Health Phys. Abstracts，Volume 122,Number 2

SEED: An Operational Numerical Tool for Dosimetric Reconstruction in Case of External Radiological Overexposure

F. Entine1,2, G. Garnier2, M. Dondey2, Y. Rizzi1, A. Gobert1, C. Bassinet1, S. Papin2, I. Pennacino2, A. Cazoulat2, J.C. Amabile3, C. Huet1

(1.Institute for Radiation Protection and Nuclear Safety (IRSN), 31 avenue de la Division Leclerc - 92260 FONTENAY-AUX-ROSES, France;2. French Defense Radiation Protection Service (SPRA), 1 bis rue du lieutenant Raoul Batany - CS500 - 92141 CLAMART Cedex, France;3. Armed Forces Medical Service Head quarters (DCSSA), 60 boulevard du général Martial Valin - CS 21 623 - 75509 PARIS Cedex 15, France)

Abstract:In the event of a radiological accident involving external exposure of one or more victims and potential high doses, it is essential to know the dose distribution within the body in order to sort the victims according to the severity of the irradiation and then to take them to the most suitable medical facilities. However, there are currently few techniques that can be rapidly deployed on field and capable of characterizing an irradiation. Therefore, a numerical simulation tool has been designed. It can be implemented by a doctor/physicist pairing, projected within a limited time as close as possible to the irradiation accident and emergency response teams. Called SEED (Simulation of External Exposures & Dosimetry), this tool (dedicated to dose reconstruction in case of external exposure) allows a rapid modeling of the irradiation scene and a visual exchange with the victims and witnesses of the event. The user can navigate in three dimensions in the accident scene thanks to a graphical user interface including a “first person” camera. To validate the performance of the SEED tool, two dosimetric benchmarking exercises were performed. The first consisted in comparing the dose value provided by SEED to that given by a reference calculation code: MCNPX. The purpose of the second validation was to perform an experiment irradiating a physical dummy equipped with dosimeters and to reconstruct this irradiation using SEED. These two validation protocols have shown satisfactory results with mean difference less than 2% and 12% for the first and second exercises, respectively. They confirm that this new tool is able to provide useful information to medical teams in charge of dosimetric triage in case of a major external exposure event.

Keywords: accidents; handling; computer calculations; dose assessment; Monte Carlo

Health Phys. 122(2):271-290; 2022

WorldAtmosphericCO2,Its14CSpecificActivity,Non-fossilComponent,AnthropogenicFossilComponent,andEmissions(1750-2018)

Kenneth Skrable, George Chabot, Clayton French1

(1.University of Massachusetts Lowell, 1 University Avenue, Lowell, MA 01854)

Abstract:After 1750 and the onset of the industrial revolution, the anthropogenic fossil component and the non-fossil component in the total atmospheric CO2concentration,C(t), began to increase. Despite the lack of knowledge of these two components, claims that all or most of the increase inC(t) since 1800 has been due to the anthropogenic fossil component have continued since they began in 1960 with “Keeling Curve: Increase in CO2from burning fossil fuel.” Data and plots of annual anthropogenic fossil CO2emissions and concentrations,C(t), published by the Energy Information Administration, are expanded in this paper. Additions include annual mean values in 1750 through 2018 of the14C specific activity, concentrations of the two components, and their changes from values in 1750. The specific activity of14C in the atmosphere gets reduced by a dilution effect when fossil CO2, which is devoid of14C, enters the atmosphere. We have used the results of this effect to quantify the two components. All results covering the period from 1750 through 2018 are listed in a table and plotted in figures.These results negate claims that the increase inC(t) since 1800 has been dominated by the increase of the anthropogenic fossil component. We determined that in 2018, atmospheric anthropogenic fossil CO2represented 23% of the total emissions since 1750 with the remaining 77% in the exchange reservoirs. Our results show that the percentage of the total CO2due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming.

