net-zero - Tracking tritium to enable efficient fusion fuel cycles

The UK government has legislated to deliver 'net-zero' greenhouse gas emissions by 2050 and committed to "doubling down on our ambition to be the first country to commercialise fusion energy technology" by establishing the STEP programme to build a prototype compact power plant by 2040 - a hugely exciting venture for the UK! Building STEP is a very substantial technological challenge but one for which the UK has excellent pedigree and expertise.

Additionally, the UK has also associated to the Euratom Research and Training programme, so remains a full participant in the much larger ITER (international fusion project in southern France) and the EUROfusion DEMO powerplant programme, targeting fusion electricity 20 years after ITER begins its first fusion experiments. Whilst STEP and DEMO are comprehensive power plant design programmes driven by net-zero targets, considerable technical uncertainties must still be overcome in parallel.

This proof-of-concept proposal, led by the University of Bristol (UoB), partnered with the UKAEA (the government research organisation which leads fusion research in the UK), will seek to address a key technology 'blocker' for fusion power stations: the challenge of monitoring tritium, the radioactive fuel component for fusion energy. Tritium is a weak beta-emitting heavy isotope of hydrogen, with beta radiation energies averaging 5.7keV, meaning that the stopping range of tritium-derived beta particles in detector materials is extremely limited, on the order of microns. There is a need to monitor the abundance of tritium in numerous different parts of a fusion power station from the core, where it is extremely hot) to the breeder blanket (where tritium is created) to the back end separation and storage plants, where cryogenic (very cold) temperatures are used to aid the processes. Hence any detector needs to be able to withstand extremes of temperature and still be able to work in a reliable way.

This project will produce the first compact, solid-state detector for tritium, with a unique device structure made from diamond that will make it able to operate in both extreme cold and heat and from very low amounts of tritium to very high amounts of tritium. Developing this device will require development of the materials, with a unique layer on layer growth methodology and also the development of electronics, which can rapidly count the beta particles impinging on the detector. Accordingly this exciting project will involve modelling, material growth, electronic design, device testing and calibration. All towards creating a new type of detector that will be critical to helping a fusion powerplant run.