ADVANCES IN AM | COVER STORY
“The essential point is stable, repeatable material quality once a process is selected and qualified,” he tells NEi. Unlike prototyping environments where manufacturing parameters may vary from job to job, additive manufacturing requires statistical consistency equivalent to or exceeding forging or casting routes. Although the manufacturing route differs from
the more conventional forging or casting approach, the governing requirements on toughness, ductility, corrosion resistance and fatigue performance for nuclear applications remain unchanged. Zouari explains: “We are not reinventing metallurgy; the material must still meet the mechanical properties specified by the codes”. Indeed, the industrialisation of these novel AM processes is supported by accumulated data across multiple materials, geometries, and manufacturing sequences, including experience from items installed in operating reactors.
Addressing the supply chain challenge with AM The rationale for additive adoption is rooted in technical constraints inherent to conventional supply chains. Many nuclear-grade components rely on castings or forgings with long lead times, variable availability and a strictly limited pool of suppliers. Furthermore, for several critical materials, notably nickel alloys,
martensitic stainless steels and large austenitic components, global capacity is already tight even ahead of the widely anticipated ramp up in nuclear development over the coming years. While additive techniques do not remove the need for
large forgings, for reactor pressure vessels, for example, they can reduce supply chain pressure on medium- sized components and on complex geometries where conventional processes introduce multiple welding operations or multi-piece assemblies. The Romans-sur-Isère plant integrates several processes that target different component sizes and
metallurgical requirements: ● Powder bed fusion with lasers is used for small to medium components with high geometric complexity. The process allows detailed control of melt pools, enabling repeatable microstructures after post- build heat treatment. Framatome has focused on stabilising the parameter sets for key stainless steels and nickel alloys. The equipment that will be installed at the new site reflects these constraints: build chambers sized for components up to roughly ~500 mm with inert gas recirculation systems capable of maintaining oxygen ppm limits compatible with nuclear material cleanliness requirements.
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