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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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16 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

A new recycling technique for the waste tires reuse

In this series of laboratory experiments, the feasibility of using fixed bed biofilm carriers (FBBC) manufactured from existing reclaimed waste tires (RWTs) for wastewater treatment was evaluated. To assess polyamide yarn waste tires as a media, the fixed bed sequence batch reactor (FBSBR) was evaluated under different organic loading rate (OLRs). An experimental model was used to study the kinetics of substrate consumption in biofilm. Removal efficiency of soluble chemical oxygen demand (SCOD) ranged by 76–98% for the FBSBR compared to 71–96% in a sequencing batch reactor (SBR). Removal efficiency of FBBC was significantly increased by inoculating these RWTs carriers. The results revealed that the sludge production yield (Y{sub obs}) was significantly less in the FBSBR compared to the SBR (p < 0.01). It also produced less sludge and recorded a lower stabilization ratio (VSS/TSS). The findings show that the Stover-Kincannon model was the best fit (R{sup 2} > 99%) in a FBSBR. Results from this study suggest that RWTs to support biological activity for a variety of wastewater treatment applications as a biofilm carrier have high potential that better performance as COD and TSS removal and sludge settling properties and effluent quality supported these findings. - Highlights: • Introduced new recycling technique for reclaimed waste tire. • Fixed bed biofilm carriers (FBBC) are widely used for the clean-up of wastewaters. • FBBC were manufactured from existing reclaimed waste tire. • Stover-Kincannonmodel was selected as the best model for describing pollutant removal and FBSBR design in this study.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Tank 22 Settled Sludge Core Sample Characterization and Testing

The Savannah River National Laboratory (SRNL) was requested by Savannah River Remediation (SRR) Engineering (SRR-E) to provide sample characterization and analyses of Tank 22 settled sludge core sample and the supernatant liquids (supernate) in support of Tank 22 re-baseline data, inhalation dose potential/hydrogen generation and suspension/removal of settled sludge from the bottom of Tank 22. The approximately 9.5 inches of intact Tank 22 core sample from SRR-E, after extrusion in the SRNL Shielded Cells, showed three visually different stratification layers or regions of solids in the extruded core material. Part of the initial physical characterization of these three segments of the Tank 22 core sample included density, weight percent total solids, particle size distribution, X-ray diffractions and scanning electron microscope of each segment material. Given the dissimilarity of the three Tank 22 segment materials after the physical characterization results and the fact that there was no clear line of demarcation to indicate where each segment began and ended across the entire length of the core sample, SRNL in conjunction with the SRR-E customer decided to blend all three segments of the material to form a composite Tank 22 core sample for further analysis and characterization without taking into consideration the proportional weight or mass contribution of each segment. This compositing approach assumes that the errors introduced in any characterization of the Tank 22 core sample will be comparable to the errors when the three segments are separated and combined proportionally by weight to form the composite Tank 22 sample. This compositing approach maximized the quantity of composited Tank 22 material needed for radionuclide and other physical characterizations.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1977

Less-costly activated carbon for sewage treatment

Lignite-aided sewage treatment is based on absorption of dissolved pollutants by activated carbon. Settling sludge is removed and dried into cakes that are pyrolyzed with lignites to yield activated carbon. Lignite is less expensive than activated carbon previously used to supplement pyrolysis yield.

Ingham, J. D.↗
NASA NTRS1976

Sewage sludge treatment system

Raw sewage may be presently treated by mixing screened raw sewage with activated carbon. The mixture is then allowed to stand in a first tank for a period required to settle the suspended matter to the bottom of the tank as a sludge. Thereafter, the remaining liquid is again mixed with activated carbon and the mixture is transferred to a secondary settling tank, where it is permitted to stand for a period required for the remaining floating material to settle as sludge and for adsorption of sewage carbon as well as other impurities to take place. The sludge from the bottom of both tanks is removed and pyrolyzed to form activated carbon and ash, which is mixed with the incoming raw sewage and also mixed with the liquid being transferred from the primary to the secondary settling tank. It has been found that the output obtained by the pyrolysis process contains an excess amount of ash. Removal of this excess amount of ash usually also results in removing an excess amount of carbon thereby requiring adding carbon to maintain the treatment process. By separately pyrolyzing the respective sludges from the first and second settling tanks, and returning the separately obtained pyrolyzed material to the respective first and second tanks from which they came, it has been found that the adverse effects of the excessive ash buildup is minimized, the carbon yield is increased, and the sludge from the secondary tank can be pyrolyzed into activated carbon to be used as indicated many more times than was done before exhaustion occurs.

