London Telegraph 
Sept 13, 2011
Radioactive cesium from the crippled Fukushima Dai-Ichi nuclear plant is circulating with the currents in the Pacific Ocean and will wash up on Japan’s shores again in between 20 and 30 years.
Scientists from the government’s Meteorological Research Institute and the Central Research Institute of the Electric Power Industry announced their findings at a meeting of the Geochemical Society of Japan this week, adding that some of the cesium will also flow into the Indian Ocean and, eventually, reach the Atlantic.
The scientists estimated that some 3,500 terabecquerels of cesium-137 was released into the sea directly from the plant between March 11, when the earthquake and tsunami struck, and the end of May. Another 10,000 terabecquerels of cesium fell into the ocean after escaping from the reactors in the form of steam.
One terabecquerel is a trillion becquerels, the standard measure of radiation, and the Japanese government has set the permissible level of iodine-131 for vegetables and fish at 2,000 becquerels per kilogram (2.2lbs).