Nitrite (NO2-) is a prevalent nitrogen oxyanion in environmental and industrial processes, but its behavior in solution, including ion pair formation, is complex. This solution phase complexity impacts industries such as nuclear waste treatment, where NO2- significantly affects the solubility of other constituents present in sodium hydroxide (NaOH)-rich nuclear waste. This work provides molecular scale information into sodium nitrite (NaNO2) and NaOH ion-pairing processes to provide a physical basis for later development of thermodynamic models. Solubility isotherms of NaNO2 in aqueous mixtures with NaOH and total alkalinity were also measured. Spectroscopic characterization of these solutions utilized high-field nuclear magnetic resonance spectroscopy (NMR) and Raman spectroscopy, with additional solution structure detailed by X-ray total scattering pairwise distribution function analysis (X-ray PDF). Despite the NO2- deformation Raman band's insensitivity to added NaOH in saturated NaNO2 solutions, 23Na and 15N NMR studies indicated the Na+ and NO2- chemical environments change likely due to ion pairing. The ion pairing correlates with a decrease in diffusion coefficient of solution species as measured by pulsed field gradient 23Na and 1H NMR. Two-dimensional correlation analyses of the 2800-4000 cm-1 Raman region and X-ray PDF indicated that saturated NaNO2 and NaOH mixtures disrupt the hydrogen network of water into a new structure where the length of the OO correlations is contracted relative to the typical H2O structure. Beyond describing the solubility of NaNO2 in a multicomponent electrolyte mixture, these results also indicate that nitrite exhibits greater ion pairing in mixtures of concentrated NaNO2 and NaOH than in comparable solutions with only NaNO2.

Despite widespread industrial importance, predicting metal solubilities in highly concentrated, multicomponent aqueous solutions is difficult due to poorly understood ion-ion and ion-solvent interactions. Aluminum hydroxide solid phase solubility in concentrated sodium hydroxide (NaOH) solutions is one such case, with major implications for ore refining, as well as processing of radioactive waste stored at U.S. Department of Energy legacy sites, such as the Hanford Site, Washington State. The solubility of gibbsite (α-Al(OH)3) is often not well predicted because other ions affect the activity of hydroxide (OH-) and aluminate (Al(OH)4-) anions. In the present study, we systematically examined the influence of key anions, nitrite (NO2-) and nitrate (NO3-), as sodium salts on the solubility of α-Al(OH)3 in NaOH solutions taking care to establish equilibrium from both under- and oversaturation. Rapid equilibration was enabled by use of a highly pure and crystalline synthetic nano-gibbsite of well-defined particle size and shape. Measured dissolved aluminum concentrations were compared with those predicted by an α-Al(OH)3 solubility model derived for simple Al(OH)4-/OH- systems. Specific anion effects were expressed as an enhancement factor (Alenhc) conveying the excess of dissolved aluminum. At 45 °C, NaNO2 and NaNO3-containing systems exhibited Alenhc values of 2.70 and 1.88, respectively, indicating significant enhancement. The solutions were examined by Raman and high-field 27Al NMR spectroscopy, indicating specific interactions including Al(OH)4--Na+ contact ion pairing and Al(OH)4--NO2-/NO3- ion-ion interactions. Dynamic evolution of the α-Al(OH)3 particles including growth and agglomeration was observed revealing the importance of dissolution/reprecipitation in establishing equilibrium. These studies indicate that incomplete ion hydration, as a result of the low water activity in these concentrated electrolytes, results in: (i) enhanced reactivity of the hydroxide ion with respect to α-Al(OH)3; (ii) increased concentrations of Al(OH)4- in solution; and (iii) stronger ion-ion interactions that act to stabilize the supersaturated solutions. This information on the mechanisms by which α-Al(OH)3 becomes supersaturated is essential for more energy-efficient aluminum processing technologies, including the treatment of millions of gallons of Al(OH)4--rich high-level radioactive waste.

