Heavy ion induced damage in MgAl2O4, an inert matrix candidate for the transmutation of minor actinides

Magnesium aluminum spinel (MgAl₂O₄) is a material selected as a possible matrix for transmutation of minor actinides by neutron capture or fission in nuclear reactors. To study the radiation stability of this inert matrix, especially against fission product impact, irradiations with heavy energetic ions or clusters have been performed. The high electronic energy losses of the heavy ions in this material led to the formation of visible tracks as evidenced by transmission electron microscopy for 30 MeV C₆₀-Buckminster fullerenes and for ions of energy close to or higher than fission energy (²⁰⁹Bi with 120 MeV and 2.38 GeV energy). The irradiations at high energies showed a pronounced degradation of the spinel. Additionally, MgAl₂O₄ exhibited a large swelling for irradiation at high fluences with fission products of fission energy (here I-ions of 72 MeV) and at temperatures ≤ 500 °C. These observations are discussed from the technological point of view in the frame of using MgAl₂O₄ as an inert matrix for the transmutation of minor actinides.