The encapsulation selectivity for anionic fission products imparted by an electride

Area of Science:

• Materials Science
• Nuclear Engineering
• Computational Chemistry

Background:

• Nanoporous materials like 12CaO·7Al2O3 (C12A7) can host extra-framework species within their stable structures.
• Understanding the encapsulation of volatile fission products is crucial for nuclear waste management.

Purpose of the Study:

• To predict the efficacy of C12A7 in encapsulating volatile fission products using atomistic simulations.
• To compare the encapsulation capabilities of stoichiometric C12A7 and its electride form.

Main Methods:

• Atomistic simulations were employed to model the encapsulation process.
• Calculations were performed for both stoichiometric and electride forms of C12A7.
• Encapsulation energies for various fission products (Xe, Kr, Cs, Br, I, Te, Rb) in atomic and dimer states were evaluated.

Main Results:

• Stoichiometric C12A7 strongly encapsulates Br, I, and Te as anions, weakly encapsulates Rb, and does not capture Xe, Kr, or Cs.
• The electride form of C12A7 significantly enhances the encapsulation of Br, I, and Te as stable anions.
• Multiple Br, I, and Te anions can be successively encapsulated in adjacent cages.
• Xe, Kr, Rb, and Cs are not encapsulated in the electride form.
• Encapsulation of dimers (e.g., Br2, CsBr) within a single cage is unfavorable.

Conclusions:

• C12A7 exhibits species selectivity for encapsulating volatile fission products, particularly Br, I, and Te.
• The electride form of C12A7 demonstrates superior performance for capturing these specific fission products.
• C12A7 presents a promising material for selective separation and immobilization of hazardous fission products.