Health Phys. Abstracts，Volume 123,Number 4

AerialandCollimatedSensorRadiologicalMappingFollowingDispersalofActivatedPotassium

Bromide

Nathanael Simerl, Jace Beavers, Amir Alexander Bahadori, Walter McNeil1

(1.Alan Levin Department of Mechanical and Nuclear Engineering, Kansas State University, 3002 Rathbone Hall, 1701B Platt Street, Manhattan, KS 66506)

Abstract:The exposure rate distribution was quantified over a site of three activated potassium bromide radiological dispersal device detonations at the Idaho National Laboratory Radiological Response Training Range with unmanned aerial vehicle (UAV) and ground-based methods. Discussions on the methods’ survey characteristics, such as survey time, data spatial resolution, and area coverage, serve to inform those concerned with radiological response and cleanup efforts. Raster scans over the site at 4 ms-1with 6 m between passes at an altitude of 4 m above ground level were executed with a 2.54 cm×2.54 cm×7.62 cm cesium iodide, sodium-doped [CsI(Na)] sensor mounted to a UAV. Exposure rates were calculated from the spectra obtained by the CsI(Na) using a flux unfolding method. Data obtained from the UAV raster were interpolated to produce a continuous exposure rate map across the site. The activity on the ground, inferred from collimated, ground-based sensor (Nomad) measurements in previous work, was used to calculate exposure rate distributions at the same altitude as the UAV-mounted CsI(Na) sensor. Agreement between Nomad and UAV exposure rate distributions is observed at rates up to 1.0 mR h-1after corrections for ground effects were implemented on the Nomad data. Discrepancies in exposure rate contours are present at higher rates, directly above the detonation locations. In areas of high exposure rate gradients, it is anticipated that a faster UAV-mounted sensor and more refined scans by the UAV will improve characterization of the distribution.

Keywords: detector; radiation; monitoring; environmental; surface contamination; surveys

Health Phys. 123(4):267-277; 2022

SpecificAbsorbedFractionsforSpontaneousFissionNeutronEmittersintheICRPReferencePediatricVoxelPhantomSeries

Keith T. Griffin1,2, Keith F. Eckerman3,7, Ryan P. Manger4, Derek W. Jokisch5,7, Wesley E. Bolch6, Nolan E. Hertel1

(1.George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA;2.Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD;3.Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN;4.Department of Radiation Medicine and Applied Sciences, School of Medicine, University of California San Diego, San Diego, CA;5.Department of Physics and Engineering, Francis Marion University, Florence, SC;6.J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL;7.Center for Radiation Protection Knowledge, Oak Ridge National Laboratory, Oak Ridge, TN)

Abstract:Specific absorbed fractions (SAFs) are key components in the workflow of internal exposure assessment following the intake of a radionuclide, allowing quick conversion of particle energy released in a source region to the expected absorbed dose in target regions throughout the body. For data completeness, SAFs for spontaneous fission neutron emitters are currently needed for the recently adopted ICRP reference pediatric voxel phantom series. With 77 source regions within each reference individual and 28 radionuclides decaying via spontaneous fission, full Monte Carlo simulation requires significant computation time. In order to reduce this burden, a novel method for neutron SAF estimation was undertaken. The Monte Carlo N-Particle version 6.1 (MCNP6) simulation package was chosen to simulate the252Cf Watt fission neutron spectrum originating from 15 source regions in each phantom; dose estimation within 41 target tissues allowed for assessment of the SAF value for each source-target pair. For the remaining source regions, chord length distributions were computed using MATLAB code to determine the separation between the source-target pairs within the pediatric phantom series. These distance distributions were used in conjunction with a252Cf neutron dose point kernel calculated in soft tissue, which was modified to account for the source region’s depth from the surface of the body. Lastly, the252Cf SAF dataset was extended to the other 27 spontaneous fission neutron emitters based on differences in the Watt fission spectrum parameters of each radionuclide. This methodology has been shown to accurately estimate spontaneous fission neutron SAFs to within 20% of the Monte Carlo estimated value for most source-target pairs in the ICRP reference pediatric series.

Keywords: internal dose; International Commission on Radiological Protection (ICRP); Monte Carlo; phantom

Health Phys. 123(4):278-286; 2022

ValidationofVirtualMonochromaticImagesandEffectofBodySizeObtainedUsingaRapidkVp-switchingDual-energyComputedTomographySystem:APhantomStudy

Tung-Hsin Wu1, Yun-Lung Ting1,2, Yi-Shuan Hwang3, Chen-Shou Chui2, Cristopher K. J. Lin2

(1.Service Unit, Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan, R.O.C.;2.Service Unit, Department of Radiology, Koo Foundation Sun Yat-Sen Cancer Center, Taipei, Taiwan, R.O.C.;3.Service Unit, Department of Medical Imaging and Intervention, New Taipei Municipal, TuCheng Hospital, New Taipei City, Taiwan, R.O.C)

