Impeding (99)Tc(IV) mobility in novel waste forms.

Area of Science:

• Materials Science
• Nuclear Chemistry
• Geochemistry

Background:

• Technetium (Tc) is a mobile, long-lived radioactive fission product.
• Its mobility is primarily dictated by its oxidation state in subsurface environments.
• Immobilizing Tc is critical for radioactive waste management and environmental remediation.

Purpose of the Study:

• To investigate methods for enhancing technetium retention in glass waste forms during vitrification.
• To address the reoxidation of Tc(IV) to volatile pertechnetate (Tc(VII)) under high-temperature, oxic conditions.
• To explore the potential of doping spinels with transition metals to improve Tc immobilization.

Main Methods:

• Ab initio molecular dynamics simulations were employed to study Tc behavior at elevated temperatures.
• Experiments were conducted using doped spinels at 700°C to validate simulation predictions.
• The study focused on the effects of first-row transition metal doping (Co, Zn, Ni) in magnetite.

Main Results:

• Simulations predicted that doping magnetite with transition metals enhances Tc retention, with an order of effectiveness: Co > Zn > Ni.
• Experimental results at 700°C quantitatively confirmed the theoretical predictions.
• The study identified specific dopants that significantly improve Tc retention in magnetite.

Conclusions:

• Doping magnetite with specific transition metals is a viable strategy for enhancing technetium immobilization.
• Ab initio molecular dynamics simulations are powerful tools for designing advanced materials for nuclear waste management.
• This research provides theory-inspired design criteria for complex materials at elevated temperatures, crucial for radioactive waste containment.