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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Overview of the Lunar Gateway External Contamination Environment

As a part of the Artemis mission, Gateway will be a long duration space station in a near rectilinear halo orbit around the Moon. Gateway will be exposed to a variety of external contamination sources, which can degrade external hardware / surfaces and impact science utilization objectives. Requirements and methodologies addressing material outgassing, chemical and electric thruster plumes, vacuum venting, and visiting vehicle interactions have been developed by the Gateway Induced Environments team to ensure vehicle performance and mission success. The external contamination requirements and integration process are described along with required data deliverables. Integrated external contamination analyses are conducted by the Gateway Environments Team to assess compliance with external contamination requirements. This paper provides a current status of integration activities and analysis results, as well as future plans to improve external contamination characterization.

thruster plumes↗
DOE OSTI2024

Utilization of Ultrasonication as a Method of Reducing Organic and Inorganic Contamination in Post‐Consumer Plastic Film Waste

Post-consumer plastic film waste often carries organic and inorganic contaminants that challenge recycling processes and affect the quality of recycled products. An effective contaminant removal procedure through washing such single-used plastic films (SUPFs) can address environmental and waste management concerns. This study compares the efficiency of different washing techniques in reducing SUPF contamination. To evaluate the efficacy of each washing technique, film samples collected from material recovery facilities are individually exposed to friction, ultrasonic-assisted, and a combination of both washes. Thermal analysis indicates that the polymers' melting temperature, crystallization temperature, and crystallinity remain unaffected by the washing methods, demonstrating method aptness. Confocal laser scanning microscope images show that washing results in a cleaner sample surface. 91% ash reduction during the combined wash treatment indicates a high method efficiency compared to the individual friction and ultrasonic wash procedures. This is further validated by reducing characteristic contaminant IR bands (3600–3000, 1750–1600, and 1100–1000 cm −1 ). Elements of concern such as Cd, Cr, Hg, and Pb in SUPFs after each washing technique applied conform with regulations (<100 ppm) for packaging products. This research shows the novel ultrasonic washing reduces more contamination than friction with shorter wash times and no surfactants.

42 ENGINEERING↗
DOE OSTI2018

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario’s and risk assessment, and (6) the possibilities of novel methodologies. Here, in spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2018

Rapid Assessment of Contaminants and Interferences in Mass Spectrometry Data Using Skyline

Proper sample preparation in proteomic workflows is essential to the success of modern mass spectrometry experiments. Complex workflows often require reagents which are incompatible with MS analysis (e.g., detergents) necessitating a variety of sample cleanup procedures. Efforts to understand and mitigate sample contamination are a continual source of disruption with respect to both time and resources. To improve the ability to rapidly assess sample contamination from a diverse array of sources, I developed a molecular library in Skyline for rapid extraction of contaminant precursor signals using MS1 filtering. This contaminant template library is easily managed and can be modified for a diverse array of mass spectrometry sample preparation workflows. Utilization of this template allows rapid assessment of sample integrity and indicates potential sources of contamination. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Acetonitrile contamination in the cathode of proton exchange membrane fuel cells and cell performance recovery

Acetonitrile contamination in an operating cell and performance recovery are investigated in detail by a series of electrochemical characterizations, including constant current operation, electrochemical impedance spectroscopy, cyclic voltammetry, linear scanning voltammetry and chronoamperometry. We demonstrate that 20 ppm of acetonitrile in the air stream causes an approximate 40% reduction in cell performance at 1 A cm -2 ; however, the neat air operation completely restores the single cell. Cell performance degradation and recovery display two distinguishable periods that correspond to the effect of catalyst activity and electrolyte proton conductivity, respectively. The potential effect on acetonitrile contamination is also studied in a non-operating H 2 /N 2 cell. The results indicate that low and high potentials cause a larger proton conductivity effect than a medium potential. Two recovery methods were conducted to restore cell performance after contamination in N 2 at different potentials. The neat air operation completely mitigated the poisoning effect in approximately 5 h regardless of contamination history; however, the N 2 purge and subsequent potential scans, even scanning up to 1.5 V vs hydrogen reference electrode, did not affect the poisoned cell. The liquid water generated in catalyst layers may play an important role during the recovery from acetonitrile contamination in a proton exchange membrane fuel cell.

