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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Optimization of Saltcake Removal Flowsheet at SRS through Incorporation of Testing and In-Tank Waste Experience

Saltcake removal at SRS may be performed for several reasons: to provide space for evaporator operation (i.e., to precipitate more salt in the drop tank), to provide feed for salt processing (i.e. immobilize the waste), or to remove the salt for tank closure. Many different salt dissolution techniques have been employed in the 40 years that SRS has been performing salt removal, from a basic “Add, Sit, Remove” method (water is added on top of the saltcake and time is allowed for diffusion), to performing interstitial liquid removal, or using mixing devices to promote contact with the liquid. Lessons learned from previous saltcake removal campaigns, in addition to testing and modeling, have led to opportunities for improvements to the overall saltcake removal process. This includes better understanding of salt properties and behavior during dissolution; the primary concerns for salt dissolution are the release of radiolytic hydrogen and criticality prevention (post-dissolution). Recent developments in salt dissolution include the reuse of dilute supernate and a semi-continuous dissolution (SCD) process, where low volume mixing eductors are used to deliver water near the surface of the saltcake at the same rate as the salt solution is removed and transferred to a receipt tank.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Organic and nitrogen removal from landfill leachate in aerobic granular sludge sequencing batch reactors

Highlights: Black-Right-Pointing-Pointer Aerobic granular sludge SBR was used to treat real landfill leachate. Black-Right-Pointing-Pointer COD removal was analyzed kinetically using a modified model. Black-Right-Pointing-Pointer Characteristics of nitrogen removal at different ammonium inputs were explored. Black-Right-Pointing-Pointer DO variations were consistent with the GSBR performances at low ammonium inputs. - Abstract: Granule sequencing batch reactors (GSBR) were established for landfill leachate treatment, and the COD removal was analyzed kinetically using a modified model. Results showed that COD removal rate decreased as influent ammonium concentration increasing. Characteristics of nitrogen removal at different influent ammonium levels were also studied. When the ammonium concentration in the landfill leachate was 366 mg L{sup -1}, the dominant nitrogen removal process in the GSBR was simultaneous nitrification and denitrification (SND). Under the ammonium concentration of 788 mg L{sup -1}, nitrite accumulation occurred and the accumulated nitrite was reduced to nitrogen gas by the shortcut denitrification process. When the influent ammonium increased to a higher level of 1105 mg L{sup -1}, accumulation of nitrite and nitrate lasted in the whole cycle, and the removal efficiencies of total nitrogen and ammonium decreased to only 35.0% and 39.3%, respectively. Results also showed that DO was a useful process controlling parameter for the organics and nitrogen removal at low ammonium input.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

The dynamics of femtosecond pulsed laser removal of 20 nm Ni films from an interface

The dynamics of femtosecond laser removal of 20 nm Ni films on glass substrates was studied using time-resolved pump-probe microscopy. 20 nm thin films exhibit removal at two distinct threshold fluences, removal of the top 7 nm of Ni above 0.14 J/cm{sup 2}, and removal of the entire 20 nm film above 0.36 J/cm{sup 2}. Previous work shows the top 7 nm is removed through liquid spallation, after irradiation the Ni melts and rapidly expands leading to tensile stress and cavitation within the Ni film. This work shows that above 0.36 J/cm{sup 2} the 20 nm film is removed in two distinct layers, 7 nm and 13 nm thick. The top 7 nm layer reaches a speed 500% faster than the bottom 13 nm layer at the same absorbed fluence, 500–2000 m/s and 300–700 m/s in the fluence ranges studied. Significantly different velocities for the top 7 nm layer and bottom 13 nm layer indicate removal from an interface occurs by a different physical mechanism. The method of measuring film displacement from the development of Newton's rings was refined so it could be shown that the 13 nm layer separates from the substrate within 70 ps and accelerates to its final velocity within several hundred picoseconds. We propose that removal of the bottom 13 nm is consistent with heterogeneous nucleation and growth of vapor at the Ni-glass interface, but that the rapid separation and acceleration of the 13 nm layer from the Ni-glass interface requires consideration of exotic phases of Ni after excitation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Sustained Ability of a Natural Microbial Community to Remove Nitrate from Groundwater