Abstract:The objective of this paper is to validate virtual monochromatic computed tomography (CT) numbers and the effect of the body size of insert materials in phantoms on the findings of a dual-energy CT scanner. The material inserted in the phantom simulates human organs. This study investigated the effect of different body sizes on CT numbers to understand the accuracy of dual-energy CT. The effect of body size on virtual monochromatic CT numbers was investigated using a QRM phantom. The true monochromatic CT numbers of insert materials were calculated from coefficients obtained using NIST XCOM. The trueZeffvalues were supplied by phantom manufacturers or computed using Mayneord’s equation. The virtual monochromatic CT numbers of insert materials in both the phantoms varied with energy. The CT numbers of materials with aZeffof >7.42 (waterZeff) and <7.42 decreased and increased with energy, respectively. The CT numbers were affected by phantom size as a function of energy. For water, tissues, and air, the CT numbers in the XL phantom were considerably larger than those in other phantom sizes at 40 keV. Body size affected the CT numbers, particularly for the XL size and at low energies. For all materials, the magnitude of difference between the measured and true CT numbers was related to theZeffof the materials, potentially because the photoelectric effect is more prominent at low energies for materials with a higherZeff. The difference in CT numbers appeared to be dependent on position. The true and measuredZeffagreed to within 6% for all the materials except the SR2 brain, for which the discrepancy was 25%.

Keywords: computed tomography; dose assessment; phantom; medical radiation

Health Phys. 123(4):287-294; 2022

In-situFieldGammaSpectrometryinaRadionuclideAirSampler

Luke Lebel, Kyle Barlow, Diana Boulianne, Tony Clouthier1

(1.Canadian Nuclear Laboratories, Chalk River, ON, K0J 1J0, Canada)

Abstract:The work being presented is on the development of a system to measure the speciation of airborne radionuclide emissions from the environment during a nuclear emergency. On-site air sampling measurements that were conducted during the Fukushima Daiichi accident were limited because field teams had to be sent out to run the sampling systems and retrieve the filters for gamma spectrometry analysis in a separate laboratory. The start of air sampling was delayed, and it was impossible for emergency responders to use the information about the airborne radionuclide composition in a timely way. The goal of the current study is to develop a system that could provide live, near real-time information about the concentrations of different radionuclides in the air without having to rely on human intervention. The development of the prototype in the current work is largely being enabled by Cd-Zn-Te spectrometers, which provide reasonably high-resolution spectrometry given that it is a room temperature sensor, and allow the measurements to be conducted in the field. A custom filter cartridge has been designed to hold a pair of aerosol and iodine filters in place while keeping the gamma spectrometers as close as possible in order to obtain high count rate efficiencies. A single cartridge holds both filters and has an internal flow channel directing the air flow between them. The cartridge design also facilitates replacing the filters as the accumulated radioactivity on the filters becomes too high. An automation system can move a filter cartridge from the fresh cartridge storage bank to the sampling location (filtration and gamma spectrometry) and return the used filter cartridge to the used cartridge storage bank. The radionuclide air sampling system prototype has been designed and constructed. It has been tested with fixed sources located on the respective aerosol and iodine filters. The real-time data capture aspects of the system were also demonstrated with a live131I capture experiment. The projected performance of the system during a reactor accident was also simulated, emulating the characteristic detector efficiencies and projecting how the airborne concentrations could be reconstructed. The study has designed and constructed a radionuclide air sampler that could be used for measuring airborne radioactivity in emissions from a nuclear accident. Because the gamma spectrometry measurements are done in situ with good resolution and the system is automated, it would allow data to be transmitted back to an emergency operations center immediately rather than having to wait for additional laboratory analysis.

Keywords: aerosols; air sampling; emergencies; radiological; spectrometry; gamma

Health Phys. 123(4):295-304; 2022

NuclearRadiationKnowledgeandAnxietyLevelsamongResidentsaroundaNuclearPowerPlantinLiaoningProvince,China

Lu Sun1, Baojun Qiao1, Zhongxing Chen1, Shuang Yao1, Baochen Liu1, Di Li1, Zhuo Zhang2, Yong Cui1

(1.Liaoning Provincial Center for Disease Control and Prevention, 54 Wenhua East Road, Shenhe District, Shenyang 110015, People’s Republic of China;2.Shenyang Medical College, 146 Huanghe North Street, Shenyang 110034, People’s Republic of China)

Abstract:Awareness of radiation-related knowledge (RRK) and nuclear energy-related knowledge (NERK) among residents around a nuclear power plant (NPP), as well as their concerns about a NPP, were investigated. A face-to-face survey was conducted among 1,775 residents within 30 km around the NPP in Liaoning Province, China. A single-item Likert scale, Spearman’s/Pearson’s correlation coefficients, Student’st-test, ANOVA, and multiple-linear regression analysis were employed. Awareness of RRK and NERK among residents around the NPP was 27.7% and 36.6%, respectively. The anxiety level of respondents was negatively corelated with the distance from their residence to the NPP and age. Also, 55.6% of respondents thought that the publicity about nuclear energy/NPPs was insufficient, and 82.7% of respondents wanted to know relevant information about NPPs. Awareness of RRK and NERK among residents around the NPP was relatively low, which was related to education, occupation, and income. The anxiety level among residents was related to distance and age. The public was eager to know about RRK and NERK. These findings indicate that the publicity and education of RRK and NERK among residents around the NPP should be strengthened.