Cementitious waste forms immobilizing evaporated AP-105 off-gas condensate were used to determine radionuclide and contaminant leachability in deionized water over a 63-day period. The off-gas condensate was collected during the actual tank AP-105 low activity waste continuous laboratory-scale melter (LSM)) run performed in fiscal year 2018 and was then solidified as a cementitious waste form using the Cast Stone formulation (8 weight percent [wt%] ordinary Portland cement, 45 wt% class F fly ash, 47 wt% blast furnace slag). Here, using the U.S. Environmental Protection Agency Method 1315 leach testing procedure, the release rate of technetium 99 (Tc), iodine-129 (I), nitrate (NO3-), and sodium (Na+) from two Cast Stone specimens was measured. From these measurements, observed diffusivity values for each constituent were calculated and can be used in future iterations and maintenance of the Integrated Disposal Facility performance assessments. Furthermore, by testing Cast Stone specimens immobilizing off-gas produced while vitrifying actual tank waste, the results of this effort improve the technical defensibility of long-term waste form performance estimates for the Cast Stone formulation. Finally, 99Tc distribution within a representative waste form at the end of the 63-day leach period as well as bulk mineralogy were determined using solid phase characterization methods.

The 200-DV-1 Operable Unit (OU) is in the process of characterizing the vadose zone to support a remedial investigation and feasibility study. Contaminants disposed of at the land surface must migrate through the vadose zone before entering groundwater. Quantifying contaminant attenuation and contaminant transport processes in the vadose zone, in support of the conceptual site model (CSM) and fate and transport modeling, are important for assessing the needs for, and types of, remediation in the vadose zone and groundwater. The framework to characterize attenuation and transport processes provided in U.S. Environmental Protection Agency (EPA) guidance documents was used to guide the laboratory effort with the following objectives:

The uranium reactive gas sequestration (URGS) test described herein was conducted as an element of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau. The URGS technology was tested as a potential remedy to decrease the mobility of uranium in the vadose zone as a mechanism to protect groundwater. Information about URGS obtained from this test is intended for use in subsequent feasibility studies for Hanford Central Plateau waste sites with uranium contamination in the deep vadose zone.

A sample of off-gas condensate produced during a demonstration test of the direct-feed low-activity waste (DFLAW) Radioactive Waste Test Platform using waste retrieved from Hanford storage tank AP-105 waste was analyzed for major cations, anions, total cyanide, Resource Conservation and Recovery Act (RCRA) metals, selected radionuclides, and selected organic compounds. The remaining off-gas condensate was concentrated through evaporation and then used to produce Cast Stone waste forms. After the solid waste forms cured for 28 days, U.S. Environmental Protection Agency (EPA) Method 1311 (EPA 1992) Toxicity Characteristic Leach Procedure (TCLP) tests were conducted on two samples. The TCLP leachates were analyzed for RCRA metals, fluoride, and total cyanide. These chemical analyses were conducted to collect data on the waste form performance and to determine if the waste form will meet the disposal requirements of the Waste Control Specialists LLC (WCS) Federal Waste Disposal Facility (FWF) in Texas (WCS 2015) and the Integrated Disposal Facility at Hanford. The radionuclide results in the off-gas condensate were used to estimate concentrations in the Cast Stone waste forms; these estimates were then compared to Class C limits (30 TAC 336.362 Appendix E). With the possible exception of U-232, all measured radionuclides were determined to be below their respective Class C limits. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to measure most of the radionuclides. It is not possible to differentiate the isotope measured at mass 232 between U 232 and Th-232 by mass spectroscopy. Class C limit comparisons were made by assuming two maximum possible scenarios; one in which all the isotope at mass 232 occurred as Th-232, and another assigning the entire mass contribution to U-232. If the isotope at mass 232 is all Th-232 then the waste form is well below its Class C limit; however, if the isotope at mass 232 is all U-232, then the Class C limit would be exceeded by more than a factor of 8. A chemical procedure to separate uranium from thorium followed by reanalysis by ICP-MS would be required to resolve this issue. A similar issue occurs at mass 238, which could be U-238 or Pu-238; however, in this case Pu-238 can be ruled out as a contributor to the isotope measured at mass 238 for the following reasons. Pu-238 has a half-life of 87.7 years and its daughter product (U-234) has a half-life of 2.5 × 105 years and a measured concentration of < 0.002 µg/L. If significant concentrations of Pu-238 were present in this waste, then the amount of measurable U 234 would have increased over the decades of storage in the Hanford tanks. Because this was not observed, it is concluded that the isotope measured at mass 238 is all U-238. A total of 68 organic compounds were targeted for analysis in the off-gas condensate. Of these compounds, only nine were measured above their respective minimum reportable concentration. These compounds were acenaphthene, acetone, n-butyl alcohol, p,p'-DDT, methyl ethyl ketone, nitrobenzene, o nitrophenol, pyridine, and toluene. Of the detectable compounds, only acenaphthene, acetone, o nitrophenol, and pyridine were above wastewater standards (40 CFR 268.48 - Universal Treatment Standards). None of the organic compounds exceeded the non-wastewater standards (40 CFR 268.48 - Universal Treatment Standards). Analysis of the TCLP leachates from the Cast Stone waste forms indicated that none of the analytes exceeded the Universal Treatment Standard and, in general, all were well below the standards.

