Determination of Organically Bound Tritium(OBT)Concentration in Fish by Thermal Oxidation and Liquid Scintillation Counting Method

S. Rashmi Nayak1, Renita S. D’Souza1, Mohan M. Purushotham1, Bharath Seraje1, Dileep N. Blangat2, Ravi P. Mana1,3, Karunakara Naregundi1

(1.Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri-574199, India;

2.Environmental Survey Laboratory, Kaiga Generating Station, Kaiga-581 400, India;

3.Formerly with Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India)

Abstract:Effluents containing tritium (3H) dispersed into the fresh water or marine environment from nuclear facilities can be taken up by biota. Aquatic and marine organisms are among the important pathways through which tritium can enter into the human body, and hence, assessment of the extent of pollution of these ecosystems is very important for radiation dose assessments. Tritium present in environmental matrices can be classified as tissue-free water tritium (TFWT) and organically bound tritium (OBT). Optimization of a method for the determination of OBT in fish, based on thermal oxidation of the sample, is discussed. Samples were subjected to thermal oxidation in a pyrolyser system, and the water produced from the combustion was analyzed by liquid scintillation spectrometry. Results show that a maximum of ～2 g of processed fish sample can be combusted efficiently in the pyrolyser. Using this method, a recovery of 84% was achieved, and minimum detectable activity (MDA) for the method was determined to be 8.5 Bq kg-1(sample weight = 2 g, counting time = 30,000 s, and detection efficiency = 20%).

Keywords: health effects; radiation protection; radiation, beta; radioactivity, environmental

Health Phys. 120(1):1-8; 2021

A New Application of Sohrabi Albedo Neutron Dosimeters around a Plasma Focus Device

Mehdi Sohrabi, Zahra Soltani1

(1.Health Physics and Dosimetry Research Laboratory, Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran)

Abstract:A new application of the Sohrabi albedo neutron dosimeters is reported for the first time for determination of very low-level neutron ambient dose equivalents on and around a 3.5 kJ plasma focus device (PFD). The Sohrabi dosimeters basically use a polycarbonate track detector as bare and/or in contact with10B convertor(s) under special cadmium cover arrangements. Its sensitivity was improved by using enriched10B under new cadmium arrangements in order to detect epithermal neutrons in addition to fast and thermal neutrons. Results of 12 dosimeters installed externally around the PFD at different azimuthal (φ) and polar (θ) angles showed that azimuthal (φ) fast, epithermal, thermal, and total neutron ambient dose equivalents were symmetric and isotropic, respectively, with values 55.15 ± 8.36, 1.36 ± 02, 0.53 ± 03, and 57.04 ± 8.62 μSv/shot at ～25 cm from anode top. Polar (θ) neutron ambient dose equivalent values on z-axis relative to 90° angle were relatively higher. Results of 38 dosimeters placed on PFD facility walls for workplace monitoring and on a BOMAB phantom at operator’s location for personal dose equivalent determination showed values below minimum detection limits after exposure to 130 PFD shots. However, an operator’s personal dose equivalents at ～1.0 and ～3.0 m from the anode top were estimated to be, respectively, ～13.7 and ～1.52 mSv y-1using azimuthal angle (φ) values if the PFD operates, for example, up to 20 shots per day for 200 d y-1. Even under such an extreme assumption, annual personal dose equivalent is still much below 20 mSv, the annual ICRP dose limit for workers.

Keywords: dosimeter, albedo neutron; dose assessment; dosimetry, personnel; exposure, occupational; plasma focus device

Health Phys. 120(1):9-18; 2021

Study on a Continuous Measurement Method for Unattached Radon Progeny

Yuanyuan Zhang, Xi Kang, Libing Wang1

(1. School of Nuclear Science and Technology, University of South China, Hengyang, Hunan, 421001, China)

Abstract:A method that does not require changing wire screens is proposed to achieve continuous measurement of unattached radon progeny. This method uses cumulative activity functions to deduct the influence of previous measurements from the current measurements on the sampling wire screen. The continuous measurement method was compared with a single measurement method, including relative deviations, uncertainties, and fluctuation range, which indicated the effectiveness of the cumulative activity functions applied to the continuous measurement method. The establishment of a continuous measurement method based on alpha spectroscopy provides technical support for the monitoring device.

