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DOE OSTI2023

Surface Processes Control the Fate of Reactive Oxidants Generated by Electrochemical Activation of Hydrogen Peroxide on Stainless-Steel Electrodes

Low-cost stainless-steel electrodes can activate hydrogen peroxide (H 2 O 2 ) by converting it into a hydroxyl radical ( • OH) and other reactive oxidants. At an applied potential of +0.020 V, the stainless-steel electrode produced • OH with a yield that was over an order of magnitude higher than that reported for other systems that employ iron oxides as catalysts under circumneutral pH conditions. Decreasing the applied potential at pH 8 and 9 enhanced the rate of H 2 O 2 loss by shifting the process to a reaction mechanism that resulted in the formation of an Fe(IV) species. Significant metal leaching was only observed under acidic pH conditions (i.e., at pH <6), with the release of dissolved Fe and Cr occurring as the thickness of the passivation layer decreased. Despite the relatively high yield of • OH production under circumneutral pH conditions, most of the oxidants were scavenged by the electrode surface when contaminant concentrations comparable to those expected in drinking water sources were tested. The stainless-steel electrode efficiently removed trace organic contaminants from an authentic surface water sample without contaminating the water with Fe and Cr. With further development, stainless-steel electrodes could provide a cost-effective alternative to other H 2 O 2 activation processes, such as those by ultraviolet light.

42 ENGINEERING↗

DOE OSTI2016

Implementation of Enhanced Attenuation at the DOE Mound Site OU-1 Landfill: Accelerating Progress and Reducing Costs - 16270

A field demonstration of enhanced attenuation (EA) was initiated in 2014 to expedite the remediation of industrial solvents in the groundwater impacted by the former landfill Operable Unit 1 (OU-1) at the US Department of Energy (DOE) Mound, Ohio, Site. EA uses active engineering solutions to alter the target site so that the contaminant plume will passively stabilize and shrink. For OU-1, the EA was implemented by targeted injection of an electron donor (vegetable oil) to create 'structured geochemical zones'. Volatile organic compounds (VOCs) in the altered subsurface system encounter alternating anaerobic and aerobic environments along the plume flow path. The effect of these structured geochemical zones is effective and rapid degradation of parent compounds such as trichloroethene (TCE) and tetrachloroethene (PCE), and daughter compounds such as cis-1,2-dichloroethene and vinyl chloride. EA at Mound OU-1 provides a transition to natural attenuation and is an alternative to the baseline pump-and-treat (P and T) system. Industrial solvents (primarily TCE) and other VOCs that originated from the former solid-waste landfill contaminated the groundwater in the Buried Valley Aquifer beneath the Mound site. A groundwater P and T system was initiated in 1996 to control the plume, and a soil vapor extraction system was installed and operated from 1997 to 2003 to remove the bulk of the VOC sources from the vadose zone. Physical removal of the landfill waste and contaminated soil was performed between 2006 and 2010. Approximately 76,100 cubic meters (99,500 cubic yards) of material were removed from the OU-1 landfill area. Operation of the groundwater P and T system continued throughout this period. The principles and technical basis of the ongoing EA field demonstration were developed by the Interstate Technology and Regulatory Council. The goal of the EA implementation is to provide a bridge between active groundwater treatments and monitored natural attenuation. EA relies on understanding and manipulating the contaminant mass balance. Technologies are applied to sustainably reduce the contaminant loading from the source and/or increase the rate of natural attenuation processes within the plume. In 2014, a core team that included DOE, the US Environmental Protection Agency (EPA), the Ohio EPA, and technical support organizations evaluated remedial options for OU-1. During the 2014 evaluation, the team projected a cleanup time frame for the baseline P and T system of 26 additional years and a cleanup time frame for the EA remedy of 13 years. On the basis of that evaluation, EPA approved the implementation of the EA remedy that required the shutdown of the P and T system. The combination of technologies implemented for OU-1 EA included (a) neat vegetable oil in the vadose zone in the former landfill and (b) emulsified vegetable oil within the footprint of the groundwater plume. In the first part of the deployment, neat oil spreads laterally and forms a thin layer on the water table beneath residual soil sources to intercept and reduce future VOC loading and to reduce oxygen inputs to the local groundwater. In the second part of the deployment, emulsified oil forms active bioremediation anaerobic treatment zones within the plume footprint to degrade existing groundwater contaminants (via reductive dechlorination, co-metabolism, or both) and stimulates long-term attenuation capacity in the down-gradient aerobic plume (via co-metabolism). The results from the first year of the field demonstration indicate that the dissolved TCE and PCE plumes have decreased in size and mass. Statistical tests indicate that the VOC concentrations in the majority of the source-area wells are decreasing. The VOC concentrations throughout the plume are projected to be below the target maximum contaminant level of 2 to 5 μg/L within 5 to 10 years-sooner than the design projection of 13 years. The biogeochemistry and microbial community within the structured geochemical zones are consistent with the design and appear to be stable. At Mound OU-1, EA has accelerated progress toward the remedial action objectives and reduced costs. Ongoing monitoring will determine whether the EA remedy has transitioned the site into monitored natural attenuation status and whether the EA will continue to be effective, timely, and sustainable. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Environmental Systems Microbiology of Contaminated Environments

