Case study
Advancing Fusion Technology with SmallLab at UKAEA
Background and Motivation
At UKAEA, advancing fusion technology remains central to our mission. A key area of focus is the development of highly efficient cooling and tritium breeding technologies for future fusion power plants. These plants will require cutting-edge solutions to manage extreme heat, protect superconducting magnets, and sustain fuel production.
At temperatures exceeding 100 million degrees Celsius, no material can withstand direct contact with the plasma. To prevent damage and sustain the reaction, fusion reactors rely on superconducting magnets. The magnets create strong, stable magnetic fields that keep the plasma away from the plasma-facing walls, but prolonged exposure to heat from the plasma or neutron flux can degrade their superconducting properties, necessitating protective shielding and cooling strategies.
Liquid metals offer a promising approach to heat management due to their exceptional thermal conductivity, low activation, and resistance to erosion. They are being explored for use in critical fusion components such as the breeder blanket, divertor, and first wall. Their superior heat capacity and neutron-capturing capabilities make them especially well-suited for fusion applications.
However, the use of liquid metals in fusion machines introduces significant challenges due to complex magnetohydrodynamic (MHD) effects. When an electrically conductive liquid moves through a magnetic field, Lorentz forces create substantial flow resistance, increasing pumping power requirements. Additionally, the magnetic field’s ability to suppress turbulence can reduce convective heat transfer, impacting cooling efficiency.
These challenges necessitate innovative research methods to replicate fusion-relevant conditions, enhancing our understanding, developing mitigation strategies, and training the next generation of engineers and researchers in a safe and controlled working environment.
The Challenge
Fusion power plants, particularly tokamaks, will operate under extreme conditions, with temperatures reaching several hundred million degrees. The tokamak uses powerful external magnetic fields to confine and control the hot plasma of fusion fuels in a ring-shaped container called a ‘torus.’ Research in MHD is crucial for fusion to study the interaction between magnetic fields and electrically conductive fluids like liquid metals. This research supports component designs utilising liquid metal for cooling and/or breeding-tritium purposes.
Key challenges include:
- Efficient cooling mechanisms for sustained operation.
Mitigating adverse forces generated by liquid metal flows interacting with magnetic fields (Lorentz forces). - Developing cost-effective and safe experimental setups to simulate real-world fusion conditions.
- These challenges necessitated an innovative approach to simulate these conditions safely and effectively while preparing the next generation of engineers and researchers.
The Solution: SmallLab Facility
The SmallLab project was conceived to address these challenges. It is designed as a state-of-the-art experimental test rig that utilises a surrogate fluid, Galinstan (Indium-Gallium-Tin), which is chemically inert, non-toxic, and remains liquid at room temperature. Furthermore, SmallLab design features electromagnets enabling the study of MHD.
SmallLab is one of the few facilities worldwide employing surrogate fluids to gain deeper insights into phenomena relevant to real-world fusion conditions within a cost-effective and safe experimental environment.
This innovation enables the safe and efficient study of:
- Flow Dynamics: Investigating velocity profiles in single- and two-phase liquid metal flows.
- MHD: Understanding the interaction of magnetic fields and their impact on liquid metal flows.
- Component Testing: Experimenting with designs in various configurations, representative and/or encountered in real components.
- Sensors: Using advanced diagnostic tools, like Ultrasonic Doppler Velocimetry (UDV), and potential anemometers. The aim is their improvement for the next generations of tests, offering the means to better understand and optimise tokamak component designs.
Galinstan allows researchers to replicate and study the conditions that could be present in fusion power plants without the need for extreme temperatures or pressures.
The lab’s closed-loop test rig circulates Galinstan through pipes, driven by an electromagnetic pump. The test setup allows for the testing and trialling of a range of sensing methods and devices. This includes UDV for measuring flow characteristics and extracting information on MHD effects. This setup enables researchers to understand and mitigate adverse pressure forces caused by Lorentz forces, improving the efficiency of fusion systems.
Key Features and Innovations
- Electromagnetic Pump Technology: Ensures continuous flow of liquid metal through the closed-loop system.
- Adaptable Design: Allows for real-time changes to components, such as narrower channels for improved precision.
- Training Future Experts: Provides hands-on opportunities for engineers and researchers to gain expertise in MHD and liquid metal applications.
Key Milestones and Achievements
- First-of-its-kind Facility in the UK: SmallLab is the UK’s first facility designed specifically to study MHD with liquid metals, filling a critical gap in domestic fusion research capabilities.
- Educational and Practical Benefits: The lab provides a training ground for future engineers while enabling the development and testing of advanced sensors and diagnostics for fusion applications.
Challenges Overcome
- Limited Funding: Developed cost-efficient solutions while maintaining high research standards.
- Supplier Gaps: Engaged with UK suppliers to create a robust local ecosystem capable of supporting fusion research.
- Knowledge Transfer: Leveraged international insights while developing unique UK-specific capabilities.
Impact and Future Applications
The SmallLab not only serves as a stepping stone for larger projects like Chimera but also supports UKAEA’s broader mission of delivering fusion as a sustainable energy source. The lab’s findings will enhance our understanding of MHD and inform the design of more efficient fusion power plants.
Conclusion
As a cornerstone of UKAEA’s commitment to innovation and collaboration in fusion technology, SmallLab directly addresses key challenges in liquid metal research. Its contributions will not only drive advancements in fusion energy but also strengthen the UK’s scientific and industrial capabilities, ensuring a robust foundation for future developments.
