How mobile is tritiated water through unsaturated cement-based materials? New insights from two complementary...

Area of Science:

• Materials Science
• Nuclear Engineering
• Environmental Science

Background:

• Understanding radionuclide transport in cementitious materials is crucial for nuclear waste management.
• Tritiated water (HTO) poses a significant challenge due to its mobility.

Purpose of the Study:

• To investigate the diffusion of tritiated water (HTO) in unsaturated cement-based materials.
• To compare HTO diffusion rates with gaseous hydrogen (H2) under similar conditions.

Main Methods:

• Employed two complementary experimental approaches: osmosis-controlled suction and humidity chamber diffusion.
• Measured HTO diffusion coefficients across a range of material saturation degrees.

Main Results:

• A significant decrease in the effective diffusion coefficient of HTO was observed as saturation decreased.
• HTO diffusion was found to be approximately four orders of magnitude slower than H2 diffusion in unsaturated cement.

Conclusions:

• Cement-based materials exhibit reduced HTO permeability with decreasing saturation.
• The slow diffusion of HTO suggests the potential efficacy of cementitious barriers for containing tritium.