Environmental Systems Microbiology is well positioned to move forward in dynamic complex system analysis probing new questions and developing new insight into the function, robustness and resilience in response to anthropogenic perturbations. Recent studies have demonstrated that natural bacterial communities can be used as quantitative biosensors in both groundwater and deep ocean water, predicting oil concentration from the Gulf of Mexico Deep Water Horizon spill and from groundwater at nuclear production waste sites (16, 17, 25). Since the first demonstration of catabolic gene expression in soil remediation (34) it has been clear that extension beyond organismal abundance to process and function of microbial communities as a whole using the whole suite of omic tools available to the post genomic era. Metatranscriptomics have been highlighted as a prime vehicle for understanding responses to environmental drivers (35) in complex systems and with rapidly developing metabolomics, full functional understanding of complex community biogeochemical cycling is an achievable goal. Perhaps more exciting is the dynamic nature of these systems and their complex adaptive strategies that may lead to new control paradigms and emergence of new states and function in the course of a changing environment.

Sayler, Gary↗

DOE OSTI2016

Feasibility Studies on a Hexagonal-Lattice Core for a World-Class Cold Neutron Source

Cold neutrons have kinetic energies less than 5 meV and wavelengths greater than 4 Α. They can be transported over tens of meters through super-reflecting neutron guides with minimal losses. Cold neutrons are used to investigate the structure of larger molecular systems such as biological materials, polymers and aggregates, due to their preferential interaction with light elements and general ignorance towards heavy ones. Intense beams of cold neutrons are obtained from slowing down a source of thermal energy neutrons - which may be from either a research reactor or spallation neutron source - through some cryogenic moderator such as liquid hydrogen or deuterium. The present reactor at the NIST Center for Neutron Research (NCNR) - NBSR - is such a cold neutron source (CNS) facility which provides cold neutron beams for over 2,000 scientists performing various experiments annually. Feasibility studies on a replacement reactor for the NBSR are underway at NCNR with the primary purpose of optimized cold neutron production. Low enriched uranium (LEU) fuel is required for the new reactor to conform to nuclear non-proliferation agreements. The low thermal power rate of 20 MW is taken as a priority with a fuel cycle length designated as 30 days. A horizontal split compact core with a large D{sub 2}O reflector tank is currently proposed and studied, with the expectation of achieving much better cold neutron performance than the present NIST reactor (NBSR). A preliminary core design has been completed using MCNP6 modeling and simulation. The physics performance characteristics of the proposed new core indicate that the new design is competitive with the most notable existing advanced cold neutron sources. In previous studies, only rectangular shaped fuel elements were considered because they have similar external dimensions as the NBSR fuel elements. However, from a compact core standpoint, a square lattice is not the most effective geometry for a tight configuration. Moreover, the previous studies also showed that the square lattice of the fuel elements left little room to accommodate vertical insertion blade-type control elements. As a result, all control blades had to reside in the D{sub 2}O reflector, which made the design cumbersome (in that case the control blades must penetrate the reflector tank) and neutronically uneconomical. In this summary, a preliminary feasibility study on a hexagonal core lattice is performed to render an alternative geometry for the new reactor (HEX core) to provide sufficient space for the control elements. The identical LEU fuel (U{sub 3}Si{sub 2}/Al) with U-235 enrichment 19.75% is used in the new design. The maximum thermal power and fuel management scheme remain the same as the previous investigations (three 30-day cycled batches for each batch of three fuel elements). The horizontal split compact core concept is also applied in the hexagonal lattice core design, with the objective of creating maximum thermal flux traps between the split core halves. A detailed description of the model for the hexagonal lattice core is presented in the following section. The HEX core design achieves a number of successes over the previous split-core design. Given that much of the motivation of this work was based on implementation of control blades into a concept which lacked them, it is notable that neutron economy was well-preserved in the process of achieving conservatively effective reactivity control; start-up k{sub eff} was in fact increased by 0.23% and peak thermal flux increased by ∼25%. A useful metric in determining the efficacy of resources towards creating an environment for the production of cold neutrons - dubbed the 'quality factor' (QF) - is the ratio of peak thermal neutron flux in a system to the total thermal power produced. Because HEX core's objectives are very focused in comparison to existing research reactors, it is fitting to pursue a design which out-performs all others in terms of some specific performance metric, namely this QF term. While HFIR remains the greatest cold neutron source in the world, it does so through use of HEU fuel (which will be replaced with LEU in the near future), and suffers a greater level of fast neutron contamination that is expected from the HEX design. The new core design achieves these successes due to the hexagonal lattice fuel arrangement, a 13.5% reduction in cladding mass, and a 13.1% reduction in fuel element volume. In spite of a 5.5% reduction in fuel mass, no compromises in reactor performance were noted. Provided the favorable characteristics shown of the control blade design, refueling intervals longer than the prescribed 30 days may be considered. It can be speculated that with these quantitative benefits, the overall capital and continuous costs of the HEX core design will be less than the previously proposed split-core concept.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2022