Kalvinskas, John J.↗
DOE OSTI2016

Dewatering Innovations - 16381

The Liquid and Gaseous Waste Operations (LGWO) project, located at the Oak Ridge National Laboratory, handles wastewater from over 600 generators in 200 facilities. LGWO processes these waters, removing radioactive and chemical contaminants prior to discharge to the environment. Through these processes, LGWO generates various sludges that require dewatering prior to transportation. The original process was very inefficient. It involved placing PVC tubing in the bottom of a 90 ft{sup 3} box and sluicing the sludge into the box. Suction was then applied to the PVC tubes to remove water that would settle out of the material. The old process took several evolutions to drain/decant the liquids, which caused unnecessary worker radiation exposure. The moisture content was Near High Moisture content, which presented the possibility that liquids could be released during transport. Due to this fact, disposal costs were very high. Solutions for the 'Old' disposal process were to use liquid-rated Super Sacks, add additional Absorbent and then have the containers evaluated for liquid at TSDRF, prior to final disposal. This paper will describe the innovative packaging that was developed for the processing of these sludges, the ease with which the process was implemented, the versatility of the system and the cost savings associated with the new process. This system can be used in many other water treatment applications and erosion control. (authors)

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

Discovering Challenges and Opportunities During Sludge Removal in Savannah River Site's Tank 15 - 18415

Tank 15 is one of 43 active underground waste storage tanks in the Liquid Waste System at SRS. After receiving and storing waste containing insoluble solids (sludge), receipts stopped, and the free supernate evaporated beginning in the 1980's. Tank 15 remained a dry sludge tank for almost 30 years. In 2015, the Tank 15 sludge was rehydrated as the first step of waste removal. Submersible Mixer Pumps (SMPs) were then installed in four risers, as well as other equipment upgrades, to facilitate sludge solids removal. SMPs were successfully used in prior waste removal campaigns, but this was the first deployment of four in a tank. Automated controls were also added to better monitor and protect the SMPs during operation in the more challenging H-area sludge. Waste removal plans consisted of multiple campaigns where sludge was suspended, transferred to Tank 13 and supernate decanted back to Tank 15 for reuse after allowing solids to settle. During the first campaign, sludge solids did not settle at an adequate rate to support the operating plan, and flammability evaluations were impacted. The SMPs also experienced operational challenges. New control logic for the SMPs was useful for early identification of issues; however, some equipment failures still occurred. These challenges were overcome using a combination of additional analyses, operating plan and procedure changes, and tank mapping techniques resulting in the successful removal of the bulk of the sludge from Tank 15. (authors)

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

Utilizing Commercial Submersible Mixer Pumps for Sludge Removal in Savannah River Site's Tank 26 - 20289

