Actinides in the environment

The actinide series is a group of chemical elements with atomic numbers ranging from 89 to 102, including notable elements such as uranium and plutonium. The nuclides thorium-232, uranium-235, and uranium-238 occur primordially, while trace quantities of actinium, protactinium, neptunium, and plutonium exist as a result of radioactive decay and neutron capture of uranium. These elements are far more radioactive than the naturally occurring thorium and uranium, and thus have much shorter half-lives. Elements with atomic numbers greater than 94 do not exist naturally on Earth, and must be produced in a nuclear reactor. However, certain isotopes of elements up to californium still have practical applications which take advantage of their radioactive properties.

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