UV/chlorine advanced oxidation processes for degradation of contaminants in water and wastewater: A comprehensive review

Advanced oxidation processes (AOPs) have recently gained increasing attention as promising alternatives to conventional water and wastewater treatment technologies. As an AOP, there has been a growing interest in UV/chlorine due to its multiple disinfection modes and ability to maintain chlorine residuals in drinking water distribution systems. Compared to the popular UV/H 2 O 2 AOP treatment process, UV/chlorine AOP possesses several advantages including a higher radical production efficiency and a lower power demand. The process has recently been applied for the degradation of a wide range of natural and synthetic organic as well as inorganic compounds including pharmaceutical and personal care products, natural organic matter, herbicides and insecticides, taste and odor, and different types of water and wastewaters. The focus of the present work is to review and evaluate the efficiency of the UV/chlorine process on the oxidation of these pollutants. Here a critical overview is provided of the fundamentals of UV/chlorine, controlling factors of the process performance, and a comparison with other UV-based AOPs. The formation of disinfection by-products (DBPs), one of the concerns associated with UV/chlorine treatment, is discussed and strategies to tackle this obstacle are provided for future studies and applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1988

Analysis of the performance of the space ultravacuum research facility in attached and free-flyer mode

The old concept of using the wake of a spacecraft to obtain an ultrahigh vacuum is revisited with a somewhat different emphasis. Since it is possible to configure a wake shield so that a surface of interest does not subtend any walls that could become contaminated, it appears that it should be possible to achieve a contamination-free, ultrahigh vacuum capability with infinite pumping speed even in the presence of high heat loads and moderate gas loads. With the new interest in developing thin films with precision controlled synthetic microstructures such as superlattices, mixed metal oxide high temperature superconductors, rare-earth magneto-optical devices, and nano-crystalline alloys, the ability to work with a variety of different materials without cross contamination should be of significance. This paper analyzes the performance of the conceptual design for a Space Ultravacuum Research Facility (SURF), both in a Shuttle-attached mode and as a free-flyer. It is shown that even in the Shuttle-attached mode, it should be possible to obtain vacuum levels equivalent to 10 to the -10 Torr with O and N2 as the primary constituents. This should be sufficient to demonstrate the feasibility of the concept, particularly the infinite pumping speed and virtual elimination of contamination aspects. As a free-flyer the SURF will be limited primarily by the gas load associated with the process being performed. For chemical beam epitaxy (CBE) it is shown that equivalent vacuum levels of 10 to the -14 Torr should be possible at 300 km.

Naumann, Robert J.↗

DOE OSTI2018

Hydrogeological and hydrochemical investigation of groundwater using environmental isotopes ({sup 18}O, {sup 2}H, {sup 3}H, {sup 14}C) and chemical tracers: a case study of the intermediate aquifer, Sfax, southeastern Tunisia