Keywords:14C; emissions; atmospheric; environs; radiation protection

Health Phys. 122(2):291-305; 2022

AModificationtotheSituation-basedSchemeforSortingExposuresProposedinICRPPublication103

Yun C. Chi1

(1.Atomic Energy Council, New Taipei City, 23452 Taiwan, Republic of China (retired))

Abstract:The International Commission on Radiological Protection (ICRP) issued its current recommendations in 2007, introducing an evolution from a previously process-based protection approach (practices and interventions) to a situation-based approach (planned, existing, and emergency). In most countries, radiation protection standards are generally in line with the new recommendations by the ICRP. Unfortunately, in many cases, situations involving sources of natural or artificial origin may be in a state of contradiction. Logical incompleteness and unsoundness in the framework of exposure situations can be found in current ICRP recommendations. There are situations that do not readily fall into any category. To contribute to a more reasonable situation-based approach for the radiological protection community, we recommend here a possible framework of exposure situations, i.e., planned, unplanned, and naturally occurring, that forms one coherent system. We believe this system will provide increased clarity that will help resolve possible sorting problems.

Keywords: practices and interventions; justification; optimization; dose limits; radiation exposure; ALARA; duality; TENORM

Health Phys. 122(2):306-312; 2022

EstimationoftheThyroidEquivalentDosestoResidentsinAreasAffectedbythe2011FukushimaNuclearDisasterDuetoInhalationof131IBasedonTheirBehavioralDataandtheLatestAtmosphericTransportandDispersionModelSimulation

Eunjoo Kim1, Yu Igarashi1,2, Shozo Hashimoto1, Kotaro Tani1, Munehiko Kowatari1, Tetsuo Ishikawa3, Osamu Kurihara1

(1.National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba 263-8555, Japan;

2.The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-city, Chiba 277-8581, Japan;

3.Fukushima Medical University, 1-Hikarigaoka, Fukushima-city, Fukushima 960-1295, Japan)

Abstract:It has been challenging to obtain reliable estimates of thyroid equivalent doses (TEDs) to residents involved in the 11 March 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident because of the shortage of direct human measurements associated with131I, the largest contributor to the dose of concern. The present study attempted to perform the estimation of the TEDs by inhalation of131I to residents from Namie-town, one of the most radiologically-affected municipalities, by means of the latest atmospheric transport and dispersion model (ATDM) simulations with the Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) ver. 2, coupled with personal behavioral data containing the history of the whereabouts of individuals shortly after the accident. We analyzed 1,637 residents who underwent direct measurements with whole-body counters several months after the accident and provided their personal behavioral data. We divided the subjects into two groups based on whether the distances between their locations and the FDNPP were >20 km as of 15:00 on 12 March in relation to the timepoint of the hydrogen explosion at the Unit 1 Reactor building. As a result, the 90th percentile TEDs of the 1,249 prompt evacuees and 388 late evacuees were 3.9 mSv (adult)-6.8 mSv (10-y-old) and 24.1 mSv (adult)-35.6 mSv (5-y-old), respectively, excluding 16 persons whose TEDs exceeded 50 mSv. The 90th percentile (median) TEDs to 1-y-old children (not included in the subjects) for the prompt and late evacuation groups were 8.1 (1.0) mSv and 36.3 (19.7) mSv, respectively. Additionally, this study provided the evidence to support the view that the explosive event at the Unit 1 Reactor building on the afternoon of 12 March 2011 could have caused the critical group among Namie-town’s residents, whereas the largest release event on 15 March gave relatively small doses to the residents because their exposure took place mostly at sites that were distant from the FDNPP. However, the present dose estimation has potentially large uncertainty at the individual level; further validations are thus necessary.

Keywords:131I; dose assessment; dosimetry; internal; Fukushima Daiichi

Health Phys. 122(2):313-325; 2022

AdsorptionofPlutoniumontoSeveralNaturalSediments

Jing Yu1,2,3, Qingyu Zhang1

(1.College of Environmental and Resource Sciences of Zhejiang University, Hangzhou, 310058, P. R. China;

2. Hangzhou International Urbanology Research Center & Zhejiang Urban Governance Studies Center, Hangzhou, 311121, P.R. China;

