The nuclear reactors explode multiple times. I made a video to demonstrate.
The mods I have is Buildcraft 2.2.13, Redpower 2.0pr4e & Industrialcraft 1.81 of course.
The video should explain most of it...
EDIT: Forge version 18.104.22.168
EDIT2: Tested with Forge version 22.214.171.124, the bug is in that version too.