Major element concentrations and stable (δ{sup 18}O and δ{sup 2}H) and radiogenic ({sup 3}H and {sup 14}C) isotopes in groundwater have proved useful tracers for understanding the geochemical processes that control groundwater mineralization and for identifying recharge sources in the semi-arid region of Sfax (southeastern Tunisia). Major-ion chemical data indicate that the origins of the salinity in the groundwater are the water–rock interactions, mainly the dissolution of evaporitic minerals, as well as the cation exchange with clay minerals. The δ{sup 18}O and δ{sup 2}H relationships suggest variations in groundwater recharge mechanisms. Strong evaporation during recharge with limited rapid water infiltration is evident in the groundwater of the intermediate aquifer. The mixing with old groundwater in some areas explains the low stable isotope values of some groundwater samples. Groundwaters from the intermediate aquifer are classified into two main water types: Ca-Na-SO{sub 4} and Ca-Na-Cl-SO{sub 4}. The high nitrate concentrations suggest an anthropogenic source of nitrogen contamination caused by intensive agricultural activities in the area. The stable isotopic signatures reveal three water groups: non-evaporated waters that indicate recharge by recent infiltrated water; evaporated waters that are characterized by relatively enriched δ{sup 18}O and δ{sup 2}H contents; and mixed groundwater (old/recent) or ancient groundwater, characterized by their depleted isotopic composition. Tritium data support the existence of recent limited recharge; however, other low tritium values are indicative of pre-nuclear recharge and/or mixing between pre-nuclear and contemporaneous recharge. The carbon-14 activities indicate that the groundwaters were mostly recharged under different climatic conditions during the cooler periods of the late Pleistocene and Holocene.

58 GEOSCIENCES↗

DOE OSTI2012

LONG-TERM STEWARDSHIP AT DOE HANFORD SITE - 12575

The U.S. Department of Energy's (DOE) Hanford Site is located in southeast Washington and consists of 1,518 square kilometers (586 square miles) of land. Established in 1943 as part of the Manhattan Project, Hanford workers produced plutonium for our nation's nuclear defense program until the mid 1980's. Since then, the site has been in cleanup mode that is being accomplished in phases. As we achieve remedial objectives and complete active cleanup, DOE will manage Hanford land under the Long-Term Stewardship (LTS) Program until completion of cleanup and the site becomes ready for transfer to the post cleanup landlord - currently planned for DOE's Office of Legacy Management (LM). We define Hanford's LTS Program in the ''Hanford Long-Term Stewardship Program Plan,'' (DOE/RL-201 0-35)[1], which describes the scope including the relationship between the cleanup projects and the LTS Program. DOE designed the LTS Program to manage and provide surveillance and maintenance (S&M) of institutional controls and associated monitoring of closed waste sites to ensure the protection of human health and the environment. DOE's Richland Operations Office (DOE-RL) and Hanford cleanup and operations contractors collaboratively developed this program over several years. The program's scope also includes 15 key activities that are identified in the DOE Program Plan (DOE/RL-2010-35). The LTS Program will transition 14 land segments through 2016. The combined land mass is approximately 570 square kilometers (220 square miles), with over 1,300 active and inactive waste sites and 3,363 wells. Land segments vary from buffer zone property with no known contamination to cocooned reactor buildings, demolished support facilities, and remediated cribs and trenches. DOE-RL will transition land management responsibilities from cleanup contractors to the Mission Support Contract (MSC), who will then administer the LTS Program for DOE-RL. This process requires an environment of cooperation between the contractors and DOE-RL. Information Management (IM) is a key part of the LTS program. The IM Program identifies, locates, stores, protects and makes accessible Hanford LTS records and data to support the transfer of property ultimately to LM. As such, DOE-RL manages the Hanford LTS Program in a manner consistent with LM's goals, policies, and procedures.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Consequence Analysis of Residual Water in a Storage Canister (Preliminary Report)

The objective of this work is to examine the consequences of a residual water on change in condition of cladding and SNF during dry storage. Small amounts of residual water may remain in SNF dry storage canisters after the fuel assemblies are transferred to the canister in the spent fuel pool (SFP), the canister is removed from the SFP and drained or pumped, vacuum dried in several pressure reducing steps, and backfilled with helium. This residual water from incomplete drying could degrade fuel rod cladding, oxidize exposed fuel pellets, and cause cladding failure resulting in SNF fines’ release in canister cavity. If residual water content is high enough, it could corrode internal components inside the canister, e.g., fuel basket, and neutron absorber plates, but CNWRA work indicated that corrosion of the internal component is expected to be negligible even with 55 moles of residual water. Considering this, focus of this work to determine partitioning of residual water towards fuel and cladding oxidation. Residual water will decompose by radiolysis and create reactive oxygen species, which, at sufficient high temperatures will oxidize cladding, and UO 2 exposed by clad breaches. If a significant fraction of UO 2 in a fuel rod is oxidized to U 3 O 8 , swelling of the fuel pellets will rupture the cladding and release fuel particles, contaminating the inside of the canister and complicating retrieval of fuel assemblies, transport and ultimate disposal. The report describes an evaluation of the potential cladding and exposed SNF pellets due to residual water. An integrated quantitative approach was used to estimate the effects. The approach consisted of (i) the evolution of environmental conditions, i.e., temperature and radiation field, in the cask, (ii) the physicochemical processes that affect degradation of the materials within the cask, and (iii) the potential damage states that may result from these conditions and processes. The assessment considers the following set of cask environmental conditions: (i) the quantity of residual water after drying, (ii) internal temperature fields and their intensity decrease over time, and (iii) the strength of the internal radiation field. The quantity of residual water will affect the mass of cladding, SNF, and other components that are degraded by oxidation. Temperature controls the rate of the oxidation reactions, the phase composition of water, and, to a lesser extent, the rate at which water vapor is radiolyzed. The strength of the radiation field controls the radiolysis rate of residual water. These processes, i.e., time evolution of temperature fields and their effects on radiolysis of residual water, fuel and cladding oxidations, were modeled using the integrated approach.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

