Thermal conductivity and the isotope effect in Li2O

Highlights: ► The thermal conductivity of Li2O as calculated using molecular dynamics is in good agreement with experiment. ► At low temperatures the isotope affect is found to be significant. ► At higher, reactor operating, temperatures, the influence of the isotope effect becomes negligible. - Abstract: The thermal conductivity of condensed matter can be reduced through the introduction of isotopic disorder as the different isotopes act as mass defects that scatter phonons responsible for the transfer of heat energy. Here we investigate, using classical molecular dynamic simulations, the magnitude of this effect in the ceramic oxide Li2O, which will be artificially enriched with 6Li to improve tritium breeding potential in a future fusion reactor. The results show that while the isotope effect will be important at lower temperatures it has little influence at the expected operating temperatures of the breeder blanket.