Lithium containing Ceramics for tritum breeding

In all future nuclear fusion power production reactors, tritium must be bred in tritium breeding modules (TBMs) and then fed back into the fusion reactor. Two different generic designs have been proposed for TBMs, a liquid breeder in which lithium is in the form of either a low melting point eutectic metal or molten ionic salt, or solid breeders where the lithium is included in ceramic pebbles. Each design has technical advantages and disadvantages, and further fundamental work is needed to define the best choice for future reactor designs. This project will work closely with a leading fusion company, Tokamak Energy, to assess whether the proposed solid ceramic breeder materials can survive under in-service conditions. Compounds to be studied include lithium orthosilicate and lithium titanate, which are already widely available, and also materials like Li8ZrO6 , Li8PbO6 and Li6MnO4 that have been identified as attractive tritium breeding materials with a higher lithium content, but are not commercially available. Synthesis routes for these materials will be investigated as part of the project.
The key questions that will be explored will be the effect of radiation damage on the mechanical properties of these compounds at ambient and operational temperatures, and microstructural evolution during the irradiation process using both in-situ ion irradiation and ex-situ studies. Understanding how the mechanical properties of these materials change over time is critical for designing a robust TBM with acceptable lifetime and to allow safe disposal at end of life.

The project has two parts synthesis and characterisation of irradiation performance. In the first part novel lithium rich compounds will be synthesised through a ball milling and sintering route. This will include zirconates which are attractive from a neutronics point of view. These will be assed from a density, microstructure and micromechanical point of view.

The student will use recently installed facilities for the study of the mechanical properties and microstructure of lithium ceramic, including micro tensile and nanoindentation equipment in a dedicated SEM-glovebox system with EBSD and EDX capabilities available up to 800oC. State of the art analytical techniques, including FIB-SIMS for local Li mapping and high speed STEM from chemical mapping.

In the second part ex-situ irradiation damage will be studied using the cyclotron at the University of Birmingham and in-situ damage studies at the MIAMI2 facility in the University of Huddersfield. In both cases TEM will be used to study irradiation damage and Li-loss processes and the formation of helium bubbles. These processes are likely to be life limiting from a stability point of view and a deeper understanding of the degradation mechanisms will be used to inform microstructural design. This project offers the opportunity to work closely with Tokamak Energy staff on a problem key to the successful design of future small fusion tokamaks. This project is in the energy theme.

Identifying a sustainable energy supply is one of the biggest challenges facing humanity. Fusion energy has great potential to make a major contribution to the baseload supply - it produces no greenhouse gases, has abundant fuel and limited waste. Furthermore, the UK is amongst the world leaders in the endeavour to commercialise fusion, with a rapidly growing fusion technology and physics programme undertaken at UKAEA within the Culham Centre for Fusion Energy (CCFE). With the construction of ITER - the 15Bn Euro international fusion energy research facility - expected to be completed in the middle of the 2020's, we are taking a huge step towards fusion power. ITER is designed to address all the science and many of the technology issues required to inform the design of the first demonstration reactors, called DEMO. It is also providing a vehicle to upskill industry through the multi-million pound high-tech contracts it places, including in the UK.
ITER embodies the magnetic confinement approach to fusion (MCF). An alternative approach is inertial fusion energy (IFE), where small pellets of fuel are compressed and heated to fusion conditions by an intense driver, typically high-power lasers. While ignition was anticipated on the world's most advanced laser fusion facility, NIF (US), it did not happen; the research effort is now focused on understanding why not and the consequences for IFE, as well as alternative IFE schemes to that employed on NIF.

Our CDT is designed to ensure that the UK is well positioned to exploit ITER and next generation laser facilities to maximise their benefit to the UK and indeed international fusion effort. There are a number of beneficiaries to our training programme: (1) CCFE and the national fusion programme will benefit by employing our trained students who will be well- equipped to play leading roles in the international exploitation of ITER and DEMO design; (2) industry will be able to recruit our students, providing companies with fusion experience as part of the evolution necessary to prepare to build the first demonstration power plants; (3) Government will benefit from a cadre of fusion experts to advise on its role in the international fusion programme, as well as to deliver that programme; (4) the UK requires laser plasma physicists to understand why NIF has not achieved ignition and identify a pathway to inertial fusion energy.

As well as these core fusion impacts, there are impacts in related disciplines. (1) Some of our students will be trained in low temperature plasmas, which also have technological applications in a wide range of sectors including advanced manufacturing and spacecraft/satellite propulsion; (2) our training in materials science has close synergies with the advances in the fission programme and so has impacts there; (3) AWE require expertise in materials science and high energy density plasma physics as part of the national security and non-proliferation strategy; (4) the students we train in socio-economic aspects of fusion will be in a position to help guide policy across a range of areas that fusion science and technology touches; (5) those students involved in inertial fusion will be equipped to advance basic science understanding across a range of applications involving extreme states of matter, such as laboratory astrophysics and equations of state at extreme pressures, positioning the UK to win time on the emerging next generation of international laser facilities; (6) our training in advanced instrumentation and control impacts many sectors in industry as well as academia (eg astrophysics); (7) finally, high performance computing underpins much of our plasma and materials science, and our students' skills in advanced software are valued by many companies in sectors such as nuclear, fluid dynamics and finance.