Keywords:222Rn; monitoring, environmental; radiation monitors; radon

Health Phys. 120(1):19-23; 2021

Biokinetic Method on Simultaneous Intake of Radionuclides from Multiple Intake Scenarios for Application in Internal Exposures

Bin Zhang, Wei Sheng, Yang Zhang, Tian-Cheng Feng, Guo-Hui Yin, Jie-Ying Lei, Ming Xu, Xin-Zhao He, Huai-Cheng Ma1

(1. Northwest Institute of Nuclear Technology, Xi’an, China)

Abstract:Biokinetics underlies the basis for assessment of internal exposures. This paper develops a biokinetic method on simultaneous intake of radionuclides from multiple intake scenarios in internal exposures. With numerical techniques that transform the whole biokinetics between the coupled and decoupled representations of the same problem, this method applies to coupled biokinetics with complex structures and has no restrictions of practical importance on the number of intake scenarios, the number of intake parent radionuclides and decay products, and the complexity of decay relationships between parent and progeny nuclides. For illustration, this method is applied to an assumed case of mixed inhalation and ingestion of weapon-grade plutonium material for reference workers that is focused on241Pu and241Am. Due to coupled biokinetics between the direct intake and ingrowth parts in different intake pathways, the multiple intake results (the contents of lungs, daily excretions, and cumulative contents) display richer behaviors as compared to single intake cases. This method benefits both the prospective and retrospective assessment of internal exposures for complex intake cases in actual applications.

Keywords: algorithm; biokinetics; intake, radionuclide; plutonium

Health Phys. 120(1):24-33; 2021

Thyroid Doses to French Polynesians Resulting from Atmospheric Nuclear Weapons Tests:Estimates Based on Radiation Measurements and Population Lifestyle Data

Vladimir Drozdovitch1, André Bouville2, Marc Taquet3, Jacques Gardon4, Constance Xhaard5,6,7,8, Yan Ren5,6,7, Fran?oise Doyon5,6,7, Florent de Vathaire5,6,7

(1. Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD;

2. National Cancer Institute, Bethesda, MD (retired);

3. Research Institute for Development, Center IRD on Tahiti, Arue, Tahiti, French Polynesia;

4. Hydrosciences Montpellier, Research Institute for Development, CNRS, University of Montpellier, Montpellier, France;

5. National Institute for Health and Medical Research, Center for Research in Epidemiology and Population Health (CESP), INSERM U1018, Radiation Epidemiology Group, Villejuif, France;

6. Institute Gustave Roussy, Villejuif, France;

7. University Paris-Saclay, Villejuif, France;

8. Current affiliation: University of Lorraine, INSERM CIC 1433, Nancy CHRU, INSERM U1116, Nancy, France)

Abstract:Thyroid doses were estimated for the subjects of a population-based case-control study of thyroid cancer in a population exposed to fallout after atmospheric nuclear weapons tests conducted in French Polynesia between 1966 and 1974. Thyroid doses due to (1) intake of131I and of short-lived radioiodine isotopes (132I,133I,135I) and132Te, (2) external irradiation from gamma-emitting radionuclides deposited on the ground, and (3) ingestion of long-lived137Cs with foodstuffs were reconstructed for each study subject. The dosimetry model that had been used in 2008 in Phase I of the study was substantially improved with (1) results of radiation monitoring of the environment and foodstuffs, which became available in 2013 for public access, and (2) historical data on population lifestyle related to the period of the tests, which were collected in 2016-2017 using focus-group discussions and key informant interviews. The mean thyroid dose among the study subjects was found to be around 5 mGy while the highest dose was estimated to be around 36 mGy. Doses from131I intake ranged up to 27 mGy, while those from intake of short-lived iodine isotopes (132I,133I,135I) and132Te ranged up to 14 mGy. Thyroid doses from external exposure ranged up to 6 mGy, and those from internal exposure due to137Cs ingestion did not exceed 1 mGy. Intake of131I was found to be the main pathway for thyroid exposure accounting for 72% of the total dose. Results of this study are being used to evaluate the risk of thyroid cancer among the subjects of the epidemiologic study of thyroid cancer among French Polynesians.

