Thermal behaviour of xenon in zirconium carbide at high temperature: Role of residual zirconia and free carbon

Transition metal carbides, such as ZrC, are interesting candidates used as structural and fuel cladding materials for the 4th generation Gas cooled Fast Reactors. A study has been carried out to elucidate the role of temperature on the diffusion of xenon in zirconium carbide. For that purpose, zirconium oxycarbide samples (ZrC0.95O0.05) have been prepared from powders synthesized by carbothermal route and sintered by Spark Plasma Sintering at 2125 K. Two batches have been studied in order to evaluate the role of the presence of free carbon and zirconia during high temperature annealing. The composition and microstructural features of the sintered samples such as stoichiometry, density and grain size have been determined using complementary analytical techniques such as Nuclear Backscattering Spectrometry, Electron Microscopy and elementary chemical analysis. Ions of 136Xe2+ have been implanted at an energy of 800 keV corresponding to a mean projected range of 160 nm and at an ion fluence of 1016 cm−2 corresponding to a maximum concentration of 1 at.%. Thermal annealing has been carried out in a temperature range from 1775 to 2075 K. The xenon distribution profiles have been measured by Rutherford Backscattering Spectrometry before and after the different treatments. The results show that the presence of residual zirconia induces a strong damage of the surface and that pure ZrC sintered specimen display less degradation of the surface and better retention capabilities for xenon.