Health Phys. Abstracts，Volume 118,Number 1

USEOFROUTINEENVIRONMENTALMONITORINGDATATOESTABLISHADOSE-BASEDCOMPLIANCESYSTEMFORALOW-LEVELRADIOACTIVEWASTEDISPOSALSITE

Arthur S. Rood1, Helen A. Grogan2, H. Justin Mohler3, James R. Rocco4, Emily A. Caffrey5, Colby Mangini6, Jay Cartwright7, Travis Matthews7, Chris Shaw7, Mark E. Packard8, John E. Till9

(1.K-Spar Inc., Idaho Falls ID;2. Cascade Scientific Inc., Bend OR;3. Bridger Scientific Inc., Belgrade MT;4. Sage Risk Solutions, LLC, Aurora OH;5. Radian Scientific, LLC, Huntsville AL;6. Paragon Scientific, LLC, Germantown TN;7. Waste Control Specialists, LLC, Andrews TX;8. DDMS, Inc., Saint Paul MN;9. Risk Assessment Corporation, Neeses SC)

Abstract:A dose-based compliance methodology was developed for Waste Control Specialists, LLC, low-level radioactive waste facility in Andrews, Texas, that allows routine environmental measurement data to be evaluated not only at the end of a year to determine regulatory compliance, but also throughout the year as new data become available, providing a continuous assessment of the facility. The first step in the methodology is a screening step to determine the potential presence of site emissions in the environment, and screening levels are established for each environmental media sampled. The screening accounts for spatial variations observed in background for soil and temporal fluctuations observed in background for air. For groundwater, the natural activity concentrations in groundwater wells at the facility are highly variable, and therefore the methodology uses ratios for screening levels. The methodology compares the ratio of gross alpha to234U +238U to identify potentially abnormal alpha activity and the ratio of235U to238U to identify the potential presence of depleted uranium. Compliance evaluation is conducted for any samples that fail the screening step. Compliance evaluation uses the radionuclide-specific measurements to first determine (1) if the dose exceeds the background dose and if so, (2) the dose consequences, so that the appropriate investigation or action occurs. The compliance evaluation is applied to all environmental samples throughout the year and on an annual basis to determine regulatory compliance. The methodology is implemented in a cloud-based software application that is also made accessible to the regulator. The benefits of the methodology over the existing system are presented.

Keywords: dose assessment; environmental assessment; safety standards; waste, low-level

Health Phys. 118(1):1-17; 2020

ESTIMATIONOFRADIATIONDOSESFORACASE-CONTROLSTUDYOFTHYROIDCANCERAMONGUKRAINIANCHERNOBYLCLEANUPWORKERS

Vladimir Drozdovitch1, Victor Kryuchkov2, Elena Bakhanova3, Ivan Golovanov2, Dimitry Bazyka3, Natalia Gudzenko3, Natalia Trotsyuk3, Maureen Hatch1, Elizabeth K. Cahoon1, Kiyohiko Mabuchi1, André Bouville4, Vadim Chumak2

(1.Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Bethesda, MD;2.Burnasyan Federal Medical and Biophysical Centre, Moscow, Russia;3.National Research Centre for Radiation Medicine, Kyiv, Ukraine;4.National Cancer Institute, Bethesda, MD (retired))

Abstract:Thyroid doses were estimated for 607 subjects of a case-control study of thyroid cancer nested in the cohort of 150,813 male Ukrainian cleanup workers who were exposed to radiation as a result of the 1986 Chernobyl nuclear power plant accident. Individual thyroid doses due to external irradiation, inhalation of131I and short-lived radioiodine and radiotellurium isotopes (132I,133I,135I,131mTe, and132Te) during the cleanup mission, and intake of131I during residence in contaminated settlements were calculated for all study subjects, along with associated uncertainty distributions. The average thyroid dose due to all exposure pathways combined was estimated to be 199 mGy (median: 47 mGy; range: 0.15 mGy to 9.0 Gy), with averages of 140 mGy (median: 20 mGy; range: 0.015 mGy to 3.6 Gy) from external irradiation during the cleanup mission, 44 mGy (median: 12 mGy; range: ～0 mGy to 1.7 Gy) due to131I inhalation, 42 mGy (median: 7.3 mGy; range: 0.001 mGy to 3.4 Gy) due to131I intake during residence, and 11 mGy (median: 1.6 mGy; range: ～0 mGy to 0.38 Gy) due to inhalation of short-lived radionuclides. Internal exposure of the thyroid gland to131I contributed more than 50% of the total thyroid dose in 45% of the study subjects. The uncertainties in the individual stochastic doses were characterized by a mean geometric standard deviation of 2.0, 1.8, 2.0, and 2.6 for external irradiation, inhalation of131I, inhalation of short-lived radionuclides, and residential exposure, respectively. The models used for dose calculations were validated against instrument measurements done shortly after the accident. Results of the validation showed that thyroid doses could be estimated retrospectively for Chernobyl cleanup workers two to three decades after the accident with a reasonable degree of reliability.

