Glass Bridges – Addressing Scale-up Challenges of The Vitrification of Secondary Wastes from UK and Japanese Nuclear Decommissioning

Both the UK and Japan are facing challenges in addressing the long-term legacy of nuclear power generation, decommissioning, and site clean-up. At complex sites like Sellafield and Fukushima Daiichi, large inventories of secondary and legacy wastes remain in storage, often in forms that are difficult to manage using conventional treatment routes. These include incinerator residues, ion exchange materials, and filtration sludges – heterogeneous materials with unusual chemistries, various radionuclides, and challenging physical properties. Many sit outside standard waste classification systems and may not be well-suited to treatment by established methods. Thermal treatment technologies, such as vitrification which immobilises waste in durable glass, present a promising solution. It can reduce waste volumes, stabilise problematic radionuclides, and produce wasteforms suitable for long-term storage or disposal, and is the standard treatment route for many high-level wastes. While the science is well understood in laboratory conditions for some wastes there are many that still pose significant unknowns, and scaling these processes up to industrial levels introduces a new set of challenges. Variations in chemistry, off-gas behaviour and melt homogeneity all pose significant risks to successful implementation. Without resolving these, there is a real danger of delays, cost overruns, or failed deployments. This project aims to de-risk the use of thermal treatment for challenging, complex nuclear wastes by generating robust, scalable evidence that bridges the gap between laboratory science and industrial application. Bringing together researchers from the UK and Japan, alongside industrial and governmental stakeholders, the project aims to understand and demonstrate thermal treatment at practical scales. Partners include the UK’s National Nuclear Laboratory, Sellafield Ltd, and Glass Technology Services, as well as Japanese collaborators with specialist expertise in in-container vitrification and mid-scale ceramic melter technologies. A core feature of this work is the use of pilot scale and industrial scale melting trials, enabling validation of lab-scale findings under realistic process conditions. In the UK, trials will move from lab-scale work (200 g batches) through to larger demonstrations (30 - 50 kg per day) using industrial equipment operated by Glass Technology Services. Parallel trials will be conducted using in-container methods and a liquid-fed ceramic melter capable of 250 g per hour by our Japanese collaborators. These trials intend to cover a range of production scales and explore alternative vitrification technologies with consideration of their energy requirements, throughput capability and surrounding infrastructure requirements (pre-treatment, material handling etc). The project will develop thermochemical models and optimise wasteform compositions, by assessing their structural and radiological performance – properties that are all essential for building confidence in the safety and effectiveness of the wasteforms. Importantly, lifecycle impacts concerning economic and environmental implications will also be evaluated, helping to inform strategic decisions around investment, deployment, and future planning. Through consistent stakeholders engagement, this research ensures its findings are directly applicable to national challenges, will strengthen international collaboration, and support knowledge exchange between governmental, academic, and industrial bodies, by generating an evidence base that can support future nuclear and energy policies. This project addresses a critical barrier in the nuclear decommissioning landscape – scale-up. By moving thermal treatment closer to deployment, it has the potential to accelerate clean-up timelines, reduce long-term storage burdens, and offer reliable, long-lasting solutions for some of the most difficult radioactive wastes – benefiting not only the UK and Japan, but clean-up efforts across the nuclear world.