2020 Health Physics Society Midyear Meeting & ExhibitionMAM-A
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| Chair(s): Claude Wiblin, Bruce Biwer |
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MAM-A.1 10:00 Radioactive Dust Emissions Across Ecosystems . Whicker Jeffrey*, Los Alamos Nat. Lab.; McNaughton Michael, Los Alamos Nat. Lab.; Breshears David, Univ. Arizona jjwhicker@lanl.gov
Radionuclide resuspension by wind was initially investigated during the era of aboveground nuclear weapons testing. The concern was for increased public inhalation exposure to wind-driven radioactive dust emitted, in particular, from arid sites with sparse vegetation and erodible soil. Resulting resuspension models were developed from empirically-derived ratios of air and soil concentrations. These models were shown to generally predict air concentrations, but the model parameters were site-specific and mostly derived from arid and semi-arid environments surrounding nuclear weapons testing locations. After radionuclide releases from the nuclear power plants at Chernobyl and Fukushima, related studies provided new data on resuspension in more temperate climates. A broad range of resuspension values emerged from the combined studies revealing numerous unaccounted complexities, large uncertainties, and the environmental drivers for these large ranges were often unclear. While modeling of resuspension and downwind dispersion helps inform dose assessments, given the uncertainty and limitations inherent in these model predictions, dose estimates from resuspended dust are necessarily qualitative in nature, and conservative assumptions are generally made for upper-bound estimates. Also lacking is a more generalized picture of resuspension across the broad range of ecosystems. In contrast, wind erosion studies from the agricultural and environmental science have produced more mechanistic models and a relatively robust data set of wind erosion rates and model parameters across a range of ecosystems. Here, we combine wind erosion measurements with the radiological resuspension paradigm to attempt to provide a more integrated picture of contaminant transport by wind erosion across a broad range of ecosystems. |
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MAM-A.2 10:15 Environmental Impacts of Acid In-Situ Recovery Uranium Mining. Alemayehu Bemnet*, NRDC; McKinzie Matthew, NRDC balemayehu@nrdc.org
Commercial in-situ recovery (ISR) operations in the United States have used an alkaline lixiviant since the mid-1980s. However, the state of Wyoming has recently approved the field demonstration and testing of acid ISR uranium production. The objective of this presentation is to examine: 1) the differences between alkaline and acidic lixiviants; 2) historical groundwater impacts at other sites where acid lixiviants were used; 3) potential environmental risks; and 4) regulatory issues associated with the shift in operational chemical lixiviants. Acid lixiviants have been used almost exclusively at ISR projects internationally. Several ISR operators conducted pilot tests using acid leach systems. Results from the ISR project case studies showed groundwater contamination. Case studies that are analyzed include Reno Creek, Wyoming, Straz pod Ralskem, Czech Republic, Königstein Mine, Germany, and Irkol Deposit, Kazakhstan. Acid lixiviants, as opposed to alkaline, enhance the solubility of uranium by decreasing the pH in contact with the uranium deposits. The acidic conditions promote the release of radionuclides and toxic metals into the groundwater. The type and magnitude of release is a function of the availability of radionuclides and metals within the host rock, which can vary depending upon the geological formation. These characteristics of acid lixiviants present concerns and call for a thorough assessment of its environmental impacts. |
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MAM-A.3 10:30 Technical Basis For Clearance Of VLLW Soil To Landfills. Wiblin Claude *, Tidewater, Inc; Gaul Wayne, Tidewater, Inc; Reese James, Tidewater, Inc. claudewiblin@verizon.net
Work on comprehensive clearance criteria for items, equipment, and facilities with surface or volume radioactive materials has been ongoing for years. Clearance means the removal of radiological controls by the licensing authority. ANSI N13.12-2013 has provided a standard considering radioactive materials on surfaces and volumes but did not specifically address soil. NRC’s NUREG-1640 has provided a complete description of calculations and results estimating potential annual doses, normalized to a unit concentration, to an individual following the clearance of specific materials: scrap iron and steel, copper, aluminum, and concrete rubble. Missing is a discussion of clearance of soil specifically for use in landfills. This paper provides a description of calculations and results estimating potential annual doses, normalized to a unit concentration, to an individual following the clearance of soil to a landfill. With a view to being conservative, the estimated potential doses are calculated to account for a large number of possible variations in each of the scenarios that could occur after LLRW leaves the licensee. These scenarios encompass the full range of realistic situations likely to yield the greatest normalized doses. Critical groups included the truck driver, the landfill worker, offsite residents during and post landfill closure, and the resident farmer 30 years past closure. Each scenario was analyzed with the radionuclides considered most likely to be associated with materials from licensed nuclear facilities as listed in NUREG-1640. The design basis of the analyses is to realistically model current processes, to identify critical groups on a nuclide-by-nuclide basis, and to enable the conversion of a dose criterion to a concentration. The purpose of this evaluation is to illustrate a method that a licensee might apply with site specific parameters to develop DCGLs at the 1 mrem/y criterion that the regulator might accept for soil clearance to a landfill. |
