In-situ loading during irradiation of materials for fusion applications

The conditions materials will experience inside a fusion reactor are severe, combining high temperatures, loads and irradiation. In order to successfully design and construct a commercially-viable fusion reactor, we must have a good understanding of how the materials we use will perform during service. Unfortunately, our understanding of how structural alloys behave in conditions combining heat, load and irradiation is somewhat limited at present, and there in considerable interest in changing this. This project will aim to develop and utilise new advanced experimental capabilities in order to improve our understanding of the behaviours of alloys in fusion reactors.

The project will combine in-situ mechanical loading during proton and/or ion irradiation at Manchester's Dalton Cumbrian Facility (DCF) with high resolution characterisation post-irradiation. The project will develop mechanical rig capability on the irradiation beamline and use world-leading facilities for microscopy, microstructural analysis analysis and in-situ High Resolution Digital Image Correlation (HRDIC) as a novel deformation mapping technique, see Fig. 1. This will assess the effect of irradiation on material mechanics, providing data to aid in engineering design for STEP. By varying irradiation conditions - dose, temperature and strain rate - it will be possible to demonstrate how the variable irradiation conditions inside a fusion reactor affect material performance and therefore component lifetime. Previously, the HRDIC technique has proven highly effective in quantifying the differences in deformation between non-irradiated and irradiated zirconium alloys subjected to low damage levels [1]. Combining this analysis technique with in-situ irradiation-mechanical loading will make a significant contribution to the field and enable a more detailed understanding of the mechanisms of irradiation-induced effects, helping to improve materials - optimising them for fusion - and to validate models of material performance so that the models can be used as predictive tools for the harsh environment of a fusion power plant.

The PhD will be part of UKAEA's Spherical Tokamak for Energy Production (STEP) programme, which has been created to design and construct a prototype fusion energy plant. This PhD project will help inform the assessment of material performance when subjected to the harsh environments typically experienced during the fusion process, feeding into the experimental and modelling activities at UKAEA. Likely candidate materials for application in fusion reactors include martensitic steels, Cu-Cr-Zr alloys and Tungsten alloys. The performance of these materials depends how their mechanical properties are affected by the extreme operating conditions in a fusion reactor, especially the impact of creep and fatigue during the irradiation process.

The EPSRC Centre for Doctoral Training in Advanced Metallic Systems was established to address the metallurgical skills
gap, highlighted in several reports [1-3] as a threat to the competitiveness of UK industry, by training non-materials
graduates from chemistry, physics and engineering in a multidisciplinary environment. Although we will have supplied ~140
highly capable metallurgical scientists and engineers into industry and academia by the end of our existing programme,
there remains a demonstrable need for doctoral-level training to continue and evolve to meet future industry needs. We
therefore propose to train a further 14 UK based PhD and EngD students per cohort as well as 5 Irish students per
cohort through I-Form.

Manufacturing contributes over 10% of UK GVA with the metals sector contributing 12% of this (£10.7BN [4,5]) and
employing ~230,000 people directly and 750,000 indirectly. It is estimated that ~2300 graduates are required annually to
meet present and future growth [5]. A sizeable portion of these graduates will require metallurgical expertise and current
numbers fall far short. From UK-wide HESA data, we estimate there are ~330 home UG/PGT qualifiers in materials and
~35 home doctoral graduates in metallurgy annually, including existing AMSCDT graduates, so it is unsurprising that
industry continues to report difficulties in recruiting staff with the required specialist metallurgical knowledge and
professional competencies.

As well as addressing this shortfall, the CDT will also impact directly on the companies with which it collaborates, on the
wider high value manufacturing sector and on the UK economy as a whole, as follows:

1. Collaborating companies, across a wide range of businesses in the supply chain including SMEs and research
organisations will benefit directly from the CDT through:

- Targeted projects in direct support of their business and its future development and competitiveness.
- Access to the expertise and facilities of the host institutions.
- Involvement in the training of the next generation of potential employees with advanced technical and leadership skills
who can add value to their organisations.

2. The UK High-Value Manufacturing Community will benefit as the CDT will:

- Develop the underpinning science and advanced-level knowledge base required by future high technology areas, where
there is high expectation of gross added value.
- Provide an enhanced route to exploitation, by covering the full spectrum of technology readiness levels.
- Ensure dissemination of knowledge to the sector, through student-led SME consultancy projects, the National Student
Conference in Metallic Materials and industry events.

3. The wider UK economy will benefit as the CDT will:

- Promote materials science and engineering and encourage future generations to enter the field, through outreach
activities developed by the students that will increase public awareness of the discipline and its contribution to modern
life, and highlight its importance to future innovation and technologies.
- Develop and exploit new technologies and products which will help to maintain a competitive UK advanced
manufacturing sector, ensure an internationally competitive and balanced UK economy for future generations and
contribute to technical challenges in key societal issues such as energy and sustainability.

References:
1. Materials UK Structural Materials Report 2009
2. EPSRC Materials International Review 2008
3. EPSRC Materially Better Call 2013
4. The state of engineering, Engineering UK 2017
5. Vision 2030: The UK Metals Industry's New Strategic Approach, Metals Forum