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DOE OSTI2018

Silver-iodine secondary waste stabilization: multi-scale evaluation

Iodine-129 is a key risk driver in most low-level waste cementitious waste repositories. The objectives of this study were to determine iodine speciation in cementitious materials with slag (Grout+slag) and without slag (Grout–slag) and its impact on iodine immobilization. Additional studies were conducted to determine if grout was compatibility as a waste form for the most common adsorbent used to remove aqueous and gaseous radioiodine, silver-impregnated granular activated carbon (Ag-GAC). Rankings of iodine species by their tendency to bind to grout were: iodide << organo-iodine ≤ iodate. Similarly, ranking of grout formulations by their tendency to immobilize iodine were: Grout +slag < Grout -slag . Organo-iodine comprised >40% of the leachate solution from grout samples initially hydrated (cured) with iodide. The origin of the organic ligand comprising the organo-iodine was organic carbon in the grout material (~1200 mg/kg). Iodine in the solid phase, as determined by K-edge X-ray Absorption Near-Edge Spectroscopy, and aqueous phases were not in equilibrium and essentially no iodine speciation transformations occurred within the grout after one month of curing, irrespective of which iodine species was initially added to the mix. For the first time, these studies demonstrate that multiple iodine species can co-exist simultaneously in grout porewater, the iodine species initially added to the grout can greatly affect immobilization, and that Ag-GAC can be safely disposed in grout formulation, but not in the presence of slag. These results help explain previous data and reduce uncertainty associated with the disposal of nuclear waste.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Decontamination of uranium contaminated metals - 15 years of experience - 15528

Uranium contaminated waste is somewhat of a special case among radioactive waste as the uranium, if enriched, also is a valuable asset. Incineration and pyrolysis of uranium contaminated dry active waste (DAW) was covered during WM'14. Uranium contaminated metals is however somewhat different when it comes treatment and recovery of uranium. Since the late 1990's the Metals Treatment and Recycling Facility in Studsvik Sweden has treated approximately 1500 tonnes of metals contaminated by uranium. Depending on the metal, melt-decontamination may or may not be a way of salvaging metals if the pre-treatment was not enough. The only metals that currently are subject to melt decontamination are iron based materials as well as lead. Other metals such as aluminium, brass and copper must all be cleaned prior to melting. Recovery of uranium from the secondary waste is most likely economically feasible only from the first step, the pre-melting decontamination, as the slag is just that, a slag, which is molten at a high temperature, and thereafter cooled under non-controlled conditions so uranium is trapped inside in an unspecified chemical form. This paper will describes experiences and lessons learned from 15 years of treatment, including melt-decontamination, of uranium contaminated metals. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Computational and Experimental Characterization of Intermediate Amorphous Phases in Geological Materials

In the subsurface, MgO engineered barriers are employed at the Waste Isolation Pilot Plant (WIPP), a transuranic waste repository near Carlsbad, NM. During service, the MgO will be exposed to high concentration brine environments and may form stable intermediate phases that can alter the barriers effectiveness. Here, MgO was aged in water and three different brine solutions. X-ray diffraction (XRD) and 1 H nuclear magnetic resonance (NMR) analysis were performed to identify the formation of secondary phases. After aging, ~4% of the MgO was hydrated and fine-grained powders resulted in greater loss of crystallinity than hard granular grains. 1 H magic angle spinning (MAS) NMR spectra resolved minor phases not visible in XRD, indicating that diverse 1 H environments are present along with Mg(OH) 2 . Density functional theory (DFT) simulations for several proposed Mg-O-H, Mg-CI-O-H, and Na-O-H containing phases were performed to index peaks in the experimental 1 H MAS NMR spectra. While proposed intermediate crystal structures exhibited overlapping 1 H NMR peaks, Mg-O-H intermediates were attributed to the growth of the 1.0-0.0ppm peak while the Mg-CI-O-H structures contributed to the 2.5- 5.0ppm peak in the chloride containing brines. Overall, NMR analysis of aged MgO indicates the formation of a range of possible intermediate structures that cannot be resolved with XRD analysis alone.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2011

