Liquid lithium corrosion for nuclear fusion

The blanket module of the fusion devices of the future is likely to have a coolant, that not only cools the reactor, but breeds tritium, the fuel that is used within the plasma. This can either be PbLi eutectic or pure lithium. PbLi has been extensively studied due to its ability to multiply neutrons (Pb) and breed tritium (Li). However PbLi does not breed as much tritium as a pure lithium. Whilst there has been much corrosion testing using PbLi there has been much less using liquid lithium. Reports form the 1970’s suggest refractory metals have better compatibility in liquid lithium than other metals and more recent work in Japan suggest erbium oxide maybe be a potential coating.  We have developed a bespoke liquid lithium testing rig in Oxford to allow testing at a range of temperatures in static Li and PbLi.

To understand the tolerance of these coatings with the environment, preliminary tests in Li have been performed to understand the chemical compatibility. However, tests to understand the synergistic effects of liquid lithium and irradiation are difficulty and costly as there is a lack of testing equipment globally. So, tests in Li and irradiation environments are usually done subsequently, rather than concurrently.

This project will use a combination of proton irradiation at the National Ion Beam Centre and PbLi and Li corrosion at the new established Oxford testing facility to understand synergistic effects that may occur under these conditions.

Characterisation of the degradation process will use analytical electron microscopy including STEM-EDX, SEM-TKD and FIB-SEM tomography. Adhesive properties of the coatings will be measured using scratch testing methods developed in Oxford to understand interfacial failure mechanisms. The results from the microstructural and mechanical characterisation will be used to either engineer the alloy chemistry or coating combinations to improve the resistance to degradation and decohesion. Further development of the corrosion facilities as part of the project will include integration of the stirring within the liquid lithium crucible and oxygen level sensors. There is likely to be industrial support from a SME to this project.