History of the metric system levels of the krypton 86 atom as the new standard for the metre. The standard metre artefact was retired. In 1960, Giorgi's proposals were adopted as the basis of the "Système International d'Unités" (International System of Units), the SI. This initial definition of the SI included six base units, the metre, kilogram, second, ampere, degree Kelvin and candela, and sixteen coherent derived units. The evolution of the SI after its publication in 1960 has seen the addition of a seventh base unit, the "mole", and six more derived units, the "pascal" for pressure, the "gray", "sievert" and "becquerel" for radiation,
Comparison of Chernobyl and other radioactivity releases Comparison of Chernobyl and other radioactivity releases This article compares the radioactivity release and decay from the Chernobyl disaster with various other events which involved a release of uncontrolled radioactivity. Natural sources of radiation are very prevalent in the environment, and come from cosmic rays, food sources (bananas have a particular high source), radon gas, granite and other dense rocks, and others. The collective radiation background dose for natural sources in Europe is about 500,000 man-Sieverts per year. The total dose from Chernobyl is estimated at 80,000 man-sieverts, or roughly 1/6 as much. However, some individuals, particularly in areas adjacent