NASA NTRS2013

Hollow-Fiber Spacesuit Water Membrane Evaporator

The hollow-fiber spacesuit water membrane evaporator (HoFi SWME) is being developed to perform the thermal control function for advanced spacesuits and spacecraft to take advantage of recent advances in micropore membrane technology in providing a robust, heat-rejection device that is less sensitive to contamination than is the sublimator. After recent contamination tests, a commercial-off-the-shelf (COTS) micro porous hollow-fiber membrane was selected for prototype development as the most suitable candidate among commercial hollow-fiber evaporator alternatives. An innovative design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype for the spacesuit application. Vacuum chamber testing has been performed to characterize heat rejection as a function of inlet water temperature and water vapor back-pressure, and to show contamination resistance to the constituents expected to be found in potable water produced by the wastewater reclamation distillation processes. Other tests showed tolerance to freezing and suitability to reject heat in a Mars pressure environment. In summary, HoFi SWME is a lightweight, compact evaporator for heat rejection in the spacesuit that is robust, contamination- insensitive, freeze-tolerant, and able to reject the required heat of spacewalks in microgravity, lunar, and Martian environments. The HoFi is packaged to reject 810 W of heat through 800 hours of use in a vacuum environment, and 370 W in a Mars environment. The device also eliminates free gas and dissolved gas from the coolant loop.

Bue, Grant↗

NASA NTRSDate not supplied

Additive Manufacturing and Experimental Characterization of Nickel-Titanium Shape-Memory Alloy Wick Structures and Heat Pipes for Spacecraft Thermal Control

Shape memory alloys (SMA), such as those based on nickel-titanium (NiTi), are increasingly being applied as multifunctional spacecraft components. For thermal management applications, NiTi flow tubing hinges and self-deploying loop heat pipes have been demonstrated. Emerging additive manufacturing (AM) processes are enabling more complex SMA devices than can be formed from conventional plain wire, tubing, and sheet stock materials. This paper presents our progress toward applying powder bed fusion AM to producing porous NiTi wicks and NiTi-H2O heat pipes, which could be embedded in thermally deploying radiators for spacecraft thermal management. AM near-equiatomic NiTi (55.1 wt% Ni) porous wick specimens were produced with a range of deposition parameters. Transient acetone rate-of-rise experiments were performed to estimate wick permeability (K) and average pore radius (r_pore) values and identify parameter sets with high capillary performance. Surface treatments were evaluated to achieve hydrophilic wick structures. Evaluated treatments included chemical oxide growth with H2O2, oxide and sodium titanate growth with NaOH solution, and ultrasonic cleaning with specialty detergents that can remove hydrocarbon contaminants. The most durable hydrophilic surface conditions were obtained with the NaOH treatment. High performing wick deposition parameters were used to produce a full AM NiTi heat pipe, which was treated with NaOH solution to activate the wick. This heat pipe was operated on a test stand in the inverted configuration (upper evaporator and lower condenser), and demonstrated stable nearly isothermal operation for 150 hrs.

Thermal management↗

NASA NTRSDate not supplied

Additive Manufacturing and Experimental Characterization of Nickel-Titanium Shape-Memory Alloy Wick Structures and Heat Pipes for Spacecraft Thermal Control

Thermal management↗

DOE OSTI2012

F-Tank Farm Performance Assessment Updates through the Special Analysis Process at Savannah River Site - 12169

