I made a system that shutdown your reactor when a redstone wire is broken. I havent seen it fail with 'normal reactors' it should stop any reactor except full uranium ones because it reacts pretty fast (few seconds is enough). You could make it even faster by making it out of wood or wool but too lazy to make another one atm :). Only IC2 is needed to make this. Screenshots:
2 wires running in the reactor for extra reliability:
Emergency shutdown system in action (was done by actualy overheating the reactor):
Can also be combined with http://forum.industrial-craft.…page=Thread&threadID=1907.