China's BEST Project Completes Delivery of Seven TF Coil Boxes

On August 30, 2026, as the final BEST Toroidal Field (TF) coil box passed all acceptance inspections and was shipped, Shanghai Electric Nuclear Power Equipment Co., Ltd. completed the development of seven core coil boxes for the BEST project. The project spanned approximately two and a half years, from the initiation of the first laser weld in January 2024 to the completion of all girth welds on products by the end of May 2026.

The BEST TF coil box is a core pressure-bearing component in the magnetic field system of a tokamak device, primarily used to support the magnet structure, confine high-temperature plasma, and ensure stable device operation. Featuring an irregular and complex structure, high integration precision requirements, and demanding service conditions, this component imposes stringent requirements on specialized laser welding, precision machining, geometric tolerance control, and non-destructive testing.

During the development process, the team faced challenges including deformation control in laser welding of large-size thick plates, one-pass continuous forming of ultra-long girth welds, and high-precision machining of complex cavities. Shanghai Electric Nuclear Power Equipment Co., Ltd., in collaboration with Fusion New Energy (Anhui) Co., Ltd., the Institute of Plasma Physics at the Hefei Institutes of Physical Science, Chinese Academy of Sciences, and other organizations, conducted technical research and development. Through extensive process trials and multiple rounds of optimization of tooling fixtures and welding parameters, key issues such as weld porosity in special materials, stress deformation control, and ultra-long girth weld forming were progressively resolved.

According to Shanghai Electric Nuclear Power Equipment Co., Ltd., the delivery of the seven TF coil boxes marks the establishment of its manufacturing capabilities for core pressure-bearing components of major controlled nuclear fusion devices, spanning process development, specialized welding, precision machining, quality control, and complete package delivery. Previously, the company also participated in the development and delivery of core components for the CRAFT project, with related achievements providing engineering experience for the batch manufacturing of key equipment in future fusion devices.