Printing the parts for nuclear fusion

3D printing is branching into an unlikely domain—nuclear fusion. The sun uses nuclear fusion to produce energy, and now researchers are exploring how 3D printing can contribute to making nuclear fusion reactors on Earth.

The engineering challenges are immense. “Our 3D printing technology could fabricate complex components of a fusion reactor that are difficult to make by conventional methods,” says Shaojun Liu of the research team at the Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, in Hefai, China.

The researchers report on the development of their method in the Journal of Nuclear Materials. They also discuss significant technical insights into the metal structures that the fabrication process creates.

The work uses a specific form of 3D printing called selective laser melting (SLM). A high-powered laser is targeted at selected regions of a substrate material, causing those regions to melt and then solidify to form the desired component. The structure is built up layer by layer through repeated scans by the laser.

The procedure was used to create scaled-down metal samples suitable for the internal wall of a fusion reactor. The reactors are donut shaped structures known as tokamaks. This “first wall” surrounds the high energy nuclear plasma in which the fusion occurs. It is therefore exposed to significant physical challenges, including bombardment by neutrons released during the fusion reactions. This unique environment imposes specific demands on any material used as a first wall. To meet these demands, the researchers create their parts from a special type of steel, developed in China, that is particularly resistant to high energy neutron irradiation.

“The structure of the first wall is very complex,” Liu explains, but he says that the 3D printing was able to create it quickly and with highly efficient use of the basic raw materials. Another key advantage in building the material layer by layer is that it allows microstructural features of the orientation of the metallic grains to be analysed and controlled. Liu says that further work required to optimise the process and scale it up is now underway.

The type of steel the researchers are producing is likely to be used in the International Thermonuclear Experimental Reactor (ITER) project, of which China is a founding member. The ITER project management currently hopes to have their first plasma fusion reactor working by 2025, but the assembly of the reactor is scheduled to begin in 2018.

“ITER will be the first fusion device to maintain fusion for long periods of time,” the project website declares. If that hope is fulfilled, the hot and seething heart of the process may well be surrounded by 3D printed steel.


Read the full article: Liu, S. et al.: "Microstructure anisotropy and its effect on mechanical properties of reduced activation ferritic/martensitic steel fabricated by selective laser melting," Journal of Nuclear Materials (2018)