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Health Physics - Current Issue

Health Physics - Current Issue
  1. THE HEALTH PHYSICS SOCIETY: An Affiliate of the International Radiation Protection Association (IRPA)
    No abstract available



  2. Reconstruction of A Radiological Release Using Aerosol Sampling
    imageAbstract: Reconstructing a radiological release using offsite air sampling is considered using measurements from the WIPP site event. Demonstration of the capabilities is shown using the HotSpot code as an example of the approach in general. The results show the empirical steps that could be folded into an iterative approach to back extrapolation of a radiological release from a nuclear facility. It is shown here that the limiting factor in detection is not counting statistics of the activity but rather the statistics for aerosols having small sample population numbers due to the lognormal distribution of particle radii.



  3. RSO Interview with Nanci Burchell
    imageNo abstract available



  4. Dose Comparisons for a Site-specific Representative Person Using the Age-dependent Dose Coefficients in CAP88-PC Version 4
    imageAbstract: Most U.S. Department of Energy (DOE) facilities with radiological airborne releases use the U.S. Environmental Protection Agency’s (EPA) environmental dosimetry code CAP88‐PC to demonstrate compliance with regulations in 40CFR61, subpart H [National Emission Standards for Hazardous Air Pollutants: Radiological (NESHAP)]. In 2015, EPA released Version 4 of CAP88‐PC, which included significant modifications that improved usability and age-dependent dose coefficients and usage factors for six age groups (infant, 1 y, 5 y, 10 y, 15 y, and adult). However, EPA has not yet provided specific guidance on how to use these age-dependent factors. For demonstrating compliance with DOE public dose regulations, the Savannah River Site (SRS) recently changed from using the maximally exposed individual (MEI) concept (adult male) to the representative person concept (age- and gender-averaged reference person). In this study, dose comparisons are provided between the MEI and a SRS-specific representative person using the age-specific dose coefficients and usage factors in CAP88‐PC V.4. Dose comparisons also are provided for each of the six age groups using five radionuclides of interest at SRS (tritium oxide, 137Cs, 90Sr, 239Pu, and 129I). In general, the total effective dose increases about 11% for the representative person as compared to the current NESHAP MEI because of the inclusion of the more radiosensitive age groups.



  5. Space: The Final Frontier—Research Relevant to Mars
    imageAbstract: A critically important gap in knowledge surrounds the health consequences of exposure to radiation received gradually over time. Much is known about the health effects of brief high-dose exposures, such as from the atomic bombings in Japan, but the concerns today focus on the frequent low-dose exposures received by members of the public, workers, and, as addressed in this paper, astronauts. Additional guidance is needed by the National Aeronautics and Space Administration (NASA) for planning long-term missions where the rate of radiation exposure is gradual over years and the cumulative amounts high. The direct study of low doses and low-dose rates is of immeasurable value in understanding the possible range of health effects from gradual exposures and in providing guidance for radiation protection, not only of workers and the public but also astronauts. The ongoing Million Person Study (MPS) is 10 times larger than the study of the Japanese atomic bomb survivors of 86,000 survivors with estimated doses. The number of workers with >100 mSv career dose is substantially greater. The large study size, broad range of doses, and long follow-up indicate substantial statistical ability to quantify the risk of exposures that are received gradually over time. The study consists of 360,000 U.S. Department of Energy workers from the Manhattan Project; 150,000 nuclear utility workers from the inception of the nuclear age; 115,000 atomic veterans who participated in above-ground atmospheric tests at the Nevada Test Site and the Bikini and Enewetak Atolls and Johnston Island in the Pacific Proving Grounds (PPG); 250,000 radiologists and medical workers; and 130,000 industrial radiographers. NASA uses an individual risk-based system for radiation protection in contrast to the system of dose limits for occupational exposures used by terrestrial-based organizations. The permissible career exposure limit set by NASA for each astronaut is a 3% risk of exposure-induced death (REID) from cancer at a 95% confidence level to account for uncertainties in risk projections. The large size of the MPS will reduce the uncertainty in the risk estimates, narrowing the 95% confidence interval, and thus allow more time in space for astronauts. Further differences between men and women in their response to radiation can be more fully examined, and non-cancer outcomes, such as neurological disorders and cardiovascular disease, can be evaluated in a way not hitherto possible.


