‘‘Chernobyl might have been five times bigger, over all, but the ocean impact was much smaller,’’ Mr. Buesseler said.

http://green.blogs.nytimes.com/2011/09/28/fukushimas-contamination-produ...

"Ken Buesseler, a scientist at the Woods Hole Oceanographic Institution, who in 1986 studied the effects of the Chernobyl disaster on the Black Sea, said the Fukushima disaster appeared to be by far the largest accidental release of radioactive material into the sea.

Chernobyl-induced radiation in the Black Sea peaked in 1986 at about 1,000 becquerels per cubic meter, he said in an interview at his office in Woods Hole, Mass. By contrast, the radiation level off the coast near the Fukushima Daiichi plant peaked at more than 100,000 becquerels per cubic meter in early April."