Behavior of Cs and I in zirconia based fuel

A zirconia based ceramic is foreseen as an inert matrix fuel for burning excess plutonium in light water nuclear reactors. For reactor safety reasons the behavior of volatile fission products such as cesium and iodine must be studied since a retention of fission products is favorable for licensing the studied inert matrix fuel. In this study, implantation of Cs and I was performed into polycrystalline (Zr0.85, Y0.15)O1.925 samples. The implantation depth was selected on the basis of the ability to observe by Rutherford Backscattering spectroscopy (RBS) the behavior of Cs and I after treatment. With a 1 MeV incident energy, the ions are implanted at a depth of 200 nm as predicted by TRIM. After implantation full quantification of I and Cs concentration profiles was performed by RBS. The implantation profiles are measured as a function of sample temperature during stepwise heating programs. It is interesting to observe retention of Cs and I at relatively high temperature (e.g., for 2 h, below 900 K for Cs and below 1400 K for I). This behavior is likely to be due to the size and interactions of these species in the zirconia solid solution