Behavior of Fission Products in YSZ-Based Inert Matrix Fuel

Pu disposal has led to increased interest in the possibility of ''burning'' actinides in inert-matrix fuels. Yttria-stabilized cubic zirconia (YSZ) is a promising candidate material. The effects of fission product incorporation on the microstructure of YSZ (with 9.5 mol% of yttria) were investigated by ion implantation (using 70- to 440-keV Cs+, Sr+, and I+ ions) and transmission electron microscopy (TEM) in order to evaluate the material's performance as both an inert fuel matrix and a nuclear waste form. It was found that incorporation of an excess amount of cesium (>8 at.%) at room temperature causes amorphization of the cubic zirconia structure, which may lead to a higher leaching rate in the waste repository. On the other hand, iodine and strontium precipitate out in gas bubbles or secondary phases, respectively, at elevated temperature, leading to a lower release rate of the radionuclides