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At least 469 records · Page 26

Literature Review on the Impact of Thermolytic Hydrogen Generation Rate from the Next Generation Solvent

A literature review was undertaken to assess the thermolytic hydrogen generation potential of the Next Generation Solvent (NGS) system, which is planned to replace the Original Caustic-Side Solvent Extraction (CSSX) Solvent at the Salt Waste Processing Facility. NGS uses a new extractant and suppressor and the same modifier and organic carrier solvent as the Original CSSX Solvent at different concentrations.

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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↗

Effect of 60 Co Irradiation on Boehmite Dissolution in Caustic Solutions

Here, in this work, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to 60 Co γ radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3 M NaOH solutions were several times lower (e.g., rate constant of 0.026 vs 0.075 h –1 at 60 °C), with an apparent activation energy 40 kJ mol –1 higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, after irradiation significant binding energy shifts were detected in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change in their relative intensities indicated a lower O/Al ratio. This suggests that γ-irradiation may stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. This finding may help explain slower dissolution rates of boehmite in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste processing.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

Technical Evaluation of Accelerated Basin De-Inventory Material Addition to Sludge Batch 11 (Rev. 1)

The Accelerated Basin De-inventory (ABD) program involves discarding spent nuclear fuel that is currently stored in L-Basin to the Defense Waste Processing Facility (DWPF) for vitrification. The first ABD discards will occur during the preparation of Sludge Batch (SB) 11. Savannah River Mission Completion has requested that the Savannah River National Laboratory assess the technical gaps related to the increased gadolinium poisoning requirement and the impacts of performing the Low Temperature Aluminum Dissolution (LTAD) process in Tank 51 with H-Canyon discards present. The following summarizes the evaluation of the impacts of increasing the quantity of gadolinium (and related topics) from what was previously evaluated in the SRNL studies of gadolinium-poisoned ABD material solubility, the overall ABD flowsheet review, and increasing the fissile mass loading in glass: 1) Based on literature surveys, there is no indication that organic interactions with gadolinium will be significant at the high pH (typically >13) conditions of the Concentration, Storage, and Transfer Facilities. Any interactions of gadolinium with organics in DWPF are not expected to adversely impact DWPF or downstream facilities. Thus, there is little-to-no residual risk from organic interactions with gadolinium [Gap closed]; 2) Adding depleted uranium to ABD material, targeting 235 U enrichment of 4.90% within each transfer window, will mitigate potential impacts from an increase in soluble 235 U enrichment during sludge washing and LTAD. The plan to take advantage of previous transfers and allow 235 U enrichment of >5% during the final transfer window carries a risk that Tank 51 supernate will have a 235 U enrichment of >5%, which should be evaluated for acceptance; 3) Increasing the gadolinium mass ratio to 3.0:1 Gd: 235 U(eq SLU ) should lead to the same or higher partitioning of gadolinium into the solid phase within the DWPF Chemical Process Cell, resulting in both liquid and solid phases with expected partitioning of Gd consistent with the prior solubility study [Gap closed for SB11]; 4) There are no expected impacts on DWPF melt temperature and melter operations due to the minimal ~0.2 weight percent (wt%) increase in Gd concentration relative to previous sludge batches [Gap closed for SB11]; 5) As observed previously, Gd is expected to enter the off-gas system via physical entrainment, but at a slightly higher concentration than what was observed for SB9 melter off-gas pluggage deposits (0.07 wt%) [Gap closed for SB11] ; 6) There are no expected impacts on DWPF recycle or the Recycle Collection Tank glycolate destruction process. [Gap closed for SB11]; 7) Gd is projected to be a trace component in the SB11 glass (<0.5 wt%) and can be ignored for process control. Trace components do not significantly impact glass durability, thus the conclusions of the previous Product Consistency Test evaluation at a fissile mass loading of 2,500 g fissile/m3 glass still applies to SB11. The ~0.1 wt% increase in Gd2O3 concentration relative to the previous study will not impact the predictability of SB11 glass with the DWPF Product Composition Control System (PCCS) models for durability or the acceptability of glass according to the Waste Acceptance Product Specifications (WAPS) criterion for product consistency [Gap closed for SB11]; 8) No additional Toxicity Characteristic Leaching Procedure testing is necessary for SB11 and the hazardous waste specification of the SB11 DWPF waste form is unchanged after the addition of the ABD stream [Gap closed for SB11]. The following summarizes the evaluation of the impacts of adding two-thirds of the ABD material to Tank 51 prior to LTAD: 1) The addition of two-thirds of the ABD increases overall aluminum mass from 1.39×10 4 kg to 1.64×10 4 kg (15.5% ABD Al). The form of the insoluble portion of the Al resulting from ABD addition should be the more readily dissolved Al(OH) 3 and amorphous forms. The portion of the ABD aluminum that is processed by LTAD is expected to be completely soluble, thus requiring that less of the boehmite in the sludge be dissolved to reach the same Al target in the SB. [Gap closed for SB11]; The expected LTAD impact on other components, as related primarily to the components in ABD, are discussed. Gd is expected to remain insoluble during LTAD and not impact the solubility of other components. [Gap closed for SB11]; The addition of two-thirds of the ABD increases overall projected SB11 uranium mass from 4,740 kg to 13,100 kg (63% ABD U) and the projected plutonium mass from 86.0 kg to 89.5 kg (3.9% ABD Pu). The addition of all of the ABD increases overall projected SB11 uranium mass from 4,740 kg to 16,100 kg (70% ABD U) and the projected plutonium mass from 86.0 kg to 90.4 kg (5.3% ABD Pu). The 235 U enrichment will be ≤5%. The fissile uranium will be adequately poisoned by Gd and the fissile Pu will be adequately poisoned by Fe from the sludge. [Gap closed for SB11]; There is a low risk that ABD addition will impact the rheology or pumpability of the slurry. There is a low but higher risk of ABD addition prior to LTAD impacting the settling rate; Based on the evaluation of adding two-thirds of the ABD material and all of the ABD material prior to the LTAD process, there is no volume or mass limit that would need to be imposed on ABD additions prior to LTAD. [Gap closed for SB11]. Revision 1 of this report addresses a variation on the ABD additions and LTAD strategy where sodium hydroxide additions for LTAD may be performed intermittently or concurrently with an ABD addition window. The proposed change does not alter the conclusions of this evaluation.