Abstract Microbial‐mediated nitrate removal from groundwater is widely recognized as the predominant mechanism for nitrate attenuation in contaminated aquifers and is largely dependent on the presence of a carbon‐bearing electron donor. The repeated exposure of a natural microbial community to an electron donor can result in the sustained ability of the community to remove nitrate; this phenomenon has been clearly demonstrated at the laboratory scale. However, in situ demonstrations of this ability are lacking. For this study, ethanol (electron donor) was repeatedly injected into a groundwater well (treatment) for six consecutive weeks to establish the sustained ability of a microbial community to remove nitrate. A second well (control) located upgradient was not injected with ethanol during this time. The treatment well demonstrated strong evidence of sustained ability as evident by ethanol, nitrate, and subsequent sulfate removal up to 21, 64, and 68%, respectively, as compared to the conservative tracer (bromide) upon consecutive exposures. Both wells were then monitored for six additional weeks under natural (no injection) conditions. During the final week, ethanol was injected into both treatment and control wells. The treatment well demonstrated sustained ability as evident by ethanol and nitrate removal up to 20 and 21%, respectively, as compared to bromide, whereas the control did not show strong evidence of nitrate removal (5% removal). Surprisingly, the treatment well did not indicate a sustained and selective enrichment of a microbial community. These results suggested that the predominant mechanism(s) of sustained ability likely exist at the enzymatic‐ and/or genetic‐levels. The results of this study demonstrated the in situ ability of a microbial community to remove nitrate can be sustained in the prolonged absence of an electron donor.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Influence of partial charge on the material removal rate during chemical polishing

A partial charge-based chemical polishing model has been developed, which can serve as metric for describing the relative polishing material removal rate for different combinations of slurries and workpieces. A series of controlled polishing experiments utilizing a variety of colloidal polishing slurries (SiO 2 , CeO 2 , ZrO 2 , MgO, Sb 2 O 5 ) and optical materials [single crystals of Al 2 O 3 (sapphire), SiC, Y 3 Al 5 O 12 (YAG), CaF 2 , and LiB 3 O 5 (LBO); a SiO 2 -Al 2 O 3 -P 2 O 5 -Li 2 O glass ceramic (Zerodur); and glasses of SiO 2 :TiO 2 (ULE), SiO 2 (fused silica), and P 2 O 5 -Al 2 O 3 -K 2 O-BaO (Phosphate)] was performed and its material removal rate was measured. As previously proposed by Cook (J Non-Cryst Solids. 1990;120:152), for many polishing systems, the removal rate is governed by a series of chemical reactions which include the formation of a surface hydroxide, followed by condensation of that hydroxyl moiety with the polishing particle, and a subsequent hydrolysis reaction. The rate of condensation can often be the rate limiting step, thus it can determine the polishing material removal rate. By largely keeping the numerous other factors that influence material removal rate fixed (such as due to particle size distributions, interface interactions, pad topography, kinematics, and applied pressure), the material removal rate is shown to scale exponentially with the partial charge difference (δ wp-s ) between the workpiece and polishing slurry particle for many of the slurry-workpiece combinations indicating that condensation rate is the rate limiting step. The partial charge (δ) describes the equilibrium distribution of electron density between chemically bonded atoms and is related to the electronegativity of the atoms chemically bonded to one another. This partial charge model also explains the age-old experimental finding of why cerium oxide is the most effective polishing slurry for chemical removal of many workpieces. Finally, some of the slurry-workpiece combinations that did not follow the partial charge dependence offer insight to other removal mechanisms or rate limiting reaction pathways.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Nanoplastic removal function and the mechanical nature of colloidal silica slurry polishing

