Polonium the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium. German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.
Uranium nitride and, in particular, it undergoes an (n,p) reaction which produces significant amounts of radioactive C which would need to be carefully contained and sequestered during reprocessing or permanent storage. Each uranium dinitride complex is considered to have three distinct compounds present simultaneously because of decomposing of uranium dinitride (UN) into uranium sesquinitride (UN), and the uranium mononitride (UN). Uranium dinitrides decompose to uranium mononitride by the following sequence of reactions: Decomposition of UN is the most common method for isolating uranium sesquinitride (UN). Uranium mononitride is being considered as a potential fuel for generation IV reactors such as the Hyperion