Chernobyl disaster substantial levels of caesium, which were believed to have been passed onto them during their consumption by wild boars, a significant number of which already contained radioactive particles above the allowed level. Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in the core. Particularly dangerous are the highly radioactive fission products, those with high nuclear decay rates that accumulate in the food chain, such as some of the isotopes of iodine, caesium and strontium. Iodine-131 and caesium-137 are responsible for most of the radiation
Fukushima Daiichi nuclear disaster (Unit 3 Reactor) remote control robots were used to enter the Reactor Building and performed a series of inspections. On 27 April, TEPCO revised its estimate of damaged fuel in Unit 3 from 25% to 30%. Radiation measurements of the water in the Unit 3 spent fuel pool were reported at 140 kBq of radioactive caesium-134 per cubic centimeter, 150 kBq of caesium-137 per cubic centimeter, and 11 kBq per cubic centimeter of iodine-131 on 10 May. On 15 May, TEPCO revealed that the pressure vessel that holds nuclear fuel "is likely to be damaged and leaking water at Units 2 and 3",