GARS Directorate Seminar
"Determination of UO2 Thin Films Mechanical Properties Under Heavy Ion Irradiation Using Nanoindentation and Finite Element Modeling"
Presented by Mohamed Elbakhshwan, University of Illinois at Urbana Champaign
Monday, April 1, 2013, 10 am
Building 130, Modular Conference Room
Hosted by: Dr. Simerjeet Gill and Dr. Lynne Ecker
The mechanical response of uranium oxide fuel to displacement cascade damage is important due to a shift toward higher fuel burn up. In addition, mechanical properties of nuclear fuel have a special importance in the pellet cladding mechanical interaction. During the reactor transient periods, the cladding failure depends not only on the ductility of the cladding materials but also on the level of stresses developed into the fuel material and induce cracks on the fuel surface which depends on the fuel thermal expansion, thermal conductivity and the elastic properties of the fuel. All studies have been done on bulk samples; as technology advances, thin film geometry allows control over several properties such as microstructure, oxygen stoichiometry, and impurity concentrations, as well as to use the microanalytical techniques optimized for thin film geometry. This new ability opens the door to advance our knowledge and understanding of the behavior of uranium oxide under different conditions of irradiation and temperatures in the nanoscale, which can lead to better burn up performance and longer lifetime. In addition, thin films can give the ability to study the effect of displacement cascade damage with and without the effect of fission gas implantation and/or gas bubble formation by controlling the bombardment energy and the film thickness. This will give the ability to distinguish between the two effects and represent a reference for radiation damage simulation studies. The change in mechanical properties of single crystal uranium oxide thin films have been studied as a function of displacement cascades damage and fission gas concentration using heavy ion bombardment of 1.8 MeV Ar+ and 0.6 MeV Xe+/Kr+ respectively. The nanoindentation technique has been used to calculate the hardness and elastic modulus of irradiated thin films at different radiation doses and as a function of indentation depth. Finite element modeling is used