The Savannah River Site (SRS) Liquid Waste System (LWS) safely manages, stores, treats, and dispositions liquid radioactive waste. The LWS consists of 51 underground waste storage tanks (eight of which are operationally closed and filled with grout), waste evaporators, treatment facilities, and solidification facilities, known as the Defense Waste Processing Facility (DWPF) and Saltstone Production Facility (SPF). One of the waste storage tanks, Tank 26, was placed into service in 1980 as an F Tank Farm (FTF) Evaporator Feed Tank. From 1980 to 2013, Tank 26 received F Canyon receipts and dilute supernate that was then transferred to the 242-16F FTF Evaporator for volume reduction. In 2013, the steam tube bundle failed in the FTF Evaporator, and the decision was made not to repair/resume evaporator operation. During operation of Tank 26, solids built up to a level of 2.03 m in the tank with a volume of 1062.9 kL. Due to the evaporator failure and subsequent shutdown, the solids in Tank 26 were selected to feed Sludge Batch 10, which is collected and prepped prior to being sent to DWPF for final disposition. To accomplish solids removal, Commercial Submersible Mixer Pumps (CSMPs) were selected to slurry the solids in preparation to be sent to Tank 51. Four CSMPs were installed in Tank 26 with each one installed in a separate quadrant of Tank 26. This work would mark the first deployment of CSMPs in an SRS waste tank. The CSMPs were developed in response to operational issues from previous mixing pumps and budgetary constraints. The CSMPs use the concept of modifying commercially available equipment for nuclear waste applications. The CSMPs consist of a 230-horsepower submersible mixing pump (manufactured by GPM, Inc.) joined to a mast fabricated at SRS. For this application, Savannah River Remediation (SRR) design services was challenged to provide a mast design that required no steel superstructure support system on top of Tank 26. Also, SRR design services provided a simplified Tank 26 riser interface that did not require extensive machine parts to adjust height of the suction screen of the CSMP within the tank. Other design improvements include no requirements for tank top radiation monitors and no requirements for flushing of the CSMPs during startup/shutdown operations. The CSMPs were operated at an initial height of 2.29 m above the Tank 26 bottom for 10 days. After sludge sounding, the CSMPs were lowered to a height of 1.52 m with no issues due to proper work planning and the simplified riser interface. With the CSMPs lowered to a level of 1.52 meters above the tank bottom, the CSMPs were operated for 12 days and another sounding was performed. The sounding level came back matching the disturbance depth results of the first pump run. Chemistry samples were analyzed while the tank was left to settle. The analysis revealed enough weight percent solids to provide good feed to Sludge Batch 10. Also, the results revealed the supernate within the mixture would provide good salt solution feed to Salt Waste Processing Facility (SWPF) Salt Batch 3. So, the plan was modified to let the disturbed solids settle and decant the salt solution for addition to SWPF Salt Batch 3. Then water will be added back to Tank 26, and the CSMPs run in order to wash the solids to decrease settling time prior to being sent to Tank 51 for Sludge Batch 10. Utilizing CSMPs for waste removal in an SRS Tank has provided a cost-effective means for further waste removal efforts. In addition, the CSMPs are easier to operate by utilizing a robust and simplified design. The CSMPs performed quite well with no process shutdown or delays during operation. As a result, CSMPs are integral to the future of removing radioactive waste from storage tanks at SRS. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Characterization of the March 2017 Tank 15 Waste Removal Slurry Sample (Combination of Slurry Samples HTF-15-17-28 and HTF-15-17-29)

Two March 2017 Tank 15 slurry samples (HTF-15-17-28 and HTF-15-17-29) were collected during the second bulk waste removal campaign and submitted to SRNL for characterization. At SRNL, the two samples were combined and then characterized by a series of physical, elemental, radiological, and ionic analysis methods. Sludge settling as a function of time was also quantified. The characterization results reported in this document are consistent with expectations based upon waste type, process knowledge, comparisons between alternate analysis techniques, and comparisons with the characterization results obtained for the November 2016 Tank 15 slurry sample (the sample collected during the first bulk waste removal campaign).

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

Retrieval and Management of TRU Sludge at Hanford K-Basin - 19641

At the US Department of Energy Hanford site, the K-East and K-West reactor fuel storage basins (KE or KW Basin) were used in the 1970's and 1980's to store more than 100,000 uranium fuel rods and rod fragments that had been irradiated in the Hanford N Reactor. Approximately 2,100 metric tons of spent nuclear fuel that had been stored in the KW Basin were removed in 2004. Over time a mixture of small fuel corrosion particles, fuel rod metal fragments, and other debris accumulated in the KW Basin from the degradation of the spent nuclear fuel during storage. This is the source of the TRU sludge stored in the KW Basin. The corrosion products mixed with windblown sand, concrete dust, and other debris in the basin to form what is known as sludge. In 2006/2007 KE Basin sludge of similar origin as the KW Basin was transferred to KW Basin. Approximately 27 m{sup 3} of highly radioactive sludge was collected and consolidated underwater in six specially designed engineered containers. The mission of the Hanford Sludge Treatment Project (STP) is to develop and deploy technologies to safely retrieve, transport, and interim store the approximately 27 m{sup 3} of remote-handled transuranic (RH-TRU) sludge that is stored in the KW Basin. After extensive technology development, testing (with a bounding range of simulants), design, and procurement a sludge removal and storage system called the Engineered Container Retrieval and Transfer System (ECRTS) completed acceptance testing in 2018. The ECRTS system is designed to remotely retrieve and transport high density, highly erosive, uranium metal pieces as well as small low-density particles. The ECRTS system includes a retrieval tool based on the XAGO{sup tm} design from the United Kingdom, a heavily modified positive displacement pump, a hose-in-hose transfer system, a Sludge Transport and Storage Container (STSC), a settling and decant system, and a shielded transport system. The first sludge transfer was successfully completed on June 12, 2018 proving that the ECRTS process equipment worked as intended on the actual sludge. Three batches (i.e. transfer and decant) were required to obtain a ∼ 100% fill of the first STSC. The STSC was then transported to the on-site storage facility. Over 20 STSCs will be filled with RH-TRU sludge over approximately 16 months. This paper will discuss the issues and successes associated with this project including the operational aspects of this new system. Experience gained from this successful project should assist anyone with the need to retrieve and manage remote handled sludge from fuel storage basins. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Tank 40 final sludge batch 9 chemical and fissile radionuclide characterization results

