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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.
Caesium-134 is found in spent nuclear fuel but is not produced by nuclear weapon explosions, as it is only formed by neutron capture on stable Cs-133, which is only produced by beta decay of Xe-133 with a half-life of 3 days. Cs-134 has a half-life of 2 years and may be a major source of gamma radiation in the first 20 years after discharge.
Caesium-137 decay scheme, showing it initially undergoes beta decay. The 661 keV gamma peak associated with 137 Cs is actually emitted by the daughter radionuclide. The accompanying decay scheme diagram shows the beta decay of caesium-137. 137 Cs is noted for a characteristic gamma peak at 661 keV, but this is actually emitted by the daughter ...
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.
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 ...
A new sealed cesium-137 radiation source as it appears in its final state. A radioactive source is a known quantity of a radionuclide which emits ionizing radiation, typically one or more of the radiation types gamma rays, alpha particles, beta particles, and neutron radiation.