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Caesium-137 (137 55 Cs), cesium-137 (US), [7] or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons.
Caesium-137 concentration in the air, 19 March 2011. Radioactive materials were dispersed into the atmosphere immediately after the disaster and account for most of all such materials leaked into the environment. 80% of the initial atmospheric release eventually deposited over rivers and the Pacific Ocean, according to a UNSCEAR report in 2020. [17]
The radiation source in the Goiânia accident was a small capsule containing about 93 grams (3.3 oz) of highly radioactive caesium chloride (a caesium salt made with a radioisotope, caesium-137) encased in a shielding canister made of lead and steel. The source was positioned in a container of the wheel type, where the wheel turns inside the ...
Radioactive caesium was found in waste water discharged into Tokyo Bay from a cement factory in the prefecture Chiba east of Tokio. In September and October two water samples were taken, measuring 1,103 becquerels per liter and 1,054 becquerels per liter respectively. These were 14 to 15 times higher than the limit set by NISA. Ash from ...
It is commonly believed that, with the rate of the current radionuclide leakage, the dispersal into the water would prove beneficial, as most of the isotopes would be diluted by the water as well as become less radioactive over time, due to radioactive decay. Cesium (Cs-137) is the primary isotope released from the Fukushima Daiichi facility. [160]
The 137 Cs level is higher in the sample that was further away from the ground zero point – this is thought to be because the precursors to the 137 Cs (137 I and 137 Xe) and, to a lesser degree, the caesium itself are volatile. The natural radioisotopes in the glass are about the same in both locations.
The low decay energy, lack of gamma radiation, and long half-life of 135 Cs make this isotope much less hazardous than 137 Cs or 134 Cs. Its precursor 135 Xe has a high fission product yield (e.g., 6.3333% for 235 U and thermal neutrons ) but also has the highest known thermal neutron capture cross section of any nuclide.
Decay of caesium-137. The radioactive 135 Cs has a very long half-life of about 2.3 million years, the longest of all radioactive isotopes of caesium. 137 Cs and 134 Cs have half-lives of 30 and two years, respectively. 137 Cs decomposes to a short-lived 137m Ba by beta decay, and then to nonradioactive barium, while 134 Cs transforms into 134 ...