Steady-state Rn diffusion through tailings and multiple layers of covering materials

Area of Science:

• Environmental Science
• Geochemistry
• Nuclear Engineering

Background:

• Uranium tailings require rehabilitation to mitigate environmental risks.
• Covering tailings with earthen layers is a common rehabilitation strategy.
• Radon (Rn) gas emission is a primary concern from uranium tailings.

Purpose of the Study:

• To derive exact equations for radon concentration and flux attenuation through multi-layered covers.
• To analyze the influence of material properties and layer order on radon flux attenuation.
• To evaluate the accuracy of approximate methods compared to exact solutions.

Main Methods:

• Derivation of analytical equations for radon transport in layered media.
• Inclusion of radon partitioning between interstitial air and water.
• Numerical simulations to demonstrate errors in approximate methods.

Main Results:

• Exact equations accurately predict radon concentration profiles and flux attenuation.
• Flux attenuation is dependent on layer properties (diffusion, porosity, moisture, thickness) and placement order.
• Approximate methods can lead to significant errors in specific scenarios.

Conclusions:

• The derived exact equations provide a robust tool for designing effective radon barriers.
• Layering materials with the least permeability at the top maximizes radon flux attenuation.
• Accurate modeling is essential for effective uranium tailings rehabilitation.