A sample of Sludge Batch (SB) 9 was pulled from Tank 40 in order to obtain radionuclide inventory analyses necessary for compliance with the Waste Acceptance Product Specifications (WAPS)i. The SB9 WAPS sample was also analyzed for chemical composition, including noble metals, and fissile constituents, and these results are reported here. These analyses along with the WAPS radionuclide analyses will help define the composition of the sludge in Tank 40 that is fed to the Defense Waste Processing Facility (DWPF) as SB9. At the Savannah River National Laboratory (SRNL), the 3-L Tank 40 SB9 sample was transferred from the shipping container into a 4-L high density polyethylene bottle and solids were allowed to settle. Supernate was then siphoned off and circulated through the shipping container to complete the transfer of the sample. Following thorough mixing of the 3-L sample, a 547 g sub-sample was removed. This sub-sample was then utilized for all subsequent slurry sample preparations. Eight separate aliquots of the slurry were digested, four with HNO3/HCl (aqua regiaii) in sealed Teflon® vessels and four with NaOH/Na2O2 (alkali or peroxide fusioniii) using Zr crucibles. Three Analytical Reference Glass – 1iv (ARG-1) standards were digested along with a blank for each preparation. Each aqua regia digestion and blank was diluted to 1:100 with deionized water and submitted to Analytical Development (AD) for inductively coupled plasma – atomic emission spectroscopy (ICP-AES) analysis, inductively coupled plasma – mass spectrometry (ICP-MS) analysis, atomic absorption spectroscopy (AA) for As and Se, and cold vapor atomic absorption spectroscopy (CV-AA) for Hg. Equivalent dilutions of the alkali fusion digestions and blank were submitted to AD for ICP-AES analysis. Tank 40 SB9 supernate was collected from a mixed slurry sample in the SRNL Shielded Cells and submitted to AD for ICP-AES, ion chromatography (IC), total base/free OH-/other base, total inorganic carbon/total organic carbon (TIC/TOC) analyses. Weighted dilutions of slurry were submitted for IC, TIC/TOC, and total base/free OH-/other base analyses. Activities for U-233, U-235, and Pu-239 were determined from the ICP-MS data for the aqua regia digestions of the SB9 WAPS slurry using the specific activity of each isotope. The Pu-241 value was determined from a Pu-238/-241 method developed by SRNL AD and previously described.v

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Use of Ferrihydrite-Coated Pozzolana and Biogenic Green Rust to Purify Waste Water Containing Phosphate and Nitrate

The activated sludge treatments combined to the addition of ferric chloride is commonly used to eliminate nitrate and phosphate from waste water in urban area. These processes that need costly infrastructures are not suitable for rural areas and passive treatments (lagoons, reed bed filters…) are more frequently performed. Reed bed filters are efficient for removing organic matter but are not suitable for treating phosphate and nitrate as well. Passive water treatments using various materials (hydroxyapatite, slag…) were already performed, but those allowing the elimination of both nitrate and phosphate are not actually available. The goal of this work is to identify the most suitable iron based materials for such treatments and to determine their optimal use conditions, in particular in hydrodynamic mode. The reactivity of the iron based minerals was measured either by using free particles in suspension or by depositing these particles on a solid substrate. Pouzzolana that is characterized by a porous sponge-like structure suits for settling a high amount of iron oxides. The experimental conditions enabling to avoid any ammonium formation when green rust encounters nitrate were determined within the framework of a full factorial design. The process is divided into two steps that will be performed inside two separated reactors. Indeed, the presence of phosphate inhibits the reduction of nitrate by green rust and the dephosphatation process must precede the denitrification process. In order to remove phosphate, ferrihydrite coated pouzzolana is the best materials. The kinetics of reaction of green rust with nitrate is relatively slow and often leads to the formation of ammonium. The recommendation of the identified process is to favor the accumulation of nitrite in a first step, these species reacting much more quickly with green rust and do not transform into ammonium.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2020

