injection, the inhalation method could cause the largest difference in the calculation results.In the new model, the calculation results of retention in liver and kidney were different, but the variation tendency was similar.

Key words: biokinetic model for systemic iodine, retention, excretion, ICRP Publication No.137