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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.

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Atomic Scale Modelling of Zirconium Alloys and Hydrogen in Zirconium

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  1. 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

  2. Modelling Zirconium • Introduction: why model zirconium and hydrogen? • Methods: density functional theory. • Results: alloy solution energies. • Results: lattice Strains. • Future work.

  3. 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.

  4. 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.

  5. Introduction: Zirconium Alloys

  6. Kinetic Energy Potential Many Body Interaction Electron Density Interaction Methods: Density Functional Theory

  7. 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%).

  8. Results: Solution Energies – Nb and Y -0.135 eV 0.287 eV 0.536 eV 0.178 eV

  9. Results: Solution Energies – Sn -1.430 eV -1.229 eV

  10. Methods: Solution Energies - Intermetallics

  11. Results: Solution Energies – Sn 0.3817 eV 0.2909 eV

  12. Results: Lattice Strains Fe Cr V Nb Sn Y

  13. Thank you for your time. Any Questions? 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.

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