Protactinium was first discovered in 1913 , when Kasimir Fajans and O. H. GÃ hring encountered short-lived isotope 234m-Pa , with a half-life of about 1.17 minutes , while they were studying the decay chain of 238-U . Protactinium was first identified in 1913 , when Kasimir Fajans and Oswald Helmuth GÃ hring encountered the isotope 234Pa during their studies of the decay chains of uranium-238 : â ' â ' â ' .