AnalysisofICNIRP2020BasicRestrictionsforLocalizedRadiofrequencyExposureintheFrequencyRangeabove6GHz

Jonathan Paradis, Eric Lemay1, Gregory B. Gajda1, Gregory W. McGarr1, Mykola Zhuk1

(1.Consumer and Clinical Radiation Protection Bureau, Non-ionizing Radiation Physical Sciences Division, Health Canada, 775 Brookfield Rd., Ottawa, Ontario Canada, K1A 1C1)

Abstract:ICNIRP 2020 guidelines have defined a practical temperature elevation threshold for human health effects, namely the operational adverse health effect threshold that forms the basis of the absorbed power and energy density basic restrictions. These basic restrictions for localized exposures at frequencies above 6 GHz were evaluated by comparing numerically computed temperature rise against the target temperature rise of 2.5 ℃, which is the operational adverse health effect threshold divided by the occupational safety factor of 2. The numerical model employs the maximum absorbed power and energy density levels allowed by the occupational basic restriction for both pulsed and continuous wave exposures. These analyses were performed considering 3- and 4-tissue layer models and a variety of beam diameters, frequencies, and exposure durations. The smallest beam diameters were based on a study of theoretically achievable beam widths from half-wave resonant dipoles and show the impact of the averaging area on the computed temperature elevation. The results demonstrated that ICNIRP’s assumed occupational safety factors in the frequency range above 6 GHz were not sufficiently maintained for all exposure scenarios and particularly for short pulse exposures at frequencies of 30 GHz or higher with small beam diameters. Worst-case tissue temperature elevations were estimated to be as much as 3.6 times higher than ICNIRP’s target temperature increases. Consequently, the authors suggest a small modification in the application of the ICNIRP 2020 localized basic restrictions, thereby limiting the worst-case tissue temperature increases to 1.4 times the target value.

Keywords: electromagnetic fields; exposure; radiofrequency; safety standards; modeling; dose assessment

Health Phys. 123(3):179-196; 2022

ExcretionofPu-238duringLong-termChelationTherapybyRepeatedDTPAInhalation

Olivier Grémy1, Nicolas Blanchin2, Laurent Miccoli1

(1.CEA, Direction de la Recherche Fondamentale, Institut de Biologie Fran?ois Jacob, Université Paris-Saclay, Fontenay-aux-Roses, France;2. CEA, Service de Santé au Travail, Saint-Paul-Lez-Durance, France)

Abstract:An individual underwent an extensive diethylenetriaminepentaacetate (DTPA) chelation therapy that started several months after plutonium incorporation, most likely by inhalation of a soluble compound. After receiving multiple intravenous infusions of DTPA, the patient continued the treatment by pulmonary delivery of aerosolized DTPA. The purpose of the present work is to provide and discuss the bioassay data obtained during the DTPA aerosol therapy and compare them with those under the DTPA infusion therapy that have been largely interpreted elsewhere. As with DTPA given intravenously, each delayed DTPA inhalation increased the clearance of plutonium not only in urine but also in feces, thus demonstrating the ability to remove plutonium retained by extrapulmonary tissues. Also, the slow decline of increased plutonium urinary elimination together with enhanced fecal excretion are two features coherent with the contribution of intracellular chelation to overall decorporation. The therapeutic benefit of DTPA inhalation appeared lower than with DTPA infusion, most likely due to a lower amount of DTPA reaching the systemic compartments where plutonium chelation predominates. The results suggest that DTPA administration through aerosol could be an alternative to the invasive procedure using a needle, i.e., intravenous injection/infusion, when protracted decorporation therapy is needed following transuranic internalization. Indeed, the patient may be more inclined to undergo a chelation treatment for a longer period because taking DTPA by inhalation may make it less cumbersome and painful.

Keywords:238Pu; chelation; DTPA; inhalation

Health Phys. 123(3):197-207; 2022

TheNuclearMedicinePatientasaLineSource:TheSourceLengthIsCertainlyNotthePatientHeight,ButItIsaReasonableApproximation

David Broggio1

(1.Institut de Radioprotection et de Sreté Nucléaire, IRSN/PSE-SANTE/SDOS/LEDI, BP-17, Fontenay-aux-Roses, France)

Abstract:Nuclear medicine patients are a source of exposure and should receive instructions to restrict contact time with different categories of people. The calculation of the restriction time requires that the dose rate at a given distance, known from an initial measurement and a whole-body retention function, can be extrapolated at other distances. As a basis for this extrapolation, it has been suggested to consider the patient as a line source. However, the validity of this suggestion is based on a few studies and limited measurement distances. We collected from the literature dose rates of nuclear medicine patients measured at different distances and investigated the robustness of the line source model. The cases of18F-FDG exams,99mTc bone scan exams, and131I for hyperthyroidism treatment and remnants ablation were considered. The data were pooled, different cases of measurement time after administration were considered, and the data were fitted according to the line source model in which the half patient thickness was introduced. It was found that the line source model fits well the data put with a source length that is radionuclide-specific and significantly different from the standard adult height. However, considering a standard source length of 176 cm and neglecting the patient thickness induced at maximum an overestimation by a factor of 2.5 when extrapolating from 1 m to 10 cm. Such an overestimation is not of considerable importance in the calculation of contact restriction times.

