Mechanisms of Radiation Damage and Properties of Nuclear Materials
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1215-V04-01
Mechanisms of Radiation Damage and Properties of Nuclear Materials Gregory R. Lumpkin1, Katherine L. Smith1, Karl R. Whittle1, Bronwyn S. Thomas1, and Nigel A. Marks2 1 2
Australian Nuclear Science and Technology Organisation, Menai, NSW, Australia Nanochemistry Research Institute, Curtin University of Technology, Perth, WA, Australia
ABSTRACT Radiation damage effects in ceramics, e.g., nuclear waste forms, transmutation targets, and inert matrix fuels, may have important implications for the physical and chemical stability of these materials as the cumulative radiation dose increases over time. A key aspect of scientific research in this area is the ability to understand the fundamental damage mechanisms through the combination of experimental and atomistic modelling techniques. In this paper, we review some of the lessons learned from the significant body of data now available for pyrochlore-defect fluorite based materials, followed by an illustration of the advantages of working on simple compounds with well established interatomic potentials. We conclude the paper with a description of radiation damage processes in the LaxSr1-1.5xTiO3 defect perovskites, a system that includes phase transformations, short-range order effects, and complex defect behavior. INTRODUCTION Ceramic waste forms have been considered for many years to be viable alternatives for the disposal of nuclear waste in geological repositories. A major issue for waste forms is their behavior in response to alpha-decay damage and the presence of aqueous fluids for time scales on the order of 102 years for short-lived radionuclides (e.g., 90Sr, 137Cs) up to 103-6 years or more for long-lived fission products and minor actinides. Radiation damage effects in these materials are studied using minerals from various geological systems, synthetic materials doped with short-lived (e.g., 238Pu, 244Cm) or medium-lived actinides (e.g., 239Pu), or samples subjected to controlled irradiation sources, including electrons, alpha particles, neutrons, and ions. In the latter case, both bulk materials and thin TEM specimens can be irradiated as a function of ion mass and energy. In this report, we review some of the available data obtained by ion irradiation of TEM samples of pyrochlore-defect fluorite compounds, the TiO2 polymorphs, and the La-Sr defect perovskites. The purpose of this paper is to illustrate some of the potential advantages of combining the experimental work with atomistic simulations of the threshold displacement, defect formation, and migration energies of the constituent atoms present in these crystalline compounds in order to understand variations in the radiation tolerance. EXPERIMENTAL PROCEDURES All of the ion irradiation experiments discussed in this paper have been conducted by various groups on thin TEM samples with 0.8-1.5 MeV Kr ions at the IVEM-Tandem Facility or the (now decommissioned) HVEM-Tandem Facility at Argonne National Laboratory. Readers are referred to the cited literature for information relating to the specif
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