Protactinium (atomic number 91) is a metal discovered by Oswald Gohring and Kasimir Fajans in 1913. It was only in 1934 when the element was first isolated. Protactinium-231 was discovered by John Cranston and Frederick Soddy and Lisa Meitner and Otto Hahn in 1918.This metal is found in uranium ores while its isotopes are present in uranium-238 and uranium-235.Protactinium is a rare metal that reacts with inorganic acids, water vapor, and oxygen.It is toxic, radioactive, and harmful for human health. Because protactinium is a rare element, it is not used for commercial purposes and only for scientific research.pent nuclear fuel is also used to extract the metal. In households, it is found in smoke detectors in the form of protactinium-233 which is the product of decay of neptunium-237. The isotope itself has a half life of only 27 days (in comparison, the half life of protactinium-231 is over 32,000 years).