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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Genome reduction improves octanoic acid production in scale down bioreactors

Microorganisms in large-scale bioreactors are exposed to heterogeneous environmental conditions due to physical mixing constraints. Nutritional gradients can lead to transient expression of energetically wasteful stress responses and as a result, can reduce the titres, rates and yields of a bioprocess at larger scales. To what extent these process parameters are impacted is often unknown and therefore bioprocess scale-up comes with major risk. Designing platform strains to account for these intermittent stresses before introducing synthesis pathways is one strategy for de-risking bioprocess development. For example, Escherichia coli strain RM214 is a derivative of wild-type MG1655 that has had several genes and whole operons removed from its genome based on their metabolic cost. In this study, we engineered E. coli strain RM214 (referred to as WG02) to produce octanoic acid from glycerol in batch-flask and fed-batch bioreactor cultivations and compared it to an octanoic acid-producing E. coli MG1655 (WG01). In batch flask cultivations, the two strains performed similarly. However, in carbon limited fed-batch bioreactor cultivations, WG02 provided a greater than 22% boost to biomass compared to WG01 while maintaining similar titres of octanoic acid. Reducing the biomass accumulation of WG02 with nitrogen limited fed-batch cultivation resulted in a 16% improvement in octanoic acid titre over WG01. Finally, in a scale-down system consisting of a stirred tank reactor (representing a well-mixed zone) and plug flow reactor (representing an intermittent carbon starvation zone), WG02 again improved octanoic acid titre by almost 18% while maintaining similar biomass concentrations as WG01.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Affinity of LDR Organics to Cementitious Materials: Sorption and Leaching Tests

SRNL is working to identify and test the physiochemical interactions of organic contaminants of potential concern with minerals in grout/cementitious materials. Organic species may interact with cementitious minerals including slag, fly ash, cement, and other components/dopants like carbon in fly ash. The identification of such interactions will support the solidification process design, performance assessments for the chemicals of concern, and a proposed Resource Conservation and Recovery Act (RCRA) treatment variance specified for the Land Disposal Restriction (LDR) organics associated with Hanford tank waste. Inably expected to be present LDR organics associated with Hanford tank waste (RPP-RPT-63493, Rev 1a) was screened by functional groups, octanol-water partitioning coefficients, and detection frequency in Hanford tank waste samples. A subset of 10 compounds, spanning the identified properties, were tested using sorption and leachate tests. These compounds were subjected to traditional batch sorption tests and leaching tests on/from Cast Stone cementitious material with and without activated carbon (a potential organic adsorption additive). The interactions between organic compounds were observed in traditional batch sorption and modified Toxic Characteristic Leaching Procedure (TCLP) leachate tests for a surrogate Cast Stone material with and without an activated carbon addition. Specifically, phthalic acids (negatively charged) and 4-chloroaniline (polar) sorbed strongly to unmodified Cast Stone and a group of 3 phenolic compounds (2,4,6-Trichlorophenol, Pentachlorophenol, o-Cresol) were sorbed to and were retained by Cast Stone with a 1% activated carbon amendment.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Evaluation of Adsorption Properties for Cs and Sr Selective Adsorbents-13171