Alteration of municipal solid waste incineration bottom ash focusing on the evolution of iron-rich constituents

Municipal solid waste incineration (MSWI) bottom ash contains a considerable amount of Fe-rich constituents. The behaviors of these constituents, such as dissolution and precipitation, are quite important as they regulate the distribution of a series of ions between the liquid (percolated fluid) and solid (ash deposit) phases. This paper studied both fresh and weathered MSWI bottom ash from the mineralogical and geochemical viewpoint by utilizing optical microscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and powder X-ray diffraction. The analysis results revealed that for the fresh bottom ash, iron preferentially existed in the chemical forms of spinel group (mainly Fe{sub 3}O{sub 4}, and a series of Al- or Ti- substituted varieties), metallic inclusions (including Fe-P, Fe-S, Fe-Cu-Pb), hematite (Fe{sub 2}O{sub 3}) and unburned iron pieces. In the 1-20 years weathered bottom ash collected from a landfill site, interconversions among these Fe-rich constituents were identified. Consequently, numerous secondary products were developed, including goethite ({alpha}-FeOOH), lepidocrocite ({gamma}-FeOOH), hematite, magnetite, wustite (FeO), Fe-Si-rich gel phase. Of all these transformation products, hydrous iron oxides were the most common secondary minerals. Quantitative chemical analysis of these secondary products by SEM/EDX disclosed a strong association between the newly formed hydrous iron oxides and heavy metals (e.g. Pb, Zn, Ni, and Cu). The results of this study suggest that the processes of natural weathering and secondary mineralization contribute to reduction of the potential risks of heavy metals to the surrounding environments.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2012

RADIOACTIVE DEMONSTRATIONS OF FLUIDIZED BED STEAM REFORMING WITH ACUTAL HANFORD LOW ACTIVITY WASTES VERIFYING FBSR AS A SUPPLEMENTARY TREATMENT

The U.S. Department of Energy's Office of River Protection is responsible for the retrieval, treatment, immobilization, and disposal of Hanford's tank waste. Currently there are approximately 56 million gallons of highly radioactive mixed wastes awaiting treatment. A key aspect of the River Protection Project cleanup mission is to construct and operate the Waste Treatment and Immobilization Plant (WTP). The WTP will separate the tank waste into high-level waste (HLW) and low-activity waste (LAW) fractions, both of which will subsequently be vitrified. The projected throughput capacity of the WTP LAW Vitrification Facility is insufficient to complete the cleanup mission in the time frame required by the Hanford Federal Facility Agreement and Consent Order, also known as the Tri-Party Agreement (TPA). Therefore, Supplemental Treatment is required both to meet the TPA treatment requirements as well as to more cost effectively complete the tank waste treatment mission. Fluidized Bed Steam Reforming (FBSR) is one of the supplementary treatments being considered. FBSR offers a moderate temperature (700-750 C) continuous method by which LAW and other secondary wastes can be processed irrespective of whether they contain organics, nitrates/nitrites, sulfates/sulfides, chlorides, fluorides, and/or radio-nuclides like I-129 and Tc-99. Radioactive testing of Savannah River LAW (Tank 50) shimmed to resemble Hanford LAW and actual Hanford LAW (SX-105 and AN-103) have produced a ceramic (mineral) waste form which is the same as the non-radioactive waste simulants tested at the engineering scale. The radioactive testing demonstrated that the FBSR process can retain the volatile radioactive components that cannot be contained at vitrification temperatures. The radioactive and nonradioactive mineral waste forms that were produced by co-processing waste with kaolin clay in an FBSR process are shown to be as durable as LAW glass.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2025

Dual-Bed Radioiodine Capture from Complex Gas Streams with Zeolites: Regeneration and Reuse of Primary Sorbent Beds for Sustainable Waste Management