The nanomechanical deformations on a broad range of optical material surfaces (single crystals of Al 2 O 3 [sapphire], SiC, Y 3 Al 5 O 12 [YAG], CaF 2 , and LiB 3 O 5 [LBO]; a SiO 2 –Al 2 O 3 –P 2 O 5 –Li 2 O glass-ceramics [Zerodur]; and glasses of SiO 2 :TiO 2 [ULE], SiO 2 [fused silica], and P 2 O 5 –Al 2 O 3 –K 2 O–BaO [Phosphate]) near the elastic-plastic load boundary have been measured by nanoindentation and nanoscratching to mimic the nanoplastic removal caused by a single slurry particle during polishing. Nanoindenation in air was performed to determine the workpiece hardness at various loads using a commercial nanoindenter with a Berkovich tip. Similarly, an atomic force microscope (AFM) with a stiff diamond coated tip (150 nm radius) was used to produce nanoplastic scratches in air and aqueous environments over a range of applied loads (~20-170 μN). The resulting nanoplastic deformation of the nanoscratches were used to calculate the removal function (i.e., depth per pass) which ranged from 0.18 to 3.6 nm per pass for these materials. A linear correlation between the nanoplastic removal function and the polishing rate (using a fixed polishing process with colloidal silica slurry on a polyurethane pad) of these materials was observed implying that: (a) the polishing mechanism using colloidal silica slurry can be dominated by mechanical rather than chemical interactions; and (b) the nanoplastic removal function, as opposed to interface particle interactions, is the controlling factor for the polishing material removal rate. Furthermore, this correlation is consistent with the Ensemble Hertzian Multi-Gap (EHMG) microscopic material removal rate model described previously. The nanoplastic removal depth was also found to correlate to the measured nanoindentation hardness (H1) of the optical material, scaling as H 1 -3.5 . Two-dimensional (2D) finite element analysis simulations of nanoindentation showed a similar nonlinear dependence of plastic deformation with the workpiece material hardness. The findings of this study are used to determine an effective Preston coefficient for the material removal rate expression and enhance the predictive nature of the nanoplastic polishing rate for various materials utilizing their material properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Air Dispersion Modeling of Radioactive Releases During Proposed 236Z Rubble Pile Removal Activities

This report is part of the planning process for the removal of the 236Z rubble remaining as of January 1, 2018, at the Plutonium Finishing Plant (PFP) on the Hanford Site. This report documents an analysis considering standard techniques for the removal of demolition rubble. It does not document any decisions about the removal approaches. This document is intended to guide the establishment of a boundary for the application of an air monitoring regime. Atmospheric dispersion modeling using estimated release rates has been conducted to provide information on the location and levels of radioactive contamination that may be expected as the result of rubble removal activities. Hourly meteorological data collected over a 6-year period (2004–2009) were used to examine the effects of wind speed, direction, and stability on projected concentrations of contaminants in air and deposited on nearby surfaces. The source terms modeled in this report were based on the residual transuranic contamination levels that are anticipated to remain in the 236Z rubble following building demolition. The potential airborne concentrations were established using the five-factor formula from DOE-HDBK-3010 (DOE 1994) considering material-at-risk, damage ratio, airborne release fraction, respirable fraction, and leak path factor. Radioactive contamination emissions were calculated by release mechanism and rubble pile area for on-shift and off-shift activities. The emissions from the applicable sources were combined to provide emissions estimates for each day from each cleanup area. The U.S. Environmental Protection Agency’s (EPA’s) AERMOD computer code was used to estimate atmospheric dispersion and deposition of the released radioactive materials in the immediate vicinity of the planned rubble removal activities Both airborne and surface concentrations were modeled with AERMOD. Hourly derived air concentrations (DAC) were modeled for an array of receptors covering the rubble pile site and surrounding area. Peak (95th and 99th percentile) values of time-integrated air concentrations at these receptor points are derived from these hourly values, with modeling results reported as total incremental air concentrations in DAC-hours occurring over the selected time period. Total accumulated deposition amounts were also evaluated with AERMOD using the same array of receptors, with results reported as disintegrations per minute (dpm) per 100 cm2. Each rubble pile was considered in terms of its size, location, and estimated contamination levels. The modeling was based on the assumed sequence of the rubble removal activities. The results in this report are based on cleanup schedules and methods proposed by CHPRC. As of January 1, 2018, there are broadly three large rubble piles (west, footprint, and east) remaining of the 236Z Building process cell. It is assumed that the overall cleanup will require either 1) 30 days over a 6-week period, or 2) 60 days over a 12-week period. Work was assumed to be performed during 10-hour day shifts. The analysis shows that some releases of radioactive material are to be anticipated during the cleanup of the 236Z rubble piles. The modeling results presented here are closely tied to the details of how the rubble removal is to be conducted. The results indicate that for the rubble removal, the radiological exposures from the planned activities are predicted to be well below the designated limits for air and soil exposures. The cleanup of the 236Z main process cell rubble is expected to release some alpha-emitting radionuclides. However, results based on 6 years of hourly climatological data, two representative cleanup periods, realistic mitigating actions, and a bounding source term indicate that concentrations at the fence line of the PFP facilities should remain well below 12 DAC-hours/week. The results presented in this report are a reevaluation of a subset of the results presented in PNNL-20173 Rev. 4.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Irradiation of Mo-100 Targets and Testing Fe(ll)CI 2 Precipitation for Tc-99 Removal

