Isotope separation is too costly compared to cheaper alternatives. Ĭaesium-137 is not widely used for industrial radiography because it is hard to obtain a very high specific activity material with a well defined (and small) shape as caesium from used nuclear fuel contains stable caesium-133 and also long-lived caesium-135. In industry, it is used in flow meters, thickness gauges, moisture-density gauges (for density readings, with americium-241/beryllium providing the moisture reading), and in gamma ray well logging devices. In medicine, it is used in radiation therapy. In small amounts, it is used to calibrate radiation-detection equipment. Uses Ĭaesium-137 has a number of practical uses. One gram of 137Cs has an activity of 3.215 terabecquerel (TBq). A total of 85.1% of 137Cs decay generates gamma ray emission in this manner. Barium-137m decays to the ground state by emission of photons having energy 0.6617 MeV. Barium-137m has a half-life of about 153 seconds, and is responsible for all of the gamma ray emissions in samples of 137Cs. The remainder directly populates the ground state of 137Ba, which is stable. Ībout 94.6% decays by beta emission to a metastable nuclear isomer of barium: barium-137m ( 137mBa, Ba-137m). The characteristic 662 keV peak does not originate directly from 137Cs, but from the decay of 137mBa to its stable state.Ĭaesium-137 has a half-life of about 30.05 years. Seaborg and Margaret Melhase.ġ37Cs gamma spectrum. After being deposited onto the soil as radioactive fallout, it moves and spreads easily in the environment because of the high water solubility of caesium's most common chemical compounds, which are salts. Caesium-137 has a relatively low boiling point of 671 ☌ (1,240 ☏) and easily becomes volatile when released suddenly at high temperature, as in the case of the Chernobyl nuclear accident and with atomic explosions, and can travel very long distances in the air. It is among the most problematic of the short-to-medium-lifetime fission products. Trace quantities also originate from spontaneous fission of uranium-238. ), cesium-137 (US), 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.
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