Dual-sorbent systems are proposed for radioiodine management with a regenerated primary bed for multiple cycles of use in complex conditions and a secondary bed for disposal with higher waste loadings. Sorbent approaches for the effective capture of gaseous radioiodine (isotopes 129 I and 131 I) produced from a range of nuclear processes have been studied for over half a century. (1−5) Whether or not a sorbent (e.g., molecular sieve) is required to physically screen/trap or chemically bind a radionuclide of interest through chemisorption, the complexity of the gas stream has a large impact on the performance (e.g., loading capacity, selectivity) and active life of a sorbent bed. (3) Silver mordenite (AgZ), the U.S. Department of Energy baseline sorbent for radioiodine capture from nuclear processes, performs well within acidic conditions and at elevated temperatures (6) and can be consolidated into a chemically durable waste form for long-term disposal. (7,8) However, new sorbents are being sought because optimal capture performance of AgZ significantly decreases in dynamic oxidizing environments with competing species, and it is expensive and it contains Ag (a toxic metal). (9) Until a new sorbent is found to replace AgZ, the regeneration and reuse of AgZ is an attractive alternative to a single-use primary sorbent bed. In this regard, a primary sorbent could be designed for enhanced capture in complex gas streams and the ability to be regenerated for reuse. Here, a secondary sorbent could then be tailored for maximum iodine loading in the gas stream and chemical durability within a disposal facility.

chemisorption↗

DOE OSTI2015

Technetium incorporation in glass for the Hanford Tank Waste treatment and immobilization plant - 15066

A priority of the United States Department of Energy (U.S. DOE) is to dispose of nuclear wastes accumulated in 177 underground tanks at the Hanford Nuclear Reservation in eastern Washington State. These nuclear wastes date from the Manhattan Project of World War II and from plutonium production during the Cold War. The DOE plans to separate high-level radioactive wastes from low activity wastes and to treat each of the waste streams by vitrification (immobilization of the nuclides in glass) for disposal. The immobilized low-activity waste will be disposed of here at Hanford and the immobilized high-level waste at the national geologic repository. Included in the inventory of highly radioactive wastes is large volumes of {sup 99}Tc (∼9 x 10 E2 TBq or ∼2.5 x 10{sup 4} Ci or ∼1500 kg). A problem facing safe disposal of Tc-bearing wastes is the processing of waste feed into in a chemically durable waste form. Technetium incorporates poorly into silicate glass in traditional glass melting. It readily evaporates during melting of glass feeds and out of the molten glass, leading to a spectrum of high-to-low retention (ca. 20 to 80%) in the cooled glass product. DOE-ORP currently has a program at Pacific Northwest National Laboratory (PNNL), in the Department of Materials Science and Engineering at Rutgers University and in the School of Mechanical and Materials Engineering at Washington State University that seeks to understand aspects of Tc retention by means of studying Tc partitioning, molten salt formation, volatilization pathways, and cold cap chemistry. Another problem involves the stability of Tc in glass in both the national geologic repository and on-site disposal after it has been immobilized. The major environmental concern with {sup 99}Tc is its high mobility in addition to a long half-life (2.1 x 10{sup 5} yrs). The pertechnetate ion (TcO{sup 4-}) is highly soluble in water and does not adsorb well onto the surface of minerals and so migrates nearly at the same velocity as groundwater. Long-term corrosion of glass waste forms is an area of current interest to the DOE, but attention to the release of Tc from glass has been little explored. It is expected that the release of Tc from glass should be highly dependent on the local glass structure as well as the chemistry of the surrounding environment, including groundwater pH. Though the speciation of Tc in glass has been previously studied, and the Tc species present in waste glass have been previously reported, environmental Tc release mechanisms are poorly understood. The recent advances in Tc chemistry that have given rise to an understanding of incorporation in the glass giving rise to significantly higher single-pass retention during vitrification are presented. Additionally, possible changes to the baseline flowsheet that allow for relatively minor volumes of Tc reporting to secondary waste treatment will be discussed. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Alteration Behaviors of Granite Minerals Forming Calcium Silicate Hydrate under Ca-Rich Highly Alkaline Conditions - 16160

