Radioactive cesium from Fukushima on tour of Pacific Ocean
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.
By Julian Ryall
15 Sep 2011
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).
Cesium is considered a more serious threat, however, because of its relatively long half-life. Cesium has a half-life of around 30 years, can accumulate in muscles and is a known cause of cancer.
The researchers believe that the cesium has initially dispersed into the Pacific from the coast of Fukushima Prefecture but will be taken to the southwest by the prevailing currents at a depth of around 1,300 feet. Just short of the International Date Line, the shifting currents will take the cesium close to the Philippines before it again turns north on the Japan Current.