seems that oak ridge labs is 3D printing with stainless steel to build a micro reactor. not sure how far this will go, but interesting none the less. there's a video of the printing process in the link.
"The US Department of Energy's Oak Ridge National Laboratory (ORNL) has developed a 3D-printed nuclear reactor core prototype, with the ultimate goal of the Transformational Challenge Reactor (TCR) Demonstration Program being to create an advanced, full-sized, 3D-printed reactor with integrated sensors and controls from fewer components by 2023. "
https://newatlas.com/science/oak-ridge-3d-printed-nuclear-reactor-core/
"The US Department of Energy's Oak Ridge National Laboratory (ORNL) has developed a 3D-printed nuclear reactor core prototype, with the ultimate goal of the Transformational Challenge Reactor (TCR) Demonstration Program being to create an advanced, full-sized, 3D-printed reactor with integrated sensors and controls from fewer components by 2023. "
https://newatlas.com/science/oak-ridge-3d-printed-nuclear-reactor-core/