3. Zhejiang Police Vocational Academy, Hangzhou, 310018, P.R. China)

Abstract:The adsorption of plutonium (Pu) onto several natural sediments was studied using batch experiments to determine the different factors influencing Pu adsorption. These factors include the possible effect of different methods for adding Pu solution, the initial oxidation state of Pu, the particle size of the sediments, the pH, and the ionic strength of solution. The method used for adding Pu solution greatly influenced the species of Pu in sediment-groundwater systems and the adsorption behavior of Pu onto the sediments. Initial oxidation state of Pu, clay mineral content, particle size of sediment, pH, and ionic strength all appear to impact adsorption. The sediments preferred to adsorb Pu(IV) rather than Pu(V). The adsorption of Pu depended on the particle size and clay mineral content of the sediments; the higher clay mineral content and the smaller particle size, the more adsorption for Pu. The insoluble species of Pu formed in sediment-groundwater systems at pH 9.3 resulted in the decrease of adsorption capacity. The adsorption capacity increased with pH increasing at pH<9. Ion exchange was the dominant mechanism for Pu adsorption onto the sediments at pH<7.5. It appeared that the ionic strength had a stronger influence on adsorption capacity than pH.

Keywords: adsorption; contamination; plutonium; sediments

Health Phys. 122(2):326-332; 2022

CompensatoryConsiderationsforRadiologicalEmergencyResponseandPublicProtectiveActionsduringtheCOVID-19Pandemic

Angela E. Leek1, Jeffrey D. Semancik2

(1.Angela E. Leek, CHP, Bureau Chief, Radiological Health, Iowa Department of Public Health;

2. Jeffrey D. Semancik, Radiation Protection Division, Connecticut Department of Energy and Environmental Protection)

Abstract:Epidemiological evidence and models have demonstrated that the current COVID-19 pandemic introduces a significant public risk to implementing large-scale community evacuations in response to disasters. While guidance documented in the US Environmental Protection Agency Protective Action Guidance (PAG) Manual is widely accepted as the standard basis for public and emergency worker protective actions for a radiological emergency, it is based primarily on assessing the risks associated with the radiological factors alone. However, as demonstrated in response to the nuclear incident in Fukushima, these events seldom occur in isolation from other risk-inducing events. Today, the COVID-19 pandemic represents a significant public health risk that must also be considered alongside the radiation risks in determining appropriate public and emergency worker protection action decisions. In particular, the significant public health risks associated with community transmission and mortality of COVID-19 challenge our most familiar and rehearsed radiological response strategies. The 1992 and 2017 US Environmental Protection Agency PAG manuals allow for considerations in protective action decision making. Much of the radiation emergency response community has been conditioned through decades of structured training and exercises to focus public protection considerations on specific guidelines referenced numerically in tables within the manual. Discussion regarding adjustment of specific PAG values is provided in the footnotes and bases portions of the PAG manual but is often not included in jurisdictional plans or routinely considered in exercises. However, when properly applied, the protective action guidance provides the necessary flexibility for decision-makers to account for additional public health risks or impediments, and jurisdictions can use this guidance to build a more effective response strategy. The authors have applied the full guidance and flexibility provided in the 2017 US Environmental Protection Agency PAG Manual to develop more specific guidance for their respective jurisdictions’ radiation emergency response plans and will outline a process for consideration of protective action decisions to maximize the protection of public health and safety.

Keywords: emergencies; radiological; exposure; population; risk analysis; dose assessment

Health Phys. 122(2):333-340; 2022

ABerger-linearBuildupApproximationforAir

Thomas J. Overcamp1

(1. Environmental Engineering and Earth Sciences, 445 Brackett Hall, Clemson University, Clemson, SC 29634-0919)

Abstract:A combination of the Berger and the linear buildup approximations with the assumption of conservation of energy was fitted for air. The values predicted by this Berger-linear buildup approximation were generally more accurate than those predicted by the Berger approximation alone. Although it is not as accurate as the geometric-progression approximation, the Berger-linear approximation is analytically simpler and makes it easier to find analytical solutions for point source kernel shielding calculations.

