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Estimation of Radionuclide Biokinetics Dependence on Intake Conditions for Internal Exposure

13 th International Congress of the International Radiation Protection Association. TS2b.8. Estimation of Radionuclide Biokinetics Dependence on Intake Conditions for Internal Exposure. Kotaro TANI 1 , Yuki FUJIMICHI 1 , Satoshi IWAI 2 , Toshiso KOSAKO 1 1 The University of Tokyo

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Estimation of Radionuclide Biokinetics Dependence on Intake Conditions for Internal Exposure

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  1. 13thInternational Congress ofthe International Radiation Protection Association TS2b.8 Estimation of Radionuclide Biokinetics Dependenceon Intake Conditions for Internal Exposure Kotaro TANI1,Yuki FUJIMICHI1, Satoshi IWAI2, Toshiso KOSAKO1 1The University of Tokyo 2Japan Nuclear Technology Institute 14th,May, 2012

  2. Internal contamination of public • Internal contamination of public by… • Inhalation in radioactive clouds • Inhalation of resuspended radioactivity from soil • Ingestion of food or drinking water ⇒ Some pathwaysandover a long period • I-131 and Cs-137 mainly became a problem in the Chernobyl and Fukushima accident Inhalation Ingestion Lung Intestines

  3. Biokinetics and internal dose evaluation • Activity in the specific organ by in vivo measurement • Thyroid for I-131 • Whole body for Cs-137 • Total intake • By the retention function • Internal dose • By the dose coefficient (Sv/Bq) Inhalation Ingestion Thyroid Lung Intestines Urine Faeces

  4. Problem and purpose • Problem • Acute inhalation (general worker’s intake situation) has been mainly assumed in dose evaluations ⇒ Retention function may change due to the difference in intake situations • Purpose • Analyze the retention function of I-131 and Cs-137 based on assuming some intake conditions • Discuss about the application of biokinetics to internal dose evaluation

  5. Biokinetic models Human Respiratory Tract Model (ICRP Publ. 66) Human Alimentary Tract Model (ICRP Publ. 100) I1 Modelization Inhalation Inhalation Ingestion k1,2 C1 k1,3 C2 Esophagus Trachea Ingestion C3 k2,3 k3,4 Lung Stomach Lapsed day Lung C4 Intestines Compartments Runge-Kuttamethod Blood Intestines Thyroid Urine Feces Urine Feces Metabolic Model (ICRP Publ. 67, 68)

  6. Conditions of biokineticanalyses • Intake conditions • Inhalation or ingestion • Acute or continuous intake • Acute inhalation • Continuous inhalation • Acute ingestion • Continuous ingestion • Basic conditions • I-131 • Type F, f1 = 1.0 • AMAD = 1µm • Metabolic parameters for 1 year old child • Cs-137 • Type F, f1 = 1.0 • AMAD = 1µm • Metabolic parameters for adult

  7. Thyroid retention functions (I-131) Thyroid remains rate [%]

  8. Whole body retention function (Cs-137) Whole body remains rate [%]

  9. Separation of inhalation and ingestion Percentage of remains rate of nasal pathway and thyroid after inhalation [%] Nasal pathway Thyroid Measure the activities of nasal pathway and thyroid (MN, MT) Estimate thyroid activities caused by inhalation (AINH) and ingestion (AING) Evaluate internal dose separately

  10. Conclusion • In internal dose evaluation, it is important to consider the biokinetics of intake conditions • Thyroid retention functions of I-131 vary 0.65 to 3.1times on the range from 1 day after to 30 days after, although whole body retention functions of Cs-137 are almost same (1.0-1.2 times) • Considering the I-131 deposition to nasal pathway, thyroid deposition activity can be separated by inhalation and ingestion and evaluated internal dose separately

  11. The Human Respiratory Tract Model

  12. The Human Alimentary Tract Model

  13. Biokinetic Model (Iodine)

  14. Biokinetic Model (Cesium)

  15. Visualization of Biokinetics (I-131) 5 hours 10 15 20 24 Inhalation Nasal pathway Thyroid Blood Ingestion Ingestion

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