The production of molybdenum-99 (Mo-99) is a critical step in the generation of technetium-99m (Tc-99m), a radioisotope widely used in medical imaging. NorthStar Medical Radioisotopes, LLC is planning to produce the important medical radioisotope Mo-99 through a photonuclear reaction on molybdenum-100 (Mo-100). Accelerator production of Mo-99 using enriched Mo-100 targets yields undesirable isotopes, such as niobium-95 (Nb-95) and zirconium-95 (Zr-95). Previous studies reported that Nb and Zr isotopes can be effectively removed from Mo-99 products through coprecipitation with Fe(III). To enable the potential utilization of the first milking of Tc-99m from a Mo-99/Tc-99m generator, it is desirable to remove long-lived Tc-99. This can be accomplished by substituting Fe(III) with Fe(II) during the precipitation step, without affecting the removal of Zr and Nb isotopes. Previous experiments demonstrated up to 99+% removal of Tc using this method. It was also observed that the presence of hydrogen peroxide significantly impacts Tc removal. This was evident in the processing of enriched Mo-100 targets, where only 25% of Tc was removed. To further investigate this, another irradiation of enriched Mo-100 disks was conducted, followed by Tc-99 removal using Fe(II). Prior to irradiation, experimental conditions for Tc removal were optimized through several test runs using Mo-100 disks spiked with Tc-99. The results of these tests are discussed in this report.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2021

Corn Stover Removal Responses on Soil Test P and K Levels in Coastal Plain Ultisols

Corn (Zea mays L.) stover is used as a biofuel feedstock in the U.S. Selection of stover harvest rates for soils is problematic, however, because excessive stover removal may have consequences on plant available P and K concentrations. Our objective was to quantify stover harvest impacts on topsoil P and K contents in the southeastern U.S. Coastal Plain Ultisols. Five stover harvest rates (0, 25, 50, 75 and 100% by wt) were removed for five years from replicated plots. Grain and stover mass with P and K concentration data were used to calculate nutrient removal. Mehlich 1 (M1)-extractable P and K concentrations were used to monitor changes within the soils. Grain alone removed 13–15 kg ha –1 P and 15–18 kg ha –1 K each year, resulting in a cumulative removal of 70 and 85 kg ha –1 or 77 and 37% of the P and K fertilizer application, respectively. Harvesting stover increased nutrient removal such that when combined with grain removed, a cumulative total of 95% of the applied P and 126% of fertilizer K were taken away. This caused M1 P and K levels to decline significantly in the first year and even with annual fertilization to remain relatively static thereafter. For these Ultisols, we conclude that P and K fertilizer recommendations should be fine-tuned for P and K removed with grain and stover harvesting and that stover harvest of >50% by weight will significantly decrease soil test M1 P and K contents.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

Atomic Oxygen Treatment for Non-Contact Removal of Organic Protective Coatings from Painting Surfaces

