I have a reactor in SMP. It is still fueled, and there are no redstone currents near it. It sends power to a mass fabricator located a fair distance away, but still visible. The power goes from the reactor through a medium voltage transformer with redstoned applied and then it's just high voltage cable all the way to the mass fabricator.
I eventually got the reactor working by breaking and resetting the high voltage cable and applying and removing redstone from the reactor. But upon logging off, it was no longer working when I logged on.