Lake Karachay The lake accumulated some 4.44 exabecquerels (EBq) of radioactivity over less than one square mile of water, including 3.6 EBq of caesium-137 and 0.74 EBq of strontium-90. For comparison, the Chernobyl disaster released 0.085 EBq of caesium-137, a much smaller amount and over thousands of square miles. (The total Chernobyl release is estimated between 5 to 12 EBq of radioactivity, however essentially only caesium-134/137 [and to a lesser extent, strontium-90] contribute to land contamination because the rest is too short-lived). The sediment of the lake bed is estimated to be composed almost entirely of high level radioactive waste deposits to
Radiation effects from the Fukushima Daiichi nuclear disaster put out a total of 85 PBq of caesium-137. However, later reporting on 12 April estimated total caesium releases at 6.1 PBq to 12 PBq, respectively by NISA and NSC – about 2–4 kg. On 23 April, NSC updated this number to 0.14 TBq per hour of caesium-137 on 5 April, but did not recalculate the entire release estimate. On 12 October 2011 a concentration of 195 becquerels/kilogram of Strontium-90 was found in the sediment on the roof of an apartment building in the city of Yokohama, south of Tokyo, some 250 km from the plant in Fukushima. This first