TPM-D - Internal Dosimetry Centennial Ballroom 300D 14:30 - 17:30
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| Chair(s): Sara Dumit
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TPM-D.1
14:30 Revision of the ICRP 141 Pu Systemic Model to Incorporate the HAT Model and the Hepatic Portal Vein DJ Strom*, Washington State University
; M Avtandilashvili, Washington State University; AS Felsot, Washington State University; SM McComish, Washington State University; M Šefl, Washington State University; G Tabatadze, Washington State University; SY Tolmachev, Washington State University
Abstract: The human liver typically receives about 25% of systemic blood circulation. The liver is unusual in that it has two separate input streams of blood: the hepatic artery supplies oxygenated blood and about 20% of blood flowing into the liver; and the hepatic portal vein brings nutrient-rich oxygen-depleted blood from the alimentary tract and associated secretory organs, and accounts for about 80% of the blood flowing into the liver. After the liver processes nutrients and other material from the digestive system, the streams combine and exit the liver via the hepatic vein. While the ICRP 100 human alimentary tract (HAT) model explicitly includes the HPV, the ICRP 141 models for actinides and for plutonium do not, and in fact show uptake from the small intestine directly to blood. The fact that all blood from the HAT first passes through the liver before mixing with systemic circulation is critical for understanding the metabolism and toxicity of chemicals, as well as understanding the processing of all materials entering from the gut. The liver selectively removes plutonium from blood and retains a significant fraction of a body’s systemic Pu. This paper proposes a modification to the ICRP 141 Pu systemic model to harmonize the entire ICRP 100 HAT model with the systemic model, explicitly modeling the first stop in the liver for all blood containing Pu. Since it is doubtful whether existing data can be used to determine all the new model parameters, some simplification may be required, but the product of such efforts must retain the fundamental fact that any uptake of Pu from the HAT first visits the liver. It is unknown if this anatomically and physiologically improved model would provide a better understanding of Pu biokinetics, and we pose several questions regarding how inclusion of the HPV may impact the kinetics of Pu in the liver.
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TPM-D.2
14:45 Misclassification of Causes of Death Among USTUR Registrants: Death Certificates vs. Autopsy Reports SL McComish*, U.S. Transuranium and Uranium Registries, Washington State University
; X Liu, Weill Cornell Medicine; FT Martinez, U.S. Transuranium and Uranium Registries, Washington State University; JY Zhou, U.S. Department of Energy; SY Tolmachev, U.S. Transuranium and Uranium Registries, Washington State University
Abstract: The USTUR performs autopsies on each of its Registrants as a part of its mission to follow up occupationally-exposed individuals. This provides a unique opportunity to explore death certificate misclassification errors among this small population of former nuclear workers. Underlying causes of death (UCOD) from death certificates and autopsy reports were coded using the 10th revision of the International Classification of Diseases (ICD-10). These codes were then used to quantify misclassification rates among 240 individuals for whom both death certificates and autopsy reports were available. ICD-10 categorizes diseases using 22 chapters. Death certificates incorrectly identified the UCOD ICD-10 disease chapter in 28.3% of cases. The misclassification rates for the most common disease chapters were: 13.8% neoplasms, 15.0% circulatory, 64.0% respiratory, 23.5% external causes, and 40.0% nervous system. Death certificates often include fields that indicate if the autopsy report was used to determine the cause of death. The misclassification rate was 18.4% for death certificates that used the autopsy report to determine the UCOD, 38.0% for those that did not, and 23.1% for those where use was unknown. The difference between the misclassification rate for death certificates that used the autopsy report to determine the UCOD and those that did not was statistically significant.
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TPM-D.3
15:00 Dose Assessment following Pu-238 Glovebox Breach at Los Alamos National Laboratory JA Klumpp, Los Alamos National Laboratory
; L Bertelli, Los Alamos National Laboratory; S Dumit, Los Alamos National Laboratory; D Poudel*, Los Alamos National Laboratory
Abstract: Recently, a glovebox breach occurred at the Los Alamos National Laboratory plutonium facility which impacted multiple employees. An individual working in a Pu-238 glovebox removed his hands from the gloves and was in process of securing the gloves when a portable continuous area monitor (CAM) in the room alarmed. At the sound of the alarm, the individual, exited to the corridor immediately outside of the room. However, there were fourteen other individuals working in the room, several of whom did not hear the first alarm. Minutes later, all of the other CAMs alarmed and all of the employees had vacated the room. All of the employees were issued urine bioassays, several of which detected plutonium. Because the solubility characteristics of the released material were not known, it was not immediately possible to place reasonable upper bounds on the dose. This presentation discusses the incident and subsequent dose assessment.