25 ENERGY STORAGE↗
DOE OSTI2023

Geophysical signatures of soil AFFF contamination from spectral induced polarization and low field nuclear magnetic resonance methods

Few field methods are available for characterizing source zones contaminated with aqueous film forming foam (AFFF). Non-invasive geophysical characterization of AFFF source zone contamination in situ could assist with the delineation and characterization of these sites, allowing for more informed sampling regimes aimed at quantifying subsurface poly- and perfluoroalkyl substances (PFAS) contamination. In this study, we present initial results from the investigation of the sensitivity of two existing surface and borehole-deployable geophysical technologies, spectral induced polarization (SIP), and low field nuclear magnetic resonance (NMR), to soils impacted with AFFF. To investigate the sensitivity of these methods to AFFF-impacted soil, bench-scale column experiments were conducted on samples consisting of natural and synthetic soils and groundwater. While our findings do not show strong evidence of NMR sensitivity to soil PFAS contamination, we do find evidence that SIP has sufficient sensitivity to detect PFAS sorption to soils. This finding is based on evidence that AFFF constituents associated with the pore surface produce a measurable polarization response in both freshly contaminated synthetic soils and in soils historically impacted with AFFF.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Comparison of potential drinking water source contamination across one hundred U.S. cities

Abstract Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. Because water quality sampling surveys are often piecemeal, regionally inconsistent, and incomplete with respect to unregulated contaminants, the United States lacks a detailed comparison of potential source water contamination across all of its large cities. Here we combine national-scale geospatial datasets with hydrologic simulations to compute two metrics representing potential contamination of water supplies from point and nonpoint sources for over a hundred U.S. cities. We reveal enormous diversity in anthropogenic activities across watersheds with corresponding disparities in the potential contamination of drinking water supplies to cities. Approximately 5% of large cities rely on water that is composed primarily of runoff from non-pristine lands (e.g., agriculture, residential, industrial), while four-fifths of all large cities that withdraw surface water are exposed to treated wastewater in their supplies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY2018

Desert Research Institute (DRI) is conducting a field assessment of the potential for contaminated soil to be transported from the Smoky Site Contamination Area (CA) as a result of storm runoff. This activity supports U.S. Department of Energy (DOE) Environmental Management Nevada Program (EM NV) efforts to establish post-closure monitoring plans for the Smoky Site Soils Corrective Action Unit (CAU) 550. The work is intended to confirm the likely mechanism of transport and determine the meteorological conditions that might cause the movement of contaminated soils, as well as determine the particle size fraction that is most closely associated with transported radionuclide-contaminated soils. These data will facilitate the design of the appropriate post-closure monitoring program. In 2011, DRI installed a meteorological monitoring station on the west side of the Smoky Site CA and a hydrologic (runoff) monitoring station within the CA, near the east side. The meteorological station collects air temperature, wind speed, wind direction, relative humidity, precipitation, solar radiation, barometric pressure, soil temperature, and soil water content data. The maximum, minimum, and average or total values (as appropriate) for each of these parameters are recorded for each 10-minute interval. The maximum, minimum, and average water depth in the flume installed at the hydrologic station are also recorded for each 10-minute interval. This report presents the data collected from these stations during fiscal year (FY) 2018. During the FY2018 reporting period, the warmest months were June, July, and August and the coldest were December through March. Solar radiation showed the same seasonal trend. Monthly mean wind speeds were highest in the spring (March through May) and early summer (June). Winds were generally from the west during the summer and from the north throughout the fall and winter. The monthly average relative humidity ranged from the mid-teens to approximately 50 percent. Humidity was lowest in the fall and highest in the winter. Monthly total precipitation ranged from 0 in October, December, and June to approximately 1.38 inches (in) (35.05 millimeters [mm]) in July. Total precipitation for FY2018 was 3.86 in (98.04 mm). During the reporting period, two runoff events were recorded at the flume. One occurred on July 14, 2018, in response to precipitation earlier the same day. This event produced a peak water depth of 11.26 in (28.60 centimeters [cm]) in the flume, which is equivalent to a discharge of 1.86 cubic feet per second (cfs) (0.05 cubic meters per second [cm/s]) and a velocity of 3.97 feet per second (fps) (1.21 meters per second [m/s]) through the flume. Applying the flume hydraulic measurements to the channel geometry at the nearest surveyed cross-section it was determined that the velocity through the channel was 1.29 fps (0.39 m/s), which is sufficient to transport silts and fine sands. The second flow event occurred in response to earlier precipitation on September 4, 2018. This event produced a peak water depth of 0.78 in (1.98 cm) in the flume, which is equivalent to a discharge of 0.03 cfs (0.001 cm/s) and a velocity of 1.17 fps (0.36 m/s) through the flume. Applying the flume hydraulic measurements to the channel geometry at the nearest surveyed cross-section it was determined that the velocity through the channel was 0.03 fps (0.01 m/s). Although neither runoff event produced sufficient flow velocities through the natural channel to cause local erosion and transport of coarser bedload materials, the velocity of the first runoff event was sufficient to transport silts and fine sands, which have been shown to be preferentially associated with radionuclide contaminants. Therefore, a sampling event was planned after the first flow event in conjunction with a periodic maintenance inspection. As no suspended load sampling is available at this location, bedload samples were collected from the vicinity of the flume on August 7, 2018. The collected sediment was separated into three particle size fractions and each fraction was analyzed for americium-241 (Am-241), plutonium-238 (Pu-238), and plutonium-239/240 (Pu-239/240) by alpha spectrometry. The two smaller particle size fractions had higher concentrations of all three radionuclides than the largest particle size fraction. Additionally, Pu-239/240 had the highest concentration and Pu-238 had the lowest concentration in all samples. The same relationship between the concentrations of Pu-238 and Pu-239/240 was seen in samples reported in FY2013 and FY2014. Observation of meteorological and environmental conditions that lead to storm runoff will help identify parameters and threshold conditions that should be incorporated into postclosure monitoring plans for this and similar sites as well as aid in determining appropriate closure strategies for other Soils CAUs.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1995