Keywords: Health effects; nuclear weapons; radiation dose; thyroid

Health Phys. 120(1):34-55; 2021

Evaluation of Potential Optical Radiation Hazards from LED Flashlights

Robert J. Landry1?, Robert H. James1?, Sharon A. Miller2, Ilko K. Ilev1

(1. Optical Therapeutics and Medical Nanophotonics Laboratory, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD20993;

2. Office of In Vitro Diagnostics and Radiological Health, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland 20993. ?These authors contributed equally to this work)

Abstract:We performed optical radiation safety evaluations of LED flashlights to determine if they pose potential ocular hazards. Six commercially available flashlight samples were randomly selected from various vendors online. They were evaluated in accordance with specifications provided in the American National Standards Institute/Illuminating Engineering Society of North America (ANSI/IESNA) Standards RP 27.1 and RP 27.3. Four of the flashlights were found to have relatively high blue-light-weighted radiance values with short times (40 to 50 s) to reach the exposure limit specified in RP 27.1. These flashlights are in Risk Group 2 and present a moderate risk for retinal damage. Two of the flashlights are in Risk Group 1 and present a low risk for retinal damage. None of the flashlights present an ultraviolet (UV) radiation hazard or a retinal thermal hazard. Cautionary labeling on the packaging as required by RP 27.3 and on the flashlight handle is recommended for flashlights and on other handheld light sources that are in Risk Group 2 or Risk Group 3.

Keywords: exposure; radiation; nonionizing; risk analysis; safety standards

Health Phys. 120(1):56-61; 2021

Methods and Influencing Factors for the Simple and Rapid Identification of Depleted Uranium Weapon Use under Battlefield Conditions

Tao Yu1, Ya-Ru Yin1, Bing-Hui Lu1, Lu-Xun Yang1, Jing Liu1, Jiong Ren1, Zhang-You Yang1, Yu-Hui Hao1, Wei-Dong Wang2, Rong Li1

(1.State Key Laboratory of Trauma, Burns and Combined Injury, Institute of Combined Injury, College of Preventive Medicine, Army Military Medical University, Chongqing 400038, China;

2. Department of Radiotherapy, Sichuan Cancer Hospital, Sichuan, China)

Abstract:The purpose of this paper is to explore how to rapidly and easily identify depleted uranium (DU) samples under battlefield conditions and to study the factors that influence their measurement. The air-absorbed dose rate and surface contamination levels for DU samples of 2-330 g were measured using a patrol instrument and portable energy spectrometer. The results were analyzed in accordance with IAEA standards for judging radioactive substances. The energy spectra of 5 g quantities of DU samples were analyzed using a high-purity germanium gamma spectrometer, and the uranium content of 100 mg DU samples was determined with an inductively coupled plasma mass spectrometer to clarify the type and composition of the uranium. The same batches of DU samples were identified using a portable gamma-ray spectrometer. We added 0-5 g environmental soil powders at different proportions. After sealing, the spectra were collected with a detection distance of 1-5 cm for 10 min. The activities of238U and235U nuclides in the samples were detected with an NaI(TI) scintillation detector. The238U and235U mass abundances in samples were calculated from measured specific activities. The sample was determined to contain DU if the235U to238U ratio was below 0.00723. It is found that for detecting DU materials with a low activity, surface contamination level measurements are more effective than calculating the air-absorbed external irradiation dose rate. Hence, for low-activity samples suspected to be radioactive, a radiometer with a high sensitivity for surface contamination is recommended, and the optimal measurement distance is 1-3 cm. Under all detection conditions,238U can be identified using a portable gamma spectrometer, whereas235U can only be detected under certain conditions. If these nuclides can be detected simultaneously, a235U to238U ratio of below 0.00723 indicates the presence of DU. The main factors affecting this identification include the sample mass, sample purity, measurement distance, and measurement time. For the rapid identification of DU with a portable gamma-ray spectrometer, the mass of uranium in the sample must be more than 1 g, the measuring distance needs to be less than 1 cm, and the measuring time must be 1-10 min. It is feasible to use a portable gamma-ray spectrometer to rapidly identify the types and composition of nuclides in DU samples. The detection of235U activity is a precondition for the identification of DU.

Keywords:238U; fallout; uranium, depleted; weapons

Health Phys. 120(1):62-71; 2021

A Comprehensive Approach for Estimating Collective and Average Effective Doses of Galactic Cosmic Radiation Received by Pilots

Zi-Yi Yang, Rong-Jiun Sheu1

(1. National Tsing Hua University, Hsinchu, Taiwan)

