Actually it's not the reactor that is vulnerable, it is the spent fuel rods that need to be cooled 24/7 for up to 20 years. If cooling stops the spent fuel rods could heat up and cause a melt down. I never considered this until I saw an episode of History Channel's: Life After People. For example, if all the nuclear plants were to melt down at once most of the planet Earth would be covered in nuclear waste dust. This probably wouldn't be good for most life on Earth.
I was for more nuclear plants in the US, but they no longer appeal to me as a feasible solution.