Sub-ppb Oxygen Contaminant Detection in Semi-Conductor Processing

Gaseous contaminants such as oxygen, water vapor, nitrogen and hydrocarbons are often present in the processing environment in semiconductor device fabrication and in containerless materials processing. The contaminants arise as a result of outgassing from hot surfaces or they may be part of the impurities in commercial ultra-high purity gases. Among these gaseous contaminants, oxygen is the most reactive and, therefore, has the most adverse effects on the end product. There has been an intense effort at the Jet Propulsion Laboratory to develop different types of oxygen sorbents to reduce oxygen concentration in a microgravity processing environment to sub-ppb (parts-per-billion) levels. Higher concentrations can lead to rapid surface oxide formation, hence reducing the quality of semiconductor devices. If the concentration of oxygen in a processing chamber at 1000oC is in the ppb level, it will only take approximately 10 seconds for an oxide layer to form on the surface of a sample. The interaction of oxygen with the water surface can lead to the formation of localized defects in semi-conductor devices, hence decreasing the manufacturing yield. For example, efficient production of 64 Mb RAM chips requires contaminations below ppb levels. This paper describes a technique for measuring trace quantities of oxygen contaminants by recording the monoatomic negative ions, O-, using mass spectrometry. The O- formation from the e--O2 interaction utilizes the electron dissociative attachment method that is greatly enhanced at the resonant energy (6.8 eV). The device combines a small gridded electron ionizer with a compact mass spectrometer. The concentrations of oxygen have been measured using the method of standard additions by diluting O2 in N2. The lowest detection limit obtained was 1.2 kHz (O- count rate) at a concentration of 10-10, corresponding to 0.1 ppb.

Sub-ppb Contaminant↗
NASA NTRS2015

Contamination Control for Thermal Engineers

The presentation will be given at the 26th Annual Thermal Fluids Analysis Workshop (TFAWS 2015) hosted by the Goddard Spaceflight Center (GSFC) Thermal Engineering Branch (Code 545). This course will cover the basics of Contamination Control, including contamination control related failures, the effects of contamination on Flight Hardware, what contamination requirements translate to, design methodology, and implementing contamination control into Integration, Testing and Launch.

