Pictures of radioactive dating
Thus polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10 Further radionunclides may occur in nature in virtually undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions.
Radionuclides are produced as an unavoidable result of nuclear fission and thermonuclear explosions.
There are about 730 radionuclides with half-lives longer than 60 minutes (see list of nuclides).
Thirty-two of those are primordial radionuclides that were created before the earth was formed.
Further radionuclides can be created from irradiation of the nuclear fuel (creating a range of actinides) and of the surrounding structures, yielding activation products.At least another 60 radionuclides are detectable in nature, either as daughters of primordial radionuclides or as radionuclides produced through natural production on Earth by cosmic radiation.More than 2400 radionuclides have half-lives less than 60 minutes.Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides.Secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare.
An imaging tracer made with radionuclides is called a radioactive tracer.