The development of effective treatment and disposal methods is very urgent and important subject. Tohoku University and UNION SHOWA have developed various selective adsorbents (zeolites, zeolite sheets and composites loaded with insoluble ferrocyanides) for the effective decontamination of radioactive Cs{sup +} and Sr{sup 2+} As for Cs{sup +} adsorption, CST, chabazite and insoluble ferrocyanides composites had relatively large distribution coefficients (K{sub d}) above 10{sup 3} cm{sup 3}/g and excellent adsorption kinetics in seawater. Even after high temperature calcination at 1,100 deg. C, cesium was still immobilized in the calcined products of Cs{sup +}-zeolites, suggesting high immobilization ability of zeolites for Cs{sup +}. As for Sr{sup 2+} adsorption, A and X zeolites had relatively large K{sub d} values around 10{sup 2} cm{sup 3}/g, and zeolite sheet (A zeolite) exhibited excellent adsorption kinetics in seawater. Considering the decontamination of radioactive Sr{sup 2+} in groundwater, the effects of Ca{sup 2+} and Mg{sup 2+} ions on the K{sub d} value of Sr{sup 2+} were further examined by batch method. The K{sub d} value of Sr{sup 2+} was almost independent of Mg{sup 2+} concentration up to 2,500 ppm, while gradually lowered in the presence of Ca{sup 2+} above 200 ppm, due to the differences in the ionic radius of hydrated ion. The Cs{sup +} and Sr{sup 2+} adsorption ability for KNiFC-A (composite of A zeolite loaded with insoluble ferrocyanides) was examined by batch method. Here the matrix of composite (A zeolite) and loaded ferrocyanides (KNiFC) have high selectivity towards Sr{sup 2+} and Cs{sup +}, respectively. The K{sub d} values of Sr{sup 2+} and Cs{sup +} in seawater were estimated to be above 10{sup 2} and 10{sup 3} cm{sup 3}/g, respectively, indicating the effectiveness for the decontamination of both Sr{sup 2+} and Cs{sup +}. The basic data on the Cs{sup +} and Sr{sup 2+} adsorption properties for selective adsorbents are effective for the practical decontamination processes of these metal ions in seawater and groundwater. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Lignocellulose solubilization and conversion by extremely thermophilic Caldicellulosiruptor bescii improves by maintaining metabolic activity

Abstract The extreme thermophile Caldicellulosiruptor bescii solubilizes and metabolizes the carbohydrate content of lignocellulose, a process that ultimately ceases because of biomass recalcitrance, accumulation of fermentation products, inhibition by lignin moieties, and reduction of metabolic activity. Deconstruction of low loadings of lignocellulose (5 g/L), either natural or transgenic, whether unpretreated or subjected to hydrothermal processing, by C. bescii typically results in less than 40% carbohydrate solubilization. Mild alkali pretreatment (up to 0.09 g NaOH/g biomass) improved switchgrass carbohydrate solubilization by C. bescii to over 70% compared to less than 30% for no pretreatment, with two‐thirds of the carbohydrate content in the treated switchgrass converted to acetate and lactate. C. bescii grown on high loadings of unpretreated switchgrass (50 g/L) retained in a pH‐controlled bioreactor slowly purged (τ = 80 hr) with growth media without a carbon source improved carbohydrate solubilization to over 40% compared to batch culture at 29%. But more significant was the doubling of solubilized carbohydrate conversion to fermentation products, which increased from 40% in batch to over 80% in the purged system, an improvement attributed to maintaining the bioreactor culture in a metabolically active state. This strategy should be considered for optimizing solubilization and conversion of lignocellulose by C. bescii and other lignocellulolytic microorganisms.

Straub, Christopher T.↗
DOE OSTI2017

Experimental and Modeling Studies for the Removal of Crystal Violet Dye from Aqueous Solutions using Eco-friendly Gracilaria corticata Seaweed Activated Carbon/Zn/Alginate Polymeric Composite Beads

This research article describes, an eco-friendly activated carbon prepared from the Gracilaria corticata seaweeds which was employed for the preparation of biodegradable polymeric beads for the efficient removal of crystal violet dye in an aqueous solution. The presence of chemical functional groups in the adsorbent material was detected using FTIR spectroscopy. The morphology and physical phases of the adsorbent materials were analyzed using SEM and XRD studies respectively. Batch mode dye adsorption behavior of the activated carbon/Zn/alginate polymeric beads was investigated as a function of dosage, solution pH, contact time, initial dye concentration and temperature. Maximum dye removal was observed at a pH of 5.0, 1 g of adsorbent dosage with 60 mg/L dye concentration, 50 min of contact time and at 30 °C. The equilibrium modeling studies were analyzed with Freundlich and Langmuir adsorption isotherms and the adsorption dynamics was predicted with Lagergren’s pseudo-first order, pseudo-second order equations and intra particle diffusion models. The process of dye removal followed a pseudo second-order kinetics rather than pseudo first order. The thermodynamic parameters like standard Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were determined and the results imply that the adsorption process was spontaneous, endothermic and increases the randomness between the adsorbent and adsorbate. The results from the experimental and correlation data reveal that the Gracilaria corticata activated carbon/Zn/alginate polymeric beads have proved to be an excellent adsorbent material for the removal of CV dye.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Geomechanical Characterization of Geo-architectured Rock Specimens Using Gypsum-based 3D Printing

