Data Package for Secondary Waste Form Down-Selection—Cast Stone

Available literature on Cast Stone and Saltstone was reviewed with an emphasis on determining how Cast Stone and related grout waste forms performed in relationship to various criteria that will be used to decide whether a specific type of waste form meets acceptance criteria for disposal in the Integrated Disposal Facility (IDF) at Hanford. After the critical review of the Cast Stone/Saltstone literature, we conclude that Cast Stone is a good candidate waste form for further consideration. Cast stone meets the target IDF acceptance criteria for compressive strength, no free liquids, TCLP leachate are below the UTS permissible concentrations and leach rates for Na and Tc-99 are suiteably low. The cost of starting ingredients and equipment necessary to generate Cast Stone waste forms with secondary waste streams are low and the Cast Stone dry blend formulation can be tailored to accommodate variations in liquid waste stream compositions. The database for Cast Stone short-term performance is quite extensive compared to the other three candidate waste solidification processes. The solidification of liquid wastes in Cast Stone is a mature process in comparison to the other three candidates. Successful production of Cast Stone or Saltstone has been demonstrated from lab-scale monoliths with volumes of cm3 through m3 sized blocks to 210-liter sized drums all the way to the large pours into vaults at Savannah River. To date over 9 million gallons of low activity liquid waste has been solidified and disposed in concrete vaults at Savannah River

Kd Values for Agricultural and Surface Soils for Use in Hanford Site Farm, Residential, and River Shoreline Scenarios

This report provides best estimate Kd values and a minimum and maximum range of Kd values to be used for agricultural soils and Columbia River bank sediments that exist today or would exist in the future when portions of the Hanford Site are released for farming, residential, and recreational use after the U. S. Department of Energy (DOE) completes clean up of defense waste on the site. The Kd values should be used to determine the fate and transport rates of contaminants and their availability for plant and animal uptake in selected non-groundwater scenarios included in Hanford Site environmental impact statements, risk assessments and specific facility performance assessments. This report describes scenarios such as a small farm where drilling of a well inadvertently goes through buried waste and brings waste to the surface, allowing the tailings to become available for direct human exposure or incorporation into garden crops and farm animals used for food by the farm family. The Kd values recommended in this report can also be used to calculate sediment-water partitioning factors used to predict plant and animal uptake from interaction with the contaminated soil

Characterization of 200-UP-1 and 200-ZP-1 Operable Unit Aquifer Sediments and Batch Adsorption Distribution Coefficients for Contaminants of Concern--Fiscal Year 2006 Progress

A total of six core samples from 200-UP/ZP-1 OUs and two additional outcrop samples were characterized during FY2006 by PNNL. One sample (C4971) was identified as slough and not used, but the five other samples identified as intact core samples were used for further analyses. The C4977 sample is gravel-sandy silt and C4990 samples are fine-sandy silt from the Ringold formation. Although the sediments from these two boreholes have similar mineralogical composition, C4990 samples show higher values of Fe oxide content, clay/silt content, and surface area compared those in C4977. The measured Tc Kd values ranged 0–0.2 mg/L for both samples, while U(VI) Kd for C4990 (4.23 mg/L) is much higher than that for C4977 (0.76 mg/L). A key finding from the Kd measurements is that detailed sediment and pore water characterization is necessary to understand the variation in Kd values seen in the empirical batch tests. Without the ancillary characterization of the sediments and pore waters, one might form misleading interpretations of the mechanisms that control the Kd values. Thus, physical, geochemical, and hydrological characterization of the sediments and pore waters should be conducted to increase our understanding of the site-specific Kd measurements. More details for methods and results will be provided in the formal technical report in FY 2007

Secondary Waste Cast Stone Waste Form Qualification Testing Plan

The Hanford Tank Waste Treatment and Immobilization Plant (WTP) is being constructed to treat the 56 million gallons of radioactive waste stored in 177 underground tanks at the Hanford Site. The WTP includes a pretreatment facility to separate the wastes into high-level waste (HLW) and low-activity waste (LAW) fractions for vitrification and disposal. The LAW will be converted to glass for final disposal at the Integrated Disposal Facility (IDF). Cast Stone – a cementitious waste form, has been selected for solidification of this secondary waste stream after treatment in the ETF. The secondary-waste Cast Stone waste form must be acceptable for disposal in the IDF. This secondary waste Cast Stone waste form qualification testing plan outlines the testing of the waste form and immobilization process to demonstrate that the Cast Stone waste form can comply with the disposal requirements. Specifications for the secondary-waste Cast Stone waste form have not been established. For this testing plan, Cast Stone specifications are derived from specifications for the immobilized LAW glass in the WTP contract, the waste acceptance criteria for the IDF, and the waste acceptance criteria in the IDF Permit issued by the State of Washington. This testing plan outlines the testing needed to demonstrate that the waste form can comply with these waste form specifications and acceptance criteria. The testing program must also demonstrate that the immobilization process can be controlled to consistently provide an acceptable waste form product. This testing plan also outlines the testing needed to provide the technical basis for understanding the long-term performance of the waste form in the disposal environment. These waste form performance data are needed to support performance assessment analyses of the long-term environmental impact of the secondary-waste Cast Stone waste form in the ID

Uranium Contamination in the 300 Area: Emergent Data and their Impact on the Source Term Conceptual Model

