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
Caesium-137 populates the ground state of barium-137, which is stable. Ba-137m has a half-life of about 153 seconds, and is responsible for all of the emissions of gamma rays in samples of caesium-137. 85.1% of metastable barium then decays to ground state by emission of gamma rays having energy 0.6617 MeV. One gram of caesium-137 has an activity of 3.215 terabecquerel (TBq). The main photon peak of Ba-137m is 662 keV. Caesium-137 has a number of practical uses. In small amounts, it is used to calibrate radiation-detection equipment. In medicine, it is used in radiation therapy. In industry, it is used