Intercomparison of diffusion coefficient derived from the through-diffusion experiment using different numerical...

Area of Science:

• Geochemistry and Environmental Science
• Nuclear Engineering and Safety
• Radiochemistry

Background:

• Diffusion is a primary process governing the movement of released radioactive nuclides.
• The through-diffusion method is standard for determining diffusion coefficients (D).
• Existing models (CC-CC, CC-VC, VC-CC, VC-VC) have limitations, with VC-CC models being understudied.

Purpose of the Study:

• To develop analytical methods for interpreting radioactive nuclide diffusion experiments, incorporating decay effects.
• To introduce simplified formulas for CC-CC and CC-VC models to determine diffusion coefficients.
• To propose new methods for straightforward diffusion coefficient determination using the VC-VC model.

Main Methods:

• Development of CC-CC and CC-VC models that account for radioactive decay.
• Derivation of simplified formulas for the CC-CC and CC-VC methods.
• Proposal of two simplified VC-VC methods based on concentration changes in the inlet (IR) and outlet (OR) reservoirs.

Main Results:

• The proposed methods enable the determination of three diffusion coefficients from a single experiment.
• Validation against existing data shows comparable diffusion coefficients within the same order of magnitude.
• A formula for conceptual critical time (Tc) is introduced to guide the selection between CC-VC and VC-VC methods.

Conclusions:

• The developed analytical methods improve the accuracy of diffusion coefficient determination in radioactive nuclide transport.
• The new approaches offer a more efficient way to analyze through-diffusion experiments, reducing experimental time.
• The ability to derive multiple coefficients and determine critical time enhances the applicability and utility of through-diffusion testing.