Protactinium was first identified in a short-lived form in 1913 by Kasimir Fajans and Oswald Gohring, who called it brevium, and the long-lived isotope was characterised in 1917 and 1918 by Otto Hahn and Lise Meitner in Germany and, independently, by Frederick Soddy and John Cranston in Britain. Its name means parent of actinium, from the Greek protos, first. Protactinium is a dense, silvery, highly radioactive metal, one of the rarest and most expensive natural elements. Extracted only in tiny amounts from spent reactor fuel or uranium ore, protactinium has no uses outside research, where its isotopes help to date marine sediments and reconstruct past climate; its scarcity and radioactivity make it one of the least studied of the elements.
Almost the entire world's usable stock of protactinium, roughly 125 grams, was extracted in 1961 by the United Kingdom Atomic Energy Authority from some 60 tonnes of radioactive waste material left over from uranium ore processing, at a cost reported at around half a million US dollars; that single, expensive extraction effort supplied most of the protactinium used in research laboratories worldwide for decades afterward, since no comparable large-scale purification has been repeated since.