The Precipitation of Hydrides in Zirconium Alloys

  • Matthew Blackmur

Student thesis: Phd


This alternative format thesis is submitted by Matthew Sebastian Blackmur to The University of Manchester for the degree of Doctor of Philosophy in the year of 2015, entitled "The Precipitation of Hydrides in Zirconium Alloys". The thesis first introduces the topic of nuclear energy and provides a brief section on plant familiarisation, after which zirconium nuclear fuel cladding is explained, and an in-depth literature review is presented on the in-service degradation of this component from hydriding. The concept of synchrotron X-ray diffraction is elucidated, and examples of its use are given, relevant to the topic of this work.The experimental section discusses an initial quantification of the Zircaloy-4 material used throughout the present work, and documents in minutia the process of collecting and analysing in-situ synchrotron X-ray diffraction data. The experimental campaign discussed within involved a series of consecutive thermal cycles designed to investigate the redistribution of hydrogen as a function of thermal and concentration gradients; the kinetics of precipitation during isothermal dwells at reactor relevant temperatures; and the evolution of strain in the matrix and hydride during these dwells. As an alternative style thesis, these three topics are separated into three independent proposed manuscripts, produced in a format ready for publication.The diffusion and redistribution paper observes localised enrichment and depletion that occurs as a function of time and temperature, investigating the flux of hydrogen that results from concentration and thermal gradients, and introduces the concept of hydrogen trapping. The second manuscript documents evidence of the rate limiting kinetics for hydride precipitation seen at elevated temperatures, and describes a model for nucleation, developed to support the experimentally produced results. The final manuscript investigates the nature of the strains that evolve in the matrix and hydride phases during precipitation and growth, highlighting slow-strain rate relaxation in both phases and examining the constraining effect that the matrix has on the hydride precipitates.Lastly, the themes from each of the three manuscripts are drawn together in a final conclusion, after which further experimental analysis that is to be performed as part of this experimental campaign is outlined.
Date of Award31 Dec 2015
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorMichael Preuss (Supervisor) & Joseph Robson (Supervisor)


  • Nucleation
  • Diffusion
  • Strain Evolution
  • Kinetics
  • Synchrotron
  • Zircaloy-4
  • Hydrides
  • X-Ray Diffraction
  • Zirconium

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