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Nitric-glycolic flowsheet testing for maximum hydrogen generation rate

The Defense Waste Processing Facility (DWPF) at the Savannah River Site is developing for implementation a flowsheet with a new reductant to replace formic acid. Glycolic acid has been tested over the past several years and found to effectively replace the function of formic acid in the DWPF chemical process. The nitric-glycolic flowsheet reduces mercury, significantly lowers the chemical generation of hydrogen and ammonia, allows purge reduction in the Sludge Receipt and Adjustment Tank (SRAT), stabilizes the pH and chemistry in the SRAT and the Slurry Mix Evaporator (SME), allows for effective adjustment of the SRAT/SME rheology, and is favorable with respect to melter flammability. The objective of this work was to perform DWPF Chemical Process Cell (CPC) testing at conditions that would bound the catalytic hydrogen production for the nitric-glycolic flowsheet.

08 HYDROGEN↗

Environmental Program

NASA's White Sands Test Facility has six core environmental compliance capabilities: remote hazardous testing of reactive, explosive and toxic materials and fluids; hypergolic fluids materials and systems testing; oxygen materials and system testing; hypervelocity impact testing; flight hardware processing; and, propulsion testing. The facility's permit status and challenges are reviewed. Historic operations and practices dating from the 1960s through the early 1980s resulted in contamination of the facility's groundwater. An environmental restoration effort has been employed to protect public health and the health of the workforce. The restoration seeks to properly handle hazardous materials and waste processes; determine the nature and extent of the contamination; stop the migration of contaminated groundwater; stabilize the plume front which has been assessed as the greatest risk to public health; and, clean-up the environment to restore it to preexisting conditions. The Plume Front Treatment System is operational and seeks to stop the westward movement of the plume to protect drinking water and irrigation well. Specifically, the treatment system will extract contaminated water from the aquifer, remove chemical using the best available technology, and return (inject) the treated water back to the aquifer. The Mid-Plume Interception Treatment System also seeks to stop the migration of containment, as well as to evaluate new technologies to accelerate cleanup, such as bioremediation.