  6. Modeling Considerations for Ingestion Pathway Dose Calculations Using CAP88
    imageAbstract: The CAP88‐PC computer model was developed by the U.S. Environmental Protection Agency to demonstrate compliance under the National Emission Standards for Hazardous Air Pollutants (NESHAPS). The program combines atmospheric transport models with the terrestrial food chain models in the U.S. Nuclear Regulatory Commission Regulatory Guide 1.109 to compute the radionuclide concentrations in the air, on ground surfaces and plants, and the concentrations in food to estimate the dose to individuals living in the area around a facility emitting radionuclides into the atmosphere. CAP88 allows the user to select the size of the assessment area and the receptor locations used to calculate the radionuclide concentrations in non-leafy vegetables, leafy vegetables, milk, and meat consumed by the receptors. Depending on the food scenario selected and the type of calculation (“Population” or “Individual”) chosen, the annual effective dose from ingestion can depend on both the size of the assessment area and the location of the receptors. Illustrative examples demonstrate the effect of the choice of these input parameters on the annual effective dose from ingestion. An understanding of the model used in CAP88 and the differences between “Population” and “Individual” run types will enable the CAP88 user to better model the ingestion dose.



  7. Further Developments in Beta-Gamma to Alpha Ratios
    imageAbstract: An emphasis on alpha-emitting nuclides at nuclear power plants has produced methods for assessing the relative hazard of alpha versus other species. From the relative hazards, or ratios, decisions on the level of effort for worker protection and monitoring are made. The Electric Power Research Institute (EPRI) has issued technical guidance on relative alpha hazard and action level beta-gamma to alpha ratios. This paper shows the development of the ratio concept from first principles and brings hard-to-detect species into consideration. Outcomes from the exercise of computational forms of the ratios are compared to the EPRI results and the differences are noted. Some discussion of the implications and advantages of the developed forms then follows.



  8. Using the Health Physics Student Volunteer Program for a Research Project Sponsored by the Medical Section of the Health Physics Society
    Abstract: The Health Physics Society (HPS) Medical Health Physics Section (MHPS) received a request to research data on radiation safety guidance related to the death of patients who have recently received therapeutic doses of sealed or unsealed therapy sources. The MHPS elected to use student volunteers to perform this research. The purpose of this manuscript is to describe and provide a template for the process used by the MHPS to develop a student volunteer program. To implement the student volunteer program, the MHPS collaborated with the HPS Student Support Committee to develop a research proposal and a student volunteer selection process. The research proposal was sent to HPS student members in a call for volunteers. Two student volunteers were chosen based on predetermined qualifications to complete the work effort outlined in the research proposal. This project progressed with the use of milestones and culminated with the students presenting their findings at the annual HPS meeting. The students received HPS student travel awards to present at the conference. This work effort proved to be extremely beneficial to all parties involved.



  9. TRANSITION
    No abstract available



  10. 137Cs Dosimeter Irradiation Facilities: Calibration Frequency, Precision, and Accuracy
    imageAbstract: Many dosimeter and instrument calibration sources, especially 137Cs irradiators permanently installed in facilities, are infrequently calibrated since their geometry is not subject to large variation, their mechanisms are simple, and their operation can be visibly error-free for decades. Only decay corrections are needed to know delivered doses at fixed locations once a thorough characterization of such facilities is completed. For one such 137Cs source, however, collected current values in a span of a few days were found to drop significantly. Malfunction of the internal positioning mechanisms through wear were found to be the cause. This paper suggests periodic source calibrations for the timely identification of source failures that could cause gross errors in dose delivery. In addition, a rigorous analysis of the magnitude of uncertainties and errors in dose delivery using a calibration source is included, which is based upon newly collected experimental data. This provides a technical basis for calibration procedures to ensure a given accuracy and precision of dose delivery.


  11. ERRATUM
    No abstract available



  12. Investigation of Workplace-like Calibration Fields via a Deuterium-Tritium (D-T) Neutron Generator
    imageAbstract: Radiation survey meters and personal dosimeters are typically calibrated in reference neutron fields based on conventional radionuclide sources, such as americium-beryllium (Am-Be) or californium‐252 (252Cf), either unmodified or heavy-water moderated. However, these calibration neutron fields differ significantly from the workplace fields in which most of these survey meters and dosimeters are being used. Although some detectors are designed to yield an approximately dose-equivalent response over a particular neutron energy range, the response of other detectors is highly dependent upon neutron energy. This, in turn, can result in significant over- or underestimation of the intensity of neutron radiation and/or personal dose equivalent determined in the work environment. The use of simulated workplace neutron calibration fields that more closely match those present at the workplace could improve the accuracy of worker, and workplace, neutron dose assessment. This work provides an overview of the neutron fields found around nuclear power reactors and interim spent fuel storage installations based on available data. The feasibility of producing workplace-like calibration fields in an existing calibration facility has been investigated via Monte Carlo simulations. Several moderating assembly configurations, paired with a neutron generator using the deuterium tritium (D-T) fusion reaction, were explored.