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TPM-D.4
15:15 Modeling of a plutonium-238 inhalation incident treated with DTPA at Los Alamos National Laboratory S Dumit*, Los Alamos National Laboratory
; G Miller, Retired; D Poudel, Los Alamos National Laboratory; L Bertelli, Los Alamos National Laboratory; JA Klumpp, Los Alamos National Laboratory
Abstract: Accidental inhalation of plutonium at the workplace is a non-negligible risk, even when rigorous safety standards are in place. The intake and retention of plutonium in the human body may be a source of concern. Thus, if there is a suspicion of a significant intake of plutonium, medical countermeasures such as chelation treatment may be administered to the worker. The present work aimed to interpret the bioassay data of a worker involved in an inhalation incident due to a glovebox breach at Los Alamos National Laboratory’s plutonium facility. The worker was treated with intravenous injections of calcium salts of diethylenetriaminepentaacetic acid (DTPA), as an attempt to eliminate plutonium from the body and, therefore, reduce the internal radiation dose. It is well known in the internal dosimetry field that the administration of chelation treatment poses additional challenges to the dose assessment. Hence, a recently developed chelation model was used for the modeling of the bioassay data. The objectives of this work are to describe the incident, model the chelation-affected and non-affected bioassay data, estimate the plutonium intake and assess the internal radiation dose.
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TPM-D.5
15:30 BREAK
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TPM-D.6
15:45 Tools for effective communication with radiation workers: Improving how to listen, relate, empathize, and communicate internal doses S Dumit*, Los Alamos National Laboratory
; T Matta, Oak Ridge National Laboratory; JA Klumpp, Los Alamos National Laboratory
Abstract: As Occupational Internal Dosimetrists, it is part of our job to communicate internal doses and explain internal dosimetry concepts to radiation workers and regulators when necessary. Thus, it is in our best interest to improve our communication and interpersonal skills to perform our job with excellence. In this study, some tools for effective communication with radiation workers and interested parties are provided. We interviewed a total of eleven experienced internal dosimetrists, who voluntarily agreed to share their experiences and provide relevant advice to the current and next generations of occupational internal dosimetrists. In addition, relevant teachings from the literature were compiled in order to bring knowledge from the science of relating and communicating to the internal dosimetry field. Although an extensive amount of information could be presented, the focus of this work is on ways to improve how to listen, relate, empathize, and communicate internal doses at work. This study aims to share the experts’ insight collected during the interviews and also to provide the audience with resources on how to apply the concepts into their daily work.
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TPM-D.7
16:00 Improvements In Collecting Performance Statistics For Hanford In Vivo Counting Systems A Lungu*, Hanford Mission Integration Solutions (HMIS)
; LJ Stamper, Hanford Mission Integration Solutions (HMIS); CL Antonio, Hanford Mission Integration Solutions (HMIS)
Abstract: The Department of Energy’s (DOE) standard, DOE-STD-1112-2019 Department of Energy’s Laboratory Accreditation Program (DOELAP) for Radiobioassay, requires testing to validate the continued performance of a direct radiobioassay measurement system. The America National Standard Institute (ANSI) N13.30-2011 Performance Criteria for Radiobioassay, provides acceptance criteria to meet the DOELAP performance testing requirements for accuracy, false negatives and false positives. However, neither standard provides rigid instructions on how to perform the tests, instead allowing each facility to determine the best implementation available to them. Many in-vivo monitoring facilities do not have access to multiple sources with various activities to perform each of these tests but instead have on hand one source activity for each radionuclide they monitor. This presents problems for labs to accomplish the performance tests without spending significant resources on multiple sources, but options exist to accomplish the testing. This presentation describes the procedure used at Hanford to meet the requirements for quality control and blind testing programs. Statistics generated include root mean square, minimum detectable activity (MDA), decision level (DL), sensitivity evaluations, false positive and false negative rates.
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TPM-D.8
16:15 A Novel Biokinetic Model for Chromium and its Intent for Health Physics Applications MM Hiller*, CheMin GmbH
; RW Leggett, Oak Ridge National Laboratory
Abstract: A novel biokinetic model describing the behavior of radioactive chromium in the human body was developed by the authors of this presentation (Hiller and Leggett, 2020). This presentation describes the model and discusses the usefulness and properties of the model that are of interest for radiation protection and health physics applications.
The model describes the behavior of chromium in both common valence states, tri- and hexavalent, in the human body. After deposition in the human body, Cr(VI) is largely reduced to Cr(III) over a period of hours. Chromium has five radioisotopes with a half-life of over a few minutes with 51Cr having the longest half-life of 27.7 d.