Keywords: Chernobyl, cleanup worker, thyroid, radiation, dose

Health Phys. 118(1):18-35; 2020

REASSESSMENTOFINTERNALTHYROIDDOSESTO1,080CHILDRENEXAMINEDINASCREENINGSURVEYAFTERTHE2011FUKUSHIMANUCLEARDISASTER

Eunjoo Kim1, Kazuaki Yajima1, Shozo Hashimoto1, Kotaro Tani1, Yu Igarashi1,2, Takeshi Iimoto2, Nobuhito Ishigure1, Hideo Tatsuzaki1, Makoto Akashi1, Osamu Kurihara1

(1.National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan;2. University of Tokyo, Chiba, Japan)

Abstract:The dose reconstruction of populations potentially affected by the accident at the Fukushima Daiichi nuclear power plant in March 2011 is of great importance. However, it has been difficult to assess internal thyroid doses to Fukushima residents (mainly from their intake of131I) due to the lack of direct measurements. For the residents, only about 1,300 data points related to131I are available, and 1,080 of the data points were obtained from the screening campaign that was conducted by the Nuclear Emergency Response Local Headquarters at the end of March 2011 in Kawamata Town, Iwaki City, and Iitate Village. Here, we reassessed thyroid doses to 1,080 subjects aged ≤15 y old using new age-specific conversion factors to determine131I thyroid contents from net signals of the devices used, with consideration for the possible uncertainty related to the measurements. The results demonstrated that thyroid equivalent doses to the subjects were <30 mSv (excluding outliers). We also demonstrate dose distributions of each age group from the above three municipalities and those of subjects from Minamisoma City and Fukushima City. One of the findings was that the131I intake was similar among different age groups in each of the three municipalities. This was consistent with the assumption that ingestion was a dominant route of intake rather than inhalation. The range of thyroid doses to Iitate Village residents was similar to that to Iwaki City residents even though the131I concentration in tap water was much higher in Iitate Village than Iwaki City. The range of thyroid doses to Minamisoma City residents was similar to that to Iitate Village and Iwaki City residents, and the range for Fukushima City residents was smallest among the five municipalities. Since the major route of intake has remained unclear, this paper presents the plausible upper and lower thyroid doses, between which the actual doses are thought to mostly exist, based on two intake scenarios: single inhalation and repeated ingestion. Further research is thus necessary to extract useful evidence from the individual evacuation behaviors for improving the present internal thyroid dose assessment.

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

Health Phys. 118(1):36-52; 2020

TRABECULA:ARANDOMGENERATOROFCOMPUTATIONALPHANTOMSFORBONEMARROWDOSIMETRY

E.A. Shishkina1,2, Y.S. Timofeev1, A.Y. Volchkova1, P.A. Sharagin1, V.I. Zalyapin3, M.O. Degteva1, M.A. Smith4, B.A. Napier4

(1.Urals Research Centre for Radiation Medicine (URCRM), Chelyabinsk, Russia;2.Chelyabinsk State University (ChelSU), Chelyabinsk, Russia;3.Southern Urals State University (SUSU), Chelyabinsk, Russia;4.Pacific Northwest National Laboratory, Richland, WA)

Abstract:This study was motivated by the efforts to evaluate radiation risk for leukemia incidence in the Techa River cohort, where the main bone marrow dose contributors were89,90Sr (bone-seeking beta emitters). Energy deposition in bone marrow targets was evaluated by simulating radiation particle transport using computational phantoms. The present paper describes the computer program Trabecula implementing an algorithm for parametric generation of computational phantoms, which serve as the basis for calculating bone marrow doses. Trabecula is a user-friendly tool that automatically converts analytical models into voxelized representations that are directly compatible as input to Monte Carlo N Particle code.

