TY  - CONF
A1  - Zencker, Uwe
T1  - Analysis of Zirconium Hydride Structures in Spent Fuel Claddings Subjected to Storage Conditions
N2  - Pre-storage drying and the early stage of storage can subject spent fuel claddings to higher temperatures and higher tensile hoop stresses than those associated with in-reactor operation. Under these conditions, existing circumferential hydrides in zirconium-based alloys can be partly reoriented into radial ones that may result in embrittlement of the cladding material. As a consequence, the failure limits may be reduced under mechanical loads caused by handling or during transport after storage. The potential occurrence of brittle fracture strongly depends on the specific location, size, and orientation of the zirconium hydrides. The morphology of such hydride structures was experimentally investigated in unirradiated, hydrogen-loaded samples made of a zirconium-based alloy. The hydrogen was introduced into the cladding sample by means of a cathodic charging process. The loading process was followed by a thermal treatment to precipitate the hydrides in the circumferential direction and then a thermomechanical treatment to reorient the hydrides in the radial direction. Metallographic methods were used to describe and classify the hydride morphology. The resulting metallographic micrographs were evaluated using suitable radial hydride metrics. The determination of the maximum length of a hydride structure was carried out in two different ways, each with its own advantages and disadvantages. Both methods consider neighboring hydrides as continuous according to the definition of the Radial Hydride Continuity Factor (RHCF). The first option is to measure the Euclidean distance between the two most distant pixels of the hydride structure in the image analysis, whereby the actual maximum size of the hydride structure is determined. The second possibility is to measure the maximum size of a hydride or a hydride structure within a certain arc length in the radial direction of the cladding tube. This value is of particular interest because the ratio of the maximum radial size of a hydride structure to the wall thickness of the cladding tube is used for the safety assessment of spent fuel claddings with radial hydrides using the RHCF.
T2  - 21st International Symposium on the Packaging and Transportation of Radioactive Materials - PATRAM 2025
CY  - San Antonio, TX, USA
DA  - 27.07.2025
KW  - Extended Interim Storage
KW  - Nuclear Fuel Cladding
KW  - Zirconium Hydride Structure
KW  - Ring Compression Test
KW  - Micrograph Analysis
PY  - 2025
AN  - OPUS4-63876
LA  - eng
AD  - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER  -