Implications of Non-Bingham Rheology

One of the key challenges now facing the US Department of Energy (DOE) is the fate of radioactive waste remaining from World War II and the Cold War which is stored underground in tanks some 75 feet in diameter and over 30 feet tall. Over time, the waste has segmented into multiple layers with sludges and slurries at the bottom with salt crust layers often at the top and liquid in between. DOE’s current official baseline plans call for remaining sludges and slurries to be removed from the tanks and converted into a more stable glass waste form. Minimizing worker exposure to radiation drives DOE to use slurry processing techniques to suspend, mobilize, transport, mix, and process the waste. Therefore, a clear and quantitative understanding of Hanford waste rheology is essential for the success of the DOE mission. Historically much of the waste has been characterized using Eugene Bingham’s model more than a century old that provides a straight line fit to higher shear rate data with the intercept suggesting a yield stress and the slope providing the consistency. Yet, Bingham fits overestimate the shear stress at a given shear rate for low to intermediate shear rates, exactly the range of shear rates typically encountered in pipe flow, where shear rates peak along the pipe wall and vanish in the center. This model produces a fictitious yield stress for some of the wastes that do not exhibit yield phenomena. While over estimating the yield stress may be prudent, safe, and conservative for some applications (e.g., pump sizing to ensure that pumps can handle yield stresses), over estimating the rheology may be inaccurate and non-conservative for other applications (e.g., eroding settled particle beds). Therefore, this paper evaluates the slurry rheology of Hanford and Savannah River wastes using a more modern rheological model that fits the full range of experimental data. Although a bias has been recognized and alternative models proposed, the magnitude of this bias and the implications for tank waste have only been qualitatively suggested. The purpose of this paper is to evaluate quantitatively implications of the poor quality of fit between a Bingham model for rheology and experimental data at modest shear rates. We first demonstrate the magnitude of the bias between the data and the Bingham extrapolation. We then evaluate quantitatively the velocity profile under laminar conditions. This analysis shows that the bias may be large (hundreds of percent or more) at modest shear rates and that modest shear rates dominate pipe velocity profiles.

Rheology, Radioactive waste↗
DOE OSTI2019

Recovery of Rare Earth Elements from Coal Mining Waste Materials

The objective of this proposed project was to locate coal overburden material that had rare earth elements (REEs) at concentrations of 300 ppm or higher. After securing the feedstock the next goal was to efficiently extract and purify the feedstocks to a purity of greater than 95%. A techno economic analysis was conducted to determine the economic viability of mining and processing REEs associated with Appalachian coal deposits. All aspects of mining, mineral processing, by-product potential, waste management, permitting and economics were examined. Attention was paid to the separation, degree of purification and marketing of Rare Earth elements. Along with REEs we evaluated the economics of the recovery of other metals of interest aong with the REEs. Our site location chosen was at the Jeddo Coal Site near Hazleton, Pennsylvania. The primary site was at the Upper Leigh High Mine. However, that changed to the North Eckley Mine site. We have analyzed a third site that will now be our second alternative to North Eckley. That site is the Highland mine site. This site is in a similar basin as the North Eckley site. During this project we evaluated various acids and extraction conditions. We have settled on using HCl as the acid of choice. One of the advantages of using HCl is it allows for easy removal of the highest contaminating metal, iron. When iron reacts with HCl in the presence of high chlorides it creates the anion complex FeCl 4 -1 . This FeCl 4 -1 complex will bind with an anion exchange resin. Greater than 99.8% of the iron is removed with this technique. Once the FeCl 4 -1 complex is bound to the anion exchange resin it can be released easily by just passing water over it. This water dilutes the FeCl 4 -1 to form FeCl 3 which is not anionic and therefore not attracted to the anion exchange resin. The FeCl 3 solution is a popular water flocculating agent used all over the world for water purification. We plan on this being one of our products produced. One of our goals was to create a multipurpose facility that was capable of handling multiple feedstocks. The proposed multipurpose facility will be able process all coal biproducts and coal products. These include 1.) clays that can easily be leached with ion exchange or acid 2.) Hard mineral deposits that can be leached with high pressure acid digestion 3.) Fly ash can be leached in the high-pressure acid digestion reactor. Fly ash is not a focus of this proposal but, the beneficial aspect of its utilization in this design cannot be overlooked. 4.) Acid Mine Drainage (AMD) Sludge is a high source of REE’s and can easily be dissolved to form a pregnant leach solution. Not shown on this simplified block flow diagram but crucial to its success is the recycle of acids. Our REE separation system is a continuous ion exchange process. The first stage is the separation of the non-REEs from the REEs. This is accomplished because the REEs are relatively larger than most of the non-REEs and typically have higher oxidation states (+3) than the non-REEs. In this step all the elements stick onto the column. However, as the columns are rinsed with various concentrations of acids different elements come off. For example, monovalent elements such as sodium and potassium elute off the column with a 1M HCl solution. Divalent elements such as calcium and magnesium do not elute until a 2M HCl solution is passed over the columns. The trivalent elements (REEs) are not eluted until a much higher concentrated acid is passed of the columns. Iron is also a trivalent, but it was removed in a prior anion exchange system. Aluminum is trivalent too, but it is much smaller than the REE atoms and elutes near the end of the 2 M HCl with the divalents. At the stage 2 and 3 our volume and masses have become too small to run on the continuous system. Therefore, we used a batch chromatography column or a flash chromatography column. The stage 2 process separates these REEs into 3 different fractions. A light, mid and heavy fraction. We calculated that we recovered greater than 90% of the REEs. This third column was packed with a different stationary phase. Five elements were chosen and purified to higher than 95% purity as shown by our internal testing. These elements were shipped to the DOE.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

