The Japan reactor survived the earthquake which is one of the largest in our recorded history.
It was the tsunami that knocked it out of operations. When the back-up generators get washed away then you have problems as we are seeing now. The plant was designed to survive a 6.3m tsunami, but unfortunately this one was 7.0m.
The Reactor facility in Japan was 40 year old technology ! It was scheduled for shut down later this year.
One BIG difference between that facility and the newer plants is the Japanese reactor cores at that location relied on ACTIVE Cooling that requires POWER.
It seems counter intuitive, but that generation of nuclear power plant REQUIRES outside power to remain "safe" in the event of a shutdown.
The plant survived the earthquake and shut down just as it was designed to do.
The problem has been created by the Tsunami that wiped out the generators that were to provide power to the cooling pumps.
Point of my post is this. Most if not all of the newer designs are designed with gravity fed, or passive cooling systems in the event of a emergency shutdown.
Between the moratorium/permatorium on drilling in the Gulf of Mexico, and the moratorium on nuclear power plants that will likely result from this event,
I'm thinking that before long we will be rubbing two sticks together when we need to keep warm.
