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Alloy Design For A Fusion Power Plant

Explore the challenges and solutions in designing stable materials for fusion power plants, addressing activation and irradiation problems. Learn about radiation damage mechanisms and the role of numerical and neural network modeling in optimizing material properties.

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Alloy Design For A Fusion Power Plant

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  1. Alloy Design For A Fusion Power Plant Richard Kemp

  2. Objective • Design a material, with the right properties, that is stable under irradiation • One of the biggest problems in commercial fusion power research

  3. Fusion Power • Combination of light nuclei into heavier nuclei • Same process as occurs in the sun • Produces heat • Releases neutrons

  4. Surface Damage

  5. First Wall Material Design Problems • Activation • Swelling • Irradiation Hardening • Irradiation Creep

  6. Activation • Material becomes radioactive waste • Need low activation alloying elements

  7. Radiation Damage • Cascade formation of vacancies and interstitials • Often measured in dpa • Formation of defect structures • Preferential diffusion

  8. Radiation Damage - Cascades

  9. Radiation Damage

  10. Swelling • Transmutation helium produced in material • Bubbles form and grow • Macroscopic shape changes are undesirable

  11. Swelling

  12. Irradiation Hardening • Microstructural changes • Vacancy loops • Radiation induced precipitation • Helium bubbles • Shift in DBTT

  13. Irradiation Creep • Increased diffusion within material • Related to dose rate rather than temperature • Can lead to premature failure of material

  14. Solutions • Reduced activation steels • Low swelling steels • Careful study of changes of properties under irradiation

  15. Approaches • Numerical modelling • CULRAM and EASY software • Neural network modelling

  16. Numerical Modelling • Useful for solving systems of differential equations • Rate Theory approach Rate of change = diffusion + sources - sinks

  17. Neural Network Modelling • Used for fitting curves to points • Mechanical properties as a function of composition and heat treatment • Need a good data set! • RAFM database • Physically sensible inputs

  18. Neural Network Modelling • Irradiation hardening in F82H • Inputs: estimated increase in dislocation density and bubble size • Output: Increase in yield strength

  19. Neural Network Modelling

  20. Ongoing work • Modelling and optimisation of properties of low activation steels • Greater understanding of swelling processes and how to minimise this

  21. Acknowledgments • Harry Bhadeshia • Geoff Cottrell • Culham Labs

  22. Any questions?

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