FY24 Task 5: Leachate Disposition

Directly feeding sludge solids to the high-level waste (HLW) Waste Treatment Plant represents an alternative flowsheet seeking to initiate sludge processing as soon as possible. Key processing functions previously captured during baseline pretreatment operations include leaching and washing prior to solids concentration. These operations should be considered in the potential direct feed flowsheets to maximize waste feed loading, minimize HLW volume, and mitigate corrosion challenges associated with vitrification of high phosphate and fluoride concentrations. Additionally, single-shell tank (SST) retrievals and waste transfers to double-shell tanks (DSTs) in a direct feed flowsheet would likely also benefit from some level of leaching, washing, and solids concentration in order to reduce DST space and mission duration. These operations could occur in a new facility or potentially in available DSTs. If washing and leaching are utilized, an effective disposition pathway for the wash water and leachate solutions are needed. Three target species that benefit significantly from leaching and washing are phosphate, fluoride and aluminum. Phosphate (PO 4 3- ) and fluoride (F - ) can contribute substantially to the amount of carrier fluid needed for dissolution, and the resulting volume of liquid generated. Disposition of this retrieval solution should be evaluated in order to prevent crystallization of these anions throughout system processing. Since there is a high probability that any retrieval solutions will be at or near their PO 4 3- and F - solubility limits, evaporation or blending with a high Na supernate (>3.5 M) is not recommended for the wash water streams without a method to remove precipitants prior to solution disposal. Additionally, aluminum present in the southeast quadrant of the Hanford site represents roughly 60% of the waste solids in the initial processing tanks. These aluminum solids are in the form of gibbsite (Al(OH) 3 ) and can pose significant challenges for processing due to the fast-settling times and high solids loading associated with these materials. Easily remediated by caustic addition to the solids, these wash solutions could be processed through crystalline silicotitanate (CST) ion exchange columns to prepare the supernate solutions for disposition. The current target for feed conditions to the Low Activity Waste (LAW) melter are waste streams that contain nominally 5-6 M Na. Fractions within the tanks contain upwards of 0.2 M phosphate and fluoride in solution at 3.5 M Na. Concentrating these solutions above 5 M Na would result in an exceedance of the solubility limits, and potential for uncontrolled precipitation of the phosphate and fluoride crystal material. The resulting crystalline salt material is typically sodium fluoride phosphate, also referred to as natrophosphate (Na 7 FPO 4 ·19H 2 O). Salt phases are of importance in tank waste due to their chemical reactivity, which can result in precipitation, dissolution, or transformation, impacting any downstream processes (Bolling et al. 2020, Russell, Snow, and Peterson 2010). Salt generation and precipitation could pose challenges by causing system plugging and melter corrosion if left in the supernate stream, or limit sodium molarity of the supernate that would be accepted without incident in waste operations. To understand the impact of this salt generation, the crystallization of natrophosphate in multiple simulant feed matrices was studied to understand the implications of various tank waste supernate chemistries. Three matrices were examined: high PO 4 3- /low F - , low PO 4 3- /high F - , and an average matrix. Subsequent testing was performed with the average matrix with the inclusion of CsNO 3 , and a final run with the average matrix including CsNO 3 and a 137 Cs spike for tracer purposes.

