Caesium-137 alienation around the Chernobyl nuclear power plant. Together with caesium-134, iodine-131, and strontium-90, caesium-137 was among the isotopes distributed by the reactor explosion that constitute the greatest risk to health. The mean contamination of caesium-137 in Germany following the Chernobyl disaster was 2000 to 4000 Bq/m. This corresponds to a contamination of 1 mg/km of caesium-137, totaling about 500 grams deposited over all of Germany. In Scandinavia, some reindeer and sheep exceeded the Norwegian legal limit (3000 Bq/kg) 26 years after Chernobyl. As of 2016 the Chernobyl caesium-137 has decayed by half, but could have been locally concentrated by much
Timeline of the Fukushima Daiichi nuclear disaster Economist reports that high levels of radioactive particles, including plutonium have been found in an extended irregular zone that extends well outside the 30 km evacuation radius around the Fukushima Dai-ichi nuclear power plant. A French study by the Institute for Radiological Protection and Nuclear Safety revealed that the Fukushima nuclear disaster caused the biggest discharge of radioactive material into the ocean in history. The radioactive caesium that flowed into the sea from the Fukushima Dai-Ichi nuclear plant was 20 times the amount estimated by its owner, Tokyo Electric Power Co. Atmospheric releases were cited as amounting to 35,800 terabecquerels