Numbers, please: The history of metal number 18 – uranium

A pharmacist presented a newly discovered metal to the public 230 years ago: He called it uranium – as uranium it would later shape world history.

Exactly 230 years ago to the day, the pharmacist and chemist Martin Heinrich Klaproth presented a new metal in front of the Royal Prussian Academy of Science: Klaproth, who discovered titanium and zirconium oxide, had ground pitchblende from the Georgswagsfort mine near Johanngeorgenstadt and mixed it with various salt solutions processed. Under the title “Advertisement of a newly discovered semi-metal” it says: “I hope to have increased the number of the previously known 17 metals by a new one, which I attribute to the name uranite.” Klaproth chose the name after the planet Uranus, which was discovered by Friedrich Wilhelm Herschel eight years earlier. A year later, Klaproth’s uranite was renamed uranium. How many calories in uranium?

For the miners who mined silver in the Saxon Ore Mountains, pitchblende was the sign of the drying up of a silver vein. They were just unlucky when they came across this substance and cleared the uranium ore on the heap, where it oxidized. It was a stroke of luck for Klaproth to examine this overburden. “The yellow earth that accompanies this fossil, as well as the self-breaking green mica, or chalcolite, also belong to this new metallic substance,” he recognized. The powder produced by Klaproth, an oxide of uranium, was soon used in the production of uranium glass in Bohemia. Pure uranium could only be produced 50 years after it was discovered by Klaproth.

Uranium’s real career began on March 1, 1896, when the French physicist Henri Becquerel noticed that a photographic plate had been exposed even though it was stored in a dark room. Becquerel, who was experimenting with uranium salts, had stored his preparations made from uranium potassium sulfate in this room and was thus able to track down a radiation that he called uranium rays. After Wilhelm Conradt Röntgen and the X-rays , Becquerel is the second discoverer of invisible radiation. For his explanation of radioactivity – the name itself comes from Marie Curie – he and the Curie couple were awarded the Nobel Prize in Physics in 1903.

While Becquerel worked with uranium salts, the Curie couple experimented with pitchblende from the spoil from St. Joachimsthal in the Ore Mountains, today’s Jáchymov. Technically, the Curies evaluated the tailings – fine-grain residues from the processing of ores. They made the discovery that the material was much more active than other pitch blends and concluded that there must be more radioactive elements. This led to the discovery of the elements radium and polonium. In 1911 Marie Curie therefore received the Nobel Prize in Chemistry.

Back to uranium: In 1938 Otto Hahn and Fritz Straßmann tried their hand at the fission of uranium, which the emigrated Jewish project partner Lise Meitner described more generally and theoretically as nuclear fission in Sweden . Via Meitner and the Dane Niels Bohr, the findings reached the USA, where Enrico Fermi succeeded in the first chain reaction with uranium and uranium oxide in 1942 with the Chicago Pile . The age of nuclear energy could begin – as an arms race in the Cold War: The USA had completed its first atomic bomb in 1945, the Russian bomb was ready for use in 1949, and the first nuclear power plant went online in 1956.

Nowadays, when mining uranium, 1 ton of uranium is extracted from 10,000 tons of uranium ore as uranium oxide. This yellowcake contains 75 percent uranium and is exported in this form from the leading uranium mining countries Kazakhstan, Canada and Australia for energy production. What remains are the tailing basins that contaminate the mining area. They are known as the sacrificial zone in the USA, where there is hardly any uranium mined .

The yellow cake is converted into uranium hexafluoride and then goes to the enrichment plant, in which the proportion of fissile uranium-235 is increased to 3 to 5 percent for the production of fuel elements for nuclear power plants. Enrichment to 90 percent is necessary for military use as a nuclear warhead. The great differences between the two forms of use currently form the nucleus for the debates about the nuclear agreement with Iran, which is intended to limit Iran’s nuclear program to the peaceful use of nuclear energy.