Investigation of the temporal rearrangement of zirconium hydride precipitates in cladding material for the interim and final storage period

Within the scope of the pending search for a final storage site location for highly radioactive waste such as used fuel assemblies, the cladding integrity in case of a relocation of the rod from an interim storage to a final storage cask remains uncertain. In order to assess the potential reduction of the rod integrity by hydride precipitation and reorientation, a study of the long-term behaviour of hydrides in Zircaloy 2 is carried out. The focus is on simulation and analysis of the precipitation behaviour under different load conditions such as starting temperatures of 673 K, hoop stresses of up to 150 MPa and cooling rates between 4 and 1 K/h. The analytical methods comprised microscopic investigations as well as X-ray diffraction analyses and first results from imaging with X-rays.