Technetium Immobilization on Carbon Steel Corrosion Products Under Simulated Geological Radioactive Waste Repository...

Area of Science:

• Geochemistry
• Materials Science
• Environmental Science

Background:

• Technetium-99 (Tc-99) migration is a major concern for deep geological disposal of radioactive waste.
• Carbon steel (St3) is the proposed container material for vitrified waste at the Yeniseysky site DGR.
• Container degradation may expose steel to low-salinity solutions, leading to corrosion and Tc-99 release.

Purpose of the Study:

• To investigate technetium immobilization by carbon steel corrosion products.
• To simulate aerobic and anaerobic conditions relevant to the Yeniseysky site.
• To assess the impact of other repository materials on technetium immobilization.

Main Methods:

• Simulated repository conditions (aerobic/anaerobic) at the Yeniseysky site.
• Analysis of technetium immobilization by carbon steel corrosion products.
• Measurement of distribution coefficients (Kd) for technetium.

Main Results:

• Carbon steel acts as a chemical barrier, reductively immobilizing technetium.
• Ferrihydrite corrosion products showed the highest immobilization efficiency (Kd: 1.4–1.6 × 10³ cm³/g).
• Bentonite clay reduced immobilization by 50% due to adsorption of corrosion products.

Conclusions:

• Carbon steel containers contribute to technetium immobilization through reductive pathways.
• Repository material interactions, particularly bentonite, significantly influence technetium mobility.
• Findings are crucial for modeling long-term technetium behavior in geological repositories.