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Calculation and Use of Internal Dose Coefficients

Monday 02/06/2023

Room: Memorial Union 49

13:15 - 17:00

Chair(s): Derek Jokisch, Caleigh Samuels

MPM-A.1  13:15  Computational Internal Dosimetry 101. Martinez Nicole E *, Clemson University, Oak Ridge National Laboratory; Samuels Caleigh, Oak Ridge National Laboratory; Jokisch Derek, Francis Marion University, Oak Ridge National Laboratory; Leggett Richard, Oak Ridge National Laboratory

“Dosimetry” refers generally to the determination of radiation dose, whether that is by measurement, modeling, or a combination of both, or whether the associated radiological exposure occurs externally or internally. Typically, dosimetry consists of the conversion of activity distributed in the human body (internal exposure) or the environment (external exposure) to tissue-specific absorbed doses (or other similar quantities of interest). This presentation discusses the foundational concepts of the computational models used for this purpose in internal dosimetry, including broad consideration of three primary types of models and associated data sources: (1) biokinetic, which considers where radionuclides move in the body, (2) radiation transport, which models the physical interactions of radiation in the body, and (3) dosimetric, which converts energy deposition into radionuclide-specific doses. Such models are used in the development of national (e.g., EPA Federal Guidance Series) and international (e.g., ICRP Occupational Intakes of Radionuclides series) radiation protection guidance.

MPM-A.2  13:50  Biokinetic Modeling and a New Systemic Model for Radon. Samuels Caleigh*

The biokinetic models applied by the International Commission on Radiological Protection (ICRP) are first-order models that simulate the time-dependent retention and distribution of radionuclides in the human body. These biokinetic models incorporate anatomical and physiological features of the human body but also rely on element-specific empirical data for development of transfer rates between compartments and rates of loss from the body. The biokinetic models are used in combination with nuclear decay data and dosimetric models to develop dose coefficients for radionuclide intake and to reconstruct doses from bioassay or other monitoring data. Currently the ICRP is updating and expanding its age-specific biokinetic models for members of the public in a series of reports called the EIR (Environmental Intake of Radionuclides) series. This presentation describes the basis for an age-specific biokinetic model for inhaled or ingested radon developed by the authors and adopted by the ICRP for use in Part 1 of the EIR series. The radon model incorporates reference age- and sex-specific anatomical and physiological features of the human body and describes the rate of transfer between blood and tissue in terms of physical laws governing the rate of transfer of a non-reactive and soluble gas between materials. Empirical data from the medical literature are used to describe the age-specific rate of expiration of radon.

MPM-A.3  14:25  Using Specific Absorbed Fraction to Compute Dose Coefficients. Jokisch Derek*

The internal dose coefficient provides the desired dose quantity per unit activity of a radionuclide taken into the body. These coefficients are used in prospective radiation protection, retrospective dose assessments, nuclear medicine dosimetry, and for calculating risk coefficients for internal exposures. The quantities involved in the calculation include time-dependent activity distributions, S-coefficients (S-values), specific absorbed fractions, and radionuclide emission properties. This session will describe these quantities which go into computing internal dose coefficients, where they come from, and how they couple together in the calculation. Special attention will be given to the specific absorbed fraction value and the improvements in the most recent ICRP publications.

MPM-A.4  15:00  Break.    

MPM-A.5  15:15  We Have Dose Coefficients. Now What? Fulmer Philip*

Internal dose coefficients are used for a variety of purposes in the workplace. In addition to performing actual dose calculations, the dose coefficients form the basis for making decisions on (a) posting potential airborne areas, (b) frequency and type of bioassay measurements, (c) the need for special bioassay in certain work activities, and (d) the need for respiratory protection in certain work activities. This session will discuss the ICRP’s latest dose coefficients, the tools provided by ICRP in using the coefficients for bioassay interpretation, and the application of the dose coefficients in operational aspects of the health physics program.

MPM-A.6  15:50  The Calculation and Application of Risk Coefficients. Stuenkel David*, U.S. EPA

Risk coefficients provide estimates of the probability of a radiogenic cancer in the population from the inhalation or ingestion of radioactive material per unit intake, or the exposure to radioactive material in the air or on the ground per unit time-integrated exposure. Federal Guidance Report No. 13 and its associated technical products provided morbidity and mortality cancer risk coefficients for approximately 820 radionuclides. Federal Guidance Report No. 16, currently under development, will provide updated risk coefficients for the 1,252 radionuclides of 97 elements included in International Commission on Radiation Protection (ICRP) Publication 107, “Nuclear Decay Data for Dosimetric Calculations”. These risk coefficients are based on dosimetry (i.e., specific absorbed fractions and biokinetic models); age-dependent intakes of air, food, and drinking water; and risk models. This session provides an overview of the quantities and methods used to calculate risk coefficients, as well as a discussion of how to apply risk coefficients to estimate the risks for acute and chronic intakes and exposures.

MPM-A.7  16:25  Introducing DEPDOSE, a Tool to Calculate Dose Coefficients to Members of the Public for Radioactive Aerosols. Klumpp John A*, Los Alamos National Laboratory; Bertelli Luiz, Los Alamos National Laboratory; Nelson Matthew, Los Alamos National Laboratory; Brown Mike, Los Alamos National Laboratory; Wedell Liam, Los Alamos National Laboratory; Eckerman Keith, Los Alamos National Laboratory

This presentation describes DEPDOSE, an open-source computer application which combines the KDEP respiratory tract deposition software with committed equivalent dose coefficient tables from the DC_PAK internal dosimetry package. DEPDOSE allows the user to rapidly produce tables of dose coefficients to workers and members of the public inhaling a precisely defined, user-specified aerosols using the ICRP 60 series methodology. Combined with a plume dispersion modeling system such as QUIC, this makes it possible to predict radiation doses downstream from an accidental or intentional release of radioactive materials. For this work, a radioactive plume was calculated to members of the public downstream from a plausible release of radionuclides into the atmosphere.

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