  13. Radiation Exposure and Safety Precautions Following 131Cs Brachytherapy in Patients with Brain Tumors
    imageAbstract: Cesium‐131 (131Cs) brachytherapy is a safe and convenient treatment option for patients with resected brain tumors. This study prospectively analyzes radiation exposure in the patient population who were treated with a maximally safe neurosurgical resection and 131Cs brachytherapy. Following implantation, radiation dose rate measurements were taken at the surface, 35 cm, and 100 cm distances. Using the half-life of 131Cs (9.69 d), the dose rates were extrapolated at these distances over a period of time (t = 30 d). Data from dosimetry badges and rings worn by surgeons and radiation oncologists were collected and analyzed. Postoperatively, median dose rate was 0.2475 mSv h−1, 0.01 mSv h−1, and 0.001 mSv h−1 and at 30 d post-implant, 0.0298 mSv h−1, 0.0012 mSv h−1, and 0.0001 mSv h−1 at the surface, 35 cm, and 100 cm, respectively. All but one badge and ring measured a dose equivalent corresponding to ~0 mSv h−1, while 1 badge measured 0.02/0.02/0.02 mSv h−1. There was a significant correlation between the number of seeds implanted and dose rate at the surface (p = 0.0169). When stratified by the number of seeds: 4–15 seeds (n = 14) and 20–50 seeds (n = 4) had median dose rates of 0.1475 mSv h−1 and 0.5565 mSv h−1, respectively (p = 0.0015). Using National Council on Radiation Protection guidelines, this study shows that dose equivalent from permanent 131Cs brachytherapy for the treatment of brain tumors is limited, and it maintains safe levels of exposure to family and medical personnel. Such information is critical knowledge for the neurosurgeons, radiation oncologists, nurses, hospital staff, and family as this method is gaining nationwide popularity.



  14. Contributions from Women to the Radiation Sciences: A Brief History
    Abstract: Contributions from men to radiation science are well known, particularly the early contributions from such luminaries as William Roentgen, James Chadwick, Niels Bohr, Robert Oppenheimer, and the like. Although not ignored per se, beyond Marie Curie and Lise Meitner, the contributions of female nuclear scientists are not as widely recognized. This paper provides a concise historical summary of contributions to radiation science from the discovery of radiation through the current status of international leadership within the radiation protection community. Beyond lead scientists and academics, this paper also considers support personnel as well as the role women have played in the advancement of radiation epidemiology.



  15. Accuracy of Cloudshine Gamma Dose Calculations in the CAP-88 Dispersion Model
    imageAbstract: The U.S. Environmental Protection Agency dispersion model, CAP‐88, calculates ground-level dose using the ground-level concentration and the semi-infinite cloud approximation. Doses can be underestimated for elevated plumes during stable atmospheric conditions at receptor locations within a kilometer downwind of a stack. The purpose of this paper is to identify when CAP‐88 calculations of gamma dose from cloudshine are inaccurate and provide estimates of the inaccuracy. The method used compares CAP‐88 estimates with Monte Carlo N-Particle (MCNP) estimates. Comparisons were made at distances of 800 m and 3,000 m downwind of the stack and for plume heights from 0 to 50 m. For these conditions, the annual dose calculated by CAP‐88 is greater than or equal to that calculated by MCNP.


  16. Review of Gender and Racial Diversity in Radiation Protection
    imageAbstract: The rapidly changing demographics of the United States workforce include a large number of women and members of minority groups that are currently underrepresented in science and engineering-related education and careers. Recent research indicates that while singular incidents of sexism do exist, gender bias more often affects women in various subtle ways. The effects of stereotype threat and the lack of appropriate mentoring and female role models are samples of the possible factors contributing to performance and longevity for women in math-intensive fields. To address how this issue affects those in radiation protection, the current status of women in the field is reviewed as a progression through the scientific pipeline, from education and employment to positions in scientific bodies and professional recognition, with primary focus on American women and institutions. Racial diversity demographics are reviewed where available. Findings indicate women and minority racial groups are underrepresented in multiple aspects of education, research, and leadership. While gender diversity across the field has not yet reached gender parity, trending indicates that the percentage of women earning degrees in radiation protection has consistently increased over the last four decades. Diversity of racial groups, however, has remained fairly consistent and is well below national averages. Diverse perspectives have been documented in collective problem-solving to lead to more innovative solutions.



  17. HEALTH PHYSICS SOCIETY • 2017 AFFILIATE MEMBERS
    No abstract available



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