This report describes the results from grout formulation and cementitious waste form testing performed by Pacific Northwest National Laboratory for Washington River Protection Solutions, LLC (WRPS). These results are part of a screening test that investigates grout formulations proposed for encapsulating a wide range of compositions predicted to be present in evaporator bottoms wastes from the Hanford Effluent Management Facility (EMF). This work supports the technical development need for alternative treatment and disposition paths for the EMF evaporator bottoms waste and future direct-feed low-activity waste (DFLAW) operations at the Hanford Site. High-priority activities included simulant production, grout formulation, and cementitious waste form testing. The work contained within this report relates to waste form development and testing, but does not directly support the 2017 Integrated Disposal Facility (IDF) performance assessment (PA). However, this work contains information useful for future PA updates [beyond fiscal year (FY) 2017] and future waste form development efforts. These analytical results can be used by (i) cementitious waste form scientists to further the understanding of cementitious leach behavior of contaminants of concern (COCs), (ii) decision makers interested in off-site waste form disposal, and (iii) the U.S. Department of Energy, their Hanford Site contractors, and stakeholders as they continue to assess the IDF PA program at the Hanford Site. The reported results help fill existing data gaps, support final selection of a cementitious waste form for the EMF evaporator bottoms waste, and improve the technical defensibility of long-term waste form risk estimates.

A laboratory study was conducted to quantify contaminant attenuation processes and associated contaminant transport parameters that are needed to evaluate transport of contaminants through the vadose zone to the groundwater. The laboratory study information, in conjunction with transport analyses, can be used as input to evaluate the feasibility of Monitored Natural Attenuation and other remedies for the 200-DV-1 Operable Unit at the Hanford Site.

The objective of this study is to evaluate the significance of co-contaminants on the migration and transformation of iodine species in the Hanford subsurface environment. These impacts are relevant because remedies that target individual contaminants like iodine, may not only impact the fate and transport of other contaminants in the subsurface, but also inhibit the effectiveness of a targeted remedy. For example, iodine (as iodate) co-precipitates with calcite, and has been identified as a potential remedy because it immobilizes iodine. Since uranium also co-precipitates with calcite in field sediments, the presence of uranium may also inhibit iodine co-precipitation. Another potentially significant impact from co-existing contaminants is iodine and nitrate. The presence of nitrate has been shown to promote biogeochemical reduction of iodate to iodide, thereby increasing iodine species subsurface mobility (as iodide exhibits less sorption). Hence, this study reports on both laboratory batch and column experiments that investigated a) the change in iodate uptake mass and rate of uptake into precipitating calcite due to the presence of differing amounts of uranium, b) the amount of change of the iodate bio-reduction rate due to the presence of differing nitrate concentrations, and c) whether nitrite can reduce iodate in the presence of microbes and/or minerals acting as catalysts.