The primary objectives of this characterization activity were to: 1) determine the extent of uranium contamination in the sediments, 2) quantify the leachable (labile) concentration of uranium in the sediments, and 3) create a data set that could be used to correlate the present data to existing 300 Area data. In order to meet these objectives, sediments collected from wells 399-2-5 (C5708), 299-3-22 (C5706) and 299-4-14 (C5707) were analyzed for moisture content, 1:1 sediment:water extracts (which provide soil pH, electrical conductivity [EC], cation, and anion data), total carbon and inorganic carbon content, 8 M nitric acid extracts (which provide a measure of the total leachable sediment content of the contaminants), microwave-assisted digestion (which results in total digestion of the sediment), and carbonate leaches (which provide an assessment of the concentration of labile uranium present in the sediments). Additionally, pore waters present in select samples were extracted using ultracentrifugation. The mobility characteristics of uranium vary within the multiple subsurface zones that contain residual contaminant uranium. Principal subsurface zones include 1) the vadose zone, 2) a zone through which the water table rises and falls, 3) the aquifer, and 4) a zone where groundwater and river water interact beneath the river shoreline. Principal controls on mobilization include the form of the residual uranium (e.g., crystalline minerals, amorphous precipitates/coatings, sorbed onto sediment), the transporting medium (e.g., water infiltration from the land surface, groundwater), and the rate of exchange between the form and transporting medium. The bicarbonate content of aqueous media strongly influences the rate of exchange, with relatively higher content enhancing mobility. Groundwater has a higher bicarbonate content than river water or other freshwater sources, such as utility and potable water systems. The variety of processes affecting the mobility of uranium in the subsurface, along with the numerous potential compartments where residual contamination may be located, presents challenges for predicting uranium movement through environmental pathways. The processes responsible for the persistence of the plume may involve cycling of uranium between the aquifer and overlying zone through which the water table fluctuates. Contaminated groundwater is moved upward into the lower vadose zone, and when the water table subsequently falls, contaminated moisture is left behind. Some of the uranium in groundwater may become sorbed to sediment in that zone, to subsequently slowly release. Also, near the Columbia River in the zone of groundwater/river water interaction, where the bicarbonate content is lowered because of infiltrating river water, the tendency for uranium to adsorb onto sediment is enhanced, thus slowing dissipation via the groundwater pathway. Fluctuations in the Columbia River stage are the driving mechanism for the rise and fall of the water table beneath the 300 Area, and also for creating the dynamic hydraulic and geochemical environment found in the zone of interaction beneath the shoreline

Applicability of the Linear Sorption Isotherm Model to Represent Contaminant Transport Processes in Site-Wide Performance Assessments

This paper addresses the applicability of the linear sorption model to the complex wastes of the Hanford Site

Geochemical Characterization Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

This data package discusses the geochemistry of vadose zone sediments beneath the single-shell tank (SST) farms at the U.S. Department of Energy’s (DOE’s) Hanford Site. The purpose of the report is to provide a review of the most recent and relevant geochemical information available for the vadose zone beneath the SST farms and the Integrated Disposal Facility (IDF)

Uranium Contamination in the Subsurface Beneath the 300 Area, Hanford Site, Washington

This report provides a description of uranium contamination in the subsurface at the Hanford Site's 300 Area. The principal focus is a persistence plume in groundwater, which has not attenuated as predicted by earlier remedial investigations. Included in the report are chapters on current conditions, hydrogeologic framework, groundwater flow modeling, and geochemical considerations. The report is intended to describe what is known or inferred about the uranium contamination for the purpose of making remedial action decisions

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

This data package discusses the geochemistry of vadose zone sediments beneath the single-shell tank farms at the U.S. Department of Energy’s (DOE’s) Hanford Site. The purpose of the report is to provide a review of the most recent and relevant geochemical process information available for the vadose zone beneath the single-shell tank farms and the Integrated Disposal Facility. Two companion reports to this one were recently published which discuss the geology of the farms (Reidel and Chamness 2007) and groundwater flow and contamination beneath the farms (Horton 2007)

Laboratory-Scale Bismuth Phosphate Extraction Process Simulation To Track Fate of Fission Products

Recent field investigation that collected and characterized vadose zone sediments from beneath inactive liquid disposal facilities at the Hanford 200 Areas show lower than expected concentrations of a long-term risk driver, Tc-99. Therefore laboratory studies were performed to re-create one of the three processes that were used to separate the plutonium from spent fuel and that created most of the wastes disposed or currently stored in tanks at Hanford. The laboratory simulations were used to compare with current estimates based mainly on flow sheet estimates and spotty historical data. Three simulations of the bismuth phosphate precipitation process show that less that 1% of the Tc-99, Cs-135/137, Sr-90, I-129 carry down with the Pu product and thus these isotopes should have remained within the metals waste streams that after neutralization were sent to single shell tanks. Conversely, these isotopes should not be expected to be found in the first and subsequent cycle waste streams that went to cribs. Measurable quantities (~20 to 30%) of the lanthanides, yttrium, and trivalent actinides (Am and Cm) do precipitate with the Pu product, which is higher than the 10% estimate made for current inventory projections. Surprisingly, Se (added as selenate form) also shows about 10% association with the Pu/bismuth phosphate solids. We speculate that the incorporation of some Se into the bismuth phosphate precipitate is caused by selenate substitution into crystal lattice sites for the phosphate. The bulk of the U daughter product Th-234 and Np-237 daughter product Pa-233 also associate with the solids. We suspect that the Pa daughter products of U (Pa-234 and Pa-231) would also co-precipitate with the bismuth phosphate induced solids. No more than 1 % of the Sr-90 and Sb-125 should carry down with the Pu product that ultimately was purified. Thus the current scheme used to estimate where fission products end up being disposed overestimates by one order of magnitude the partitioning Sr-90, Cs-137, and Sb-125 and by at least two orders of magnitude the portioning of Tc-99 to the first and subsequent cycle waste streams that went to cribs. Conversely, the current scheme underestimates the lanthanide and yttrium fission product quantities that went to cribs by a factor of about 3