Please do my homework - Charlie's Diary
The last blog essay on space colonization led to some discussion of space industrialization, and thereby to much neepery about 3D printers, and it led me, in turn, to ask a question on Mastodon: "can 3D printing be considered a mature technology suite before it's capable of printing a working nuclear reactor in situ?" (Qualifications: add coolant and neutron initiator source after the event, more than one type of deposition process is permissible, maybe ask if it's possible to print fuel elements and moderator control as well.)
Somebody immediately pointed me at this report that Oak Ridge National Laboratory is working on designs for 3D printed nuclear reactors (for realz); so this isn't just an SF author spitballing.
But before commenting, I urge you to look at 3D printing (wikipedia), which points out that there are multiple 3D depositional technologies, with at least seven categories in use (notably: vat photopolymerization, material jetting, binder jetting, powder bed fusion, material extrusion—this is the familiar one used in cheap PLA extruders you can find in toy shops—directed energy deposition, and sheet lamination). 3D printing isn't a single technology and most of these methods are unfamiliar to the general public: it's like talking about "Carnot cycle engines" rather than Diesel, gas turbine, or Stirling engines.
Anyway, here's your chew toy while I'm away: can 3D printing, in principle, be used to manufacture a ready-to-run nuclear reactor (for energy production, not just isotope irradiation)? Posit a supply of fissionable material to be turned into fuel rods (part of the problem). Not permitted: nebulous invocations of molecular nanotechnology. Bear in mind that the physical properties of most materials change under high neutron flux: zirconium expands, graphite blocks develop lattice defects that expand into fractures, and so on.