Abstract:This study proposes a feasible and comprehensive approach for estimating collective and average effective doses of galactic cosmic radiation received by pilots on the basis of data in publicly available civil aviation annual statistical reports. Large uncertainties are associated with the estimation of these quantities because the radiation environment at aviation altitudes is complex, and a large number of flights operated by various air carriers is involved. A best estimate can be obtained through this approach because it considers all passenger, cargo, and charter flights operated during a long period of time instead of subjectively selecting some representative flights for dose evaluation. The approach becomes feasible and practical with the aid of a special feature called automatic batch analysis in theNTHUFlightDoseCalculator. There are two international airlines in Taiwan: China Airlines and EVA Air. As a demonstration, the collective effective dose received by the 2,513 pilots from the two airlines in 2018 was estimated to be 4,947 person-mSv, and the average effective dose per pilot was 1.97 mSv. These estimates were considered representative because they were based on all 151,526 flight segments operated that year. The assessment of the annual effective doses received by pilots in Taiwan from 2006 to 2018 was performed. The results varied in the range of 1.70-2.97 mSv because of variations in solar activity and operational flight routes. A regression model that can effectively reproduce the derived average effective dose rates on board aircraft was obtained for future application in aircrew dosimetry.

Keywords: dose, collective; effective dose; exposure, occupational; space radiation

Health Phys. 120(1):72-79; 2021

Can SUVmaxof68Ga-labeled PSMA Ligand and18F-choline PET/CT Be Used to Predict the Radiation Dose in Prostate Cancer Patients?

Zeinab Khansa1, Nemer Neaimeh2, Mahmoud Korek1, Mohamad Haidar2

(1.Department of Physics, Beirut Arab University, P.O. Box 11-5020, Beirut 1107 2809, Lebanon;

2. Diagnostic Radiology department, American University Medical Center, P.O. Box 11-0236, Riad ElSolh 1107 2020, Beirut, Lebanon)

Abstract:Gallium-68 (68Ga)-PSMA and18F-Choline are two radionuclides that have already shown high potential for the detection of prostate cancer. The comparison between these two radionuclides has several advantages in radiation protection. The aim of this prospective study was to identify which of these two radionuclides can help in predicting the equivalent dose using the maximum standard uptake value (SUVmax) of normal organs, the kidneys. Two groups of 40 patients (totaln=80) who underwent PET/CT using68Ga or18F for diagnosis of prostate cancer between April 2018 and December 2018 at the American University of Beirut Medical Center were included. First, the dose rates were measured after 1 h of radionuclide uptake at 1 m distance with background of 0.015 μSv h-1. Then, SUVmaxfor kidneys were determined from images obtained with PET/CT 1 h after injection of both radionuclides. The ratios of the equivalent doses to the SUVmaxfor kidneys were compared for both68Ga-PSMA and18F-Choline. There is a positive moderate relationship between the SUVmaxfor kidneys and the68Ga dose rate after 1 h of injection at 1 m distance from the abdomen (p-value = 0.023 < 0.05). This relationship is statistically significant. However, there is a very low negative relationship between the SUVmaxkidney and18F dose rate after 1 h of injection at 1 m distance from the abdomen (p-value = 0.93>0.05). This relationship is not statistically significant. This leads to the suggestion that we can predict the equivalent dose due to68Ga by indicating the SUVmaxfrom the PET/CT images.

Keywords: cancer; dose; dose equivalent, effective; radiation protection

Health Phys. 120(1):80-85; 2021

Use of Commercially Available Optically Stimulated Luminescence Dosimeter As Extremity Dose Estimator

David L. Georgeson, Byron H. Christiansen1

(1. Radiological Control Division, Idaho National Laboratory, Idaho Falls, ID 83415)

Abstract:In 2009, Idaho National Laboratory (INL) transitioned to an external dosimetry program using optically stimulated luminescent (OSL) technology. This process led to the introduction of the Landauer, Inc., nanoDot dosimeter and MicroStar reader to INL’s radiological control program. At the time, a small, self-contained, single chip OSL dosimeter that could be easily read in the field was recognized as having many potential applications for a radiological control program. The ability to achieve a realistic extremity-dose estimate in the field shortly following work where significant exposure is expected is a much sought-after capability at INL. It was proposed to employ the Landauer nanoDot dosimeter as a supplemental extremity monitor as an alternative to time-motion dose analyses based on direct radiation measurements, which had proven to be inaccurate and operationally inefficient. Additionally, this process does not involve the nanoDot in the US Department of Energy Laboratory Accreditation Program (DOELAP) process, which significantly reduces operational complexity. A dose conversion value for the nanoDot dosimeter was derived from direct comparisons with a DOELAP-accredited extremity dosimeter. The geometry or placement of the nanoDot relative to the accredited extremity dosimeter was kept as proximate as possible to best replicate the expected results from the accredited extremity dosimeter. Upon implementation, the nanoDot has proven to be effective in providing reasonable and timely extremity-dose estimates for operational control.

