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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.
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.
Caesium-137 is one such radionuclide. It has a half-life of 30 years, and decays by beta decay without gamma ray emission to a metastable state of barium-137 (137m Ba). Barium-137m has a half-life of a 2.6 minutes and is responsible for all of the gamma ray emission in this decay sequence. The ground state of barium-137 is stable.
Figure 1: Sodium iodide gamma spectrum of caesium-137 (137 Cs) An example of a NaI spectrum is the gamma spectrum of the caesium isotope 137 Cs —see Figure 1. 137 Cs emits a single gamma line of 662 keV. The 662 keV line shown is actually produced by 137m Ba, the decay product of 137 Cs, which is in secular equilibrium with 137 Cs.
Caesium-137, with a half-life of 30 years, is the main medium-lived fission product, along with Sr-90. Cs-137 is the primary source of penetrating gamma radiation from spent fuel from 10 years to about 300 years after discharge.
OSLO (Reuters) -Norway said on Wednesday that elevated levels of radioactive caesium (Cs-137) it had detected near the Arctic border with Russia were likely due to a forest fire near Chornobyl in ...
The isotope responsible for most of the gamma exposure in fuel reprocessing plants (and the Chernobyl site in 2005) is caesium-137. Iodine-129 is a major radioactive isotope released from reprocessing plants.
A mining company dropped a tiny capsule of caesium-137 somewhere along an 870-mile stretch of Western Australia’s Great Northern Highway. The plan is to find it before someone gets hurt, Liam ...