Abstract
Based on the results of electron back scattered diffraction (EBSD) analysis of samples hydrogenated at temperatures from 900 to 1200 K (which is a typical temperature range for loss-of-coolant accident (LOCA)) some questions related to hydrogen embrittlement of zirconium and Zircaloy - 4 are being discussed in the present work. These questions affect: hydride origination and development; evolution of microstructure and microtexture; material properties degradation; the application of already known hydrogen embrittlement mechanisms (due to hydride formation, hydrogen-enhanced decohesion, hydrogen-enhanced localised plasticity); a hydrogen-induced crack initiation and propagation phenomena detected inside the furnace at constant temperature of 1000 and 1100 K. The Scanning Electron Microscopy of the ruptured surface was performed to observe the fracture behaviour with respect to hydrogen content. Change in lattice parameters "a" and "c" of hexagonal close-packed α zirconium lattice and the presence of δ - and γ - hydrides were measured after each hydrogenation test by means of the X - ray diffraction (XRD) analysis. This series of experimental tests was performed at Karlsruhe Institute of Technology (KIT) in the framework of the new QUENCH-LOCA program.
