Dr Simon Gill, Reader in Mechanics of Materials, School of Engineering, University of Leicester, UK

Modelling the stress-driven reorientation of zirconium hydrides
When Feb 17, 2020
from 02:00 PM to 03:00 PM
Where LR1
Contact Name
Contact Phone 01865 273651
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Zirconium (Zr) and its alloys are used in nuclear fuel claddings and pressure tubes because of their low neutron absorption, good strength and corrosion resistance at high temperatures. Despite these desirable material properties, Zr alloys suffer from an important weakness. During operation in nuclear power plants, and in the storage period after usage, the Zr claddings are constantly being water-cooled, causing hydrides to form. These hydrides lead to embrittlement and fracture through delayed hydride cracking. Hydride orientation plays an important role in the embrittlement of the claddings and tubes. Radially oriented hydrides have been shown to be much more detrimental to mechanical properties than circumferentially oriented hydrides. Hydride reorientation occurs during the transition of nuclear fuel rods between wet and dry storage, during which the hydrides dissolve into the matrix as the temperature rises and then precipitate again upon cooling. Hydrides prefer to re-precipitate in the same location, but if a large tensile stress is present, they will reorient perpendicular to the load. A model is presented for investigating how the balance between the thermodynamic driving forces for phase change and the mechanical deformation lead to hydride reorientation.