Due to natural heterogeneity in rock specimens, classifying rock characteristics can present difficulties. 3D printing geo-architectured rock specimens has the potential to reduce the heterogeneity and help evaluate characteristics with reproducible microstructures, bedding, and strength to advance mechanical interpretations. This testing focused on 3D printing effects on strength and rock behavior by varying amount of binder, printing direction, and atmospheric conditions. A powder-based Gypsum 3D printer was used to create 1.5-inch diameter cylindrical samples. Unconfined compressive strength (UCS) testing was completed on these samples to gather failure plots and peak strength. Multiple batches of cylindrical samples were printed with varying printing direction, binder amount, and atmospheric conditions. UCS results show that the strongest samples were those that were printed perpendicular to the loading direction compared to those printed parallel or 45 degrees. Due to reactions of the printing material with water, those at dry conditions were the strongest. Samples with the most binder amount proved to also be stronger than those with less. 3D printing of rock samples has to the potential to reduce heterogeneity rock presents, however additional factors introduced by the printing process can affect overall rock strength and behavior. Test results of the 3D printed geo-architected rock specimens demonstrated reasonable reproducibility and appear to be a promising path towards increasing the ability to characterize natural rock.

36 MATERIALS SCIENCE↗
DOE OSTI2018

On-Line Monitoring and Real-Time Characterization of Low Level Waste and Off-Gas Condensate Samples using Raman Spectroscopy

The demand for Hanford waste property analysis is expected to significantly increase as the U.S. Department of Energy River Protection Project progresses toward transferring waste to the Hanford Waste Treatment and Immobilization Plant. The analysis of waste includes chemical, radionuclide, and physical property characterizations, with the goal of achieving safe/informed transfer and processing. Waste sampling followed by offline laboratory analysis is the current baseline analytical approach. The addition of field-deployed/in situ instruments has the potential to provide improvements and benefits over offline analysis in the areas of 1) Worker Safety: by reducing the need for sampling and thereby reducing the need for worker interaction with waste during sample handling; 2) Operational Efficiency: by reducing analysis turnaround times and offsetting demand on analytical laboratories; and 3) Accuracy: continuous analysis of a flowing waste stream allows cumulative results to be produced for the batch, which is likely to be more representative than discrete samples of batch properties. This paper describes the development and application of an online monitor to provide chemical characterizations; specifically, Raman spectroscopy is utilized to identify and quantify tank components. Accurate quantification is achieved through the use of chemometric analysis, which can be configured to provide real-time analysis in field deployment settings.

Lines, Amanda M.↗
DOE OSTI2025

Glass-Bonded Monazite Waste Forms for Lanthanide and Actinide Immobilization: From Theoretical Design to Scale-Up Production and Characterization

The development of nuclear waste forms for both existing and future nuclear wastes is critical to ensuring global environmental safety. This study focuses on waste management from molten salt reactors, where fuel exists in a salt form and could be processed in real time for the removal of neutron poisons such as xenon isotopes (e.g., 135 Xe) and rare earth elements (REEs, e.g., 149 Sm). To ensure safe, stable, and long-term disposal in geological repositories, REEs must be incorporated into a durable waste form. Iron-phosphate glasses are a promising candidate due to their low melting points, high chemical durability, and their ability to incorporate high concentrations of REEs. In this study, we successfully prepared iron-phosphate glass waste forms with high Nd loadings (up to 37 mass %) in batch sizes ranging from small (23 g) to large (1600 g). The resulting materials contained up to 75 mass % NdPO 4 , contributing to their mechanical resilience and exceptional chemical durability. These findings highlight the potential of iron-phosphate glasses as high-efficiency, chemically durable waste forms and demonstrate the successful transition from theoretical design to scaled-up production.