Cementitious materials used for geological disposal systems leach large amounts of alkaline ions (Ca{sup 2+}, Na{sup +}, K{sup +}) into groundwater, and alter the pH of groundwater by up to 13. The altered groundwater contacts the host rock and forms Calcium Silicate-Hydrate (CSH) through the interaction of Ca ions and the silicate species, which in turn clogs the flow paths of the host rock. This clogging effect in the flow paths is expected to retard the migration of radionuclides. A previous study reported the heterogeneous formation of CSH on the surface of granite under Carich and highly alkaline conditions. To clarify the formation process of CSH, this study examined the CSH formation with the dissolution of some minerals contained in the granite under Ca-rich and highly alkaline conditions. In the experiments, the granite block and the crushed minerals contained in the granite were immersed in a 6.4-8.5 mM Ca(OH){sub 2} solution adjusted pH to 12.5 by adding NaOH solution. As a result, biotite and anorthite supplied more Si to the formation of CSH than other minerals. Furthermore, most of the formed CSH precipitated on the solid surface although a little CSH remained in liquid phase as supernatant. These results suggest that under Ca-rich highly alkaline conditions the CSH formed as a secondary mineral will retard the migration of radionuclides released from the repository because of the clogging effect of the flow path. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

Experimental investigation of wood combustion in a fixed bed with hot air

Highlights: • Upward combustion is a new combustion concept with ignition by hot primary air. • Upward combustion has three stages: short drying, rapid devolatilization and char combustion. • Variation of fuel moisture and inert content have little influence on the combustion. • Experimental comparison between conventional and upward combustion is presented. - Abstract: Waste combustion on a grate with energy recovery is an important pillar of municipal solid waste (MSW) management in the Netherlands. In MSW incinerators fresh waste stacked on a grate enters the combustion chamber, heats up by radiation from the flame above the layer and ignition occurs. Typically, the reaction zone starts at the top of the waste layer and propagates downwards, producing heat for drying and devolatilization of the fresh waste below it until the ignition front reaches the grate. The control of this process is mainly based on empiricism. MSW is a highly inhomogeneous fuel with continuous fluctuating moisture content, heating value and chemical composition. The resulting process fluctuations may cause process control difficulties, fouling and corrosion issues, extra maintenance, and unplanned stops. In the new concept the fuel layer is ignited by means of preheated air (T > 220 °C) from below without any external ignition source. As a result a combustion front will be formed close to the grate and will propagate upwards. That is why this approach is denoted by upward combustion. Experimental research has been carried out in a batch reactor with height of 4.55 m, an inner diameter of 200 mm and a fuel layer height up to 1 m. Due to a high quality two-layer insulation adiabatic conditions can be assumed. The primary air can be preheated up to 350 °C, and the secondary air is distributed via nozzles above the waste layer. During the experiments, temperatures along the height of the reactor, gas composition and total weight decrease are continuously monitored. The influence of the primary air speed, fuel moisture and inert content on the combustion characteristics (ignition rate, combustion rate, ignition front speed and temperature of the reaction zone) is evaluated. The upward combustion concept decouples the drying, devolatilization and burnout phase. In this way the moisture and inert content of the waste have almost no influence on the combustion process. In this paper an experimental comparison between conventional and reversed combustion is presented.

