Keywords: Mecanique des sols ; Drainage ; Ecoulement souterrain Reference Record created on 2004-09-07, modified on 2016-08-08

Applications of soil physics.

Worldwide, the mining of uranium has generated 938 × 10 6 m 3 of mill tailings. The radioactivity of these tailings depends on the grade of ore mined and varies from less than 1 Bq/g to more than 100 Bq/g. The most common mode of disposal is near-surface impoundment in the vicinity of the mine or mill. The principal radiation risks from uranium tailings are gamma radiation, essentially from radium decay; windblown radioactive dust dispersal; and radon gas and its radioactive progeny, which are known to cause lung cancer. Uranium mill tailings are also often associated with elevated concentrations of highly toxic heavy metals, which are a major source of surface and groundwater contamination. Due to their high sulfide content (a few to tens of wt%), tailings may acidify groundwater, accelerating the release of radioactive and hazardous elements.

Uranium Mill Tailings: Geochemistry, Mineralogy, and Environmental Impact

A graded approach for evaluating radiation doses to aquatic and terrestrial biota

Adsorption–desorption reactions are important processes that affect the transport of contaminants in the environment. Various empirical approaches, such as the distribution coefficient and Freundlich and Langmuir isotherm equations, have been used to represent adsorption. The empirical approaches are not capable of accounting for the effects of variable chemical conditions, such as pH, on adsorption reactions. This can be done using chemical models such as surface complexation models. These models define specific surface species, chemical reactions, equilibrium constants, mass balances, and charge balances, and their molecular features can be given thermodynamic significance. Ion adsorption mechanisms and surface configurations for the surface complexation models can be established from independent experimental observations. These include both indirect measurements, such as point of zero charge shifts, ionic strength effects, and calorimetry, and direct spectroscopic techniques, including vibrational spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and X-ray absorption spectroscopy. Surface complexation models were developed for single mineral phases but have now been applied to natural mineral assemblages using both component additivity (CA) and generalized composite (GC) approaches. Surface complexation models have been incorporated into subsurface transport models at several field sites, although simplifying assumptions are needed to deal with heterogeneous materials. Surface complexation models for contaminant adsorption have the potential to increase the confidence and scientific credibility of transport modeling by reducing the uncertainty in quantifying retardation and providing a means of quantifying that uncertainty.

Adsorption–Desorption Processes in Subsurface Reactive Transport Modeling

Optimal soil physical quality inferred through structural regression and parameter interactions

This manual provides information on the design and application of the RESidual RADioactivity (RESRAD) code. It describes the basic models and parameters used in the RESRAD code to calculate doses and risks from residual radioactive materials and the procedures for applying these models to calculate operational guidelines for soil contamination. RESRAD has undergone many improvements to make it more realistic in terms of the models used in the code and the parameters used as defaults. Version 6 contains a total of 145 radionuclides (92 principal and 53 associated radionuclides), and the cutoff half-life for associated radionuclides has been reduced to 1 month. Other major improvements to the RESRAD code include its ability to run uncertainty analyses, additional options for graphical and text output, a better dose conversion factor editor, updated databases, a better groundwater transport model for long decay chains, an external ground radiation pathway model, an inhalation area factor model, time-integration of dose and risk, and a better graphical user interface. In addition, RESRAD has been benchmarked against other codes in the environmental assessment and site cleanup arena, and RESRAD models have been verified and validated.

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User's manual for RESRAD version 6.

A pathway analysis computer code called RESRAD has been developed for implementing US Department of Energy Residual Radioactive Material Guidelines Hydrogeological, meteorological, geochemical, geometrical (size, area, depth), and material-related (soil, concrete) parameters are used in the RESRAD code This handbook discusses parameter definitions, typical ranges, variations, measurement methodologies, and input screen locations Although this handbook was developed primarily to support the application of RESRAD, the discussions and values are valid for other model applications

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Data collection handbook to support modeling the impacts of radioactive material in soil

The RESRAD and RESRAD-BUILD codes are part of the RESRAD family of codes developed by the U.S. Department of Energy. For many years, these deterministic codes have been used as dose assessment tools for cleanup of sites contaminated with radioactive materials. The RESRAD code applies to the cleanup of soils, and the RESRAD-BUILD code applies to the cleanup of buildings and structures. This report is the third in a series documenting the procedures used to enhance the deterministic RESRAD and RESRAD-BUILD codes for probabilistic dose analysis. A six-step procedure was used in developing default parameter distributions and the probabilistic analysis modules. These six steps include (1) listing and categorizing parameters, (2) ranking parameters, (3) developing parameter distributions, (4) testing parameter distributions for probabilistic analysis, (5) developing probabilistic modules, and (6) testing probabilistic modules and integrated codes. These six steps are discussed and summarized in this report. Steps 4 and 5 are documented in separate NUREG/CR reports (NUREG/CR-6676 [Kamboj et al., 2000] and NUREG/CR-6692 [LePoire et al., 2000]). The reports for steps 1, 2, 3, and 6 are included in this report as attachments. The probabilistic versions of RESRAD and RESRAD-BUILD codes provide tools for studying the uncertainty in dose assessment caused by uncertain input parameters. The codes are designed to be user-friendly, but they can be misused. Therefore, it is important that potential users be trained in the proper use of the codes consistent with the guidance in NRC's Standard Review Plan (SRP) for Decommissioning (NRC, 2000) for dose modeling and analysis. Furthermore, it is important that the code users follow the guidance in the Multi-Agency Radiation Survey and Site Investigation Manual (NRC, 1997) on collecting site-specific data for developing probabilistic distributions of parameter values to be used in the RESRAD and RESRAD-BUILD codes. They need to collect enough data to develop values that are as close to real-world distributions of these values as possible to produce meaningful and technically defensible results.

Development of probabilistic resrad 6.0 and resrad-build 3.0 computer codes

The RESRAD-BUILD computer code is a pathway analysis model designed to evaluate the potential radiological dose incurred by an individual who works or lives in a building contaminated with radioactive material. The transport of radioactive material within the building from one compartment to another is calculated with an indoor air quality model. The air quality model considers the transport of radioactive dust particulates and radon progeny due to air exchange, deposition and resuspension, and radioactive decay and ingrowth. A single run of the RESRAD-BUILD code can model a building with up to three compartments, four source geometries (point, line, area, and volume), 10 distinct source locations, and 10 receptor locations. The volume source can be composed of up to five layers of different materials, with each layer being homogeneous and isotropic. A shielding material can be specified between each source-receptor pair for external gamma dose calculations. The user can select shielding material from eight different material types. Seven exposure pathways are considered in the RESRAD-BUILD code: (1) external exposure directly from the source, (2) external exposure to materials deposited on the floor, (3) external exposure due to air submersion, (4) inhalation of airborne radioactive particulates, (5) inhalation of aerosol indoormore » radon progeny and tritiated water vapor, (6) inadvertent ingestion of radioactive material directly from the source, and (7) ingestion of materials deposited on the surfaces of the building compartments. Various exposure scenarios may be modeled with the RESRAD-BUILD code. These include, but are not limited to, office worker, renovation worker, decontamination worker, building visitor, and residency scenarios. Both deterministic and probabilistic dose analyses can be performed with RESRAD-BUILD, and the results can be shown in both text and graphic reports.« less

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C. Yu

Papers

User's manual for RESRAD version 6.

Data collection handbook to support modeling the impacts of radioactive material in soil

Development of probabilistic resrad 6.0 and resrad-build 3.0 computer codes

User's manual for RESRAD-BUILD version 3.

Long-term contaminant migration and impacts from uranium mill tailings