Hydrogeology and Geochemistry Services

The Center for Nuclear Waste Regulatory Analyses (CNWRA) provides effective solutions to a wide range of hydrogeologic and geochemical problems. Sophisticated computational and visualization resources and fully equipped laboratories allow the CNWRA staff to solve diverse scientific and engineering problems for government and industry.

The CNWRA is operated by Southwest Research Institute (SwRI), an independent nonprofit research and development organization in operation for nearly 50 years. With 13 technical divisions, SwRI provides extensive resources, such as laboratory facilities, analytical capabilities, and staff expertise in a broad range of scientific and engineering specialties.

The CNWRA technical expertise includes:

• Physical and earth sciences
• Engineering and material sciences
• Hazard assessment
• Environmental science
• Regulatory interpretation, implementation, and compliance demonstration

The Center offers expertise in the assessment and interpretation of hydrologic flow and the consequent transport of environmental contaminants in diverse geochemical systems.

CNWRA scientists have developed a modeling approach that identifies key chemical parameters to predict sorption behavior over a wide range of conditions. This diagram shows the variation of U(6+) sorption on montmorillonite clay as a function of solution pH and the ratio of solid-mass to solution-volume (M/V). The model was calibrated against a series of CNWRA sorption experiments and extrapolated using the Environmental Protection Agency code MINTEQA2 and a thermodynamic database prepared at CNWRA.

Numerical Modeling and Code Development

The CNWRA develops and applies numerical modeling codes for a variety of computer systems. In addition to developing original geochemical and hydrologic computer modeling codes, staff members have modified codes and used available codes to meet client needs in:

• Multiphase isothermal and nonisothermal flow modeling
• Reactive contaminant transport calculation
• Infiltration analysis
• 3-D heterogeneity modeling
• Lagrangian particle tracking evaluation
• Perched water zone formation
• Sorption modeling

This three-dimensional geological framework model of Yucca Mountain, Nevada, integrates geologic, hydrologic, geochemical, and geomorphic data. Integration of diverse data allows CNWRA scientists and engineers to effectively evaluate complex process interactions that may affect contaminant transport.

Field Investigations

The Center has conducted extensive field studies worldwide to evaluate contaminant transport and to assess geologic structures, volcanologic effects and hazards, and seismic risk.

CNWRA field expertise includes:

• Infiltration, permeability, and moisture measurements
• Regional and site-scale topographic mapping
• Surface and underground geologic mapping
• Rock, mineral, water, soil gas, and vegetation sampling
• Contact gamma radiation mapping
• Transient electromagnetic soundings for perched water zones
• Magnetometry surveys
• Radon measurements

Using coupled moisture flux and energy balance simulations, CNWRA scientists estimate hydrologic infiltration into fractured bedrock in an arid environment, identifying areas of high infiltration (reds) and areas of lower infiltration (blues). This example calculated infiltration as a function of climatic parameters, hydraulic properties, alluvium depth, and erosion.

Engineers predict contaminant concentration fields in a two-layer, highly heterogeneous, unsaturated geologic medium using SUFLAT, a CNWRA numerical code that performs stochastic flow and transport assessments.

Laboratory Facilities

Extensive state-of-the-art laboratories are equipped for:

• Rock sample preparation and physical testing
• Saturated and unsaturated flow properties measurement
• Scale-model studies in environmentally controlled chambers
• Aqueous and solid-phase geochemical analyses (including natural and synthetic radioactive materials)
• Microbiological studies

These facilities support understanding and problem resolution in:

• Thermally driven moisture redistribution
• Mineral solubilities and ion exchange properties
• Mineral sorptive properties
• Radiochemistry
• Microbial viability and processes in earth materials

Regulatory Analyses

The Center analyzes various federal and state regulations and prepares review methods and criteria to demonstrate or evaluate regulatory compliance. The CNWRA regulatory experience includes working with:

• U.S. Environmental Protection Agency
• U.S. Mine Safety and Health Administration
• U.S. Nuclear Regulatory Commission
• U.S. Department of Energy
• U.K. Department of the Environment
• Swedish Radiation Protection Institute

The CNWRA

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