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Here's what you get when an electrical engineer gets to nuclear power plant design. Full imgur album: http://imgur.com/a/WkRtZ
It's a Mark I reactor that relies on active cooling via a big fat supply of ice blocks. The main feature is that all the safety-critical subsystems are monitored to make sure the reactor never blows up. If something goes wrong, the red lights in the control room will let you know (so you can go off and fix it.)
Switchyard - trying to make this look like a real electrical substation. (It'll be years before I get to design one of these in real life.)
Fault trips panel - red lights are bad.
Overview of reactor complex:
This was built as a proof of concept using NEI and creative mode. Next step is to build it legitimately (for real!) on a Tekkit server.
More screenshots in the Imgur album [ http://imgur.com/a/WkRtZ ]. If you want the save-world, more screenshots or building instructions for a particular part, ask.