Keywords: health effects; nuclear power plant; pubic information; radiation protection

Health Phys. 123(4):305-314; 2022

PilotStudyofThoronConcentrationinanUndergroundThoriumMine

R. Lindsay1, S. Mngonyama1,2, P. Molahlehi1, X. E. Ngwadla1, G. J. Ramonnye1

(1.Department of Physics and Astronomy, University of Western Cape, Private Bag X17 Bellville 7535, South Africa;2.University of Zululand, Department of Physics and Engineering, kwaDlangezwa, 3886, South Africa)

Abstract:The Steenkampskraal mine in the Western Cape Province in South Africa provides some interesting challenges for radiation protection practitioners in view of the high thoron values encountered in this mine. The mine contains high natural thorium concentrations that lead to high thoron activity concentrations, as will be shown in this paper. The influence of ventilation has been studied, and the source term has been investigated by considering the thorium content of the rocks and the thoron exhalation. The thoron activity concentrations are around 10 kBq m-3at a monazite seam, and the thorium exhalation is consistent with these levels. The thoron concentrations can be reduced by ventilation but not eliminated. However, the thoron progeny can probably be reduced dramatically. Issues that affect the thoron levels are also discussed. Further studies are needed, but the thoron may well not be a radiation protection problem despite the high thoron concentrations.

Keywords: monitoring; personnel; occupational safety; thoron; ventilation

Health Phys. 123(4):315-321; 2022

APracticalMethodforEPRDosimetryUsingAlaninePowder

Amna Hassan, Margarita Tzivaki, Lukas Felner, Edward Waller1

(1.Ontario Tech University, Faculty of Energy Systems and Nuclear Science, 2000 Simcoe St. N., Oshawa, ON, Canada)

Abstract:This work investigates alanine powder, an inexpensive and versatile material compared to alanine pellets, as a standardized dosimeter for the alanine-EPR system using a Bruker EMX-Micro spectrometer. The feasibility of this method was investigated, and a calibration curve was produced using 40 dosimeters, which were prepared by tightly packing DL-alanine powder in polypropylene microcentrifuge tubes. The dosimeters were irradiated to doses ranging from 0.2-20 Gy using a60Co source. A dosimeter handling and measurement protocol was established for all dosimeters. The dosimetric signal was evaluated by measuring the peak-to-peak height of the central resonance peak, and the dose response of alanine powder dosimeters showed a linear behavior in the investigated dose range with relative errors below 13%. Measurement repeatability and reproducibility were tested to show the errors associated with sample placement in the cavity and with the overall measurement method, with both tests showing relative errors below 7%. As an inexpensive material compared to pellet dosimeters, alanine powder has a strong potential to be used as a standardized material for radiation dosimetry applications. The scope of this work is to present an effective and comprehensive methodology with accompanying analysis scripts for dosimetry with alanine powder that is useful in a wide range of applications and dose requirements.

Keywords: operational topics; dosimetry; alanine powder; EPR spectroscopy

Health Phys. 123(4):325-331; 2022

StudyofLow-DoseRadiationWorkersIonizingRadiationSensitivityIndexandRadiationDose-EffectRelationship

Gang Liu, Rong Zhang, Ye Li, Xiao Qin Wu, Li Mei Niu, Yin Yin Liu, Xue Zhang1

(1.Gansu Province Center for Disease Control and Prevention (Joint Laboratory of Institute of Radiology, Chinese Academy of Medical Sciences), No. 310 Dong Gang West Road, Lanzhou, Gansu, China)

Abstract:In the present study, we analyzed radiation injuries to Chinese workers exposed to low-dose radiation. We discuss the relationships between dose and injury.

Methods: This study randomly selected 976 radiation workers who underwent occupational health monitoring. The radiation workers were divided into 5 different types of work: radiation diagnosis, radiation therapy, interventional therapy, nuclear medicine, and industrial inspection. This research was approved by the Bioethics Committee at the Gansu Provincial Center for Disease Control and Prevention.

Results: The average annual cumulative dose to interventional radiation workers was the highest, i.e., 0.86 mSv. The detection rate of lens opacity was 37%, but 99.70% of lens opacities occurred in the peripheral cortex. Posterior subcapsular opacification was detected less than 1.00% of the time. The rate of chromosomal aberrations was highest for radiological workers with more than 20 years of service. Annual cumulative dose reached 2.04 mSv, and the monitoring dose for 3 months was as high as 1.62 mSv. Dicentric chromosomes were also detected. The manual packaging and drug delivery nuclear medicine staffs totaled 14 individuals.131I was detected in the thyroids of 4 workers (28.57%). The detection rate of thyroid131I was higher in the hand-packed and administered group than in the automatic administration group.

Conclusion: Radiation workers exposed to low doses of radiation can sustain injuries. Interventional radiology workers receive the highest doses and sustain the most significant effects. This study suggests that chromosome aberration analysis is an important index in occupational health monitoring of radiological workers. Monitoring of internal radiation exposure cannot be ignored for nuclear medicine staff.

Health Phys. 123(4):332-339; 2022