Current techniques for removal of varnish (lacquer) and other organic protective coatings from paintings involve contact with the surface. This contact can remove pigment, or alter the shape and location of paint on the canvas surface. A thermal energy atomic oxygen plasma, developed to simulate the space environment in low Earth orbit, easily removes these organic materials. Uniform removal of organic protective coatings from the surfaces of paintings is accomplished through chemical reaction. Atomic oxygen will not react with oxides so that most paint pigments will not be affected by the reaction. For paintings containing organic pigments, the exposure can be carefully timed so that the removal stops just short of the pigment. Color samples of Alizarin Crimson, Sap Green, and Zinc White coated with Damar lacquer were exposed to atomic oxygen. The lacquer was easily removed from all of the samples. Additionally, no noticeable change in appearance was observed after the lacquer was reapplied. The same observations were made on a painted canvas test sample obtained from the Cleveland Museum of Art. Scanning electron microscope photographs showed a slight microscopic texturing of the vehicle after exposure. However, there was no removal or disturbance of the paint pigment on the surface. It appears that noncontact cleaning using atomic oxygen may provide a viable alternative to other cleaning techniques. It is especially attractive in cases where the organic protective surface cannot be acceptably or safely removed by conventional techniques.

Rutledge, Sharon K.↗
NASA NTRS1995

Removal of Burkholderia cepacia biofilms with oxidants

Iodine is used to disinfect the water system aboard US space shuttles and is the anticipated biocide for the international space station. Water quality on spacecraft must be maintained at the highest possible levels for the safety of the crew. Furthermore, the treatment process used to maintain the quality of water on research must be robust and operate for long periods with minimal crew intervention. Biofilms are recalcitrant and pose a major threat with regard to chronic contamination of spacecraft water systems. We measured the effectiveness of oxidizing biocides on the removal and regrowth of Burkholderia (Pseudomonas) cepacia biofilms. B. cepacia, isolated from the water distribution system of the space shuttle Discovery, was grown in continuous culture to produce a bacterial contamination source for biofilm formation and removal studies. A 10(7) CFU ml-1 B. cepacia suspension, in distilled water, was used to form biofilms on 3000 micrometers2 glass surfaces. Rates of attachment were measured directly with image analysis and were found to be 7.8, 15.2, and 22.8 attachment events h-1 for flow rates of 20.7, 15.2, and 9.8 ml min-1, respectively. After 18 h of formation, the B. cepacia biofilms were challenged with oxidants (ozone, chlorine, and iodine) and the rates of biofilm removal determined by image analysis. Fifty percent of the biofilm material was removed in the first hour of continous treatment with 24 mg l-1 chlorine or 2 mg l-1 ozone. Iodine (48 mg l-1) did not remove any measurable cellular material after 6 h continuous contact. After this first removal of biofilms by the oxidants, the surface was allowed to refoul and was again treated with the biocide. Iodine was the only compound that was unable to remove cellular debris from either primary or secondary biofilms. Moreover, treating primary biofilms with iodine increased the rate of formation of secondary biofilms, from 4.4 to 5.8 attachment events h-1. All the oxidants tested inactivated the B. cepacia associated with both primary and secondary biofilms. The amount of biocide needed to inactivate 50% of planktonic B. cepacia in 10 min at 25 degrees C was 8.4, 0.5, and 0.2 mg l-1 for iodine, chlorine, and ozone, respectively. The data suggest that iodine maynot be the best chemical for treating of biofilms when removal of cellular material is required.

NASA Discipline Environmental Health↗
NASA NTRS2011

Manned Mission Planning Considerations when Using a Non-Regenerable CO2 Removal System

