A preliminary study of the controls on melting during in situ vitrification
In situ vitrification (ISV), developed by Pacific Northwest Laboratory and patented for the US Department of Energy, is one method used to stabilize contaminated soils in place. ISV involves inserting four electrodes in a square array into contaminated soil and applying an electrical potential to the electrodes. The soil is heated to above its melting point, and the molten zone expands with time to encompass the contaminated zone. After cooling, the resulting solid material is usually a mixture of glass and crystalline material that has a significantly higher resistance to leaching than did the original soils. Nonvolatile elements (most radionuclides and metals) are dissolved into the melt or encapsulated in glass if their solubility in the melt is low. Organic compounds tends to be pyrolyzed, with the decomposition products diffusing to the surface and combusting on exiting the molten zone. A hood is placed over the vitrification zone to collect off-gas particulates and volatiles into a processing trailer that scrubs contaminants from the off-gas. The current study identified key parameters and processes in the ISV melt cycle and developed an improved understanding of ISV. Analytical approximations for several properties of molten soil were determined from available data. Using a simplified geometrical approximation for melt geometry, an analytical approximation for the rate of melting (depth) vs time was derived that is consistent with data from field experiments. At small times, the depth of melting increases linearly with time. After approximately 10 h in large-scale tests, however, the depth increases as the square root of time. Existing data is also consistent with a relationship that shows the volumetric growth rate of the melt to be directly proportional to time. These conclusions suggest that heat transfer processes controlling the ISV process may be at the transition between weak convection and conduction.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5866840
- Report Number(s):
- ORNL/ER-30; ON: DE92008025
- Resource Relation:
- Other Information: Environmental Sciences Division Publication 3608
- Country of Publication:
- United States
- Language:
- English
Similar Records
In situ vitrification: Test results for a contaminated soil melting process
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
HAZARDOUS MATERIALS
VITRIFICATION
SOILS
IN-SITU PROCESSING
MELTING
HEAT TRANSFER
LEACHING
TIME DEPENDENCE
DISSOLUTION
ENERGY TRANSFER
MATERIALS
PHASE TRANSFORMATIONS
PROCESSING
SEPARATION PROCESSES
540220* - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)
540230 - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (1990-)
052001 - Nuclear Fuels- Waste Processing