Characteristics of GdxMyOz (M = Ti, Zr or Al) as a burnable absorber

A heterogeneous type burnable absorber needs a diluent material to adjust its gadolinium concentration. TiO2, ZrO2 or Al2O3 was added to Gd2O3, separately and GdxMyOz (M = Ti, Zr or Al) pellets were fabricated by a powder process. Pellets with a single Gd2TiO5 or Gd2Ti2O7 were fabricated and their phases were confirmed by XRD. Thermal properties of the GdxMyOz were measured and their thermal conductivities were determined. The thermal expansion was largest in Gd2Ti2O7, and it decreased with a gadolinium concentration increase. GdAlO3 had the highest thermal conductivity, next were the GdxTiyOz phases in a reverse order of the gadolinium concentration increase. The selected candidate pellets of GdxTiyOz were irradiated in the HANARO reactor, and post-irradiation examinations of the pellets were carried out in a hot cell. The examination results indicate that the thermal properties of the BP pellets should be considered to ensure an in-reactor integrity.