As the commercial spacecraft industry increases in size, there will be a corresponding increase in the number of manned spacecraft built and operationally flown each year. Industry teams for these new spacecraft will have multiple design and operational choices to make for each of these spacecraft s subsystems. The carbon dioxide (CO2) removal subsystem of the environmental control and life support system is one that presents such challenges. This paper seeks to aid industry in making design and operations choices by providing a document containing lessons learned by the Space Shuttle Program s Operations team, with specific focus given to the non-regenerable CO2 removal system currently used by the Space Shuttle. Carbon dioxide, one of the key byproducts of respiration, can lead to injury and death if allowed to build up in a spacecraft s habitable environment. Therefore, any spacecraft s environmental control and life support system must contain a method for removing this hazard. These removal systems can either be non-regenerable or regenerable. While this paper defines the difference between these types and presents a generic comparison of their capabilities, the focus is specifically on the Space Shuttle s CO2 removal systems. This will include a short discussion of the Space Shuttle s regenerable amine solid absorption system that was part of the Extended Duration Orbiter (EDO) modification, however, emphasis is given to the non-regenerable Lithium Hydroxide canister system used as the prime removal method employed by the Space Shuttle, including a discussion on why this method was chosen over a regenerable system. A full exposition is given on all of the considerations required for mission planning when using a non-regenerable CO2 removal system. Key discussion items include: airflow lessons learned, recent physiological issues related to short term and long term exposure and how lower levels may be more harmful than previously thought, lithium hydroxide dust issues, mass vs. stowage comparisons, cost, complexity considerations, operational margin considerations, timing considerations with respect to the crew s schedule, and logistical management. The conclusion of the paper finalizes the discussion and contains a listing of considerations in regards to CO2 management using a non-regenerable removal system in the near future.

DeSimpelaere, Edward↗
NASA NTRS2005

Removing Pathogens Using Nano-Ceramic-Fiber Filters

A nano-aluminum-oxide fiber of only 2 nanometers in diameter was used to develop a ceramic-fiber filter. The fibers are electropositive and, when formulated into a filter material (NanoCeram(TradeMark)), would attract electro-negative particles such as bacteria and viruses. The ability to detect and then remove viruses as well as bacteria is of concern in space cabins since they may be carried onboard by space crews. Moreover, an improved filter was desired that would polish the effluent from condensed moisture and wastewater, producing potable drinking water. A laboratory- size filter was developed that was capable of removing greater than 99.9999 percent of bacteria and virus. Such a removal was achieved at flow rates hundreds of times greater than those through ultraporous membranes that remove particles by sieving. Because the pore size of the new filter was rather large as compared to ultraporous membranes, it was found to be more resistant to clogging. Additionally, a full-size cartridge is being developed that is capable of serving a full space crew. During this ongoing effort, research demonstrated that the filter media was a very efficient adsorbent for DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and endotoxins. Since the adsorption is based on the charge of the macromolecules, there is also a potential for separating proteins and other particulates on the basis of their charge differences. The separation of specific proteins is a major new thrust of biotechnology. The principal application of NanoCeram filters is based on their ability to remove viruses from water. The removal of more than 99.9999 percent of viruses was achieved by a NanoCeram polishing filter added to the effluent of an existing filtration device. NanoCeram is commercially available in laboratory-size filter discs and in the form of a syringe filter. The unique characteristic of the filter can be demonstrated by its ability to remove particulate dyes such as Metanyl yellow. Its particle size is only 2 nanometers, about the size of a DNA molecule, yet the NanoCeram syringe filter is capable of retaining the dyes as the fluid is passed through the syringe, without much back-pressure. Endotoxins, which are contaminants that are part of the residue of destroyed bacteria, can cause toxic shock and are therefore of major concern in pharmaceutical products. The NanoCeram syringe filter is capable of removing greater than 99.96 percent of the endotoxins.