Fischer, Holger↗

Effect of Cr(III) Adsorption on the Dissolution of Boehmite Nanoparticles in Caustic Solution

Incorporation of relatively minor impurity metals onto metal (oxy)hydroxides can strongly impact solubility. In complex highly alkaline multicomponent tank waste such as that at the Hanford Nuclear Reservation, tests indicate that the surface area-normalized dissolution rate of boehmite ($γ$-AlOOH) nanomaterials is at least an order of magnitude lower than that predicted for the pure phase. In this work we examine the dissolution kinetics of boehmite coated by adsorbed Cr(III), which adheres at saturation coverages as sparse chemisorbed monolayer clusters. Using 40 nm boehmite nanoplates as a model system, temperature-dependent dissolution rates of pure versus Cr(III)-adsorbed boehmite showed that the initial rate for the latter is consistently several times lower, with an apparent activation energy 16 kJ·mol -1 higher. Although the surface coverage is only around 50%, solution analytics coupled to multimethod solids characterization reveals a phyicochemical armoring effect by adsorbed Cr(III) that substantially reduces the number of dissolution-active sites on particle surfaces. Such findings could help improve kinetics models of boehmite and/or metal ion adsorbed boehmite nanomaterials, ultimately providing a stronger foundation for the development of more robust complex radioactive liquid waste processing strategies.

54 ENVIRONMENTAL SCIENCES↗

The Space Exploration Initiative: a challenge to advanced life support technologies: keynote presentation

President Bush has enunciated an unparalleled, open-ended commitment to human exploration of space called the Space Exploration Initiative (SEI). At the heart of the SEI is permanent human presence beyond Earth orbit, which implies a new emphasis on life science research and life support system technology. Proposed bioregenerative systems for planetary surface bases will require carefully designed waste processing elements whose development will lead to streamlined and efficient and efficient systems for applications on Earth.

Ecological Systems, Closed↗

Product Consistency Testing of Hot Isostatically Pressed Iodine-containing Waste Forms

Silver-exchanged mordenite (AgZ) is currently under evaluation for the capture of iodine from the off-gas streams that are expected to arise during the reprocessing of used nuclear fuel. A final waste form for AgZ loaded with radioactive iodine has not yet been identified. The applicability of hot isostatic pressing (HIPing) to convert iodine-loaded, reduced silver-exchanged mordenite (I-Ag{sup 0}Z) into a suitable waste form is currently being evaluated at Oak Ridge National Laboratory (ORNL). Because production of such a waste form requires little preprocessing of the I-Ag{sup 0}Z, HIPing could prove very attractive from both safety and economic perspectives. It is desirable to produce a waste form with a distinct iodine-containing mineral phase as the major constituent. Such a mineral phase is thought to increase long-term iodine retention and overall stability. Furthermore, the transformation of the material into a known iodine-containing mineral phase would limit the additional experimental testing and modeling required to determine the long-term stability of the pressed pellet, as much of that information has already been learned for several common iodine-containing minerals. For these reasons, the current work has investigated the possibility of converting I-Ag{sup 0}Z into an iodine-containing sodalite, similar to the efforts documented by Sheppard et al. in which they transformed other silver zeolite structures into sodalite through HIPing. Building on our initial work we are now producing hot isostatically pressed waste forms using mixtures of pure sodium mordenite, AgZ, and silver iodide. The composition of these samples is well known, in contrast with the previously used commercially available, binder-containing AgZ, which has a composition that is proprietary and uncharacterized. It is expected that by controlling the initial sample composition, we might be able to control the mineral phases present in the processed waste form. Transformation of the component material into a well-characterized iodine-containing mineral phase would be desirable; however, this is not an absolute requirement for success. (authors)

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NASA's Advanced Life Support Systems Human-Rated Test Facility

Future NASA missions to explore the solar system will be long-duration missions, requiring human life support systems which must operate with very high reliability over long periods of time. Such systems must be highly regenerative, requiring minimum resupply, to enable the crews to be largely self-sufficient. These regenerative life support systems will use a combination of higher plants, microorganisms, and physicochemical processes to recycle air and water, produce food, and process wastes. A key step in the development of these systems is establishment of a human-rated test facility specifically tailored to evaluation of closed, regenerative life supports systems--one in which long-duration, large-scale testing involving human test crews can be performed. Construction of such a facility, the Advanced Life Support Program's (ALS) Human-Rated Test Facility (HRTF), has begun at NASA's Johnson Space Center, and definition of systems and development of initial outfitting concepts for the facility are underway. This paper will provide an overview of the HRTF project plan, an explanation of baseline configurations, and descriptive illustrations of facility outfitting concepts.

