5Comments
Uranium is a metallic element that defined the first half of the 20th century. From the discovery of radioactivity in 1896 and the development of nuclear weapons to providing a window into the subatomic world and providing electricity in nuclear power plants.
Science, politics, and art have been massively influenced by this one particular chemical element.
What is Uranium?
Uranium is one of the heaviest naturally occurring elements. In its nucleus, there are 92 protons and a variable number of neutrons, between 140 and 146. But only some of these combinations occur spontaneously, and the most abundant are Uranium-238 (92 protons and 146 neutrons) and Uranium-235 (92 protons and 146 neutrons).
Being such an extreme natural element, it can only be formed in an extreme event. This is called an r-process and happens in certain supernovae and in neutron stars collisions. From those events, it spread through the cosmos and became a crucial component of our planet despite its rarity. The reason why Earth has internal heat is the presence of uranium decaying.
And that's the crucial characteristic of uranium: Over time, it emits radiation in the form of helium atoms, turning into usually thorium. Almost all uranium isotopes (the version with a different number of neutrons) have a very long half-life, the time it takes for a sample to halve its uranium content. Uranium-238 has a half-life of 4.5 billion years.
Who Discovered Uranium?
Uranium has been used since Roman times as a yellow glaze in ceramics and glass. It found a resurgence in the Middle Ages as pitchblende and was still employed as a dye in glassmaking. In 1789 German chemist Martin Heinrich Klaproth mixed nitric acid and pitchblende, then neutralized the solution with sodium hydroxide. This reaction created a yellow substance that sank to the bottom.
When heated with charcoal it reduce to a black powder, which Kalproth erroneously believed to be pure uranium but it was most likely an oxide. He named the new element after the planet Uranus, discovered just eight years before by Willaim Herschel. It took until 1841 for the first pure sample of Uranium to be isolated. That accomplishment was achieved by Chemist Eugène-Melchior Péligot.
What Is Uranium Used For?
Uranium’s use is no longer in coloring glasses and glazes but in its radioactive properties, discovered by Henri Becquerel in 1896. Four decades later, in 1934 a team of Italian physicists led by Enrico Fermi bombarded uranium with neutrons discovering that it emits electrons and positrons. It is the work of Otto Hahn and Fritz Strassmann, that show that Uranium can break into lighter element and Lise Meitner and her nephew Otto Robert Frisch explain and named the process of nuclear fission.
And this is what makes Uranium a game-changer, for better or worse. One kilogram of Uranium-235 if led through complete fission is equivalent to the chemical energy that can be extracted by burning 1.5 million kilograms of coal. This ability to store such energy and release it in a well-understood way allowed the use of this element in nuclear power plants.
Equally, the sudden and explosive release of energy from uranium was employed in the atomic bombs.
In nuclear power plants, the radioactive emission of fuel rods made of uranium heats up a coolant which in turn is used used to heat up the water in another container and turn it into steam. The steam pushes turbines attached to a generator, creating electricity — and, crucially, doesn't produce greenhouse gas emissions.
Enriched And Depleted Uranium
In either scenario, uranium as it is commonly found is not ideal in many reactors. Over 99.2 percent of uranium mined on Earth is Uranium-238, with Uranium-235 making almost all the rest. This latter isotope is very good at creating a nuclear chain reaction which makes it possible to have a steady and sustained reaction. But you need to have enough of it in your fuel rod. This is known as critical mass and enriched uranium usually has between 3 and 5 percent.
The leftover from the enrichment process is the creation of Depleted uranium, which has less Uranium-235. This has been employed as containers to transport radioactive material, industrial radiography equipment, as well as military uses such as armor plating and armor-piercing projectiles. Its widespread use in wars had many concerned about long-term health effects.