Tepper, Frederick↗
DOE OSTI2015

Commercial submersible mixing pump for SRS tank waste removal - 15223

The Savannah River Site Tank Farms have 45 active underground waste tanks used to store and process nuclear waste materials. There are 4 different tank types, ranging in capacity from 2839 m{sup 3} to 4921m{sup 3} (750,000 to 1,300,000 gallons). Eighteen of the tanks are older style and do not meet all current federal standards for secondary containment. The older style tanks are the initial focus of waste removal efforts for tank closure and are referred to as closure tanks. Of the original 51 underground waste tanks, six of the original 24 older style tanks have completed waste removal and are filled with grout. The insoluble waste fraction that resides within most waste tanks at SRS requires vigorous agitation to suspend the solids within the waste liquid in order to transfer this material for eventual processing into glass filled canisters at the Defense Waste Processing Facility (DWPF). SRS suspends the solid waste by use of recirculating mixing pumps. Older style tanks generally have limited riser openings which will not support larger mixing pumps, since the riser access is typically 58.4 cm (23 inches) in diameter. Agitation for these tanks has been provided by four long shafted standard slurry pumps (SLP) powered by an above tank 112 kW (150 HP) electric motor. The pump shaft is lubricated and cooled in a pressurized water column that is sealed from the surrounding waste in the tank. Closure of four waste tanks has been accomplished utilizing long shafted pump technology combined with heel removal using multiple technologies. Newer style waste tanks at SRS have larger riser openings, allowing the processing of waste solids to be accomplished with four large diameter SLPs equipped with 224 kW (300 HP) motors. These tanks are used to process the waste from closure tanks for DWPF. In addition to the SLPs, a 224 kW (300 HP) submersible mixer pump (SMP) has also been developed and deployed within older style tanks. The SMPs are product cooled and product lubricated canned motor pumps designed to fit within available risers and have significant agitation capabilities to suspend waste solids. Waste removal and closure of two tanks has been accomplished with agitation provided by 3 SMPs installed within the tanks. In 2012, a team was assembled to investigate alternative solids removal technologies to support waste removal for closing tanks. The goal of the team was to find a more cost effective approach that could be used to replace the current mixing pump technology. This team was unable to identify an alternative technology outside of mixing pumps to support waste agitation and removal from SRS waste tanks. However, the team did identify a potentially lower cost mixing pump compared to the baseline SLPs and SMPs. Rather than using the traditional procurement using an engineering specification, the team proposed to seek commercially available submersible mixer pumps (CSMP) as alternatives to SLPs and SMPs. SLPs and SMPs have a high procurement cost and the actual cost of moving pumps between tanks has shown to be significantly higher than the original estimates that justified the reuse of SMPs and SLPs. The team recommended procurement of 'off-the-shelf' industry pumps which may be available for significant savings, but at an increased risk of failure and reduced operating life in the waste tank. The goal of the CSMP program is to obtain mixing pumps that could mix from bulk waste removal through tank closure and then be abandoned in place as part of tank closure. This paper will present the development, progress and relative advantages of the CSMP. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Optimization of salt-cake removal flowsheet at SRS through incorporation of testing and in-tank waste experience - 15263

Salt-cake removal at SRS may be performed for several reasons: to provide space for evaporator operation (i.e., to precipitate more salt in the drop tank), to provide feed for salt processing (i.e. immobilize the waste), or to remove the salt for tank closure. Many different salt dissolution techniques have been employed in the 40 years that SRS has been performing salt removal, from a basic 'Add, Sit, Remove' method (water is added on top of the salt-cake and time is allowed for diffusion), to performing interstitial liquid removal, or using mixing devices to promote contact with the liquid. Lessons learned from previous salt-cake removal campaigns, in addition to testing and modeling, have led to opportunities for improvements to the overall salt-cake removal process. This includes better understanding of salt properties and behavior during dissolution; the primary concerns for salt dissolution are the release of radiolytic hydrogen and criticality prevention (post-dissolution). Recent developments in salt dissolution include the reuse of dilute supernate and a semi-continuous dissolution (SCD) process, where low volume mixing eductors are used to deliver water near the surface of the salt-cake at the same rate as the salt solution is removed and transferred to a receipt tank. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Pre-combustion mercury removal with co-production of hydrogen via coal electrolysis

