Atomic Scale Modelling of Zirconium Alloys and Hydrogen in Zirconium
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Transcript of Atomic Scale Modelling of Zirconium Alloys and Hydrogen in Zirconium
Atomic Scale Modelling of Zirconium Alloys and Hydrogen in Zirconium By Simon Lumley
Supervised by Dr Mark Wenman, Prof. Robin Grimes and Dr Paul Chard-Tuckey
Modelling Zirconium
•Introduction: why model zirconium and hydrogen?
•Methods: density functional theory.
•Results: alloy solution energies.
•Results: lattice Strains.
•Future work.
Introduction: Zirconium
•The main component in the Zircaloy series of metals.
•Zircaloy is used in PWR, BWR and CANDU reactors.
•Its main use is as a fuel cladding material.
A PWR fuel assembly being placed into storage.
Introduction: Why Zirconium?
•Adequate mechanical and thermal properties.
•Good corrosion resistance.
•Low thermal neutron capture cross-section.
•But...It is subject to hydrogen embrittlement.
An optical micrograph of Zircaloy after heavy exposure to hydrogen.
Kim YS, Ahn SB, Cheong YM. J. Alloys Cmpds. 2007;429:221-226.
Introduction: Zirconium Alloys
Methods: Density Functional Theory
Kinetic Energy
Potential
Many Body Interaction
Electron Density Interaction
Methods: Solution Energies•The following cells were modelled in VASP:
• Done for niobium, tin and yttrium. Substitutional cells contained 54 atoms in total (1.85 at%).
Results: Solution Energies – Nb and Y
0.536 eV
-0.135 eV
0.178 eV
0.287 eV
Results: Solution Energies – Sn
-1.430 eV
-1.229 eV
Methods: Solution Energies - Intermetallics
Results: Solution Energies – Sn
0.2909 eV
0.3817 eV
Results: Lattice Strains
Y
SnNb
VCr
Fe
Future Work
• Extending solution energy calculations to other elements.
• Can we model hydrogen binding with intermetallic
phases?
• Does the lattice strain play a role in this?
• Do intermetallic compounds provided a location for
hydrogen to be absorbed.
Thank you for your time.
Any Questions?