amorphous materials↗
DOE OSTI2026

FY25 Ion Exchange Processing for the West Area Risk Management (WARM) Project

The West Area Risk Management (WARM) Project was established to enable near-term retrieval and pretreatment of tank waste from Hanford’s 200 West Area and to support deployment of an ion exchange (IX) system capable of producing cesium-depleted supernate suitable for offsite treatment and disposal. The WARM experimental campaign was designed to provide key data for design and operational planning of the 200 W IX system, which plans to utilize crystalline silicotitanate (CST) as the active media for cesium removal. This report documents a comprehensive FY25 experimental campaign designed to produce key technical data required for design and operational planning of the WARM IX system. Testing includes assessing Cs and Sr breakthrough performance in a 4-column system, Cs capacity batch contact testing, phosphate precipitation assessments, reduced-hydroxide feed displacement evaluation, and Sr speciation impacts on Sr removal. The experimental results provide detailed trends in Cs and Sr loading behavior, breakthrough performance across a 4-column staged IX system, distribution profiles within CST beds, and projections of operational flowrates relative to Waste Acceptance Criteria (WAC) limits. Batch contact testing established equilibrium partitioning behavior for the S1–S5 simulants and characterized how matrix chemistry influenced Cs sorption onto CST. Additionally, further evaluations on waste matrix as it pertains to precipitation potential were also determined. Collectively, these datasets support engineering design choices for WARM system throughput and pretreatment planning.

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

An Online Approach to Solve the Dynamic Vehicle Routing Problem with Stochastic Trip Requests for Paratransit Services

Many transit agencies operating paratransit and microtransit services have to respond to trip requests that arrive in real-time, which entails solving hard combinatorial and sequential decision-making problems under uncertainty. To avoid decisions that lead to significant inefficiency in the long term, vehicles should be allocated to requests by optimizing a non-myopic utility function or by batching requests together and optimizing a myopic utility function. While the former approach is typically offline, the latter can be performed online. We point out two major issues with such approaches when applied to paratransit services in practice. First, it is difficult to batch paratransit requests together as they are temporally sparse. Second, the environment in which transit agencies operate changes dynamically (e.g., traffic conditions can change over time), causing the estimates that are learned offline to become stale. To address these challenges, we propose a fully online approach to solve the dynamic vehicle routing problem (DVRP) with time windows and stochastic trip requests that is robust to changing environmental dynamics by construction. We focus on scenarios where requests are relatively sparse—our problem is motivated by applications to paratransit services. We formulate DVRP as a Markov decision process and use Monte Carlo tree search to evaluate actions for any given state. Accounting for stochastic requests while optimizing a non-myopic utility function is computationally challenging; indeed, the action space for such a problem is intractably large in practice. To tackle the large action space, we leverage the structure of the problem to design heuristics that can sample promising actions for the tree search. Our experiments using real-world data from our partner agency show that the proposed approach outperforms existing state-of-the-art approaches both in terms of performance and robustness.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2016

U.S. implementation of Q12{sup TM} zirconium alloy for improved stability of structural components

