33 research outputs found
Recommended from our members
Groundwater Flow and Transport Calculations Supporting the Immobilized Low-Activity Waste Disposal Facility Performance Assessment
This report summarizes the Hanford Site-Wide Groundwater Model and its application to the Immobilized Low-Activity Waste (ILAW) Disposal Facility Performance Assessment (PA). The site-wide model and supporting local-scale models are used to evaluate impacts from the transport of contaminants at a hypothetical well 100 m downgradient of the disposal facilities and to evaluate regional flow conditions and transport from the ILAW disposal facilities to the Columbia River. These models were used to well-intercept factors (WIFs) or dilution factors from a given areal flux of a hypothetical contaminant released to the unconfined aquifer from the ILAW disposal facilities for two waste-disposal options: (1) a remote-handled trench concept and (2) a concrete-vault concept. These WIFs are being used in conjunction with calculations of released contaminant fluxes through the vadose zone to estimate potential impacts from radiological and hazardous chemical contaminants within the ILAW disposal facility at compliance points
Recommended from our members
Summary of Tritium Tracking and Groundwater Monitoring at the Hanford Site 200 Area SALDS - FY 1998
Treated water from the 200 Area Effluent Treatment Facility (ETF) is discharged to a disposal site in accordance with the State Waste Discharge Permit ST-4500. This disposal site is referred to as the State-Approved Land Disposal Site (SALDS). In accordance with the discharge permit, the groundwater at the SALDS is routinely sampled. The results of the groundwater sampling are reported in quarterly discharge monitoring reports. In 1997, the USDOE also committed to the issuance of an annual summary report of groundwater monitoring results and evaluation with updates to the groundwater monitoring plan as appropriate. This report summarizes the groundwater information for FY 1998
Recommended from our members
2005 Closure Assessments for WMA-C Tank Farms: Numerical Simulations
In support of CH2M HILL Hanford Group, Inc.'s (CHG) closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, numerical simulations of flow and solute transport were executed to investigate different potential contaminant source scenarios that may pose long-term risks to groundwater from the closure of the C Tank Farm. These simulations were based on the initial assessment effort (Zhang et al., 2003), but implemented a revised approach that examined a range of key parameters and multiple base cases. Four different potential source types were identified to represent the four base cases, and included past leaks, diffusion releases from residual wastes, leaks during retrieval, and ancillary equipment sources. Using a two-dimensional cross section through the C Tank Farm (Tanks C-103–C-112) and a unit release from Tank C-112, two solutes (uranium-238 (U-238) and technetium-99 (Tc 99)) were transported through the problem domain. To evaluate the effect of sorption on contaminant transport, seven different sorption coefficients were simulated for U 238. Apart from differences in source releases, all four base cases utilized the same median parameter values to describe flow and contaminant transport at the WMA C. Forty-six additional cases were also run that examined individual transport responses to the upper and lower limits of the median parameter values implemented in the base case systems. For the conservative solute, Tc-99, results amongst the base cases showed that the simulations investigating past leaks demonstrated the highest peak concentrations and the earliest arrival times (48 years) due to the proximity of the plume to the water table and the high recharge rate before surface barriers were installed. Simulations investigating leaks during retrieval predicted peak concentrations ~60 times smaller than the past leak cases, and corresponding arrival times that occurred ~70 years later. The diffusion release base case predicted the lowest peak concentrations and arrival times for all solutes. Even after 10,000 years of simulation, only 11.2% of the Tc-99 mass migrated past the fence line compliance point in the groundwater. Although ancillary equipment cases released the contaminant at a similar depth as the diffusion cases, nearly all of the Tc-99 (99.0%) exited the groundwater domain by the end of the simulation due to differences in release rates. These differences were also reflected in the peak arrival times, which were ~8,500 years for the diffusion base case, and ~3,700 years for the base ancillary equipment release. In the diffusion cases, peak concentration predictions were sensitive to the rate of diffusion, but had no impact on the peak concentration arrival times. The average peak concentration was ~3.2 times higher than the base case value for the upper estimate of diffusion, and 3.2 10-3 lower for the lower bounding estimate. The past leak, ancillary equipment and retrieval leak cases were sensitive to the estimate of the pre-barrier installment recharge rate. For example, on average for the past leaks, relative concentrations increased by ~2.2 times for the upper recharge estimate, and decreased by ~0.14 times for the lower bound. Faster arrival times were associated with the upper recharge estimate, and slower arrival times with the lower estimate. Similar trends in both predicted peaks and arrival times occurred for the ancillary equipment and retrieval leaks scenarios that investigated the uncertainty in the pre-barrier installment recharge rate. Uncertainty in the plume depth also impacted predicted peak concentrations and arrival times for the past leak scenario. Trends similar to the pre-barrier installment recharge rate resulted, with higher concentrations and earlier breakthroughs associated with a lower plume depth, and lower concentrations and later breakthroughs with a higher plume depth
Recommended from our members
Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model
Pacific Northwest National Laboratory (PNNL) embarked on a new initiative to strengthen the technical defensibility of the predictions being made with a site-wide groundwater flow and transport model at the U.S. Department of Energy Hanford Site in southeastern Washington State. In FY 2000, the focus of the initiative was on the characterization of major uncertainties in the current conceptual model that would affect model predictions. The long-term goals of the initiative are the development and implementation of an uncertainty estimation methodology in future assessments and analyses using the site-wide model. This report focuses on the development and implementation of an uncertainty analysis framework
