The biological behaviour of caesium is similar to that of potassium and rubidium. Health risks Ĭaesium-137 reacts with water, producing a water-soluble compound ( caesium hydroxide). Ĭaesium-137 is also used as a radioactive tracer in geologic research to measure soil erosion and deposition its affinity for fine sediments is useful in this application. Due to the residual radioactivity and legal hurdles, the resulting material is not commonly recovered even from "spent" radioactive sources, meaning in essence that the entire mass is "lost" for non-radioactive uses.Īs an almost purely human-made isotope, caesium-137 has been used to date wine and detect counterfeits and as a relative-dating material for assessing the age of sedimentation occurring after 1945. Cobalt-60 decays to stable nickel, whereas iridium-192 can decay to either stable osmium or platinum. However, while 137Ĭs is a waste product produced in great quantities in nuclear fission reactors, 192Ĭo are specifically produced in commercial and research reactors and their life cycle entails the destruction of the involved high-value elements. 192Ĭo, are preferred for radiography, since these are chemically non-reactive metals and can be obtained with much higher specific activities by the activation of stable cobalt or iridium in high flux reactors. A large emitting volume will harm the image quality in radiography. The latter has been used in demonstration of chemically stable water-insoluble forms of nuclear waste for disposal in deep geological repositories. Other chemically inert caesium compounds include caesium- aluminosilicate-glasses akin to the natural mineral pollucite. It is possible to make water insoluble caesium sources (with various ferrocyanide compounds such as NiĦ, and ammonium ferric hexacyano ferrate (AFCF), Giese salt, ferric ammonium ferrocyanide) but their specific activity will be much lower. Also the higher specific activity caesium sources tend to be made from very soluble caesium chloride (CsCl), as a result if a radiography source was damaged it would increase the spread of the contamination. 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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