Design↗
NASA NTRS2017

Tutorial on Atomic Oxygen Effects and Contamination

Atomic oxygen is the most predominant specie in low Earth orbit (LEO) and is contained in the upper atmosphere of many other planetary bodies. Formed by photo-dissociation of molecular oxygen, it is highly reactive and energetic enough to break chemical bonds on the surface of many materials and react with them to form either stable or volatile oxides. The extent of the damage for spacecraft depends a lot on how much atomic oxygen arrives at the surface, the energy of the atoms, and the reactivity of the material that is exposed to it. Oxide formation can result in shrinkage, cracking, or erosion which can also result in changes in optical, thermal, or mechanical properties of the materials exposed. The extent of the reaction can be affected by mechanical loading, temperature, and other environmental components such as ultraviolet radiation or charged particles. Atomic oxygen generally causes a surface reaction, but it can scatter under coatings and into crevices causing oxidation much farther into a spacecraft surface or structure than would be expected. Contamination can also affect system performance. Contamination is generally caused by arrival of volatile species that condense on spacecraft surfaces. The volatiles are typically a result of outgassing of materials that are on the spacecraft. Once the volatiles are condensed on a surface, they can then be fixed on the surface by ultraviolet radiation andor atomic oxygen reaction to form stable surface contaminants that can change optical and thermal properties of materials in power systems, thermal systems, and sensors. This tutorial discusses atomic oxygen erosion and contaminate formation, and the effect they have on typical spacecraft materials. Scattering of atomic oxygen, some effects of combined environments and examples of effects of atomic oxygen and contamination on spacecraft systems and components will also be presented.

Earth orbital environments↗
NASA NTRS2022

Thinking Inside the Box: A Hands-on Student Activity for Building a Contamination Containment Glovebox to Encourage Problem Solving in a Collaborative Environment

Engineers from the National Aeronautics and Space Administration (NASA) and education experts from the Virginia Space Grant Consortium (VSGC) partnered together to create a hands-on student activity to teach students about problem solving, working in a collaborative environment, and about the unique career fields of contamination control and planetary protection. The activity focuses on contamination containment gloveboxes, which are sealed containers where operators outside the glovebox can safely manipulate hazardous or contamination-sensitive materials inside the glovebox through glove ports on the container. The activity utilizes common household materials and teams of students work together to design and build a glovebox using the materials provided. Once the glovebox has been constructed, students perform a task under a time constraint by using their glovebox to assemble a puzzle “contaminated” with corn starch. In a post-activity debrief, teams discuss lessons learned such as how the actual built glovebox differed from the sketched design, the challenge of managing a budget for materials, how the team dealt with surprises, and if their glovebox allowed enough room for the operator to perform the task. This activity has been part of VSGC’s Virginia Earth System Science Scholars (VESSS) summer academy program for high school students since 2016, and has been an engaging method to teach students teamwork, creativity, hands-on experimentation, communication, and reasoning skills while also teaching them about unique engineering fields such as contamination control and planetary protection.

Student activity↗
DOE OSTI2016

Subsoil contaminant Cr fate and transport: The complex reality of the Hanford subsurface

Chromium-contaminated subsurface sites are common throughout the globe. In this chapter the discussion will be focused on one Cr-contaminated, i.e., Hanford site, WA, USA. The chapter summarizes the work conducted at this site to study contaminant Cr6+ fate and behavior under conditions imposed by different waste chemistries ranging from acidic to hyperalkaline. The objectives of this chapter are to present an overview of different aspects of Cr interaction with minerals; present evidence of similar and contrasting Cr6+ reactions, processes and attenuation mechanisms operating in subsurface environments under different conditions imposed by acidic, neutral and alkaline waste liquids; provide inputs to conceptual Cr geochemical models (either site specific or general and suitable for many contaminated sites); present ideas on potential remedial measures. The insights presented and discussed in this chapter should be useful for other Cr contaminated sites across the world.

