Lithium containing Ceramics for tritum breeding

Lead Research Organisation: University of Oxford
Department Name: Materials

Abstract

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.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022430/1 30/09/2020 30/03/2028
2618197 Studentship EP/S022430/1 30/09/2020 29/09/2024 Pedr Charlesworth