09 BIOMASS FUELS↗

DOE OSTI2012

Sorption Behavior of Eu(III) into CSH Gel in Imitated Saline Groundwater - 12145

The sorption behavior of Eu(III) (europium (III)) into CSH (Calcium Silicate Hydrate) gel without dried processes was examined in imitated saline groundwater by using the spectro-fluorometer, Raman spectrophotometer and ICP-AES (Inductively Coupled Plasma- Atomic Emission Spectrometry). Ca/Si ratio was set to 0.4, 0.8, 1.2 and 1.6, and NaCl concentration was also set to 0.6, 0.06 and 0.006. The synthesis of each sample was conducted in a glove box saturated with nitrogen gas. The sealed sample tubes were gently shaken with 120 strokes/min. The time-period to contact Eu(III) with the CSH gel was set to 60 days. The fluorescence emission spectra suggested the incorporation of Eu{sup 3+} into CSH gel in the high Ca/Si ratio samples. On the other hand, from the decay behavior of fluorescence emission spectra, even in the low Ca/Si ratio samples, sorption behavior of Eu{sup 3+} into CSH gel was confirmed. Besides, the Raman spectra showed that the degree of polymerization of Si-O in CSH gel was raised with increasing Na ions concentration. These results suggest that the CSH gel, formed as secondary mineral, would retard the migration of radionuclides even in saline groundwater. Considering the inflow of saline groundwater into repository, this study examined the interaction between CSH gel (without dry processes) and Eu{sup 3+} by using the fluorescence emission spectra, the decay behavior of fluorescence and the Raman spectra. As a result, the fluorescence emission spectra of the sample of more than 0.8 Ca/Si ratio confirmed the intensity split into two peaks around 618 nm (5D0→7F2 transition). Furthermore, even in relatively low Ca/Si ratio samples, the fluorescence lifetimes both of the surface sorption sample and the co-precipitated samples exceeded that of the filtrate sample. These suggested that Eu{sup 3+} is not only hydrolyzed to form Eu(OH){sub 3} colloid, but is also stably incorporated into CSH gel (in Ca/Si ratio>1.2) or is forming complex on the surface of solid phase (in Ca/Si<0.8) in the co-presence of Na ions. On the other hand, the concentrations of Na, Ca and Si after 60 days in the solution filtrated through 0.2 μm membrane filter showed the ion exchange of Ca and Eu apparently in the samples of low Ca/Si ratio. Besides, in the samples with high Ca/Si ratio, Ca and Si concentrations in the solution were raised with increment of initial Na concentration. While Na ions may slightly increase the solubility of CSH gel, the CSH samples were stable, mostly maintaining the initial Ca/Si ratio synthesized. Moreover, the Raman spectra showed that the degree of polymerization of silicate chain in CSH samples increased with increasing Na concentration. Such an immobilized Na into the structure of CSH gel did not obstruct the incorporation of Eu{sup 3+} into CSH gel. The results mentioned above suggested that CSH gel (formed as a secondary mineral around the repository) also can retard the migration of radionuclides even if the repository and its surrounding are saturated by saline groundwater. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Mineral Dissolution upon Alkaline Treatment and Variable Redox Conditions

Over 200.000 kg of uranium released to vadose zone from historic leaks and improper disposal of wastes from plutonium production. U highly mobile due to presence of carbonates and oxidizing conditions with partition coefficients k{sub d} of 0.11-8 mL/g at pH 8. Ammonia (NH{sub 3}) gas injection investigated as an in situ remediation technique that will not introduce additional liquid to the subsurface. Objectives: Understand the impact of remediation with base injection on geochemical process in Hanford site vadose zone. Understand effects of different base treatments on mineral dissolution. Results: - incongruent dissolution based on mineral stoichiometry: if ratio = 1 congruent dissolution occurs, if ratio <1.0 greater leaching of Si and Al and incongruent dissolution occurs. Conclusions: incongruent dissolution occurred for both alkaline treatments and redox conditions across all minerals. By 1440 hr. all normalised Al:Si ratios were <1 representing less [Al]{sub aq} and suggesting formation of secondary Al precipitates as a function of time. [Si]{sub aq} increased and [Al]{sub aq} decreased with increasing contact time with both alkaline treatments. NaOH dissolved slightly more than NH{sub 4}OH especially for [Al]{sub aq} in all investigated minerals. No clear trend for muscovite and montmorillonite for redox conditions but slightly greater Si dissolved under anaerobic conditions for illite. Ammonia gas injection increases the pH and dissolves aluminosilicate minerals in the vadose zone. U is likely to coprecipitate with secondary minerals forming at elevated pH and as the system reequilibrates at natural neutral pH. Further, U solids may be coated with low solubility, secondary precipitates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

