A wave of 15 metres hit the nuclear power plant of fukushima daiichi.
When the eartquake happened, every nuclear power reactos tripped as designed and the nuclear fission process was stopped. But the problem is that that the fuel in a nuclear reactor continues to produce considerable amounts of heat even when fission has stopped.
Normaly, a circulating water continue to work even if the reactor has stopped in order to cool it down but in the fukushima daiichi nuclear power plants, the 1 to 3 reactors has lost the pumps that provided this cooling water. Fukushima Daiichi was designed to support a 6 metres wave but 15 metres was too much.
It is not clear how many people are still living in the evacuation zone, but reports said police had counted at least 60 families.
After the disaster the government also declared a wider 10km zone around the 20km evacuation area where people should either stay indoors or leave.
A radioactive cloud was spread from the central plant in all the world, it’s a chance for Japan that the wind comes from the continent and goes to the ocean. Because of that, Japan didn’t incure the cloud which, from most of its part, vanished in the ocean. Here is and animation of the Radioactive cloud :
But in order to cool down the dammages reactors, the autorities used the ocean seas. That commited a big polution with consequences in the future that noone can predict.