Here, pre-combustion mercury removal via coal electrolysis was performed and investigated on a bench-scale coal electrolytic cell (CEC) systemically, and factorial design was used to determine the effect of different operating conditions (coal particle size, operating temperature, operating cell voltage, and flow rate of slurry) on the percentage of mercury removal, percentage of ash removal, and dry heating value change. The results showed that the operating cell voltage, as well as the interaction between operating cell voltage and coal particle size, are significant factors in the percentage of mercury removal. There is no significant factor in the percentage of ash removal and the dry heating value change, but the coal could be purified while keeping the dry heating value almost constant after electrolysis. A co-product of hydrogen could be produced during coal electrolysis with 50% lower energy consumption compared with water electrolysis. Meanwhile, a mechanism for mercury removal in coal was proposed. The facts indicate that coal electrolysis is a promising method for pre-combustion mercury removal.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Comparison of removal and spatial mark‐resight models for estimating wild pig density

Density estimation is critical to effectively manage invasive species and elucidate areas of highest concern. For wild pigs (Sus scrofa), the ability to estimate density is complicated because of their variable home range sizes and social structure. Common methods for estimating density (e.g., mark-recapture) may be unsuitable in management applications because additional data needs to be collected before and after management. Removal models offer a suitable alternative to estimate density changes following management and can be applied broadly across areas where management of wild pigs is ongoing. We collected wild pig removal and camera trap data from 25 private properties ranging in size from approximately 0.5 km 2 to 95 km 2 across 3 ecoregions in South Carolina, USA, from 2020–2023. We compared factors affecting consistency and precision of property-level density estimates between removal and spatial mark-resight (SMR) models. In general, excluding 1 large outlier, density estimates from removal models were between 0.60 and 15.85 wild pigs/km 2 (median = 5.34) with a median coefficient of variation (CV) of 0.76 and 95% confidence intervals for the CV between 0.70 and 0.94. Similarly, excluding 1 large outlier, density estimates from SMR were between 0.22 and 30.97 wild pigs/km 2 (median = 5.48) with a median CV of 0.39 and 95% confidence intervals for the CV between 0.38 and 1.20. We found the precision of removal models was affected primarily by the number of wild pigs dispatched in the removal period (3 months) and the ecoregion in which they were removed. None of the covariates, including the number of recaptures (a corresponding measure of sample size), influenced precision of the SMR models, although recaptures did influence the density estimates. At the individual property level, density estimates from our 2 estimators were dissimilar from each other in approximately 80% of instances, although none of the covariates we examined influenced dissimilarity. Our results provide unique insight into how sample size affects density estimates using 2 common methods and into novel SMR models that incorporate both marked and unmarked detections. In addition, the density estimates in this study can be used as a reference for wild pig densities in common land cover types throughout the southeastern United States.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Biomass Production and Nutrient Removal by Perennial Energy Grasses Produced on a Wet Marginal Land

Growing dedicated bioenergy crops on marginal land can provide beneficial outcomes including biomass production and energy, resource management, and ecosystem services. We investigated the effects of harvest timing (peak standing crop [PEAK] or after killing frost [KF]) and nitrogen (N) fertilizer rates (0, 56, and 112 kg N ha -1 ) on yield, nutrient concentrations, and nutrient removal rates of perennial grasses on a wet marginal land. We evaluated three monocultures, including switchgrass (Panicum virgatum L., SW), Miscanthus x giganteus (MG), prairie cordgrass (Spartina pectinata Link, PCG), and a polyculture mixture of big bluestem (Andropogon gerardii Vitman), Indiangrass (Sorghastrum nutans (L.) Nash), and sideoats grama (Bouteloua curtipendula Torr., MIX). Increasing the application of N did correlate with increased biomass, concentration, and subsequent removal of nutrients across almost all treatment combinations. In all grass treatments except MG, PEAK harvesting increased yield and nutrient removal. At PEAK harvest, switchgrass is ideal for optimizing both biomass production and nutrient removal. While our results also suggest short-term plasticity for farmers when selecting harvest timing for optimal nutrient removal, KF harvest is recommended to ensure long-term stand longevity and adequate nutrient removal. If the KF harvest is adopted, MG would be the ideal option for optimizing biomass yield potential. Additionally, we found that the yield of polyculture did not vary much with harvest timing, suggesting better yield stability. Future studies should give consideration for long-term evaluation of polyculture mixtures to assess their biomass yields and nutrient removal capacities.

54 ENVIRONMENTAL SCIENCES↗