Keywords:90Sr; bone marrow; dose, bone; phantom, mathematical

Health Phys. 118(1):53-59; 2020

EFFECTIVEHALF-LIFEOF134CsAND137CsINFUKUSHIMAPREFECTUREWHENCOMPAREDTOTHEORETICALDECAYMODELS

Joshua M. Hayes1, Thomas E. Johnson1, Donovan Anderson2, Kenji Nanba2

(1.Environmental and Radiological Health Sciences Faculty, Colorado State University, Fort Collins, CO;2. Institute of Environmental Radioactivity, Fukushima University, Fukushima, Kanayagawa, Japan)

Abstract:On 11 March 2011, a 9.0 magnitude earthquake struck the Tohoku region of Japan. The earthquake caused a 15 m tsunami that bombarded the east coast of the island nation. Among the losses was the damage to the Fukushima Daiichi nuclear reactor that lost onsite power and was unable to cool the reactor cores. The reactors melted down and released a plume of radionuclides into the environment. Radiocesiums (134Cs and137Cs) are the long-lived radionuclides of concern that were deposited along the plume and were distributed on the soil. Radiological decay models are typically used to determine the reduction in external radiation dose over time. However, these radiological decay models do not take into account physical removal by wind and water erosion, or sedimentation in soil outside expected depths. Thirty-five fixed dose-rate monitors were used to record dose rates at 1 mo intervals from the time of installation in Fukushima Prefecture in April 2012 until December 2018 and were used to estimate the effective half-life for radiocesium contamination based on external radiation dose rates. The effective half-life of cesium in the environment was calculated to be 3.2 ± 0.5 y, compared to a theoretical half-life of 7.8 y.

Keywords: cesium; contamination, environmental; environmental assessment; Fukushima Daiichi

Health Phys. 118(1):60-64; 2020

DIFFERENTMETHODSOFMEASURINGNEUTRONDOSE/FLUENCEGENERATEDDURINGRADIATIONTHERAPYWITHMEGAVOLTAGEBEAMS

Bagher Farhood1, Mehdi Ghorbani2, Nouraddin Abdi Goushbolagh3, Masoud Najafi4, Ghazale Geraily5

1.Department of Medical Physics and Radiology, Faculty of Paramedical Sciences, Kashan University of Medical Sciences, Kashan, Iran;2. Biomedical Engineering and Medical Physics Department, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran;3. Medical Physics Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran;4. Radiology and Nuclear Medicine Department, School of Paramedical Sciences, Kermanshah University of Medical Sciences, Kermanshah, Iran;5. Medical Physics and Medical Engineering Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran)

Abstract:Medical linear accelerators (linacs) are the most frequently applied radiation therapy machines in the locoregional treatment of cancers by producing either high-energy electron or photon beams. However, with high-energy photons (>8 MeV), interaction of these photons with different high-Z nuclei of materials in components of the linac head unavoidably generates neutrons. On the other hand, the average energy of these generated neutrons has almost the highest radiation-weighting factor. Therefore, the produced neutrons should not be neglected. There are various tools for the measurement of neutron dose/fluence generated in a megavoltage linac, including thermoluminescent dosimeters, solid-state nuclear track detectors, bubble detectors, activation foils, Bonner sphere systems, and ionization chamber pairs. In this review article, each of the above-mentioned dosimetric methods will be described in detail.

Keywords: accelerators, medical; neutron dosimetry; radiation therapy; radiation, medical

Health Phys. 118(1):65-74; 2020

THERADIATIONSAFETYOFFICERASANADVOCATEFORPATIENTSAFETY

Thomas L. Morgan1

(1.Versant Medical Physics and Radiation Safety, 116 S. Riverview Drive, Kalamzoo, MI 49004)

Abstract:The role of the radiation safety officer is to maintain radiation exposures as low as reasonably achievable. Traditionally, the focus has been on reducing or eliminating unnecessary occupational exposure to employees and ensuring exposure of visitors and members of the public is maintained below regulatory limits. Over the last three decades there has been increasing concern expressed in the medical literature on the potential risks of radiation exposure to patients undergoing diagnostic medical imaging procedures. This paper will discuss the need for advocacy and processes by which the radiation safety officer can expand the focus of a medical radiation safety program to include advocacy for applying the principles and practices of maintaining exposures as low as reasonably achievable to patients.

Keywords: patient radiation safety, radiation safety officer, advocacy

Health Phys. 118(1):75-78; 2020

DIAGNOSTICREFERENCELEVELS,DETERMINISTICANDSTOCHASTICRISKSINPEDIATRICINTERVENTIONALCARDIOLOGYPROCEDURES

Chadia Rizk1,2, Georges Fares2, Filip Vanhavere3, Zakhia Saliba4, Jad Farah5

(1.Lebanese Atomic Energy Commission, National Council for Scientific Research, 11-8281 Beirut, Lebanon;2.Faculty of Sciences, Saint Joseph University, 11-514 Beirut, Lebanon;3. Belgian Nuclear Research Centre (SCKCEN), BE-2400 Mol, Belgium;4. Department of pediatrics, Hotel Dieu de France Hospital, Beirut, Lebanon;5. Radiology and Nuclear Medicine Department, Paris-Sud University Hospitals, 94270 Le Kremlin-Bicêtre, France)

