Japanese Seismologist in 2004 on Risk of Nuclear Accident: "It's Like a Kamikaze Terrorist Wrapped in Bombs Just Waiting to Explode"
Of all the places in all the world where no one in their right mind would build scores of nuclear power plants, Japan would be pretty near the top of the list...Japan sits on top of four tectonic plates, at the edge of the subduction zone, and is in one of the most tectonically active regions of the world...I realized that Japan has no real nuclear-disaster plan in the event that an earthquake damaged a reactor's water-cooling system and triggered a reactor meltdown. 
It is not a question of whether or not a nuclear disaster will occur in Japan; it is a question of when it will occur.
And the New York Times points out today:
In an admission of how long the cooling process may take, Hidehiko Nishiyama, deputy director general of the Nuclear and Industrial Safety Agency, Japan's nuclear regulator, said late Tuesday: "We will have to continue cooling for quite a long period. We should be thinking years."
Kuni Yogo, a former atomic energy policy planner in the Japan Science and Technology Agency, said: "There is some trial and error, but this is the beginning of a three- to five-year effort."
Of course, if all goes well, the reactor cores and spent fuel rods should cool down considerably over the next couple of months. But the fact that the Japanese might need to sustain the cooling effort for years on end is stunning.