San Francisco Biofuel Program: Brown Grease to Biodiesel Demonstration (Project Report)

Municipal wastewater treatment facilities have typically been limited to the role of accepting wastewater, treating it to required levels, and disposing of its treatment residuals. However, a new view is emerging which includes wastewater treatment facilities as regional resource recovery centers. This view is a direct result of increasingly stringent regulations, concerns over energy use, carbon footprint, and worldwide depletion of fossil fuel resources. Resources in wastewater include chemical and thermal energy, as well as nutrients, and water. A waste stream such as residual grease, which concentrates in the drainage from restaurants (referred to as Trap Waste), is a good example of a resource with an energy content that can be recovered for beneficial reuse. If left in wastewater, grease accumulates inside of the wastewater collection system and can lead to increased corrosion and pipe blockages that can cause wastewater overflows. Also, grease in wastewater that arrives at the treatment facility can impair the operation of preliminary treatment equipment and is only partly removed in the primary treatment process. In addition, residual grease increases the demand in treatment materials such as oxygen in the secondary treatment process. When disposed of in landfills, grease is likely to undergo anaerobic decay prior to landfill capping, resulting in the atmospheric release of methane, a greenhouse gas (GHG). This research project was therefore conceptualized and implemented by the San Francisco Public Utilities Commission (SFPUC) to test the feasibility of energy recovery from Trap Waste in the form of Biodiesel or Methane gas. The research goals are given below: To validate technology performance; To determine the costs and benefits [including economic, socioeconomic, and GHG emissions reduction] associated with co-locating this type of operation at a municipal wastewater treatment plant (WWTP); To develop a business case or model for replication of the program by other municipal agencies (as applicable). In order to accomplish the goals of the project, the following steps were performed: 1. Operation of a demonstration facility designed to receive 10,000 to 12,000 gallons of raw Trap Waste each day from private Trap Waste hauling companies. The demonstration facility was designed and built by Pacific Biodiesel Technologies (PBTech). The demonstration facility would also recover 300 gallons of Brown Grease per day from the raw Trap Waste. The recovered Brown Grease was expected to contain no more than 2% Moisture, Insolubles, and Unsaponifiables (MIU) combined. 2. Co-digestion of the side streams (generated during the recovery of 300 gallons of Brown Grease from the raw Trap Waste) with wastewater sludge in the WWTP's anaerobic digesters. The effects of the side streams on anaerobic digestion were quantified by comparison with baseline data. 3. Production of 240 gallons per day of ASTM D6751-S15 grade Biodiesel fuel via a Biodiesel conversion demonstration facility, with the use of recovered Brown Grease as a feedstock. The demonstration facility was designed and built by Blackgold Biofuels (BGB). Side streams from this process were also co-digested with wastewater sludge. Bench-scale anaerobic digestion testing was conducted on side streams from both demonstration facilities to determine potential toxicity and/or changes in biogas production in the WWTP anaerobic digester. While there is a lot of theoretical data available on the lab-scale production of Biodiesel from grease Trap Waste, this full-scale demonstration project was one of the first of its kind in the United States. The project's environmental impacts were expected to include: Reduction of greenhouse gas emissions by prevention of the release of methane at landfills. Although the combustion product of Biodiesel and Methane gas produced in the Anaerobic digester, Carbon Dioxide, is also a greenhouse gas; it is 20 times weaker for the same amount (per mole) released, making its discharge preferable to that of Methane. The use of Biodiesel in place of fossil-fuel derived Diesel was expected to reduce net Carbon Dioxide, Ash Particulate, Sulfate, Silicate, and Soot emissions, thereby improving air quality.

