Nuclear fusion is one of the great scientific and engineering challenges of our time. Success promises a future where clean, virtually limitless energy can power our world. The UK Atomic Energy Authority (UKAEA) is at the forefront of these efforts. Through its Fusion Industry Programme (FIP), it is working to create the infrastructure and technology necessary to realise fusion’s potential as a reliable energy source.
In May 2024, the UKAEA awarded £9.6 million to six organisations, comprising two universities and four private companies, including IS-Instruments, to advance projects that develop tools, technologies, and skills required to accelerate the commercialisation of fusion energy.
The UK’s last coal-fired power station closed in September 2024, and the country will need to decarbonise its electricity generation before STEP is commissioned. Given that global power demand will have doubled by 2050, a mixture of power sources will be required to ensure a steady, sustainable supply. Fusion would be a valuable, non-varying source.
Much work remains to make nuclear fusion a sustained reality and a commercially viable option. However, its potential cannot be ignored in a society committed to climate change mitigation and net-zero targets. The UK, uniquely positioned as the host of JET, can leverage its leadership in fusion research to become a global hub for fusion energy technology.
Why Pursue Fusion?
There are several points in the justification for the pursuit of fusion, including:
- Fuel Abundance – fuels used in fusion reactions are effectively inexhaustible. Deuterium is readily extracted from seawater, and tritium is produced by irradiating lithium.
- Reliability – fusion does not depend on external factors such as wind/solar
- High Fuel Efficiency: Fusion produces more energy per gram of fuel than any other process on Earth.
- No Chain Reaction – Fusion requires very specific (and high) temperature and pressure conditions to sustain the reaction.
- Shorter-Lived Waste—Fusion waste is significantly less hazardous and has a shorter half-life than the waste produced by fission reactors.
Some key challenges remain in making nuclear fusion a sustainable reality and a scalable solution to the world’s energy crisis. Fusion requires temperatures of over 100 million degrees Celsius (for magnetic confinement) or high pressures of 100-1000 GPa. This raises the issue of attaining and stably maintaining these extreme conditions, the materials that contain them, and monitoring the processes within them.
A further challenge is around the fuel required for fusion: tritium. A radioactive isotopologue of hydrogen, tritium is a critical fuel for nuclear fusion. However, naturally occurring tritium is rare, so its production, storage, and management are crucial to the commercial viability of nuclear fusion power plants.
Tritium poses challenges for measurement systems. Multiple techniques are generally necessary, such as combining online and offline measurements. Chemical sensors are widely employed. Although they are inexpensive, they lack accuracy and specificity. Gas chromatography is reliable and precise, but the instruments are large, limiting their employability, and complex, requiring specifically trained personnel to operate and interpret results. Infrared absorption is non-invasive and accurate but cannot differentiate diatomic H2, which has no IR line. Liquid Scintillation Counting offers a low detection limit but necessitates a large sample mass, cannot measure H2 or D2, requires digestion into liquid form, and generates secondary waste.
The Role of Raman
Raman offers excellent opportunities for qualitative compositional analysis of materials due to its high selectivity.
IS-Instruments is an expert in Raman spectroscopy, specialising in designing deployable Raman spectroscopy equipment for on-site materials and chemical analysis. For over five years, our flexible modular systems have been demonstrated to operate successfully in challenging measurement environments. Our involvement in the FIP’s GRADE project centres on the fusion fuel cycle, particularly in identifying hydrogen isotopes, with a focus on tritium.
The instrument involved originated from a collaboration in 2014 between the Optoelectronic Research Centre (ORC) at the University of Southampton and Amentum. The ORC is a world-leading institute dedicated to photonics research and is the largest in the UK. Fibres invented and produced in Southampton have been sent to the Moon, Mars, and the ISS. Amentum (previously Jacobs Nuclear) is a global leader in advanced engineering and innovative technology solutions across many sectors, including energy, environment, space, defence, cyber, and more. Together, we conducted a feasibility study funded by Innovate UK to design and construct a prototype benchtop spectrometer capable of analysing gaseous samples. While Raman has been a well-established technique for measuring solids and liquids, the diffuse nature of gases presents significant challenges. This collaboration examined using microstructured hollow-core fibres (HCF) to extend the laser-gas interaction path length. Through a series of Innovate UK-funded projects, the instrument successfully measured N2, O2, and H2O, followed by CH4, IPA, and CO. With GRADE, the instrument is being further developed for analysing tritium gas within the fusion fuel cycle.
The initial investigatory phase of GRADE concluded with the successful simultaneous analyses of hydrogen, deuterium, and deuterium hydride. The data collected showed the repeatable detection of varied concentrations. When compared to the current literature and extrapolated, it was determined that tritium would be detectable using the current instrument setup, which leads us to the current phase of work. During the initial phase of work, ISI worked with Amentum to design a complete rig system that would allow the instrument to be safely integrated into a tritiated environment.
Our current focus is to confirm the ability of Gas Raman technology to analyse and measure tritium successfully in real time. It could also be used to monitor tritium as it undergoes beta decay, emitting low-energy beta particles that interact with polymers, causing them to become brittle and inflexible. Beta radiation can also lead to gaseous byproducts like methane or small hydrocarbons as the polymer degrades, releasing titrated compounds into the environment.
The beta decay of tritium poses a hazard to the environment, fusion reactor operators, and equipment. Its radioactive nature also dictates the need for a specialised containment area to test each component of new monitoring equipment to ensure its radiation resistance.
Project partner Amentum has constructed a new tritium-specific glovebox to monitor the spectrometer’s ability to detect tritium as a single sample constituent and in a mixture with H2, D2 and HD. The research will also determine the HCF’s behaviour in a tritiated environment, although HCFs have already been shown to have significantly higher radiational resistance than conventional silica fibres (Medaer et al., 2023).
Jessica Gabb, ISI project lead for GRADE, said: “We have an ongoing collaboration with Amentum, and this special relationship has proven particularly beneficial when coordinating such a demanding and complex project with such a delicate instrument. We are also working with the Optoelectronic Research Centre at the University of Southampton to explore different filling techniques for the fibre to preserve the calibration values and improve the overall analysis time. Ultimately, the goal will be to use robotics to align the laser remotely, making the process safer for human operators.”
The instrument is being tested at Amentum’s specialist facilities. The next step is to determine whether it can reliably and repeatedly detect tritium. This stage will be completed before the project’s completion date at the end of March 2025.
This project has been supported by 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/
Reference: Medaer, Sacha ER, Bradley, Thomas D., Di Francesca, Diego., et al. ‘Near IR radiation-induced attenuation in nested anti-resonant nodeless fibres’. Optics Letters, 48-23. 2023.