The F-Area Tank Farm (FTF) is owned by the U.S. Department of Energy and operated by Savannah River Remediation, LLC (SRR), Liquid Waste Operations contractor at DOE's Savannah River Site (SRS). The FTF is in the north-central portion of the SRS and occupies approximately 22 acres within F-Area. The FTF is an active radioactive waste storage facility consisting of 22 carbon steel waste tanks and ancillary equipment such as transfer lines, evaporators and pump tanks. An FTF Performance Assessment (PA) was prepared to support the eventual closure of the FTF underground radioactive waste tanks and ancillary equipment. The PA provides the technical basis and results to be used in subsequent documents to demonstrate compliance with the pertinent requirements identified below for final closure of FTF. The FTank Farm is subject to a state industrial waste water permit and Federal Facility Agreement. Closure documentation will include an F-Tank Farm Closure Plan and tank-specific closure modules utilizing information from the performance assessment. For this reason, the State of South Carolina and the Environmental Protection Agency must be involved in the performance assessment review process. The residual material remaining after tank cleaning is also subject to reclassification prior to closure via a waste determination pursuant to Section 3116 of the Ronald W. Reagan National Defense Authorization Act of Fiscal Year 2005. The projected waste tank inventories in the FTF PA provide reasonably bounding FTF inventory projections while taking into account uncertainties in the effectiveness of future tank cleaning technologies. As waste is removed from the FTF waste tanks, the residual contaminants will be sampled and the remaining residual inventory is characterized. In this manner, tank specific data for the tank inventories at closure will be available to supplement the waste tank inventory projections currently used in the FTF PA. For FTF, the new tank specific data will be evaluated through the Special Analysis process. The FTF Special Analyses process will be utilized to evaluate information regarding the final residual waste that will be grouted in place in the FTF Tanks and assess the potential impact the new inventory information has on the FTF PA assumptions and results. The Special Analysis can then be used to inform decisions regarding FTF tank closure documents. The purpose of this paper is to discuss the Special Analysis process and share insights gained while implementing this process. An example of an area of interest in the revision process is balancing continuous improvement versus configuration control of agreed upon methodologies. Other subjects to be covered include: 1) defining the scope of the revisions included in the Special Analysis, 2) determining which PA results should be addressed in the Special Analysis, and 3) deciding whether the Special Analysis should utilize more qualitative or quantitative assessments. For the SRS FTF, an FTF PA has been prepared to provide the technical basis and results to be used in subsequent documents to demonstrate compliance with the pertinent requirements for final closure of FTF. The FTF Special Analyses process will be utilized to evaluate the impact new information has on the FTF PA assumptions and results. The Special Analysis can then be used to inform decisions regarding FTF tank closure documents. In preparing SAs, it is crucial that the scope of the SA be well defined within the SA, since the specific scope will vary from SA to SA. Since the SAs are essentially addendums to the PA, the SA scope should utilize the PA as the baseline from which the SA scope is defined. The SA needs to focus on evaluating the change associated with the scope, and not let other changes interfere with the ability to perform that evaluation by masking the impact of the change. In preparing the SA, it is also important to let the scope determine whether the Special Analysis should utilize more qualitative or quantitative assessments and also which results from the PA should be addressed in the Special Analysis. These decisions can vary from SA and should not be predetermined. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

Coal-Derived Warm Syngas Purification and CO 2 Capture-Assisted Methane Production

Gasifier-derived syngas from coal has many applications in the area of catalytic transformation to fuels and chemicals. Raw syngas must be treated to remove a number of impurities that would otherwise poison the synthesis catalysts. Inorganic impurities include alkali salts, chloride, sulfur compounds, heavy metals, ammonia, and various P, As, Sb, and Se- containing compounds. Systems comprising multiple sorbent and catalytic beds have been developed for the removal of impurities from gasified coal using a warm cleanup approach. This approach has the potential to be more economic than the currently available acid gas removal (AGR) approaches and improves upon currently available processes that do not provide the level of impurity removal that is required for catalytic synthesis application. Gasification also lends itself much more readily to the capture of CO 2 , important in the regulation and control of greenhouse gas emissions. CO 2 capture material was developed and in this study was demonstrated to assist in methane production from the purified syngas. Simultaneous CO 2 sorption enhances the CO methanation reaction through relaxation of thermodynamic constraint, thus providing economic benefit rather than simply consisting of an add-on cost for carbon capture and release. Molten and pre-molten LiNaKCO 3 can promote MgO and MgO-based double salts to capture CO 2 with high cycling capacity. A stable cycling CO 2 capacity up to 13 mmol/g was demonstrated. This capture material was specifically developed in this study to operate in the same temperature range and therefore integrate effectively with warm gas cleanup and methane synthesis. By combining syngas methanation, water-gas-shift, and CO 2 sorption in a single reactor, single pass yield to methane of 99% was demonstrated at 10 bar and 330°C when using a 20 wt% Ni/MgAl 2 O 4 catalyst and a molten-phase promoted MgO-based sorbent. Under model feed conditions both the sorbent and catalyst exhibited favorable stability after multiple test cycles. The cleanup for warm gas cleanup of inorganics was broken down into three major steps: chloride removal, sulfur removal, and the removal for a multitude of trace metal contaminants. Na 2 CO 3 was found to optimally remove chlorides at an operating temperature of 450ºC. For sulfur removal two regenerable ZnO beds are used for bulk H 2 S removal at 450ºC (<5 ppm S) and a non-regenerable ZnO bed for H 2 S polishing at 300ºC (<40 ppb S). It was also found that sulfur from COS could be adsorbed (to levels below our detection limit of 40 ppb) in the presence of water that leads to no detectable slip of H 2 S. Finally, a sorbent material comprising of Cu and Ni was found to be effective in removing trace metal impurities such as AsH 3 and PH 3 when operating at 300ºC. Proof-of-concept of the integrated cleanup process was demonstrated with gasifier-generated syngas produced at the Western Research Institute using Wyoming Decker Coal. When operating with a ~1 SLPM feed, multiple inorganic contaminant removal sorbents and a tar-reforming bed was able to remove the vast majority of contaminants from the raw syngas. A tar-reforming catalyst was employed due to the production of tars generated from the gasifier used in this particular study. It is envisioned that in a real application a commercial scale gasifier operating at a higher temperature would produce lesser amount of tar. Continuous operation of a poison-sensitive copper-based WGS catalyst located downstream from the cleanup steps resulted in successful demonstration.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Integrated hydrogeophysical modelling and data assimilation for geoelectrical leak detection

