Investigating extreme lattice strain in zirconium Hydrides through thermomechanical testing of differing hydride morphologies

Zirconium continues to be the primary structural material for use in nuclear reactor cores but prolonged exposure to the reactor environment leads to the absorption of hydrogen and eventual precipitation of hydrides. The presence of hydrides can lead to failure of fuel cladding if handled incorrectly and continues to be a concern in post use fuel transportation and storage. Previous in-situ SXRD studies have shown the evolution of lattice strains of up to 25,000 microstrain within hydrides which is at odds to its expected brittle nature. It has been hypothesised that a stress induced phase transformation in the hydride is responsible for the unusual lattice strain development however, others believe this response is due to load shedding from the matrix to the hydride. An investigation is proposed where the phase stability and size effect is utilised to identify the mechanism resulting in the unexpectedly large lattice strains observed in the hydrides.