AREVA NP undertook the Q12{sup TM} research and development program to optimize the contribution to fuel assembly dimensional stability of structural components fabricated from ultra-low tin Zr-1Nb-Sn-Fe quaternary alloys. Because Q12{sup TM} is an evolutionary development of the current M5 alloy metallurgy, it benefits from the extensive industrial experience already gained with the latter. The Q12{sup TM} alloy is processed in the same way as M5, with slight increases in tin (Sn) and iron (Fe) contents. For structural components, these chemistry modifications provide higher irradiation creep strength and improved corrosion performance over Zircaloy-4. Fuel assemblies with quaternary alloy guide tubes are thus expected to increase robustness with respect to fuel assembly bow, improve growth characteristics, and maintain high burnup capability. The basic material properties have been determined through various in-core and out-of-core test programs. Components made from Q12{sup TM} have undergone irradiation in lead assemblies and in batch fuel for 13 Pressurized Water Reactor (PWR) units worldwide. Fuel with Q12{sup TM} guide tubes and grids has achieved a fuel assembly average burnup of 60 GWd/tU. Post irradiation examinations of these components have demonstrated that Q12{sup TM} performs in a stable, predictable manner. AREVA NP has submitted a topical report (TR) for Q12{sup TM} as a structural material to the United States Nuclear Regulatory Commission (US-NRC). This TR outlines the material behavior and performance of Q12{sup TM} for both guide tubes and grids. Once approved, implementation of Q12{sup TM} material throughout US PWR fuel designs will enhance dimensional stability of structural components. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Delivery of Vegetable Oil Suspensions in a Shear Thinning Fluid for Enhanced Bioremediation

In situ anaerobic biological processes are widely applied for dechlorination of chlorinated solvents in groundwater. A wide range of organic substrates have been tested and applied to support the dechlorination processes. Vegetable oils are a promising substrate and have been shown to induce effective dechlorination, have limited geochemical impacts, and good longevity. Distribution of vegetable oil in the subsurface, because it is a non-aqueous phase material, has typically been addressed by creating emulsified oil solutions. In this study, inexpensive waste vegetable oils were suspended in a xanthan gum solution, a shear-thinning fluid, as an alternative oil delivery mechanism. The stability, oil droplet size and distribution, and rheological behavior of the oil suspensions that are created in the xanthan solutions were studied in batch experiments. The injectability of the suspensions and oil distribution in porous medium were evaluated in column tests. Numerical modeling of the oil droplet transport and distribution in porous media was conducted to help interpret the column-test data. Batch studies showed that simple mixing of vegetable oil and xanthan solution produced stable suspensions of the oil as micron-size droplets. The mixture rheology retains shear-thinning properties that facilitate improved uniformity of substrate distribution in heterogeneous aquifers. Column tests demonstrated successful injection of the vegetable oil suspension into porous medium. This study provided evidence that vegetable oil suspensions in xanthan are a potential substrate to support in situ anaerobic bioremediation with favorable injection properties.

Zhong, Lirong↗
DOE OSTI2024

Data for Pilot-Scale Processing of Miscanthus x giganteus for Recovery of Anthocyanins Integrated with Production of Microbial Lipids and Lignin-Rich Residue

Chemical-free hydrothermal pretreatment of Miscanthus x giganteus (Mxg) at the lab scale using high liquid-to-solid ratios resulted in the recovery of anthocyanins and enhanced enzymatic digestibility of residual biomass. In this study, the process is scaled up by using a continuous hydrothermal pretreatment reactor operated at a low liquid-to-solid ratio (50 % w/w solids) as an important step towards commercialization. Anthocyanin yield was 70 % w/w at the pilot scale (50 kg of Mxg), compared to the 94 % w/w yield achieved at the lab scale (0.5 g of Mxg). The pretreated biomass was subsequently refined mechanically using a disc mill to increase the accessibility of cellulose by cellulases. Enzymatic saccharification of the pretreated and disc-milled residue yielded 238 g/L sugar concentration by operating in fed-batch mode at 50 % w/v solids content. Two strains of Rhodosporidium toruloides were evaluated for converting the hydrolysate sugars into microbial lipids, and strain Y-6987 had the highest lipid titer (11.0 g/L). Further, the residue left after enzymatic saccharification was determined to be enriched 1.7-fold in the lignin content. This lignin-rich residue has value as a feedstock for the production of sustainable aviation fuel precursors and other high-value lignin-based chemicals. Hence the proposed biorefinery based on Mxg creates an opportunity for generating revenue from multiple high-value products. As the demand for biofuels and biobased products is rising, the biorefinery products from Mxg would create a niche in the industrial sector.