Keywords: dose; external; exposure; population; nuclear medicine; radiation; medical

Health Phys. 123(3):208-217; 2022

AccidentSimulationStudyforNuclearPowerPlantsImpactingLouisiana:Differencesin2017vs.1992ProtectiveActionGuidelines

Michael D. McMahon1,2, Jeffery C. Chancellor1,3,4

(1.Department of Physics & Astronomy, Louisiana State University, Baton Rouge, LA;2.Tulane University, Office of Environmental Health and Safety, New Orleans, LA [formerly at Louisiana Department of Environmental Quality, Baton Rouge, LA];3. Department of Preventative Medicine & Population Health, University of Texas Medical Branch, Galveston, TX;4. Outerspace Institute, University of British Columbia, Vancouver, Canada)

Abstract:Louisiana has aligned its radiological emergency program with the 2017 US Environmental Protection Agency Protective Action Guides Manual but has added a child thyroid dose evacuation threshold in lieu of distributing potassium iodide to the public. The nuclear power plants will continue to align with the 1992 manual for the foreseeable future, which could lead to possible accident scenarios in which state recommendations would differ from those of the utility. The objective of this study is to predict what accident and weather conditions will lead to a differing set of recommendations. This study performs a representative set of simulations of potential nuclear power plant accidents using a combination of the RASCAL software package, provided by the Nuclear Regulatory Commission, and a Software system used by Entergy combining an older RASCAL dose modeling methodology with plant-specific input. Four preliminary results of this study are presented: a spent fuel fire where differences in whole body dose lead to very different evacuations, a loss of coolant accident in which the child thyroid dose is the determining factor, a core melt accident using stack monitors to locate the evacuation threshold point, and a spiked coolant accident that could lead to an evacuation order before the plant declares a General Emergency. Weather plays as great a role as accident conditions in determining whether the evacuation recommendations differ. The completed results of this study can provide guidance to states as they evaluate the transition to the 2017 guidelines.

Keywords: accidents; power reactor; emergency planning; nuclear power plant; regulatory guides

Health Phys. 123(3):218-228; 2022

AssessmentofOccupationalExposuretoEyeLensDosimetryforInterventionalRadiologyWorkersinChinaduring2017-2019

Mengxue Li1, Shengnan Fan1, Xianpeng Zhang2, Shuxia Hao1, Yu Zhao3, Jun Deng1, Quanfu Sun1

(1.National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China; 2.Shandong Center for Disease Control and Prevention, Jinan 250014, China;3.Heilongjiang Provincial Center for Disease Control and Prevention, Harbin 150030, China)

Abstract:The eye lens is a sensitive tissue to ionizing radiation and recently has been recognized as more radiosensitive than previously considered. The International Commission on Radiological Protection (ICRP) has recommended a considerable reduction in the equivalent dose limit of eye lens from 150 mSv y-1to 20 mSv y-1, averaged over a defined period of 5 y. In this paper, the eye lens dose of interventional radiology workers in China during 2017-2019 is analyzed to understand the current status of eye lens occupational exposure and to provide decision-making suggestions for health supervision departments using data obtained from the National Radiological Health Information Platform in China. A total of 3,026 eye lens dose records of interventional radiology workers were collected. The average annual eye lens dose (AAELD) for interventional radiology workers ranged from 1.07 to 1.51 mSv during 2017-2019 and was 1.44 mSv for all monitored interventional radiology workers, with 2,973 records (98.2%) lower than the public limit of 15 mSv and 33 records (1.1%) exceeding the newly revised occupational eye lens dose limit of 20 mSv y-1. During the period of 2017-2019, the AAELDs of interventional radiologists (1.61 mSv) and of interventional cardiologists (1.59 mSv) were significantly higher than that of other interventional workers (0.62 mSv); the AAELD of doctors (1.50 mSv) was significantly higher than that of nurses (1.01 mSv); the AAELD of western China (2.00 mSv) was significantly higher than that of eastern (1.11 mSv) and central China (1.27 mSv); and the AAELD of males (1.59 mSv) was significantly higher than that of females (0.84 mSv). The eye lens dose of interventional radiology workers meets the Chinese standard limit of 150 mSv y-1, while some cases exceed the one recommended by ICRP. The study shows that the interventional radiology workers’ eye lens dosimetry data complied with the existing Chinese eye lens dose limits. However, education, training, and supervision of radiation protection also should be strengthened continuously for interventional radiology workers, especially for the interventional radiologists and interventional cardiologists. Significant attention should be paid to the radiation protection of underdeveloped regions in China in future works.