Time-lapse electrical resistivity tomography (ERT) measurements provide indirect observations of hydrological processes in the Earth's shallow subsurface at high spatial and temporal resolution. ERT has been used in the past decades to detect leaks and monitor the evolution of associated contaminant plumes. Specifically, inverted resistivity images allow visualization of the dynamic changes in the structure of the plume. However, existing methods do not allow the direct estimation of leak parameters (e.g. leak rate, location, etc.) and their uncertainties. We propose an ensemble-based data assimilation framework that evaluates proposed hydrological models against observed time-lapse ERT measurements without directly inverting for the resistivities. Each proposed hydrological model is run through the parallel coupled hydro-geophysical simulation code PFLOTRAN-E4D to obtain simulated ERT measurements. The ensemble of model proposals is then updated using an iterative ensemble smoother. In this paper, we demonstrate the proposed framework on synthetic and field ERT data from controlled tracer injection experiments. Our results show that the approach allows joint identification of contaminant source location, initial release time, and solute loading from the cross-borehole time-lapse ERT data, alongside with an assessment of uncertainties in these estimates. We demonstrate a reduction in site-wide uncertainty by comparing the prior and posterior plume mass discharges at a selected image plane. This framework is particularly attractive to sites that have previously undergone extensive geological investigation (e.g., nuclear sites). It is well suited to complement ERT imaging and we discuss practical issues in its application to field problems.

58 GEOSCIENCES↗

DOE OSTI2015

Baseline Risk Assessment Supporting Closure at Waste Management Area C at the Hanford Site Washington

The Office of River Protection under the U.S. Department of Energy is pursuing closure of the Single-Shell Tank (SST) Waste Management Area (WMA) C under the requirements of the Hanford Federal Facility Agreement and Consent Order (HFFACO). A baseline risk assessment (BRA) of current conditions is based on available characterization data and information collected at WMA C. The baseline risk assessment is being developed as a part of a Resource Conservation and Recovery Act (RCRA) Facility Investigation (RFI)/Corrective Measures Study (CMS) at WMA C that is mandatory under Comprehensive Environmental Response, Compensation, and Liability Act and RCRA corrective action. The RFI/CMS is needed to identify and evaluate the hazardous chemical and radiological contamination in the vadose zone from past releases of waste from WMA C. WMA C will be under Federal ownership and control for the foreseeable future, and managed as an industrial area with restricted access and various institutional controls. The exposure scenarios evaluated under these conditions include Model Toxics Control Act (MTCA) Method C, industrial worker, maintenance and surveillance worker, construction worker, and trespasser scenarios. The BRA evaluates several unrestricted land use scenarios (residential all-pathway, MTCA Method B, and Tribal) to provide additional information for risk management. Analytical results from 13 shallow zone (0 to 15 ft. below ground surface) sampling locations were collected to evaluate human health impacts at WMA C. In addition, soil analytical data were screened against background concentrations and ecological soil screening levels to determine if soil concentrations have the potential to adversely affect ecological receptors. Analytical data from 12 groundwater monitoring wells were evaluated between 2004 and 2013. A screening of groundwater monitoring data against background concentrations and Federal maximum concentration levels was used to determine vadose zone contamination impacts on groundwater. Waste Management Area C is the first of the Hanford tank farms to begin the closure planning process. The current baseline risk assessment will provide valuable information for making corrective actions and closure decisions for WMA C, and will also support the planning for future tank farm soil investigation and baseline risk assessments.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

