Fusion energy devices require radiation-hardened actuators to support critical functions such as remote handling, diagnostics, and maintenance. Tokamaks and stellarators generate intense neutron flux and gamma radiation, which degrade conventional actuator materials and electronics, leading to performance failures, reduced operational lifespan, and increased hazardous waste. To address this challenge, UKAEA commissioned M5tec to design and build a prototype radiation-hardened actuator.
This rad-hard actuator is based on the v3 rotary actuators used in the MASCOT 6 bilateral telerobotic system, which provides real-time haptic feedback for precision remote operations. Traditionally deployed for maintenance and inspection of the JET tokamak, MASCOT 6 now plays a critical role in decommissioning JET, which concluded operations in late 2024 after four decades of service.
The actuator incorporates radiation-hardened components, including a specialised motor and a gearbox engineered to withstand ionizing radiation and electromagnetic interference. Designed for dry operation, it eliminates wet lubricants, mitigating contamination risks in sensitive fusion environments. Optimised for continuous maximum torque usage, it minimises maintenance cycles while reducing hazardous waste generation.

Built for operation in high-risk environments, including tritium and beryllium exposure, the actuator features modular construction to ensure backward compatibility with the legacy MASCOT 6 system. Its interchangeable components enable simplified servicing and future upgrades, while its high-performance design balances precision control with durability, essential for demanding remote maintenance tasks.
The actuator’s gearbox integrates aluminium alloy and case-hardened steel for enhanced durability and radiation tolerance. Gears feature a 1mm module, achieving optimal power transmission within tight spatial constraints. The refined design offers a significant speed increase, operating at 39.75 Nm continuous torque at 188 rpm (19.63 rad/s)—three times the speed of previous iterations. Additionally, a resolver-based electromagnetic transducer ensures high positional accuracy, critical for bilateral force reflection and teleoperation fidelity.

By achieving higher speeds without compromising torque, eliminating wet lubrication, and enhancing radiation resistance, the rad-hard actuator sets a new standard for fusion and nuclear-rated systems. Its emphasis on backward compatibility protects infrastructure investments while improving operational performance and safety in confined, hazardous spaces such as fusion machine maintenance and radioactive waste management.