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Updated: Aug 6, 2025
12:22
Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films
Published on: November 9, 2015
11.4K
Evolving radon diffusion through earthen barriers at uranium waste disposal sites
Mark Fuhrmann1, Todd G Caldwell2, William J Likos3
1Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Rockville, MD, 20852, USA.
Journal of Environmental Radioactivity
|March 22, 2023
Summary
Compacted clay radon barriers show effective radon diffusion coefficients (DRn) influenced by preferential pathways, not just water saturation. These findings assess long-term cover performance at uranium waste disposal sites.
Area of Science:
- Geotechnical Engineering
- Environmental Science
- Radiological Protection
Background:
- Compacted clay barriers are crucial for isolating radioactive waste.
- Assessing long-term performance of engineered barriers is vital for environmental safety.
- Radon-222 (Rn) gas migration is a key concern in uranium waste disposal.
Purpose of the Study:
- To evaluate the performance of compacted clay radon barriers after 20 years.
- To determine effective radon diffusion coefficients (DRn) in situ.
- To investigate the influence of water saturation on DRn and identify factors affecting barrier performance.
Main Methods:
- Field measurements of Rn-222 fluxes from clay barrier surfaces.
- Calculation of effective DRn using field data.
- Analysis of soil core samples to determine water saturation (SW).
Main Results:
- Effective DRn values ranged from 6.0 × 10-9 to 7.4 × 10-7 m2/s, averaging 1.42 × 10-7 m2/s.
- Water saturation had less control over DRn than predicted by steady-state models, especially at higher moisture levels.
- Preferential pathways (cracks, root channels, burrows) significantly influenced DRn, requiring model modifications to account for fast and slow diffusion pathways.
Conclusions:
- Engineered earthen barriers exhibit complex DRn behavior influenced by structural heterogeneities.
- Modified diffusion models incorporating preferential pathways provide a better representation of field data.
- Understanding these pathways is critical for accurate long-term performance predictions of radon barriers.
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