Synchrotron X-Rays for Microstructural Investigations of Advanced Reactor Materials
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I.
INTRODUCTION
ADVANCED future nuclear (Generation IV) fission and fusion plants require materials that sustain extreme service conditions, such as temperatures of up to 1000 C, irradiation damage of more than 100 displacement per atom (dpa), and hostile environments such as impure helium, sodium, liquid metal, or water.[1] These conditions can cause thermally- or irradiation-induced microstructural changes and defects in the materials. Degradation of the materials due to static loads (creep) and alternating loads (fatigue) must also be taken into account. An additional challenge concerns the lifetime of some components, such as pressure vessels or core internals, where 60 years of service are envisaged. Methods for damage assessment under these conditions are required not only for established materials, but also for newer materials that have inadequate long-term assessment databases. A powerful methodology to predict and design materials and their behavior is the multiscale approach, which combines mechanical testing of sample sizes ranging from large scale to subsized complemented with synergistic multiscale modeling.[2] Although failure of a component is usually considered as a macroscopic event, the main portion of damage during exposure time occurs on a microscopic and even nanoscopic level. The determination of the dependence of
local mechanical properties from the microstructure is therefore of utmost importance. X-ray beamline techniques provide very powerful tools for analyzing material damage at the microscopic level, which are complementary to the well-established techniques of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Table I lists the main properties of advanced X-ray beamline techniques relevant to damage characterization. Reliable modeling of materials necessitates experimental validation. Comparison must be done at the microstructural level, indicating the significance of using the microstructural techniques available at synchrotron irradiation facilities in this field. Extended X-ray absorption fine structure (EXAFS) and X-ray magnetic circular dichroism (XMCD) coupled with photoemission electron microscopy (PEEM) are used as examples of synchrotron techniques to demonstrate their application to advanced microstructural analysis. The work presented in this article concerns three materials that are currently under worldwide investigation for advanced fission applications: an oxide dispersion strengthened (ODS) ferritic steel (PM2000), a zirconium alloy (Zircaloy), and binary Fe-Cr alloys, which are the basis of many ferritic steels.
II.
EXPERIMENTAL DETAILS
A. Materials WOLFGANG HOFFELNER, Project Manager, and ANNICK FROIDEVAL, MANUEL POUCHON, JIACHAO CHEN, and MARIA SAMARAS, Scientists, are with the Paul Scherrer Institute, Nuclear Energy and Safety Department, CH-5232 Villigen PSI, Switzerland. Contact e-mail: wolfgang.hoff[email protected] This article is based on a presentation given in the symposium entitled ‘‘Materials Issues for Advanced Nuclear Systems,’’ whic
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