Fukushima Daiichi nuclear disaster for caesium-137, which is about 11% of Chernobyl emissions. Earlier estimations were 150 PBq and 12 PBq. In 2011, scientists working for the Japan Atomic Energy Agency, Kyoto University and other institutes, recalculated the amount of radioactive material released into the ocean: between late March through April they found a total of 15 PBq for the combined amount of iodine-131 and caesium-137, more than triple the 4.72 PBq estimated by TEPCO. The company had calculated only the direct releases into the sea. The new calculations incorporated the portion of airborne radioactive substances that entered the ocean as rain. In the
Isotopes of caesium only long after the nuclear explosion is over. The combined yield of Cs and Cs is given as 6.7896%. The proportion between the two will change with continued neutron irradiation. Cs also captures neutrons with a cross section of 140 barns, becoming long-lived radioactive Cs. Caesium-134 undergoes beta decay (β), producing Ba 134 directly and emitting on average 2.23 gamma ray photons (mean energy 0.698 MeV). Caesium-135 is a mildly radioactive isotope of caesium with a half-life of 2.3 million years, decaying, via emission of a low-energy beta particle, into the stable isotope barium-135. Caesium-135 is one of the 7