Hanford subsurface↗
DOE OSTI2017

Remediation of 130 mSv/hr. Soil Contamination Under a Hot Cell - 17301

Department of Energy (DOE) contractor CH2M HILL Plateau Remediation Company (CH2M) is currently engineering a system to safely remove and dispose of highly contaminated soil underneath Building 324 located adjacent to the Columbia River on the Hanford Site in Washington State. Cleaning up the waste site will allow for the eventual demolition of the building, which is a top priority for DOE and CH2M due to the proximity of the Columbia River and City of Richland. Building 324 at Hanford was originally constructed in 1966 and was operated for a number of years serving various missions. One of the missions involved development of treatment processes for liquid high activity waste. As of result of one particular mission, liquid high activity waste was spilled in one of the building's hot cells (known as 'B' Cell) and the liquid leaked from a breach in a sump and through construction joints in the hot cell floor and into the soil. Sampling efforts using borehole technology revealed significant under-building contamination with dose rates measuring has high as 130 mSv/hr (13,000 R/hr.). The Hanford Federal Facility Agreement and Consent Order (Tri-Party Agreement) between the Washington State, Department of Ecology (Ecology), the U.S. Environmental Protection Agency and the DOE has established a 2021 milestone for demolition and removal of the Building 324. Before building demolition can be undertaken, the highly contaminated soil must be removed from beneath the hot cell while the hot cell structure remains in place to provide shielding and containment during the soil remediation. CH2M will fabricate and install remotely operated equipment that will remove debris and grout in the cell, the floor of the hot cell, and the contaminated soil beneath the hot cell and package that soil for disposal. To ensure that the structure remains intact and does not shift during soil removal, support for the building structure must also be constructed as a prerequisite for the planned work. CH2M will use a full-scale mock-up of the Building 324 B Cell and airlock area to assist in the testing of the remotely operated equipment and the training of the soil removal team in a contamination-free environment to ensure efficient and safe performance of the challenging work of the project. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Remediation of Occupied Commercial Property Subject to Widespread Radium-226 Contamination: Update from WM2012 Paper - 16652

Amec Foster Wheeler was contacted by a company that managed commercial office space. High Rn-222 measurements had been observed throughout the facility and the landlord had been advised to commission a radiological survey of the site. The site had been purchased by the client in the 1990's. Initial desk studies found that the building had operated for around 50 years as a compass factory. Non-intrusive investigation identified widespread Ra-226 contamination. Ra-226 was found in the fabric of the building, in attic spaces, buried under floor boards and underlying car parks. Intrusive investigation was undertaken to estimate volume(s) of waste, waste categories, activity concentrations and the total inventory of radioactive materials on site. This work identified the presence of 180 GBq of Ra-226 on site. A programme of work is currently underway to remediate the site tackling areas posing the greatest risk to site occupants as a priority. We have worked closely with Regulators, our client, and tenants, to decontaminate the fabric of the building whilst areas of the building remain occupied. Early decontamination works identified that radon levels within the building were stubbornly high despite the removal of radium contamination. An independent radon source was suspected. A contaminated drain was discovered leading to a blocked-off river race running under the old mill building. A significant quantity of radium contaminated sludge was identified within the river race. This was believed to be the source of the excessive radon concentrations within the building. The paper will present work undertaken to investigate and remediate the inventory of sludge from beneath the building. It will describe the operational difficulties of working within a dynamic environment impacted by high dose rates, high radon concentrations, water ingress and waste retrieval challenges. The paper will present the radiological and environmental impacts of the work and detail the achieved end points. This was a challenging project working in confined spaces impacted by physical and radiological constraints. The remedial action undertaken significantly reduced radon concentrations in the building metres above the river race. It also significantly reduced the likelihood of radium contamination being mobilised into the river and the wider environment. The achieved end point permitted the building to return to uncontrolled commercial use. The end point achieved within the river race will ensure a safe working environment for future regular structural survey work. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Sensing and Sampling of Trace Contaminations by a Dexterous Hexrotor UAV at Nuclear Facilities - 18600

