The International Thermonuclear Experimental Reactor (ITER), under construction in St. Paul-lez-Durance, France, will be the world’s most expensive and complex scientific instrument ever built when it is completed. Its goal is to demonstrate workable fusion energy once and for all.
To help keep the project’s costs within budget, the US ITER team at Oak Ridge National Laboratory has begun desktop three-dimensional printing, also known as additive printing, to help them design and configure components more efficiently and affordably.
Nuclear fusion engineering design processes have traditionally depended on mock-ups and prototypes. Full-scale models, either cast or machined from metal and other materials, will continue to be a valuable part of the development process, in addition to 3D computer modeling. The affordability and accessibility of desktop 3D printing, however, offer a number of advantages.
Tactile Advantages for 3D Design
ITER engineer Kevin Freudenberg explained,
“Now for pennies instead of tens of thousands of dollars, we can have impact right away with 3D printing. It lets us see what the part actually looks like. On 3D CAD (computer-aided design) displays, you can’t feel the shape of an object. You just see it. Many people have trouble seeing 3D projections or find them tiresome to view over time. With the 3D printed objects, you can run your finger over the surface and notice different things about the scale and interfaces of the component.”
A standard part of the engineering process is finding interferences or design problems before a component’s fit, size, and form are finalized.
“It’s a lot more time-consuming and expensive when you find that mistake in a metal prototype than it is in a 3D printed component”, said Mark Lyttle, an engineer working on the pellet injection and plasma disruption mitigation systems for US ITER. “3D printing is very low cost. With metal, you may have to start over if you can’t re-machine it.”
3D printed mock-up parts are also changing how manufacturers interact with the ITER designs.
“We went to a vendor meeting recently. We looked at line drawings for a minute, and then the vendors spent hours looking at and discussing the 3D parts. Most of the meeting was spent talking about the parts. Having something in your hand that is tactile can show what machine processes and best practices to use in manufacturing,”
Toy Scale Parts
The central solenoid, a one thousand ton, 60-foot high stack of magnets and superconducting [niobium-3-tin](http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scex2.html) cables which will sit in the middle of the doughnut-shaped plasma chamber, needs to be printed at “toy” scale; other components can be printed at one to one scale, actual size, like the fast gas valve for the disruption mitigation system shown in the photo above.
“On the screen, some components don’t look especially bulky,” Lyttle added. “But when you make it in metal, it will be a hunk of material that is too heavy and hard to handle. When you have a physical model, it is easier to spot opportunities to save material and make the design more efficient and the manufacturing less expensive.”
Just being able to handle objects at even the toy scale is helpful; it brings massive components into the hands of engineers and manufacturers and spurs new analysis.
3D printing parts also lets engineers better check the interfaces for possible collisions.
“You can put it together, move it a bit and visualize how it’s going to be built. You can see problems like a weld you can’t get to or a screw head that is inaccessible,”
Degradable Plastics 3D-printed Using Salt
Theses 3d-printed polymers degrade quickly under the right circumstances. Ideally, they will disintegrate into small molecules. Heavy metals or bacteria won't be able to travel along in these smaller molecules.