Reactor containment chamber made from iron lulz?
That's just asthetics. The reactor is surrounded by a 6x7x7 box of obsidian. Also, wiring is correct. It's bugged.
I can tell you from experience that this IS bugged.
The fix I found was don't have the power cable come out from the bottom only - also have it come out from the side.
I installed Industrial Craft as part of the Technic Pack, so it could be as a result of mod conflict. I'll try this.