Keywords: accidents, nuclear; dose assessment; dosimetry, external; dosimetry, thermoluminescent

Health Phys. 120(1):86-93; 2021

Power Function Retention of Radionuclides in a Wound

Ronald E. Goans1

(1. 1422 Eagle Bend Drive, Clinton, TN 37716)

Abstract:NCRP Report 156 describes soluble radionuclide retention kinetics in a wound, segregated into four retention categories: weak (W), moderate (M), strong (S), and avid (A). An alternate single-parameter model, the negative power function,t-γ, is presented in this paper to describe the time behavior of radionuclide retention. With this mathematical description,γis a single parameter that can be used to assign the wound retention category rapidly. Using the power function description of wound retention, the various wound categories present as straight lines on log scales with different slopes corresponding to the various retention categories. Regression analysis of average retention values in NCRP 156 showsγ= 0.735 ± 0.132, 0.514 ± 0.015, 0.242 ± 0.016, and 0.053 ± 0.023 for the weak, moderate, strong, and avid categories, respectively. A case study is presented (REAC/TS Registry case 1284) where a power function is shown to fit retention data in a Pu239/Am241hand wound up to 2,000 d (5.4 y) post-accident.

Keywords:241Am;239Pu; kinetics; wound

Health Phys. 120(1):94-97; 2021

A Cyclotron Decommissioning Radiological Assessment Exercise Performed by Student Mentees Underrepresented in the Radiation Safety Profession

Jessie R. Zapata1, Justice Stewart1, Kalifa O. Kelly2, Aaron R. Taylor2,3, Erika I. Martinez3,4, Kofi Amoako1, Janet M. Gutierrez5, Robert J. Emery5, Sai Yan Cheng5, Scott J. Patlovich5, Mark C. Harvey1*

(1. Department of Physics, Texas Southern University, Houston, TX 77004;

2. Department of Chemistry, Texas Southern University, Houston, TX 77004;

3. Department of Mathematics, Texas Southern University, Houston, TX 77004;

4. Department of Computer Science, Texas Southern University, Houston, TX 77004;

5. Safety, Health, Environment & Risk Management, The University of Texas Health Science Center at Houston, TX 77054)

Abstract:Cyclotrons used in nuclear medicine imaging accelerate protons, deuterons, and helium ions to bombard a target, which produces nuclear reactions that generate positron-emitting radionuclides. Secondary neutrons are nonuniformly emitted in these reactions and induce heterogeneous activation of the cyclotron components and concrete vault enclosure. This poses radioactive waste management complications when decommissioning a cyclotron facility, since the objective is to ensure that exposures are within regulatory limits and as low as reasonably achievable (ALARA). The McGovern Medical School in The University of Texas Health Science Center in Houston housed a Scanditronix MC40 cyclotron that produced short-lived radioisotopes for Positron Emission Tomography (PET) imaging from 1984 to 2001 until Tropical Storm Allison rendered it inoperable. The purpose of this study was to provide underrepresented Science, Technology, Engineering and Mathematics (STEM) students an ALARA experience with a practical problem encountered in the radiation safety profession. Gamma dose rate measurements were performed with both a Mirion InSpectorTM1000 spectrometer and Fluke 451P survey meter in the vault at locations identified as hotspots based on preliminary scoping surveys with the Ludlum model 44-9 detector. However, gamma spectra were measured with the spectrometer exclusively at hotspots along the west wall. Results indicated the maximum gamma dose rate of 129 ± 31 nSv h-1was about 2 times background near the central beam transport line of the now inoperable cyclotron. Furthermore, gamma emission peaks were identified in the spectra from trace amounts of60Co and152Eu in the vault’s concrete walls.

Keywords: operational topics;60Co;152Eu; accelerators, decommissioned; positron emission tomography

Health Phys. 120(1):105-111; 2021

Tritium Air Concentration Calculation Using Passive Monitors

Todd Culp, Alexandra Robinson1

(1.Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185)

Abstract:Passive tritium air monitoring was conducted at Sandia National Laboratories’ Z-Machine located in New Mexico. When conducting low-level measurements, indication of the measurement’s uncertainty and of the detection limit of the counting technique are important to understand. Therefore, a calculational methodology is presented to enable the determination of the airborne tritium concentration by analysis of the minimum detectible activities for the Passive Tritium Monitoring System and the laboratory counting system used. General discussions of the advantages and disadvantages of the Passive Tritium Monitoring System are provided.

Keywords: operational topics; air sampling; occupational safety; tritium

Health Phys. 120(1):112-116; 2021