The model for systemic chromium is composed of several interacting sub-models, with the systemic Cr(III) sub-model describing the distribution, retention, and excretion of Cr(III) following its injection or absorption into blood. To describe the reduction of Cr(VI) to Cr(III), Cr(VI) is modeled as being fed into a separate systemic sub-model that transfers into the systemic Cr(III) sub-model after the reduction of Cr(VI) to Cr(III) in red blood cells, liver, kidneys and other compartments. A generic respiratory tract model was developed to describe the fate of inhaled tri- or hexavalent chromium. The Human Alimentary Tract Model (HRTM) of the International Commission on Radiological Protection (ICRP) describes the alimentary transport and absorption of ingested forms of chromium, or chromium moving from the respiratory tract to the alimentary tract. Following deposition of inhaled chromium in the respiratory tract, absorbed Cr(III) and Cr(VI) are assigned to blood pools in the Cr(III) and Cr(VI) sub-models, respectively. Ingested Cr(VI) is assumed to be reduced to Cr(III) in the stomach and partly absorbed into the systemic Cr(III) sub-model.
The Cr(III) sub-model was adopted in ICRP Publication 151 (Occupational Intakes of Radionuclides (OIR), part 5) for application to occupational intakes of all forms of radioactive chromium, considering that internally deposited Cr(VI) is soon converted to Cr(III).
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TPM-D.10
16:30 Review of Uncertain Parameters in ICRP 66 Human Respiratory Tract Model (HRTM) DE Margot*, Georgia Institute of Technology
; AE Kalinowski, Sandia National Laboratories; LD Cochran, Sandia National Laboratories; CM Jelsema, Sandia National Laboratories; SA Dewji, Georgia Institute of Technology
Abstract: For internal dosimetry, International Commission on Radiological Protection (ICRP) Publication 66 outlines the human respiratory tract model (HRTM) for the inhalation pathway. In the scope of dose projections for protection of the public and workers in a nuclear/radiological emergency, computation of inhalation dose coefficients from the internalization of source radionuclides depend on a plurality of variables, including but not limited to particle size, deposition, and clearance. Reference biokinetic transfer coefficient and dosimetric absorbed fraction parameters are used to compute internal dose coefficients using International Commission on Radiological Protection (ICRP) Publication 72 data, stemming from the ICRP Publication 66 HRTM. However, source-specific variables in the assessment of uptakes for consequence management necessitate an expansion beyond reference biokinetic and dosimetric parameters.
A joint National Nuclear Security Administration-supported effort between Georgia Tech and Sandia National Laboratories is developing the methodology and framework to quantify the uncertainty in inhalation dose coefficients derived from the HRTM. This presentation will provide an analysis of the parameters defined as uncertain within the HRTM, as well as the distributions currently used by various studies to solve the model. An in-depth review of the softwares currently employing the HRTM and the distributions utilized by them, as well as a review of constituents to the model that ICRP outlines within and beyond Publication 66, including uncertainty from data sources, will be used to inform the development of an HRTM modeling software and uncertainty distributions. This parametric analysis serves as a basis for continuing work in quantification of dose coefficient uncertainty as it pertains to radiological dose assessment so as to ensure appropriate public and worker protection emergency response decisions are defensible.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-1203 A
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TPM-D.9
16:45 Uncertainty Propagation in ICRP 66 Human Respiratory Tract Model (HRTM) LD Cochran*, Sandia National Laboratories
; CM Jelsema, Sandia National Laboratories; AE Kalinowski, Sandia National Laboratories; DE Margot, Georgia Institute of Technology; SA Dewji, Georgia Institute of Technology
Abstract: For internal dosimetry, International Commission on Radiological Protection (ICRP) Publication 66 outlines the human respiratory tract model (HRTM) for the inhalation pathway. The model has many parameters, covering particle deposition, particle clearance, and dosimetric values. The parameters are distinct point values for biokinetic transfer rates, tissue energy absorption fractions, and dosimetric reference values to compute a deterministic dose. A joint National Nuclear Security Administration-supported effort between Georgia Tech and Sandia National Laboratories is developing the methodology and framework to quantify the uncertainty in inhalation dose coefficients derived from the ICRP 66-based HRTM that are used in Turbo FRMAC for consequence management dose projections. This uncertainty information is needed in order to enable full uncertainty analyses for derived response level calculations in Turbo FRMAC.
This presentation will provide a brief overview of the probability distributions of various HRTM input variables and the statistical methods used to characterize uncertainty in inhalation dose coefficients. The dose coefficient uncertainty quantification framework and inhalation dose coefficient probability distributions resulting from this work will be useful for uncertainty analyses by the broader radiological dose assessment community, but are critical to understanding the uncertainty associated with dose projections for nuclear/radiological emergencies and therefore ensuring that appropriate public and worker protection decisions are supported by defensible analysis.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-1205 A
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TPM-D.11
17:00 It Takes Energy to Calculate Dose MG Stabin*, NV5/Dade Moeller
Abstract: Dose calculations are standardized for radiological and nuclear medicine procedures. Dose is energy/unit mass. We say this is how we protect patients and the public from radiation. ‘Dose’ is a reliable quantity in some, but not all, situations. LD 50/30, skin dose, yes, but in many radiobiological experiments, dose is not meaningful. It appears that energy, not energy per unit mass, is of consequence. Implementing that in a radiation protection paradigm is challenging.
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