Keywords: dose assessment; exposure; occupational; medical radiation; radiation dose

Health Phys. 123(3):229-237; 2022

BearingExtremes:ImpactsfromSimulatedOuterSpaceConditionsandEffectiveUltravioletRadiationShieldingMaterialsonTardigradeLifeHistory

Amy Zhu, Johnny Stone1

(1.Department of Biology and Origins Institute, McMaster University Hamilton ON L8S 4K1 Canada)

Abstract:Questions about astrobiological resilience, whether entities with evolutionary histories on Earth would survive in outer space or on distant planets, for instance, no longer reside exclusively in the science fiction realm. In this study, we assess life history characteristics for individuals in the tardigrade speciesGreveniusannulatuspost exposure to simulated outer space conditions with nonionizing radiation as a proxy for anticipated oxidative stress and damage incurred from exposure to full-spectrum environmental radiation. Using a planetary environment simulator, we exposed unshielded and shielded specimens to UVB and UVC radiation for 30 min and monitored and recorded subsequent life history characteristics. Survivorship was lower in an unshielded group relative to control as well as Kevlar and polyethylene shielded groups, demonstrating that Kevlar and polyethylene reduce impact from these types of nonionizing radiation, which are not expected to fully penetrate the shields. Cumulative egg production was lowest in the unshielded group, but egg viability and average egg production rate was highest. Due to insignificant differences, additional research to determine the relative effectiveness for Kevlar and polyethylene as shielding materials from survivorship and reproduction perspectives is warranted. This work provides a progressive step from which important conditions excluded in the current study, like vibrations, temperatures, debris-impacts, and ionizing radiation, can be included in future studies.

Keywords: aquatic organisms; health effects; radiation effects; ultraviolet radiation

Health Phys. 123(3):238-244; 2022

Radon-222CharcoalCanisterSteadyStateModelCalibrationsPerformedinaHighlyControlledEnvironmentalChamberandaNaturalIndoorEnvironment

Thomas W. Kennings, Jordan D. Noey, Loren A. Mata, Kimberlee J. Kearfott1

(1.Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109-2104)

Abstract:Charcoal canisters are a common method of222Rn screening. The calibrations of different batches of activated charcoal used in different canister designs are typically performed in large volume controlled environmental chambers with known and controlled radon concentration, temperature, and humidity. Radon screening could be facilitated in locations without ready access to environmental chambers if canisters could be accurately calibrated and undergo quality control in less controlled environments. This study compares charcoal canister calibrations from a highly controlled radon chamber with calibrations from a basement storage area experiencing temporally varying radon. In addition, the impacts of exposure time and spectral region of interest selection on calibration accuracy are investigated by comparing calibrations calculated using three different choices. Approximately 30 mo after calibrations were completed, groups of canisters were exposed for different durations of time to investigate measurement accuracy and calibration validity over an extended time. A digital simulation of charcoal canister kinetics was also performed to establish limits on how stable radon must be in a space for equilibrium-based calibration to be performed there. Overall, the accuracy of measurements using calibrations from each space differed by less than 10% after 2 d exposure time, showing that carefully controlled conditions are not necessary for the accurate calibration of charcoal canisters. Measurement accuracy differed by less than 2% for different spectral region selections. Accuracy improved slightly with canister exposure duration. Simulations suggest that radon instability is most tolerable near the beginning of canister calibration exposures, but this merits further experimental study.

Keywords: operational topics; calibration; charcoal canisters; radon

Health Phys. 123(3):248-256; 2022

RatiosofEyeLensandHandEquivalentDoseswithWhole-BodyEffectiveDosesforOperatorsPerformingInterventionalRadiologicalProcedures

Wan-Chih Tsai1, Wei-Han Chu2, Rong-Jiun Sheu1,3

(1.Institute of Nuclear Engineering and Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan;2.Institute of Nuclear Energy Research, 1000, Wen-Hua Road, Longtan, Taoyuan, Taiwan;3.Department of Engineering and System Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan)

Abstract:Estimating radiation doses for operators performing interventional radiological procedures is crucial in the occupational radiation protection of medical staff. In this study, Monte Carlo simulations coupled with an anthropomorphic phantom were used to model various exposure scenarios during the procedures. Conversion coefficients of the dose-area product of X rays for the eye lens equivalent dose, hand equivalent dose, and whole-body effective dose of the operator were calculated. Accordingly, the relationships between these dose quantities in typical interventional configurations were established, considering various source locations, tube voltages, and use of protective equipment or not. The results are presented in a systematic way for easy comparison and use. Tables and figures of the data can be helpful to provide estimates of eye lens and hand equivalent doses when records of specific dosimeters are absent, such as in the retrospective assessment of operators’ eye lens and hand equivalent doses in past practices.

Keywords: operational topic; fluoroscopy; Monte Carlo; equivalent dose; effective dose

Health Phys. 123(3):257-264; 2022