Beamline Investigations on Advanced VHTR Materials

W. Hoffelner (Sp), M. Pouchon, C. Degueldre, Paul-Scherrer-Institute, Villingen (Switzerland) 
In order to meet the requirements of very high temperature reactors, materials must be able to operate at temperatures above 900 C, in impure helium and - if close to the core or in core - also under irradiation. Reliable life-time prediction under these conditions requires information on microstructural damage. Conventional methods of damage analysis suffer either from the fact that mainly surface areas are monitored or that thin foils are investigated (TEM) where particularly bulk properties like stress distributions in and around inclusions or stress dependent phase transitions might not be properly represented. With the availability of synchrotron X-rays bulk material properties can be investigated and also in-situ analyses for thermal treatment or creep can be performed. X-ray diffraction as well as X-ray absorption can be used for microstructural analyses. The paper will demonstrate some capabilities of beamline techniques taking oxide dispersion strengthened materials, intermetallics and ceramics for gas cooled reactor applications as an example.

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