Oxford Sigma, Kyoto Fusioneering, and STEP Programme Publish Collaborative Research Exploring Novel Configurations and Materials for Tritium Breeding in Spherical Tokamaks
Oxford Sigma, Kyoto Fusioneering, and STEP (Spherical Tokamak for Energy Production) have published new research exploring innovative approaches to tritium breeding in spherical tokamaks. The study, published in Fusion Engineering and Design, investigates the feasibility of breeding tritium in the central column, a key challenge for spherical tokamak configurations owing to the small area available, focusing on the use of advanced materials that perform roles in breeding, providing radiation shielding and also structural support. This effort has demonstrated that collaboration is a powerful methodology to generate novel ideas to solve unique challenges in fusion.
The scientific publication is found in the Fusion Engineering and Design journal. It provides the first stage proof of concept of the team’s optimisation. The publication is available here and cited as:
The research evaluates two novel high-temperature concepts for the inboard breeder blanket design, using confined spaces typical of spherical tokamaks. Key findings include:
- A tungsten-rhenium-hafnium-carbide lithium-based design, which demonstrated the highest tritium breeding ratio (TBR) in the study. Optimised for shielding and thermal requirements, this design achieved a global TBR of 0.135 in 3D neutronics calculations using a configuration of W-24.5Re-2HfC (wt%), lithium enriched to 90% in Li-6, a thin layer of beryllium titanate, and tungsten pentaboride (W2B5) as shielding material.
- A silicon carbide and lead-lithium concept, which was also investigated as an alternative breeding configuration, by comparison achieved a global TBR of 0.048.
While the results suggest that the local TBR of these designs remains well below 1 (the minimum required TBR for self-sufficiency), especially for the lead-lithium concept, the fractional contribution they provide in boosting tritium breeding could support development of next-step practical solutions to achieving tritium self-sufficiency—a critical challenge for commercial fusion energy.
Mark Anderton, Senior Engineer at Oxford Sigma, and lead author of the paper, commented: “The study highlights the importance of innovative materials in addressing a key challenge involving the coupling of tritium breeding and radiation shielding. This collaboration has enabled us to explore new design spaces for the central column of spherical tokamaks, demonstrating how advanced materials can help reduce barriers to fusion commercialisation.”
Dr. Richard Pearson, Chief Innovator at Kyoto Fusioneering, and a co-author on the paper, added: “This research represents the essence of what Kyoto Fusioneering stands for: tackling challenging problems with a research-driven, yet application-focused approach. By working collaboratively with Oxford Sigma and STEP, we’ve combined complementary expertise to address a unique issue in fusion plant design, pushing known boundaries, and gaining insights that may one day lead to delivery of new technologies that will enable new avenues for fusion energy.”
Dr. Simon Kirk, Vessel and In-Vessel Systems Design Integration Lead at UKIFS, added: “This project is a great example of fusion organisations working together with a spirit of openness and meant the technical expertise from the different organisations could be combined to address the difficult challenge on centre column tritium breeding in spherical tokamaks.”
About Kyoto Fusioneering
Kyoto Fusioneering, established in 2019, is a privately funded technology startup with facilities in Tokyo and Kyoto (Japan), Reading (UK), Karlsruhe (Germany) and Seattle (USA). The company specializes in developing advanced technologies for commercial fusion power plants, such as gyrotron systems, tritium fuel cycle technologies, and breeding blankets for tritium production and power generation. Working collaboratively with public and private fusion developers across the globe, Kyoto Fusioneering’s mission is to make fusion energy the ultimate, sustainable solution for humanity’s energy needs. Explore more about KF’s vision for the future of energy at www.kyotofusioneering.com/en/ or by contacting media@kyotofusioneering.com.
About Oxford Sigma
Oxford Sigma tackles energy security and climate change by accelerating the commercialisation of fusion energy. Oxford Sigma’s mission is to deliver materials technology, materials solutions, and fusion design services in order to accelerate the commercialisation of fusion energy. Oxford Sigma is internationally recognised as a key fusion materials and technological leader within the market. Get in touch at info@oxfordsigma.com.
About STEP/ UKIFS
STEP (Spherical Tokamak for Energy Production) is a major technology and infrastructure programme that will demonstrate net energy from fusion, fuel self-sufficiency and a route to plant maintenance. UKAEA is STEP’s fusion partner and will work alongside STEP’s industry partners – one in engineering and one in construction – expected to be announced at the end of 2025/early 2026.
The STEP programme is being delivered by UK Industrial Fusion Solutions Ltd (UKIFS) a wholly owned subsidiary of UKAEA Group. UKIFS will lead STEP’s integrated delivery team to design and build the prototype plant at West Burton site in Nottinghamshire, targeting first operations in 2040.