Recommended from our members
Estimation of the release and migration of lead through soils and groundwater at the Hanford Site 218-E-12B Burial Ground. Volume 2, Appendices
This report describes the technical basis for a groundwater transport analysis that was conducted to evaluate migration of potentially hazardous materials from the Hanford Site 218-E-12B burial ground. The analysis characterized the geologic, chemical, and hydrologic properties of the disposal site, and used that information to perform a screening analysis for transport of materials from the burial ground to downgradient groundwater locations and to the Columbia River. Subsequent sections of the appendix describe the geologic setting, geochemistry, and hydrology of the disposal site and their relationship to the transport analysis
Recommended from our members
Technical review of entrained design report
Morgantown Energy Technology Center (METC) is planning to expand its in-house coal gasification R&D capabilities by installing a research facility that can address a number of concepts including entrained, fluid bed, and catalytic gasification and flash pyrolysis. This Advanced Gasification Concepts (AGC) facility design, as it currently stands, includes piping and instrumentation diagrams, vessel drawings and specifications, instrumentation lists and specifications, and equipment layout and isometric drawings. Before the design is finalized, a critique is needed to ensure that the intended flexibility and objectives can be met. The design approach was evaluated to determine whether the present design will meet the research objectives, including the need for flexibility. Heat and material balances, critical velocity requirements, vessel arrangements, potential operational problems, and instrumentation were reviewed. The mechanical design review included a critique of the drawings and specifications, adherence to standards and codes, materials of construction, vessels, piping, valves, heaters, and fittings. In addition, utilities requirements, heat transfer and particulate removal calculations, and pumping and heat exchanger requirements were checked. An evaluation of the equipment cost includes a critique of the reliability of the equipment cost breakdown, the areas of cost uncertainty, and the areas for potential cost savings. A safety analysis is also provided
Perceptions of the unregistered healthcare worker’s role in pre-registration student nurses’ clinical training
Simulation of unsaturated flow and solute transport at the Las Cruces trench site using the PORFLO-3 computer code
The objective of this work was to test the ability of the PORFLO-3 computer code to simulate water infiltration and solute transport in dry soils. Data from a field-scale unsaturated zone flow and transport experiment, conducted near Las Cruces, New Mexico, were used for model validation. A spatial moment analysis was used to provide a quantitative basis for comparing the mean simulated and observed flow behavior. The scope of this work was limited to two-dimensional simulations of the second experiment at the Las Cruces trench site. Three simulation cases are presented. The first case represents a uniform soil profile, with homogeneous, isotropic hydraulic and transport properties. The second and third cases represent single stochastic realizations of randomly heterogeneous hydraulic conductivity fields, generated from the cumulative probability distribution of the measured data. Two-dimensional simulations produced water content changes that matched the observed data reasonably well. Models that explicitly incorporated heterogeneous hydraulic conductivity fields reproduced the characteristics of the observed data somewhat better than a uniform, homogeneous model. Improved predictions of water content changes at specific spatial locations were obtained by adjusting the soil hydraulic properties. The results of this study should only be considered a qualitative validation of the PORFLO-3 code. However, the results of this study demonstrate the importance of site-specific data for model calibration. Applications of the code for waste management and remediation activities will require site-specific data for model calibration before defensible predictions of unsaturated flow and containment transport can be made. 23 refs., 16 figs., 3 tabs
Recommended from our members
Hanford Site ground-water model: Geographic information system linkages and model enhancements, FY 1993
Models of the unconfined aquifer are important tools that are used to (1) identify and quantify existing, emerging, or potential ground-water quality problems, (2) predict changes in ground-water flow and contaminant transport as waste-water discharge operations change, and (3) assess the potential for contaminants to migrate from the US Department of Energy`s Hanford Site through the ground water. Formerly, most of the numerical models developed at the Hanford Site were two-dimensional. However, contaminant concentrations cannot be accurately predicted with a two-dimensional model, which assumes a constant vertical distribution of contaminants in the aquifer. Development of two- and three-dimensional models of ground-water flow based on the Coupled Fluid, Energy, and Solute Transport (CFEST) code began in the mid- 1980s. The CFEST code was selected because of its ability to simulate both ground-water flow and contaminant transport. Physical processes that can be modeled by CFEST include aquifer geometry, heterogeneity, boundary conditions, and initial conditions. The CFEST ground-water modeling library has been integrated with the commercially available geographic information system (GIS) ARC/INFO. The display and analysis capabilities of a GIS are well suited to the size and diversity of databases being generated at the Hanford Site. The ability to visually inspect large databases through a graphical analysis tool provides a stable foundation for site assessments and ground-water modeling studies. Any ground-water flow model being used by an ongoing project should be continually updated and refined to reflect the most current knowledge of the system. The two-dimensional ground-water flow model being used in support of the Ground-Water Surveillance Project has recently been updated and enhanced. One major enhancement was the extension of the model area to include North Richland