Safe and efficient cleanups are a priority for decontamination and decommissioning of nuclear facilities. The contaminations of byproducts and wastes in such nuclear facilities pose a serious problems while decommissioning, to both the operators and public. Sensing these contaminations and cleaning them is an essential part of the safety procedures. The contaminations might range from low-energy to high-energy byproducts. Sensing these byproducts would require contact based or non-contact based sensing, based on its energy levels. Byproducts such as americium, are low-energy which makes it difficult to sense and sample without contact. Therefore, the workers need to physically swab the surfaces to collect the samples of these contaminations. These tasks pose a great danger for the safety of the human workers which includes the risk to reach greater heights, exposure to the radiation and sampling the entire building. A robotic solution is much more desirable in these cases, where the worker can safely handle the contaminations from a safe area. Use of robotic technologies inside these hazardous environments ensures the safety and enhances the performance. The more suitable robotic solution for reaching great heights and covering large areas of nuclear facilities, are aerial vehicles. Multi-rotor unmanned aerial vehicle (UAV) are chosen for their ability to hover at a position and also fly around in confined spaces. Quadrotors are a common choice of multi-rotor UAVs both research and industry because of its ease to fly and commercial availability. For the applications during the cleanups we need the UAV to not only hover and fly in confined spaces, but also interact with the physical world. Despite of quadrotor's advantages, they are not a best suit as they can't interact with the physical world. The tasks involving physical interactions would require the UAV to apply arbitrary forces and torques in all six degrees of freedom (DOF). As quadrotors are under-actuated and non-holonomic in motion, they cannot exert all the required forces. At Collaborative Robotics Lab, Purdue University, we developed a novel multi-rotor UAV solution, Dexterous Hexrotor, which can exert arbitrary forces and torques in all six DOF, independently and instantaneously. This enables the UAV platform to quickly respond to the external disturbances and precisely hold its position during the mission. The Dexterous Hexrotor serves as a robotic tool for the workers to perform sensing and sampling during the cleanups. Workers can operate Dexterous Hexrotor manually and/or semi-autonomously with human intervention. Manual control requires the worker to fly the Dexterous Hexrotor using a remote control. So the workers should possess knowledge on flying the UAV and to perform physical interaction. A semiautonomous Dexterous Hexrotor requires human input to some extent and requires very less knowledge of flying. The autonomy is designed to operate in flight mode and sampling mode. In flight mode, Dexterous Hexrotor takes off from a 'safe' area, reaches the desired altitude, and fly autonomously towards a sampling point. This sampling point is the target position specified on the 2D reference map. This mode also includes navigation towards the sampling point, avoiding the obstacles in the constrained environment. After reaching a stopping point, Dexterous Hexrotor waits for the human input for a target location to swab and collect samples. The Dexterous Hexrotor is now in sampling mode and waits for the human input. The human operator selects the swabbing location through the live streaming video from onboard camera. Through visual servoing, aided by the map, the UAV will move closer towards the target position. It then transitions to the impact control scheme to perform physical interaction with the wall and collects samples. Once the sample is collected, it autonomously returns back to the takeoff position in 'safe' area for the analysis by mass spectrometry. In this paper, we majorly focus on the physical interaction strategy and the required components which enables the autonomy. Decommissioning of nuclear facilities requires decontamination inside the entire buildings. Decontamination of nuclear facilities involves sensing and sampling the huge buildings, long shafts, etc. Sampling the entire facility is not possible due to the limitation in Dexterous Hexrotor's flight time. But this can be achieved by using a swarm of Dexterous Hexrotors to cover larger areas. The onboard robotic arm can be designed based on the applications such as cleaning, applying sealants, etc. The modularity of the design allows us to switch components as per the requirements of the task. These kind of robotic solutions functioning as tools for the workers, aims to make the work environment safer and playful. (authors)

42 ENGINEERING↗
DOE OSTI2019

Stability of a Uranium-Contaminated Plume in a Karst Aquifer in Northwest New Mexico - 19574

