What is Protactinium?
'''Protactinium''' is a very radioactive [[chemical element]] with the symbol '''Pa''' and [[atomic number]] 91. The density of this element is 231.04 == Notable characteristics == Protactinium is a silver [[metal]]lic element that is in the [[actinide]] group, with a bright metallic shine that it keeps for some time in the air. It is [[Superconductivity|superconductive]] at temperatures below 1.4 [[Kelvin|K]]. == Applications == Due to its [[scarcity]], high radioactivity and toxicity, there are currently no uses for protactinium outside of basic research. Protactinium-231 (which is made by the [[alpha decay]] of [[Uranium-235]] followed by [[beta decay]] of [[Thorium-231]]) could possibly sustain a nuclear [[chain reaction]] and might be used to build a nuclear weapon. The [[critical mass]], according to [[Walter Seifritz]], is 750±180 kg. Other authors conclude that no chain reactions are possible in Protactinium-231. == History == Protactinium was first discovered in [[1913]], when [[Kasimir Fajans]] and [[O. H. Göhring]] 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. They gave the new element the name ''Brevium'' ([[Latin]] ''brevis'', brief, short); the name was changed to ''Protoactinium'' in [[1918]] when two groups of scientists ([[Otto Hahn]] and [[Lise Meitner]] of [[Germany]] and [[Frederick Soddy]] and [[John Cranston]] of the [[United Kingdom|UK]]) independently discovered 231-Pa. The name was shortened to ''Protactinium'' in [[1949]]. In [[1961]], the United Kingdom Atomic Energy Authority was able to produce 125 g of 99.9% pure protactinium, processing 60 tons of waste material in a 12-stage process and spending 500,000 USD. For many years to come, this was the world's only way to get the element. It is said that the metal was sold to laboratories for a cost of 2,800 USD / g in the following years. == Precautions == Protactinium is both toxic and highly radioactive. It requires precautions similar to those u