Conversion↗
DOE OSTI2012

Tank 21 and tank 24 blend and feed study: blending times, settling times, and transfers

The Salt Disposition Integration (SDI) portfolio of projects provides the infrastructure within existing Liquid Waste facilities to support the startup and long term operation of the Salt Waste Processing Facility (SWPF). Within SDI, the Blend and Feed Project will equip existing waste tanks in the Tank Farms to serve as Blend Tanks where salt solutions of up to 1.2 million gallons will be blended in 1.3 million gallon tanks and qualified for use as feedstock for SWPF. In particular, Tanks 21 and 24 are planned to be used for blending and transferring to the SDI feed tank. These tanks were evaluated here to determine blending times, to determine a range of settling times for disturbed sludge, and to determine that the SWPF Waste Acceptance Criteria that less than 1200 mg/liter of solids will be entrained in salt solutions during transfers from the Tank 21 and Tank 24 will be met. Overall conclusions for Tank 21 and Tank 24 operations include: (1) Experimental correction factors were applied to CFD (computational fluid dynamics) models to establish blending times between approximately two and five hours. As shown in Phase 2 research, blending times may be as much as ten times greater, or more, if lighter fluids are added to heavier fluids (i.e., water added to salt solution). As the densities of two salt solutions converge this effect may be minimized, but additional confirmatory research was not performed. (2) At the current sludge levels and the presently planned operating heights of the transfer pumps, solids entrainment will be less than 1200 mg/liter, assuming a conservative, slow settling sludge simulant. (3) Based on theoretical calculations, particles in the density range of 2.5 to 5.0 g/mL must be greater than 2-4 {micro}m in diameter to ensure they settle adequately in 30-60 days to meet the SWPF feed criterion (<1200 mg/l). (4) Experimental tests with sludge batch 6 simulant and field turbidity data from a recent Tank 21 mixing evolution suggest the solid particles have higher density and/or larger size than indicated by previous analysis of SRS sludge and sludge simulants. (5) Tank 21 waste characterization, laboratory settling tests, and additional field turbidity measurements during mixing evolutions are recommended to better understand potential risk for extended (> 60 days) settling times in Tank 21.

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

Engineered Option Treatment of Remediated Nitrate Salts: Surrogate Batch-Blending Testing

This report provides results from batch-blending test work for remediated nitrate salt (RNS) treatment. Batch blending was identified as a preferred option for blending RNS and unremediated nitrate salt (UNS) material with zeolite to effectively safe the salt/Swheat material identified as ignitable (U.S. Environmental Protection Agency code D001). Blending with zeolite was the preferred remediation option identified in the Options Assessment Report and was originally proposed as the best option for remediation by Clark and Funk in their report, Chemical Reactivity and Recommended Remediation Strategy for Los Alamos Remediated Nitrate Salt (RNS) Wastes, and also found to be a preferred option in the Engineering Options Assessment Report: Nitrate Salt Waste Stream Processing. This test work evaluated equipment and recipe alternatives to achieve effective blending of surrogate waste with zeolite.

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

Monitoring of U(VI) Bioreduction after ARCADIS demonstration at Savannah River Site F-Area - 15699

