Characterisation and development of advanced structural alloys for nuclear fusion reactors

Sparks, Tay Jonathan Zachary (2024). Characterisation and development of advanced structural alloys for nuclear fusion reactors. University of Birmingham. Ph.D.

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Abstract

The breeder blanket fulfils a crucial function in the design of future magnetically confined fusion reactors, allowing for harvest of energy emitted from the fusion reaction and production of tritium fuel. Several designs are considered for the breeder blanket, which employ different structural materials as supports for the breeding material. As a result of the breeder blanket’s proximity to the fusion plasma and bombardment by high energy fusion neutrons, candidate materials must exhibit resistance to high temperature and irradiation degradation, and easy component recycling after appreciably long lifetimes.
Front-runner candidate structural materials include the reduced activation ferritic martensitic steel EUROFER97, an oxide dispersion strengthened variant of EUROFER97, and the vanadium alloy, V-4Cr-4Ti. In this work high energy synchrotron X-ray diffraction during tensile testing is employed to characterise the microstructural evolution of these candidate structural materials at elevated temperature by way of the changing X-ray diffraction patterns collected during testing. Such characterisation allows for the determination of fundamental elastic properties (single crystal elastic constants, elastic modulus, Poisson’s ratio, etc) and evaluation of the dislocation density behaviour during deformation. Experimental characterisation of the high temperature elastic properties supplements and supports modelling work necessary in the development of breeder blanket structures, and dislocation density evolution shows the cause of temperature dependency in the EUROFER97/ODS EUROFER97 steels during tensile and cyclic testing through consideration of the constitutive flow stress and dislocation recovery mechanisms. The final experimental chapter looks beyond the currently considered candidate structural materials, considering the effect of tantalum addition on the mechanical properties of vanadium-based alloys, given tantalum’s excellent high temperature properties and low activation. A pilot scheme of laboratory scale V-Ti-(Cr)-Ta alloys were arc melted and heat treated – their mechanical properties assessed relative to V-4Cr-4Ti by means of micro- and macro- indentation hardness testing.
The 2020-2050 period is anticipated to be an important period for the development of fusion as an energy source, with several key fusion projects slated for fulfilment within this window. The results presented in this work can be used to contrast the high temperature performance of current candidate structural materials, and the basic mechanical properties of a proposed next generation structural material class against the existing.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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