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

Use of In Situ Acoustic Backscatter Systems to Characterize Spent Nuclear Fuel and its Separation in a Thickener - 19288

To aid in the transportation, dewatering and storage of radioactive UK legacy waste sludges at Sellafield Ltd., the application of an Acoustic Backscatter System (ABS) was investigated in this study, as a method for monitoring suspended solids concentration and consolidation of cohesive and aggregated sludges (that form the basis of many wastes at Sellafield). An ABS represents a particularly promising technology, as they can be used with minimal intrusion, to measure both particle size and concentration depending on prior system knowledge, through inversion of the return echo voltage response of pulse-echo signals in the MHz range. To assess the application for continuous, high concentration (∼30 % v/v) thickened wastes, an ABS was utilised to characterise a pseudo-steady state laboratory thickener over hours, using flocculated calcite as a representative test material. Measurements were taken both horizontally through a consolidated bed using a 1 MHz transducer and vertically downwards with a 2 MHz transducer to measure sediment concentration above the settled bed and track bed height via the interface reflection. Characterisation of flocculated aggregate diameters was initially determined to be ∼510 μm, using an in-line Focussed Beam Reflectance Measurement (FBRM) device. The submerged 2 MHz probe indicated that there were only limited changes to the dispersion concentration or size over time. Changes in settled bed density, due to increasing bed height and changes in the underflow flow rate, were qualitatively measured via differences to the acoustic signal attenuation over time. An initial increase in attenuation with bed height was observed as the bed densified due to local compression. Once an equilibrium bed height was reached, the acoustic attenuation remained fairly constant with time, although the bulk underflow density was reduced with the increase in underflow rate. The solids residence time in the bed, determined from a transitive volume-balance model, was found to be ∼3200 s for pseudo-steady state operation at a maintained bed height of ∼0.175 m. Results of the study highlight the potential the ABS as a remote process monitoring tool for both relatively dilute suspensions and concentrated thickened mineral sludges, with potential applications across waste processing sites at Sellafield. (authors)

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

Retained Hydrogen Literature Study for DWPF

During Defense Waste Processing Facility (DWPF) operation in the Slurry Receipt and Adjustment Tank (SRAT) and the Slurry Mix Evaporator (SME), hydrogen is primarily produced by radiolysis and catalytic generation. The hydrogen is released from the sludge by agitation and removed from the vapor space by purging with air. Upon loss of agitation, the hydrogen begins accumulating in the sludge, and releases rapidly upon the resumption of agitation. If enough hydrogen accumulated in the sludge, and released rapidly upon the start of agitation, the hydrogen concentration in the vapor space could exceed the lower flammability limit (4 vol %). Savannah River Remediation (SRR) currently manages the risk for retained hydrogen in the DWPF vessels by implementing a Retained Hydrogen Program. The program primarily relies on the timely operation of vessel agitators to ensure that the retained hydrogen eruptions that could lead to flammable vapor spaces do not occur. The current program relies on conservative assumptions concerning gas release and retention (e.g., instantaneous release, conservative hydrogen bubble fraction, no release during quiescent periods) to develop allowable vessel quiescent times (Q-times). SRR would like to relax the conservative assumptions to the Retained Hydrogen Program and allow the Retained Hydrogen Program to extend past Sludge Batch 9. Relaxing the assumptions could potentially allow longer Q-times during agitator stoppages. SRR requested Savannah River National Laboratory (SRNL) personnel to perform a literature study to extract industry data pertaining to retained hydrogen and apply it to the DWPF process. The authors conducted a review of the technical literature, including work from the Savannah River Site (SRS), SRNL, the Hanford site, Pacific Northwest National Laboratory (PNNL), and the Sellafield site to identify literature describing the retention and release of gases with non-Newtonian slurries. The study was undertaken with the knowledge that SRS wastes are unique which makes using non-SRS data challenging. The literature search focused on the following topics: Mixing or blend time in Newtonian and non-Newtonian fluids, Quiescent release of gas from an unagitated non-Newtonian fluid, Release of gas from an agitated non-Newtonian fluid, and Changes in fluid rheology as a function of settling time.

08 HYDROGEN↗