On the 7th of May, the UK Atomic Energy Authority (UKAEA) held a showcase day to highlight the successes achieved under its Fusion Industry Programme (FIP). IS-Instruments’ Jessica Gabb presented the results of the GRADE – Gas RAman DEtection of tritium project, accompanied by Dr Rhea Sam and Dr Michael Foster.
UKAEA launched its FIP programme in 2022 to accelerate the growth and commercialisation of the UK’s fusion energy sector. To achieve this, it has fostered collaboration and partnerships among public and private organisations. This showcase brought together innovators, suppliers, UKAEA staff, and industry stakeholders to reflect on progress and highlight emerging technologies that aim to overcome current challenges.
One critical challenge surrounds the measurement of tritium, particularly in deuterium-tritium (D-T) plasma reactions that play a vital role in fusion. Tritium’s production, storage, accountancy, and safe management are crucial for the commercial viability of nuclear fusion power plants. The real-time monitoring and control of gaseous tritium levels throughout a plant is essential to ensure optimal reactor performance and safety. This often needs to occur at varying pressures and across a wide range of concentrations. Furthermore, monitoring systems must be able to distinguish between the various hydrogen isotopologues, such as deuterium, deuterium hydride, and tritium deuteride. Tritium is also radioactive; consequently, its management presents several technical and safety challenges.
Typically, measurements are made using multiple techniques, usually offline, and often conducted in laboratory environments, involving a combination of sampling methods. Under the GRADE project, ISI and partners have developed a gas-phase Raman spectroscopy system that offers aworking solution to this problem – providing a single, online solution that is compact, reliable, user-friendly, and economically advantageous.
The system was initially conceived in 2016 during a collaboration with Amentum and the University of Southampton’s Optoelectronic Research Centre (ORC), which specialises in the design of hollow core microstructured optical fibres (HCFs). Whilst Raman is a long-established and effective technique for measuring solids and liquids, the diffuse nature of gases makes them more challenging to measure. Hollow core microstructure fibres are a way of overcoming this. Here, the hollow fibre is filled with the target gas, and the laser is transmitted down the fibre, extending the interactive path length and allowing for a clearer Raman signal to be collected. The three organisations continued their collaboration, developing the system during the first FIP-supported GRADE project. During this stage, we successfully demonstrated its capability to clearly distinguish between deuterium, deuterium hydride, and hydrogen in gas samples. Whereas alternative systems require post-processing software, this system produces high-qualityraw data with good peak separation.
Neutron radiation testing took place at ISIS Nile. Both tests yielded successful outcomes with no silica-based radiolytically induced attenuation detected. In April 2025, the system reached a significant milestone: the successful detection of tritium at Amentum’s Science and Engineering laboratories at Birchwood.
Jessica Gabb (MCHEM), ISI’s project lead, said:
“Successfully measuring tritium is a significant breakthrough, demonstrating the potential of our Raman system to become an integral part of future fusion fuel cycle diagnostics. It has shown the potential to provide precise isotopic analysis at various points across a reactor system without the need for offline handling or multiple measurement methods. This system could conceivably become a core component for making tritium measurements – a fundamental factor for a commercially viable fusion future.”
Looking to the future, Dr Rhea Sam sees plenty of potential for the system: “Ultimately, there’s still work to be done to make it commercially viable, scalable and widely deployable. However, a robust, tritium-compatible instrument that can repeatedly detect multiple gas species simultaneously in a varied range of atmospheric conditions will have immeasurable benefits for the fusion industry. And if, as we anticipate, we can develop a hand-held instrument, it’s literally going to be a game-changer.”
Dr Michael Foster commented, “The FIP Showcase Day was an excellent opportunity to meet other scientists and stakeholders in this venture to make fusion a reality. I feel the GRADE project exemplifies what the Fusion Industry Programme was designed to do: accelerate innovation, close technical gaps, and bring advanced technologies closer to deployment in real fusion environments.”
GRADE 3 is due to commence in July 2025.
This project has been supported by the UK Atomic Energy Authority through the Fusion Industry Programme. The Fusion Industry Programme is stimulating the growth of the UK fusion ecosystem and preparing it for future global fusion powerplant market. More information about the Fusion Industry Programme can be found online: https://ccfe.ukaea.uk/programmes/fusion-industry-programme/
