Mechanical properties of stabilized zirconia and zirconate pyrochlore were evaluated by experiment, MD simulation and ab initio calculation.

Ion irradiation induced phase transformations in three normal spinel compounds MgAl2O4, MgCr2O4 and ZnAl2O4 have been investigated by X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy. This work presents a unified framework to describe the radiation effects in normal spinels. Irradiation modifies the atomic and mesoscopic structures of theses spinels in different ways. At the atomic scale, it produces the inversion of the cations in the spinel structure which can always be described within its usual Fd-3m space group. At the mesoscopic scale, it produces microdomains, responsible for the important changes in the X-ray diffraction patterns.

PuO2 and AmO2 solid solutions: (Pu, Am)O2 are one of the candidates of fuels in a sub-critical accelerator-driven system (ADS). To understand the fuel performance, the thermophysical properties such as thermal conductivity and heat capacity are quite important. However, it is very hard to experimentally determine the physical properties of plutonium as well as americium compounds due to their handling-difficulties. Molecular dynamics (MD) would be a specific method to describe the physical properties of such materials. In the present study, we have investigated thermophysical properties of PuO2, AmO2, and their solid solutions in the temperature range from 300 to 2,500 K. The lattice parameter, compressibility, heat capacity, linear thermal expansion coefficient, and thermal conductivity were evaluated. A Morse-type potential function added to the Busing-Ida type potential was employed as the potential for interatomic interactions. The calculated lattice parameters of (Pu, Am)O2 obeyed Vegard's law, and the values increased with temperature. The heat capacities of (Pu, Am)O2 were similar in any compositions. The thermal conductivities of (Pu, Am)O2 were lower than those of PuO2 and AmO2, indicating that a point-defect scattering effect of phonons could be realized in the MD calculations.

Atomic scale computer simulation based on a density functional approach was used to predict the behaviour of uranium, zirconiumand titanium nitrides. In addition to perfect lattice structures, defects associated with nonstoichiometry were also considered. Predictions were favourably compared with experimental data.

Three kinds of Fe-based model alloys, Fe-0.02wt%Cu, Fe-0.6wt%Cu, and Fe-1.2wt%Cu were irradiated with 2MeV electrons at 250°C. After the irradiation, the hardness was measured by using a micro Vickers hardness tester at room temperature. It was found that the hardness change by electron irradiation is proportional to the product of the copper concentration and the square root of electron fluence. The result is discussed in terms of the dispersion strengthening by Cu precipitates.

Development of structural materials is historically a long and costly process, particularly for nuclear energy applications due to the long proof testing period to validate the performance of the material in the hostile irradiation environment. Utilization of recently developed materials science tools including computational thermodynamics and multiscale radiation damage computational models in conjunction with rapid science-guided experimental validation (nonirradiation and irradiation environments) may offer the potential for a transformational reduction in the time period to develop and qualify structural materials for advanced nuclear energy systems. Several examples of rapid development of high-performance structural materials will be given, with a focus on austenitic and ferritic/martensitic steels (less than two years from project initiation to commercial production of multi-ton prototypic heats). In many cases, the key for development of improved mechanical properties and superior radiation stability is the presence of a uniform high-density dispersion of highly stable nanoscale particles. This research was sponsored in part by the Office of Fusion Energy Sciences, U.S. Department of Energy under contract DE-AC05-00OR22725 with UT-Battelle, LLC.