Thorium mobilization in a terrestrial environment
The mobilization of naturally-occurring thorium from an ore body containing about 30,000 metric tons has been used to assess the potential for tetravalent plutonium transport from a deep geologic waste repository that has been eroded to the surface of the earth and breached by groundwater. Thorium mobility from the deposit was assessed due to water erosion and groundwater solubilization. The ore body is estimated to be about 60 million years old and is located, in an exposed and highly weathered condition, near the summit of a hill in the State of Minas Gerais, Brazil. Rainfall during the one year period of study (177 cm) was close to the 30 year mean of 170 cm. Most of the precipitation occurs during a four month rainy season. It was found that storm runoff yields a fractional removal rate of 10/sup -6/ yr/sup -1/ mainly by surface erosion while groundwater solubilization resulted in a removal rate of 10/sup -9/ yr/sup -1/. Thus, physical transport in surface runofff dominates by three orders of magnitude and is the primary mechanism for thorium removal from the ore body under current environmental conditions. The mean life of the thorium in the deposit is 10/sup 6/ years if controlled by rainfall erosion and 10/sup 9/ years if controlled by groundwater solubilization, respectively. Because of the improbability that a deep geologic repository will become exposed at the surface of the earth, groundwater solubilization is a more relevant mobilization mechanism than erosion.
- Research Organization:
- New York Univ., NY (USA)
- OSTI ID:
- 5984017
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
PLUTONIUM
ENVIRONMENTAL TRANSPORT
TERRESTRIAL ECOSYSTEMS
RADIONUCLIDE KINETICS
THORIUM
EROSION
GROUND WATER
RUNOFF
ACTINIDES
ECOSYSTEMS
ELEMENTS
HYDROGEN COMPOUNDS
MASS TRANSFER
METALS
OXYGEN COMPOUNDS
TRANSURANIUM ELEMENTS
WATER
510300* - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (-1989)
053000 - Nuclear Fuels- Environmental Aspects