A laboratory testing program has been conducted to optimize polyphosphate remediation technology for implementation through a field-scale technology infiltration demonstration to stabilize soluble, uranium-bearing source phases in the vadose zone and capillary fringe. Source treatment in the deep vadose zone will accelerate the natural attenuation of uranium to more thermodynamically stable uranium-phosphate minerals, enhancing the performance of the proposed polyphosphate remediation within the 300 Area aquifer. The objective of this investigation was to develop polyphosphate remediation technology to treat uranium contamination contained within the deep vadose zone and capillary fringe. This chapter presents the results of an investigation that evaluated the rate and extent of reaction between polyphosphate and the uranium mineral phases present within the 300 Area, and autunite formation as a function of polyphosphate formulation and concentration. This information is critical for identifying the optimum implementation approach and controlling the flux of uranium to the underlying aquifer during remediation. Results from this investigation may be used to design a full-scale remediation of uranium at the 300 Area of the Hanford Site.

The sidewall core samples from well 299-E24-19, which were comprised of a mixture of bentonite and silt lens material, had an average porewater chloride concentration of 376 mg/L. The sidewall core samples collected from well 299-E25-46 had calculated porewater chloride concentrations ranging from 1,200 to more than 10,000 mg/L. Clearly, the sidewall core samples tested were capable of generating porewaters with sufficient chloride concentrations to cause corrosion of the stainless steel well casing. Furthermore, analysis of the sidewall core samples yielded a clear relationship between chloride concentration and well casing corrosion. The sidewall core samples containing the greatest amount of chloride, 3000 {micro}g/g of sediment, came from the well that experienced the longest length of casing failure (4.2 feet in well 299-E25-46). All of the sidewall core samples tested from both decommissioned wells contained more chloride than the Wyoming bentonite test material. However, since chloride was present as a trace constituent in all of the sidewall core samples (less than 0.4 weight percent), it is possible that it could have been introduced to the system as a ''contaminant'' contained in the bentonite backfill material. Therefore, it is likely that chloride leached from the bentonite material and/or chloride carried by/as a constituent of the liquid waste stream caused the advanced well casing corrosion found at wells 299-E24-19 and 299-E25-46 via crevice corrosion and stress corrosion cracking. The sample of Enviroplug{trademark} No.8 high swelling Wyoming bentonite was characterized for its potential to generate porewaters of sufficient chlorinity to lead to accelerated corrosion of type 304L stainless steel. Overall, the bentonite sample had considerably high water extractable concentrations of sodium, chloride, fluoride, sulfate, and alkalinity (measured as calcium carbonate). Interpretation of the laboratory data indicated that the Wyoming bentonite test sample was capable of generating localized vadose zone porewater with chloride concentrations in excess of 700 mg/L. However, the vadose zone at Hanford is primarily composed of coarse-grained sands with an in-situ moisture content ranging from 5-12%. Therefore, it is doubtful enough moisture will be available throughout the majority of the vadose zone to sufficiently ''wet'' the bentonite and leach chloride from the material. Consequently, Wyoming bentonite material should be suitable as an annulus filling agent in all low-moisture zones and those regions that lack the potential to accumulate perched water. This report contains all the geochemical and selected physical characterization data collected on archived vadose zone sediment recovered during the early 1990s installation of four RCRA monitoring wells: 299-E24-19, 299-E24-20, 299-E24-22, and 299-E25-46, sidewall core samples collected during the decommissioning (in 2004) of wells 299-E24-19 and 299-E25-46, splitspoon core samples collected during the installation (in 2004) of two RCRA monitoring wells: 299-E24-33 and 299-E25-95, a sample of Wyoming bentonite, as well as a perched water sample collected during the installation of well 299-E24-33. Laboratory tests were conducted to characterize the sediment and to identify water-leachable constituents. Testing consisted primarily of 1:1 sediment:water extractions, which were used to calculate the elemental concentrations of water soluble constituents in the solid and to estimate in-situ porewater chloride concentrations. Additionally, 8M nitric acid extractions and X-ray diffraction analysis of the solids were used to provide a measure of the total leachable sediment content of constituents and to search for the formation of new crystalline phases that may have formed during the corrosion process, respectively.

