On March 11, 2011, a giant tsunami from the Pacific Ocean swept over the 10-meter sea wall surrounding six reactors at the Fukushima power plant on Japan’s east coast. The crashing water caused reactor cores to overheat and melt, and subsequent hydrogen explosions damaged three reactor buildings.
The country shut down all of its more than 40 reactors, and investigations began into radiation exposure to tens of thousands of nearby residents, as well as to wildlife on land and sea.
Major questions still loom today, in part because the damaged reactors are too dangerous to enter, and in part because the plant’s operator, the Tokyo Electric Power Company, is reluctant to share information.
The uranium fuel in three of the six reactors eventually melted, and explosions blew holes in the roofs of three reactor buildings, releasing radioactive iodine, cesium and other fission products over land and sea.
Because the molten fuel still generates heat by radioactive decay Tepco has to keep pumping water through the reactor buildings and collecting as much as possible-some 400 cubic meters a day, stored in on-site tanks.
As a consequence, levels of cesium also remain elevated in fish such as greenlings, which feed off the sediments close to the Fukushima plant site.