|
Caesium-137 (, Cs-137), cesium-137, or radiocaesium, is a radioactive isotope of caesium which 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. It is among the most problematic of the short-to-medium-lifetime fission products because it easily moves and spreads in nature due to the high water solubility of caesium's most common chemical compounds, which are salts. ==Decay== Caesium-137 has a half-life of about 30.17 years.〔 (【引用サイトリンク】url=http://www.nist.gov/pml/data/halflife-html.cfm )〕 About 95 percent decays by beta emission to a metastable nuclear isomer of barium: barium-137m (137mBa, Ba-137m). The remainder directly populates the ground state of barium-137, which is stable. Ba-137m has a half-life of about 153 seconds, and is responsible for all of the emissions of gamma rays in samples of caesium-137. One gram of caesium-137 has an activity of 3.215 terabecquerel (TBq).〔 (【引用サイトリンク】title=NIST Nuclide Half-Life Measurements )〕 The main photon peak of Ba-137m is 662 keV. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Caesium-137」の詳細全文を読む スポンサード リンク
|