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MAM-A.4 10:45 EPRI Demonstration of an Autonomous Site Characterization Vehicle . McGrath Richard*, EPRI; Bronson Frazier, Mirion Technologies - Canberra fbronson@mirion.com
Performing radiological characterization of structures and land areas during decommissioning of a nuclear facility involved multiple surveys of land areas and large structures to support remedial action and then and eventual Final Status Survey for site release. These surveys are typically performed using manual methods, which is time consuming and labor intensive. Due to the repetitive effort of performing surveys over large areas, automation of radiological characterization techniques has a high potential to be successful and promises substantial benefit. EPRI has performed a project that started with the development and the eventual demonstration of an autonomous site characterization system. This EPRI project focused on building surfaces and the surfaces of large land areas as these configurations lend themselves more readily to automated survey. The project used an existing EPRI robot platform, but included the development of a LIDAR mapping program to define the limits of the robot pathways, and to provide location information about the robot when inside. A GPS provides the location when outside. The radiation sensors were supplied by Mirion Technologies – Canberra, and included an LED-stabilized 3x3 NaI detector, MCA, ISOCS efficiency calibration, and a Data Analyst to repeatedly collect and analyze each 3-second spectrum. Nuclide results are obtained each 3 second. Dual sensors were deployed spaced 1 or 2 meters apart to reduce the survey time. The EPRI geo-mapping algorithms are then used to generate nuclide-specific contour maps. The system was successfully demonstrated at the Kewaunee nuclear power plant site in the fall of 2019. The demonstration included autonomous surveys of floor areas inside the Auxiliary Building, and autonomous surveys of environmental areas where potentially radioactive items were stored in the past. |
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MAM-A.5 11:00 MILDOS v4.2, Development Update. Biwer Bruce*, Argonne National Laboratory; Sun Casper, U.S. Nuclear Regulatory Commission bbiwer@anl.gov
The MILDOS computer code is used to estimate the radiological impacts of airborne emissions, radon and airborne particulates, from conventional uranium ore operations and in situ recovery (ISR) facilities. The code is used by U.S. Nuclear Regulatory Commission (NRC) license applicants and NRC staff to assess radiological impact and compliance validation for routine and various uranium recovery operations. MILDOS is continually being updated to address emerging issues to meet the needs of its users. The latest version (v4.2) contains a built-in population generation module which is based on United States (US) Census block data for the conterminous US released by the Census Bureau from the 2016 “American Community Survey 5-Year Data.” The new module calculates the number of persons expected in each of the 192 population segments defined by 12 distance ranges out to an 80 km radius for 16 directions. In addition, the generation of custom detailed output graphics has been added to aid in the visualization and understanding of results that takes advantage of the database functionality of the user files. Users can drill down to visualize information on all downwind distance air, ground, and food concentrations as well as receptor doses according to variables that include receptor location, emission source, radionuclide, particle size, time, and pathway. Depending on the nature of the results to be viewed, graphs selected to be included in the output report can be generated in column, stacked column, grid, radar, and scatter formats. |
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MAM-A.7 11:15 A study of indoor radon thoron and their progeny concentration measurement in Mizoram India. Chhangte Lawrece Z*, Govt. Zirtiri Residential Science College; Pachuau Zaithanzauva, Mizoram University; Pachuau Rohmingliana, Govt. Zirtiri Residential Science College; Bawitlung Zoliana, Govt. Zirtiri Residential Science College; Sahoo Bijay K, Bhabha Atomic Research Centre; Sapra Balvinder K , Bhabha Atomic Research Centre lawrencechhangte@gzrsc.edu.in
Indoor radon, thoron and their progenies as environmental pollutant is now widely accepted as the most important component of radiation exposure to the public due to the inhalation. The level of health risk associated with average indoor level is much higher than those due to other environmental carcinogens. They the most significant source of natural background radiation, contributing about 50% of the natural background radiation dose to the public and are identified as the leading environmental cause of lung cancer next to smoking. The fact that Mizoram has the highest lung cancer incidence rate (32.6 and 29.3 per 100,000 in male and female respectively) in India report urges the need to quantify indoor concentration of these gases. The radioactive content of the main source of indoor radon and thoron concentrations like soil and commonly used building materials are also measured using gamma spectroscopy. For measurement of indoor radon and thoron concentration, passive measurement technique using Solid State Nuclear Track Detector (LR-115 Type-II) in Pin-Hole Based Twin Cup dosimeters with single entry developed and calibrated at Bhabha Atomic Research Centre, Mumbai was used. The concentrations of progenies are determined through Equivalent Equilibrium Radon/Thoron Concentrations (EERC & EETC) using deposition based Direct Progeny Sensors (DRPS/DTPS) in bare modes. The annual average indoor radon, thoron and their progenies concentrations are on the higher side of the average worldwide and national average values, but below the action level recommended by the WHO and ICRP in dwellings. The activity concentration of primordial radionuclides in all the soil and building materials are lower than the critical value describes by the International Atomic Energy Agency. |