NASA Discipline Number 61-10↗

Results of the Analyses of the SRNL Solvent Components

At the request of the Savannah River Mission Completion (SRMC), personnel at Savannah River Site (SRS) performed analyses on the remaining solvent components that are being stored at the Savannah River National Laboratory (SRNL). This was done to determine if the remaining stock of materials were still suitable for use for the Salt Waste processing Facility (SWPF). Two drums of Modifier, two drums BOBCalix, four drums of MAXCalix, and four jars of TiDG*HCl were analyzed. All were found to be of acceptable purity for use.

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Modeling Efforts to Gain Insight into Historical Leak Events from the Single-Shell Tank A-105 in the Hanford 241-A Tank Farm - 20113

The 241-A Tank Farm is a single-shell tank (SST) farm constructed to store process waste from Hanford nuclear operations. Millions of gallons of nuclear waste were stored in the 241-A Tank Farm SSTs and some of the SSTs leaked in the past. In addition, spills and pipeline leaks during transfers and storage and intentional discharges to cribs and trenches resulted in releasing waste to the ground. Tank liner leaks are referred to as 'leaks' and all other discharges to the soil are referred to as 'releases.' Liquid waste that could be removed by pumping has been removed from all of the SSTs to reduce the potential for future leaks. The most significant historical leak event in 241-A Tank Farm occurred in 1965 when tank A-105 experienced a pressurized steam event. This event resulted in damage to the inner steel liner flooring of A-105, which was separated from the sidewalls over part of its circumference and buckled up to 2.5 m, vertically. During this event up to 7,570 L of contaminated liquid may have leaked to the adjacent soil. This leak occurred under extreme temperature and pressure conditions. Modeling efforts to better understand the nature and extent of historical leaks from subsurface SSTs that were used to store highly radioactive, self-boiling liquid wastes at 241-A Tank Farm have recently been undertaken. These efforts have compiled the available historical information to support a preliminary non-isothermal, multiphase flow and chemical transport modeling effort to re-create the conditions under which the leaks occurred and to formulate a conceptual model as to the extent and distribution of leaked radioactive contaminants in the adjacent soil material. The focus of this work was on developing an understanding of the key features, processes and bounding conditions related to tank A-105 leak events that occurred in the 1960's. The activities include estimation of leak composition, non-isothermal multiphase flow and transport modeling, and geochemical modeling. The STOMP{sup C} Water-Air-Energy modeling code was utilized to implement the three-dimensional representation of the subsurface tank and the surrounding flow field. Once constructed, the model was used to evaluate the conceptual understanding of leaks originating from different parts of the tank under the elevated temperature boundary conditions that were imposed by surrounding tanks at the time of the historical leaks. The chemical evolution of the liquid waste was also evaluated as it leaked from the tank under transient pressure and temperature gradients. The results of the preliminary evaluation suggested the presence of a heat-pipe effect beneath tank A-105 in which water vapor at an elevated temperature is driven away from the base of the tank to a position where water vapor cools, condenses and is then drawn back toward the tank by the strong capillary attraction of the dry soil. A non-sorbing contaminant (Tc-99) was introduced into this flow field to better understand the potential distribution patterns of leaked contaminants that may have occurred during the historical leak events. (authors)

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Designing for human presence in space: An introduction to environmental control and life support systems

Human exploration and utilization of space requires habitats to provide appropriate conditions for working and living. These conditions are provided by environmental control and life support systems (ECLSS) that ensure appropriate atmosphere composition, pressure, and temperature; manage and distribute water, process waste matter, provide fire detection and suppression; and other functions as necessary. The functions that are performed by ECLSS are described and basic information necessary to design an ECLSS is provided. Technical and programmatic aspects of designing and developing ECLSS for space habitats are described including descriptions of technologies, analysis methods, test requirements, program organization, documentation requirements, and the requirements imposed by medical, mission, safety, and system needs. The design and development process is described from initial trade studies through system-level analyses to support operation. ECLSS needs for future space habitats are also described. Extensive listings of references and related works provide sources for more detailed information on each aspect of ECLSS design and development.