09 BIOMASS FUELS↗

DOE OSTI2013

San Francisco Biofuel Program: Brown Grease to Biodiesel Demonstration

09 BIOMASS FUELS↗

DOE OSTI2013

Wastes associated with recycling spent MOX fuel into fast reactor oxide fuel

A study sponsored by the DOE has been performed by AREVA to estimate the process and secondary wastes produced from an 800 MTIHM/yr (initial metric tons heavy metal a year) recycling plant proposed to be built in the U.S. utilizing the COEX process and utilized some DOE defined assumptions and constraints. In this paper, this plant has been analyzed for a recycling campaign that included 89% UO{sub x} and 11% MOX UNF to estimate process and secondary waste quantities produced while manufacturing 28 MTIHM/yr of SFR fuel. AREVA utilized operational data from its backend facilities in France (La Hague and MELOX), and from recent advances in waste treatment technology to estimate the waste quantities. A table lists the volumes and types of the different final wastes for a recycling plant. For instance concerning general fission products the form of the final wastes is vitrified glass and its volume generation rate is 135 l/MTHM, concerning Iodine 129 waste its final form is synthetic rock and its volume generation rate is 0.625 l/MTIHM.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

Hanford Double Shell Waste Tank Corrosion Studies (Final Report)

For fiscal year (FY) 2022, the Savannah River National Laboratory (SRNL) focused on two experimental tasks related to Hanford Double Shell Tank (DST) chemistry and integrity. The first task focused on understanding risk of corrosion due to formation of either continuous layers or discrete patches of solids on the tanks' inner sidewalls and bottoms. The tank bottom solids contact corrosion testing focused on studying the effects of forming a dry adherent solids layer on a carbon steel substrate. Long-term exposure tests and electrochemical tests were performed to investigate the effect of drying (i.e., removing water) from the solids phase. The second task focused on corrosion of the exterior of the secondary liner. In previous years, vapor corrosion inhibitors (VCIs) were investigated as a means of mitigating corrosion of the exterior of the secondary liner. During FY22 the utilization of nitrogen was explored as a means of corrosion mitigation. The corrosion test results with nitrogen were compared with the corrosion mitigation performance of the VCIs.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2012

Sulfur Hexafluoride Treatment of Used Nuclear Fuel to Enhance Separations

Reactive Gas Recycling (RGR) technology development has been initiated at Savannah River National Laboratory (SRNL), with a stretch-goal to develop a fully dry recycling technology for Used Nuclear Fuel (UNF). This approach is attractive due to the potential of targeted gas-phase treatment steps to reduce footprint and secondary waste volumes associated with separations relying primarily on traditional technologies, so long as the fluorinators employed in the reaction are recycled for use in the reactors or are optimized for conversion of fluorinator reactant. The developed fluorination via SF 6 , similar to the case for other fluorinators such as NF 3 , can be used to address multiple fuel forms and downstream cycles including continued processing for LWR via fluorination or incorporation into a aqueous process (e.g. modified FLUOREX) or for subsequent pyro treatment to be used in advanced gas reactor designs such metal- or gas-cooled reactors. This report details the most recent experimental results on the reaction of SF 6 with various fission product surrogate materials in the form of oxides and metals, including uranium oxides using a high-temperature DTA apparatus capable of temperatures in excess of 1000°C. The experimental results indicate that the majority of the fission products form stable solid fluorides and sulfides, while a subset of the fission products form volatile fluorides such as molybdenum fluoride and niobium fluoride, as predicted thermodynamically. Additional kinetic analysis has been performed on additional fission products. A key result is the verification that SF 6 requires high temperatures for direct fluorination and subsequent volatilization of uranium oxides to UF 6 , and thus is well positioned as a head-end treatment for other separations technologies, such as the volatilization of uranium oxide by NF 3 as reported by colleagues at PNNL, advanced pyrochemical separations or traditional full recycle approaches. Based on current results of the research at SRNL on SF 6 fluoride volatility for UNF separations, SF 6 treatment renders all anticipated volatile fluorides studied to be volatile, and all non-volatile fluorides studied to be non-volatile, with the notable exception of uranium oxides. This offers an excellent opportunity to use this as a head-end separations treatment process because: 1. SF 6 can be used to remove volatile fluorides from a UNF matrix while leaving behind uranium oxides. Therefore an agent such as NF 3 should be able to very cleanly separate a pure UF 6 stream, leaving compounds in the bottoms such as PuF 4 , SrF 2 and CsF after the UNF matrix has been pre-treated with SF 6 . 2. Due to the fact that the uranium oxide is not separated in the volatilization step upon direct contact with SF 6 at moderately high temperatures (≤ 1000°C), this fluoride approach may be well-suited for head-end processing for Gen IV reactor designs where the LWR is treated as a fuel stock, and it is not desired to separate the uranium from plutonium, but it is desired to separate many of the volatile fission products. 3. It is likely that removal of the volatile fission products from the uranium oxide should simplify both traditional and next generation pyroprocessing techniques. 4. SF 6 treatment to remove volatile fission products, with or without treatment with additional fluorinators, could be used to simplify the separations of traditional aqueous processes in similar fashion to the FLUOREX process. Further research should be conducted to determine the separations efficiency of a combined SF 6 /NF 3 separations approach which could be used as a stand-alone separations technology or a head-end process.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2013

