In 2019, Orano Federal Services and the University of North Carolina at Charlotte explored the design of 3D-printed shock absorbers for containers used to transport spent nuclear fuel. However, the partners encountered several obstacles. Seven years later, the study has been revived, and some of those barriers now appear to have been overcome. So, is it worthwhile to 3D print these structures for the nuclear sector?
First, it is important to understand why there is a push to redesign these shock absorbers. Traditionally, they are made from balsa wood, redwood, or aluminum. Manufacturing costs can range from $250,000 to $1 million, as these are large components requiring significant amounts of raw material.
At first glance, additive manufacturing seems like a natural fit. By optimizing material usage, it could help reduce costs. That is indeed the objective. But as you might expect, the reality is more complex.
Which additive manufacturing process should be chosen for the nuclear industry?
A shock absorber, as the name suggests, is a structure designed to withstand a wide range of tests and stresses, including drops, fires, and impacts. It is a large component with strict dimensional, weight, and temperature constraints. In short, manufacturing it is no small task.
When the study began in 2019, the 3D printers available on the market were limited in terms of build volume, and researchers faced significant size constraints. This is less of a challenge today.
Two technologies were identified for producing these shock absorbers using additive manufacturing: Fused Deposition Modeling (FDM) and Laser Powder Bed Fusion (LPBF), specifically using a Nikon SLM Solutions system.
Using this metal platform, the teams report that they designed a shock absorber made up of 442 individual blocks, each measuring 25.4 × 25.4 × 50.8 cm. The assembly process alone must have been quite a feat!
442 3D-printed metal blocks are assembled to form the entire structure.
Using FFF, this number was significantly reduced to just 36 blocks, each measuring 50.8 × 50.8 × 101.6 cm.
Density, infill, and weight reduction
Beyond the specific choice of printing process, one of the key advantages of additive manufacturing lies in the ability to adjust the density of a part’s infill pattern. This makes it possible to achieve sufficient energy absorption while reducing the amount of material required.
In practice, the teams tested honeycomb structures as well as Gyroid designs. In the latter case, they achieved up to an 80% reduction in weight while maintaining greater strength in all directions, along with lower overall density. Overall, the results highlight clear performance benefits.
Using FDM, only 36 blocks were 3D-printed.
But what about costs? This remains the crux of the matter. Taking into account machine, material, and labor costs, the teams estimated savings of over $1 million for an FFF design with 5% infill. At this price, the appeal is clear.
Of course, this is not the only factor to consider. The study also highlights the lack of established nuclear-grade standards when it comes to additive manufacturing. Questions remain regarding the performance and reliability of this 3D-printed equipment. One thing is certain: accelerating research in the nuclear field could prove highly beneficial for the advancement of 3D technologies.
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*Cover Photo Credits : Orano Federal Services