As more information is available it seems that the Japan nuclear catastrophe was man made as also the Chernobyl accident and Three Mile Island partial meltdown.
The earthquake broke the containment and caused the beginning of the meltdown in Fukushima Daichi reactor one. The tsunami was just giving the other reactors also meltdowns because of total blackout and collapse of the cooling systems.
Chernobyl was caused by the plant operators risky testing of how the reactor could be steered in a total lack of outside power situation (which caused two reactors and several spent fuel pools to overheat and part of them to melt in Fukushima). But Chernobyl did blow up quickly after getting out of control. Fukushima reactors blew up after a longer time, mostly for hydrogen build-up, except the reactor -3 that seem to have had a prompt criticality nuclear detonation - most likely in the MOX-spent fuel pool.
But the main question remains unanswered until now: what should all the nuclear regulatory officials around the world do now - there are tens of risky reactors at earthquake zones that can suffer FD reactor -1 destiny - a melt through because of a seismic event that causes the reactor fatal damage.
Silence is the basic answer now. The atom- men and atom-women know excactly how risky the game that is going on in nuclear industry right now is. But they don't tell it to the politicians. They don't tell it to the people. They are afraid. Thay are ofraid of loosing whole the industry that is paying their salaries. They are afraid of loosing their status of high-ranking decicion makers in high tech industry. They stay silent or deny it all.
But they shouldn't be afraid. They could continue to be experts in nuclear industry even though all the reactors would be shut down. There is a growing demand of nuclear knowhow when decommissioning the reactors and safely storing all the millions of kilograms of highly radioactive nuclear waste for hundreds of thousands of years. Somebody got to pay for that work. And it should be the nuclear industry. But unless they don't switch quickly to large scale renewable energy generation they can't afford that fun. So I'm afraid it's you and me - the taxpayers worldwide that pay that mistakes of the past-ugly game.
Still there is an urgent need for shutting down the most dangerous nuclear reactors on active faults and EQ-zones. Immediately! All the responsible nuclear watchdogs - take the action, NOW!