The Road to 2020: Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA): Cleanup of the East Tennessee Technology Park - 17425

Uranium enrichment activities at the 890-ha (2,200-acre) East Tennessee Technology Park (ETTP), formerly the Oak Ridge Gaseous Diffusion Plant, date back to the World War II Manhattan Project. The site produced nuclear fuel for weapons and reactors for four decades. Because of these operations, ETTP has a legacy of radiologically and chemically contaminated buildings, soil, sediment, and groundwater that required remedial action to reduce the risk to human health and the environment. Since the early 1990's, the DOE Oak Ridge Office of Environmental Management (OREM) has directed the environmental cleanup of this contaminated site through the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) process. Cleanup activities have included the demolition of contaminated facilities and structures, including five gaseous diffusion buildings; remediation of contaminated soils; disposal of associated waste; and treatment of contaminated groundwater. In August 2016, DOE realized its Vision 2016, demolition of all five gaseous diffusion buildings at ETTP. This milestone marked the first time that an entire uranium enrichment complex has been demolished. The landmark cleanup included deactivation and demolition of 418,064 m{sup 2} (4.5 million ft{sup 2}) of radiologically and chemically contaminated facilities, and disposal of more than 55,000 truckloads of debris. Fulfillment of Vision 2016 was a major step toward completing ETTP cleanup by 2020. To attain 2020 cleanup, DOE and its cleanup contractor, URS - CH2M Oak Ridge LLC (UCOR), must complete demolition of the following areas: - Poplar Creek Facilities; - K-731 Switch House; - Building K-1037; - Central Neutralization Facility; - K-1200 Complex; - Toxic Substances Control Act Incinerator facilities; - Balance of Site Facilities. In addition, DOE will complete all remedial actions in accordance with current Records of Decision (RODs); as well as cleanup activities involving surface water, sediment, and groundwater that will be addressed in a final site-wide ROD. All waste, including soils, debris, and rubble from demolition and remediation activities, will be dispositioned. Final cleanup of ETTP further advances DOE's goal for re-industrialization of the site as a private sector industrial park. With risks reduced, hazards removed, and the environment restored, DOE can transfer usable ETTP building and land assets to the community for redevelopment and reuse. A history center, equipment building, viewing tower, and wayside exhibits will tell the story of the site, honoring its contributions to the nation's defense and energy needs. Approximately 1,214 ha (3,000 acres) of adjoining lands, now the Black Oak Ridge Conservation Easement (BORCE), will be used for conservation and recreational purposes, including green-ways and trail systems. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

NASA NTRS2004

Solid oxidized fuel cells seals leakage setup and testing

As the world s reserves of fossil fuels are depleted, the U.S. Government, as well as other countries and private industries, is researching solutions for obtaining power, answers that would be more efficient and environmentally friendly. For a long time engineers have been trying to obtain the benefits of clean electric power without heavy batteries or pollution-producing engines. While some of the inventions proved to be effective (i.e. solar panels or windmills) their applications are limited due to dependency on the energy source (i.e. sun or wind). Currently, as energy concerns increase, research is being carried out on the development of a Solid Oxide Fuel Cell (SOFC). The United States government is taking a proactive role in expanding the technology through the Solid State Energy Conversion Alliance (SECA) Program, which is coordinated by the Department of Energy. into an electrical energy. This occurs by the means of natural tendency of oxygen and hydrogen to chemically react. While controlling the process, it is possible to harvest the energy given off by the reaction. SOFCs use currently available fossil fuels and convert a variety of those fuels with very high efficiency (about 40% more efficient than modem thermal power plants). At the same time they are almost entirely nonpolluting and due to their size they can be placed in remote areas. The main fields where the application of the fuel cells appears to be the most useful for are stationary energy sources, transportation, and military applications. structure and materials must be resolved. All the components must be operational in harsh environments including temperatures reaching 800 C and cyclic thermal- mechanical loading. Under these conditions, the main concern is the requirement for hermetic seals to: (1) prevent mixing of the fuel and oxidant within the stack, (2) prevent parasitic leakage of the fuel from the stack, (3) prevent contamination of the anode by air leaking into the stack, (4) electrically isolate the individual cells within the stack, and (5) mechanically bond the cell components. The sealing challenges are aggravated by the need to maintain hermetic boundaries between the different flow paths within the fuel cell throughout cycled operation. Within the timeframe of my tenure, the main objective is to assist in building a state-of-art test facility.

Bastrzyk, Marta B.↗