This report contains all the geochemical and selected physical characterization data collected on vadose zone sediment recovered from 5 direct push characterization holes emplaced to investigate vadose zone contamination associated with leaks from tanks 241-TY-105 (UPR-200-W-152) and 241-TY-106 (UPR-200-W-153). Tank 241-TY-105 is estimated to have leaked 35,000 gal of tributyl phosphate (TBP) waste from the uranium recovery process to the vadose zone in 1960. Tank 241-TY-106 is estimated to have leaked 20,000 gal of TBP-uranium recovery waste to the vadose zone in 1959. Although several drywells in the vicinity of tank 241-TY-106 contain measurable quantities of cesium-137 and/or cobalt-60, their relatively low concentrations indicate that the contaminant inventory in the vadose zone around tank 241-TY-106 is quite small. Additionally, this report contains all the geochemical and selected physical characterization data collected on vadose zone sediment recovered from 7 direct push characterization holes emplaced to investigate vadose zone contamination associated with an overfill event and leak from tank 241-T-101.

Geochemical tests provide evidence for the transit of a plume of caustic waste solution through the sediment column at the Hanford 241-B and -BX Tank Farms. Direct-push samples recovered from boreholes surrounding Tanks 241-B-110 and 241-BX-102 and related waste transfer lines and diversion boxes included sediments typical of those previously recovered from other localities on the Hanford Site. The Hanford formation sediments are dominantly quartzo-feldspathic sands strewn with lithic fragments, displaying a range of particle size distributions and sorting characteristics. Some moderately well-sorted, fine-grained lithologies are interpreted as lenticular bodies irregularly dispersed in coarser-grained, more poorly sorted sediments. Tier I tests conducted on the vadose zone sediments revealed an inverse correlation between moisture content and sediment size fraction (i.e., there is greater moisture content in finer-grained sediments). The Tier I tests also showed that the pore water solutions were likely sodium-rich, moderately saline, and possessed higher pH values than background (untainted) sediments. These data are characteristic of sediments that have encountered sodium-rich, saline, caustic waste solution, as documented in other reports at other suspect contamination sites around Hanford. Analyses of solutions from 1:1 water extracts reveal relatively balanced cation and anion concentrations, indicating that most of the geochemical species have been accounted for. The water extract data for affected sediments also indicate unusually high concentrations of aluminum, iron, and phosphorus. The relatively high concentrations of aluminum and iron may be the result of dissolution of secondary amorphous phases that precipitated after a reactive plume partially dissolved aluminum- and iron-bearing phases as it migrated through the sediment column. On the other hand, the presence of elevated concentrations of phosphorous may be the tell-tale signature of wastes derived from the bismuth phosphate separation process. Elements typically mobile in the geosphere, such as technetium-99, are present at either low concentrations or are below the analytical detection limit. However, we expect that the mobile elements would be present mainly along a narrow plume front, and if this front had passed deeper into the sediment profile than depths sampled, the retention of these elements would be minor. On the other hand for the direct push sediments from around BX Tank Farm, uranium-238 was detected in nearly all sediment specimens (by acid extract experiments) at concentrations above the natural crustal average (0.763 pCi/g), and we also detected the presence of several anthropogenic radioisotopes, such as cobalt-60, cesium-137, europium-154, and europium-155 (by gamma energy analysis). These data are direct confirmation of contamination of the sediments.

The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) C. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole C4297, installed adjacent to Tank C-105, and from borehole 299-E27-22, installed directly north of the C Tank Farm. Sediments from borehole 299-E27-22 were considered to be background uncontaminated sediments against which to compare contaminated sediments for the C Tank Farm characterization effort. This report also presents our interpretation of the data in the context of sediment types, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone and groundwater below the C Tank Farm. The information presented in this report supports the A-AX, C and U Waste Management Area field investigation report(a) in preparation by CH2M HILL Hanford Group, Inc. A core log was generated for both boreholes and a geologic evaluation of all core samples was performed at the time of opening. Aliquots of sediment from the borehole core samples were analyzed and characterized in the laboratory for the following parameters: moisture content, gamma-emitting radionuclides, one-to-one water extracts (which provide soil pH, electrical conductivity, cation, trace metal, and anion data), total carbon and inorganic carbon content, and 8 M nitric acid extracts (which provide a measure of the total leachable sediment content of contaminants). Two key radiocontaminants, technetium-99 and uranium-238, along with other trace metals were determined in acid and water extracts by inductively coupled plasma mass spectrometry.