Keywords: dose; external; gamma radiation; radiation risk; shielding

Health Phys. 122(2):341-343; 2022

TestingtheNASABioSentinelPixelDosimeterUsingGamma-rayandNeutronSourcesattheLLNLCalibrationLab

J. Homan1, T. C. Lusby1, A. J. Ricco1, J. L. Mintz2, L. A. Braby3, T. Straume1

(1.NASA Ames Research Center, Moffett Field, CA;

2. Lawrence Livermore National Lab, Livermore, CA;

3. Texas A&M University, College Station, TX)

Abstract:The objective of this paper is to evaluate the accuracy of the NASA BioSentinel Pixel Dosimeter (BPD) using gamma-ray and neutron sources in a standard calibration lab. The dosimeter tested here is the ground-based version of the BPD that will be onboard the BioSentinel mission. The BPD was exposed to radiation from60Co,137Cs, and252Cf at selected distances (dose rates) at the Lawrence Livermore National Laboratory (LLNL) Radiation Calibration Laboratory (RCL), and the results were compared with NIST traceable benchmark values. It is recognized that these sources are not analogs for the space environment but do provide direct comparisons between BPD response and well characterized calibration lab values. For gamma rays, the BPD measured absorbed dose agrees to ≤3.8% compared with RCL benchmark values. For neutrons, the results show that the BPD is insensitive, i.e., the BPD detected only the gamma-ray dose component from252Cf. The LET spectra obtained for gamma rays from60Co and252Cf are consistent with expectations for these gamma-ray energies, but the LET spectrum from the137Cs gamma rays differs substantially. The potential causes for this difference are the high dose rate from137Cs and the lower secondary electron energy produced by137Cs gamma rays. However, neither of these results in errors in the absorbed dose. Based on comparisons with NIST-traceable standards, it is evident that the BPD can measure absorbed dose accurately from low LET charged particles. The sensor’s insensitivity to neutrons is unlikely to be a limitation for the BioSentinel mission due to the expected low secondary neutron fluence.

Keywords: TimePix; detector; silicon; dosimetry; space radiation

Health Phys. 122(2):344-348; 2022

A30-YearRadiationSafetyProspectusDescribingOrganizationalDrivers,ProgramActivities,andOutcomes

J. M. Gutierrez, R. J. Emery1

(1.The University of Texas Health Science Center at Houston, Environmental Health & Safety, 6431 Fannin Street, CYF G102, Houston, TX 77030)

Abstract:In 1992, the University of Texas Health Science Center at Houston (UTHealth) Radiation Safety Program began assembling data on a monthly basis that described various program drivers and associated activities. A summary of the data was assembled on an annual basis and shared with the professional health physics community at the 10-y and 20-y intervals. With the inclusion of 1991 data points, three decades (1991 to 2020) of data have now been collected and summarized into an updated program prospectus. The prospectus models a commercial enterprise prospectus provided to potential investors and displays various program indicator parameters. The consistent formatting of the data affords an easily digestible and succinct snapshot of program activities and trends. Various program stakeholder’s feedback regarding this data continues to be well received. Additionally, UTHealth provides increasing support for UT Physicians clinics throughout the greater Houston, Texas area. The prospectus allows succinct description of the drivers of the program, revealed interesting trends, and has identified training needs for both existing personnel and academic programs that support the radiation protection sciences.

Keywords: operational topics; education; health physics; occupational safety; radiation protection

Health Phys. 122(2):352-359; 2022

131IIntakeandRegulatoryComplianceFollowingAdministrationofCapsular131ISodiumIodideforTreatmentofThyroidDisorders

Mary Ellen Jafari1, David S. Paik2

Abstract:Intake of131I by nuclear medicine technologists and physician Authorized Users was evaluated using bioassay data from administration of131I sodium iodide in capsular form during a 5-year period. Maximum estimated annual intake of131I sodium iodide, based on bioassay measurements performed at 24 hours post administration, ranged from 10.9 to 35.6 kBq for all staff. Intake by Authorized Users was higher than that by nuclear medicine technologists due to state requirement for Authorized Users to physically administer therapeutic dosages of radiopharmaceuticals. All intake values were less than 10% of the131I thyroid ALI of 50 microcurie3(1,850 kBq), indicating that monitoring may be discontinued for staff participating in routine administration of131I capsules in which volatilization is not suspected. Elimination of bioassay performance has permitted more flexibility in patient scheduling and improved workflow and efficiency.

Keywords: operational topics;131I; nuclear medicine; thyroid

Health Phys. 122(2):360-364; 2022