Distribution of copper, silver and gold during thermal treatment with brominated flame retardants

Highlights: • Copper, silver and gold during thermal treatment with brominated flame retardants. • Distribution of copper, silver and gold during thermal processing. • Thermodynamic considerations of the bromination reactions. - Abstract: The growing consumption of electric and electronic equipment results in creating an increasing amount of electronic waste. The most economically and environmentally advantageous methods for the treatment and recycling of waste electric and electronic equipment (WEEE) are the thermal techniques such as direct combustion, co-combustion with plastic wastes, pyrolysis and gasification. Nowadays, this kind of waste is mainly thermally treated in incinerators (e.g. rotary kilns) to decompose the plastics present, and to concentrate metals in bottom ash. The concentrated metals (e.g. copper, precious metals) can be supplied as a secondary raw material to metal smelters, while the pyrolysis of plastics allows the recovery of fuel gases, volatilising agents and, eventually, energy. Indeed, WEEE, such as a printed circuit boards (PCBs) usually contains brominated flame retardants (BFRs). From these materials, hydrobromic acid (HBr) is formed as a product of their thermal decomposition. In the present work, the bromination was studied of copper, silver and gold by HBr, originating from BFRs, such as Tetrabromobisphenol A (TBBPA) and Tetrabromobisphenol A-Tetrabromobisophenol A diglycidyl ether (TTDE) polymer; possible volatilization of the bromides formed was monitored using a thermo-gravimetric analyzer (TGA) and a laboratory-scale furnace for treating samples of metals and BFRs under an inert atmosphere and at a wide range of temperatures. The results obtained indicate that up to about 50% of copper and silver can evolve from sample residues in the form of volatile CuBr and AgBr above 600 and 1000 °C, respectively. The reactions occur in the molten resin phase simultaneously with the decomposition of the brominated resin. Gold is resistant to HBr and remains unchanged in the residue.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

Melter Tests to Define LAW Halide, Chromium and Phosphate Concentrations, VSL-14R3070-1 (February 2014)

The Office of River Protection is examining options to optimize the Low Activity Waste (LAW) Facility and LAW glass waste form. One option under evaluation is to enhance the waste processing rate of the vitrification plant currently under construction. It is likely that the capacity of the LAW vitrification plant can be increased incrementally by implementation of a variety of low-risk, high-probability changes, either separately or in combination. The present work addressed the potential formation of secondary sulfate phases while processing high waste loading LAW formulations with elevated halide, chromium, and phosphate feed concentrations over a wide range of LAW waste types, including those with high potassium concentrations. The present work will be followed by a second phase of testing, described in a separate Test Plan, the results of which will be reported elsewhere. The combined results from these tests will be used as inputs to develop concentration limits for these components in the LAW glass property-composition models and to support the modification and updating of the current WTP LAW glass formulation algorithm.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