The US Department of Energy (DOE) Office of Legacy Management monitors groundwater contamination resulting from ore processing operations conducted between 1953 and 1982 at a former uranium mill site on property that is now part of the Bluewater, New Mexico, Disposal Site. The site is located in the Grants Mineral Belt in northwest New Mexico at the base of the Zuni Mountains. It is estimated that prior to mill tailings encapsulation in 1995, approximately 21.6 billion liters (5.7 billion gallons) of tailings fluid seeped from the main tailings impoundment into the underlying aquifers. Today, there is remnant groundwater contamination from the mill in two aquifers: the San Andres-Glorieta (SAG) bedrock aquifer and the Ancestral Rio San Jose alluvial aquifer. Groundwater contamination in the SAG aquifer is of particular concern, as the aquifer is the primary water source in the region for municipal, agricultural, and industrial use. Municipal wells for the region are located as close as 6.4 kilometers (4 miles) southeast of the Main Tailings Disposal Cell. The SAG uranium plume extends east for more than 4.8 kilometers (3 miles) beyond the site's eastern boundary, along the direction of groundwater flow. The plume intersects the Homestake Mining Company site, another former uranium mill site undergoing active remediation. The SAG aquifer contains two formations, the Lower Permian San Andres Limestone and the Glorieta Sandstone. Most of the groundwater moving through the SAG aquifer is in ancient karst features consisting of open conduits where the limestone has dissolved, resulting in flow through solution cavities, solution channels, cavernous zones, and enlarged fracture openings. These features make the San Andres Limestone extremely permeable and capable of rapidly transporting groundwater. In addition, the karst characteristics make the aquifer difficult to evaluate and the uranium plume difficult to characterize. Numerous faults in the area, including two directly under the Main Tailings Disposal Cell, further complicate characterization by impacting groundwater flow both onsite and in the vicinity. A DOE study of the SAG aquifer uranium plume at the Bluewater site, conducted in 2014, indicated that the plume had moved offsite soon after the start of milling and effectively stabilized in its present location prior to the 1980's. An updated study completed in 2018 confirmed previous information regarding general plume stability and provided insight regarding potential localized trends east and south of the Main Tailings Disposal Cell. One such trend may be decreasing uranium concentrations east of the Main Tailings Disposal Cell, potentially attributable to regional groundwater elevation decreases. Both the 2013 and 2017 plumes suggest that the dissolved uranium contamination is derived from the leaching of a secondary mineralized zone derived from seeped tailings fluids in the geologic formations and fault zones below the Main Tailings Disposal Cell at the Bluewater site. In developing the 2013 and 2017 SAG aquifer uranium plume depictions, DOE had to address challenges associated with data quality and comparability. Analytical results used to determine the plume extent were compiled from multiple sources, including the state of New Mexico, Homestake Mining Company, and DOE. Each source used different well identifiers and coordinate systems, and well information between sources was inconsistent. Also, the integrity of some wells was questionable and necessitated review; casing integrity was found to be compromised in multiple wells. Given these uncertainties, some of these wells were excluded from the characterization. Another source of uncertainty is the paucity of wells, particularly monitoring wells, near or immediately downgradient of the leading edge of the plume. Therefore, the exact extent of the SAG aquifer uranium plume is not known at this time. There is, however, no evidence or indication of milling-related contamination in municipal wells. Furthermore, due to plume stability and direction of groundwater flow, the municipal wells are not expected to be impacted. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Study of an Unrefined Humate Solution as a Possible Attenuation-based Remedy for Uranium Contamination in Acidic Groundwater - 20351

The Savannah River Site (SRS), joined the environmental cleanup program in 1981 after the Cold War, and was designated as a hazardous waste management facility. About 1.8 billion gallons of acid wastes were disposed into the F/H Area Seepage Basin that included many radionuclides and dissolved metals, resulting in highly contaminated groundwater plumes with pH of 3 - 5.5. The acidity of the plumes contributes to the mobility of several constituents of concern (COC) such as H-3, U-238, I-129, and Sr-90 for the F-Area plume and H-3, Sr-90 and mercury for the H-Area plume. An active treatment (pump-and-treat and re-injection) system was constructed and put in place in 1997 to address the removal of metals and radionuclides from the contaminated groundwater. As remediation projects advanced, active treatments were transitioned to more passive or enhanced-passive approaches such as the subsurface barrier with base injection system, which has been controlling the mobility of contaminants. However, new and more efficient attenuation-based remedies are always sought. Several studies have proposed that humic substances can be used to remediate sites contaminated with heavy metals by creating a permeable reactive barrier. Humic substances (HS) are major components of soil organic matter. HS are polyfunctional organic macromolecules formed by the chemo-microbiological decomposition of biomass or dead organic matter. These substances are usually divided into three main fractions: humin (insoluble at all pH values), humic acid (soluble at pH greater than 3.5), and fulvic acid (soluble at all pH values). Humic substances are major components of the soil at SRS and, in addition, are also helpful in the removal process of uranium. This research focuses on uranium (VI), which is a key contaminant of concern in the F-Area groundwater plume. The interaction of uranium with sediment in the presence or absence of humic substances involves complex mechanisms that are not yet well understood. The interaction of U(VI) with humic substances can affect the adsorption of U on sediment, altering its mobility in the subsurface. The objective of this study is to study the mobility of uranium in the presence of humic acid and to determine if sediments amended by humic acid can enhance the sorption of heavy metals onto sediments. In this research, experiments were conducted using background (clean) F-Area aquifer sediments to understand and predict uranium mobility. A blended material, humate, containing both humic and fulvic acids and a chemically modified humate (KW15 modified humic or mod-HA) was studied as a possible amendment for uranium remediation in SRS groundwater. Batch experiments were conducted in triplicates using 20 ml of aqueous suspension in DI water containing SRS sediment and mod-HA and studied the effect of pH, kinetics of humate sorption onto SRS sediment and also studied the sorption of uranium onto mod-HA amended SRS sediment. Results indicate that mod-HA amended sediment increases uranium removal significantly. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