Wieland, Paul↗

Safety aspects of nuclear waste disposal in space

Safety issues involved in the disposal of nuclear wastes in space as a complement to mined geologic repositories are examined as part of an assessment of the feasibility of nuclear waste disposal in space. General safety guidelines for space disposal developed in the areas of radiation exposure and shielding, containment, accident environments, criticality, post-accident recovery, monitoring systems and isolation are presented for a nuclear waste disposal in space mission employing conventional space technology such as the Space Shuttle. The current reference concept under consideration by NASA and DOE is then examined in detail, with attention given to the waste source and mix, the waste form, waste processing and payload fabrication, shipping casks and ground transport vehicles, launch site operations and facilities, Shuttle-derived launch vehicle, orbit transfer vehicle, orbital operations and space destination, and the system safety aspects of the concept are discussed for each component. It is pointed out that future work remains in the development of an improved basis for the safety guidelines and the determination of the possible benefits and costs of the space disposal option for nuclear wastes.

Rice, E. E.↗

Lab Scale Mercury Dissolution Testing

Researchers at the Savannah River National Laboratory were requested by Savannah River Mission Completion to perform laboratory testing and modeling designed to understand why the Defense Waste Processing Facility (DWPF) is not collecting elemental mercury (Hg 0 ) despite long boiling times designed to recover Hg 0 . In response to a Technical Task Request, a Task Technical and Quality Assurance Plan was written and approved to authorize this work.

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Peroxide-treated metal-organic framework templated adsorbents for remediation of high level nuclear waste

Remediation of legacy nuclear waste is one of the greatest challenges faced by the US Department of Energy, with projected cleanup efforts requiring over five decades and hundreds of billions of dollars. New materials are necessary to accelerate waste processing, achieving time and financial savings. Herein we report a peroxide treatment to a Ti metal-organic framework (MOF) and related MOF-templated adsorbents. Furthermore, the resulting materials displayed exceptional affinity for Am(III), achieving distribution coefficients in excess of 10 5 mL/g, and out-performing state-of-the-art benchmarks monosodium titanate (MST) and peroxo-treated modified MST (mMST) for removal of 85 Sr(II) and 239, 240 Pu(IV) from legacy nuclear waste simulant.

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Assessing the costs of municipal solid waste treatment technologies in developing Asian countries

Highlights: • Municipal waste treatment costs are assessed for the first time in developing Asia. • A database with primary and secondary data from existing plants was prepared. • Capital and operational expenditures patterns were analyzed and discussed. • Incineration identified by large margin as the costliest approach for treating waste. • Context specific circumstances are key to explain deviations from the norm. - Abstract: The management of municipal solid waste (MSW) is one of the main costs incurred by local authorities in developing countries. According to some estimates, these costs can account for up to 50% of city government budgets. It is therefore of importance that policymakers, urban planners and practitioners have an adequate understanding of what these costs consist of, from collection to final waste disposal. This article focuses on a specific stage of the MSW value chain, the treatment of waste, and it aims to identify cost patterns associated with the implementation and operation of waste treatment approaches in developing Asian countries. An analysis of the capital (CAPEX) and operational expenditures (OPEX) of a number of facilities located in countries of the region was conducted based on a database gathering nearly 100 projects and which served as basis for assessing four technology categories: composting, anaerobic digestion (AD), thermal treatment, and the production of refuse-derived fuel (RDF). Among these, it was found that the least costly to invest, as a function of the capacity to process waste, are composting facilities, with an average CAPEX per ton of 21,493 USD{sub 2015}/ton. Conversely, at the upper end featured incineration plants, with an average CAPEX of 81,880 USD{sub 2015}/ton, with this treatment approach ranking by and large as the most capital intensive of the four categories assessed. OPEX figures of the plants, normalized and analyzed in the form of OPEX/ton, were also found to be higher for incineration than for biological treatment methods, although on this component differences amongst the technology groups were less pronounced than those observed for CAPEX. While the results indicated the existence of distinct cost implications for available treatment approaches in the developing Asian context, the analysis also underscored the importance of understanding the local context as a means to properly identify the cost structure of each specific plant. Moreover, even though CAPEX and OPEX figures are important elements to assess the costs of a waste treatment system, these should not be considered on a standalone basis for decision making purposes. In complement to this internal cost dimension, the broader impacts – to the economy, society and the environment – resulting from the adoption of a certain treatment approach should be properly understood and, ideally, measured and expressed in monetary terms.

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Technetium recovery from high alkaline solution

Disclosed are methods for recovering technetium from a highly alkaline solution. The highly alkaline solution can be a liquid waste solution from a nuclear waste processing system. Methods can include combining the solution with a reductant capable of reducing technetium at the high pH of the solution and adding to or forming in the solution an adsorbent capable of adsorbing the precipitated technetium at the high pH of the solution.

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