Characterisation of Castable Nanostructured Alloys for Nuclear Fusion Applications (Materials Strand project)

Supervisor/s – Paul Mummery, Aneeqa Khan & Ed Pickering (University of Manchester). Huw Dawson (UKAEA)

The current generation of structural steels in nuclear fusion reactors are limited to a maximum operating temperature of 550°C [1], limiting the life of breeder blankets to 5 years. The breeder blanket is the critical structural component that houses the coolant and fuelling systems for fusion reactors. These values are unsuitable for producing a cost-effective commercial reactor and significantly better lifetimes are required. The lifetimes and upper temperature limit are controlled by the creep performance under irradiation. Therefore, it is considered vital to develop new steels with better creep and irradiation damage resistance, with excellent high-temperature stability.

UKAEA is focusing efforts to develop new alloys that can meet these new performance criteria. These alloys are being referred to as Castable Nanostructured Alloys (CNAs) since they are made through ‘traditional’ casting routes and benefit from a high density of nanoparticles in their microstructure to achieve their irradiation damage resistance and high temperature performance. This proposed work represents an important early crucial step in what is planned to be a sustained effort to develop the alloys to attain the performance required and move the alloys up the technology readiness levels; to the point where the same properties can be produced confidently and economically by industry.

An initial run of nitrogen-containing CNAs has already been cast, using thermo-mechanical treatments to introduce a high density of dislocations into the crystal structure, which then in turn act as nucleation sites for the carbo-nitrides, resulting in a high density of stable nano-precipitates. Some initial characterisation work (SEM/XRD) has identified some precipitates, but further work is needed for a fuller characterisation of the nanostructure of the material (TEM/high-resolution XRD) as well as high temperature mechanical properties. Also planned are further runs of casts, with more significant alterations to the alloy composition, such as reduction in carbon content and increase in precipitate formers to weigh the relative proportions of M23C6 and MX precipitates toward the smaller, more stable MX precipitates, as well as optimisation of the thermo-mechanical treatment.

This PHD project will focus on detailed analysis of the CNAs using a variety of techniques including microscopy and diffraction techniques at the national lab facilities at Harwell. This characterization will feed into materials development as part of the UKAEA STEP programme.

[1] Zinkle, S. J. et al. 2017. Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications. Nucl. Fusion 57.

The project will mainly be based at Manchester but will work closely with UKAEA . There may also be opportunities to use the national lab facilities at Harwell as well as collaborating with other labs.

This project is offered by The University of Machester. For further information please contact: Aneeqa Khan (Aneeqa.khan@manchester.ac.uk)

This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.