The F/H Area Seepage Basins located in the center of Savannah River Site (SRS) received approximately 1.8 billion gallons of acidic waste solutions. The acidic nature of the basin waste solutions triggered the mobilization of metals and radionuclides including soluble uranium (VI). SRS F-Area sediments are acidic and composed predominantly of quartz sand with varying amounts of fine-grained minerals and iron-oxides. In 2010, ARCADIS implemented in-situ injections of a carbohydrate substrate to establish anaerobic reactive zones for metal and radionuclide remediation via the Enhanced Anaerobic Reductive Precipitation (EARP) process at the SRS F-Area (Figure 2). The addition of the molasses substrate solution to groundwater produces anaerobic conditions with redox values in the methanogenic or sulfate-reducing range conducive to the reductive precipitation of uranium. Objectives: Determine the mineral composition of SRS fine clay fractions and identify all iron-oxide phases. Establish if ferrous carbonate and ferrous sulfide compounds will be present in the sediment after the bioreduction process has occurred. The presence of these compounds will indicate that anaerobic reductive conditions were established. Determine the types of reactions that might occur in the anaerobic aquifer. Determine if conditions will return to the initial state once samples are returned to aerobic conditions. Microcosm studies were prepared with SRS sediments treated using a basal medium solution augmented with sulfate and molasses as well as a trace metal solution. To create anaerobic conditions necessary for the experiment, a vinyl anaerobic airlock chamber from COY Lab Products was used to ensure that no oxygen reached the samples. Half of the samples were augmented with sulfate in an attempt to create iron sulfide and stabilize reduced uranium. A pH evolution study was conducted to find the type of pH changes that occurred in the samples. Samples were sieved to 180 mm before X-ray Diffraction (XRD) analysis was conducted to identify any mineralogical changes in the samples. The experimental patterns were compared against known XRD patterns for siderite and pyrite. Liquid samples were filtered through 0.45 mm filters and were diluted by a factor of 200 in nitric acid (1%) for ICP-OES analysis to determine the ferrous iron concentration. XRD analysis indicated that the sediments contained quartz, kaolinite, montmorillonite, and goethite. All of the samples have followed a similar trend, with a decline in the pH values. It was noted that samples amended with sulfates had slightly higher pH than sulfate-free samples. The pH drop can be attributed to the fermentation process of molasses and the natural acidity of SRS soil used for the microcosm study. The low pH conditions are believed to have hindered the formation of bicarbonate/carbonate ions used to form the iron precipitates. XRD results confirmed the assumption that with low pH values no iron compounds would precipitate in the samples. The experimental patterns for each sample was compared with the patterns for siderite and pyrite; the results for these analyses were negative. ICP-OES analysis confirmed that there is ferrous iron present in the samples. The highest iron concentration being 13312.8 ppb for Batch 1, Sample 1-2, the lowest were in Batch 2 Samples 2,3, and 4 which may be below the calibration curve. This may also be an indication that the iron has precipitated in these samples. Future work: Conduct ICP analysis on the Batch 2 samples using a lower dilution factor. Determine the types of reactions that might occur in the anaerobic aquifer. Verify the continued sequestration of U(VI) in relation to the possible re-oxidation of minerals from the bioreduction zone. Sulfate concentrations will be examined using an ion analysis technique. Determine pH levels, sulfate concentrations, and iron concentrations after re-oxygenation.

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

A Study on Vitrification for LLW Radioactive Wastes - 16235

Ash and ion exchange resin wastes to be vitrified were considered among various radioactive wastes in the Japanese nuclear industry. The appropriate glass composition for the waste is calculated using the computer program. The glass composition is systematically studied using a ternary diagram, considering viscosity, electrical conductivity, and durability. The optimized glass composition based on calculated parameters of vitrification process and the convenience of mixing wastes is selected for crucible experiment. Since differences between calculated values and measured values may occur upon evaluation of glass formulations using glass formulation computer simulation program, the calculated glass formulations should be verified through experiments on a laboratory scale for more meticulous development of glass formulations. For the follow-up development of glass formulations, several glass formulations are planned to be developed. The candidate glasses for treatment of ash and ion exchange resin were melted and fabricated using reagents, respectively. The chemicals were weighed out to produce the desired batch compositions and mixed thoroughly and then put into clay crucibles for melting. Next, the crucibles were introduced into an electric furnace at 1,150 deg. C in the ambient atmosphere and pressure with occasional stirring by a quartz rod. A hold time of 1 hour was introduced to promote homogenization. Finally, the melted material was poured on a graphite plate to be rapidly cooled. The viscosities of all fabricated glasses were in the desired range. After rapid cooling, the micro-structure of the glasses was analyzed using the SEM. They exhibited amorphous structure with good homogeneity. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