Abstract:To establish diagnostic reference levels (DRLs) and investigate deterministic and stochastic risks in pediatric interventional cardiology (IC) procedures. Exposure parameters were retrospectively reviewed for 373 patients treated between May 2016 and November 2018 at a single specialized hospital. Weight specific DRLs were derived for pediatric IC procedures. Additionally, peak skin dose (Dskin,max) was measured using thermoluminescent dosimeters for a sample of 7 diagnostic and 43 therapeutic procedures. Finally, using PCXMC software, organ doses were computed and the risk of exposure-induced cancer death (REID) was estimated using the risk models of the Biological Effects of Ionizing Radiation VII committee. DRLs for ventricular septal defect (VSD) occlusions, lacking in the literature, in terms of air kerma at patient entrance reference point (388 and 629 mGy) and total air kerma-area product (28 and 61 Gycm2) were proposed for patients weight-groups 5-< 15 kg and 15-< 30 kg, respectively. The mean (range)Dskin,maxwas 15 (1-30)mGy and 94 (1-491) mGy for diagnostic and therapeutic procedures, respectively. Meanwhile, VSD occlusion involved the highest organ doses where the lungs, liver, stomach, and breasts mean doses were 57, 37, 6, and 10 mGy, respectively, and the associated REID were 0.5% and 0.3% in female and male patients, respectively. DRLs were proposed for pediatric IC procedures; these will help optimize patient exposure.Dskin,maxvalues were lower than the 2 Gy threshold for skin injuries. Pediatric organ doses and the REID were the highest during VSD occlusion and may be critical for repetitive procedures.

Keywords: operational topics; children; exposure; radiation; health effects

Health Phys. 118(1):85-95; 2020

RADONEXPOSURESOFMINERSATSMALLUNDERGROUNDCONSTRUCTIONSITESINOLDMINING:RECOMMENDATIONSTOIMPROVERADIATIONPROTECTIONMEASURESBYTHESAXONRADIATIONPROTECTIONAUTHORITY

Jörg Dehnert1

(1. Saxon State Office for Environment, Agriculture and Geology, Dresden, Saxony, Germany)

Abstract:The Ore Mountains (Erzgebirge) and Vogtland are low-mountain regions in the East German state of Saxony. Here, silver deposits were found in 1168. Mining began shortly after, continues at varying intensity to this day, and has left numerous galleries and shafts. Today, eight companies with about 250 miners carry out maintenance at more than 40 small and frequently changing underground construction sites throughout the year. Miners are protected against high radon exposure by radiation protection measures such as ventilations, stoppings made of wood, foil, and expanding foam, and staff rotations. However, some of them still show high annual exposure levels; for example, in 2015 up to 14.4 mSv measured by passive radon dosimeters. Reasons for this include the high radon potential in old mining and the natural density driven mine air current through the galleries. Mine air currents can change directions during the day depending on outdoor temperatures. This paper presents the experiences of the Saxon Radiation Protection Authority in monitoring miners in old mining. For this purpose, the paper looks at seven examples of miners’ critical exposures based on measurement curves of radon activity concentration and derives respective radiation protection measures. These encompass, for example, to activate mine fans, erect stoppings, extend ventilation pipes, and change the locations of mine fans. Conclusions are drawn for the operative and strategic radiation protection in old mining.

Keywords: operational topics; radiation protection; radon; ventilation

Health Phys. 118(1):96-105; 2020

INTRODUCINGHEALTHANDMEDICALPHYSICSTOYOUNGLEARNERSINPRESCHOOLTOFIFTHGRADE

Jessica M. Fagerstrom1

(1.Northwest Medical Physics Center, 21031 67thAve W, Lynnwood, WA 98036)

Abstract:A hands-on learning activity was developed to introduce young learners to concepts and careers in health and medical physics. Inexpensive materials were used to create a work station with learning tools that were designed to be approachable and accessible for this audience. Visitors to a local independent, nonprofit science museum may interact with the activity work station to learn basic information regarding radiation in everyday life and to hear about careers in radiation sciences. Approximately 60 volunteer hours have been contributed associated with the activity. Interested physicists may adapt the lesson plan as a simple and straightforward way to participate in public education efforts in their own communities. A detailed lesson plan, equipment list, and electronic media are available upon request.

Keywords: operational topics; education; education, health physics; public information

Health Phys. 118(1):106-110; 2020