50 Fun Facts About Uranium

What is uranium's atomic number?

Its symbol is U and it sits in the actinide series; it is the highest-numbered element found naturally in significant amounts.

Uranium was named after which planet?

William Herschel had discovered the planet only eight years before the element was found in 1789.

Which German chemist is credited with discovering uranium in 1789?

He precipitated a yellow compound from the ore and thought the black powder he then made was the metal; it was actually an oxide.

In which mineral was uranium first discovered?

Pitchblende is uraninite, uranium's natural oxide, and remains the most common uranium ore.

Who first isolated uranium metal, in 1841, by heating uranium tetrachloride with potassium?

He was professor of analytical chemistry at the Conservatoire National des Arts et Métiers in Paris.

Who discovered radioactivity in 1896 using a uranium salt left on a photographic plate?

He found the plate in a drawer had become 'fogged' by invisible rays from the potassium uranyl sulfate.

Which isotope makes up over 99% of natural uranium?

It has 146 neutrons; the fissile isotope has only 143.

Which uranium isotope is fissile and used in reactors and weapons?

It is only about 0.7% of natural uranium, which is why fuel and bombs need enrichment.

What is the half-life of uranium-238?

That makes it ideal for dating the oldest igneous rocks through uranium-lead dating.

Uranium's density is about 70% higher than that of which metal?

At 19.1 g/cm3 it is only slightly less dense than gold and tungsten.

Which two scientists found barium among the products of bombarding uranium with neutrons in 1938?

The work was done in Hahn's Berlin laboratory; the theoretical interpretation came a year later.

Who published the physical explanation of uranium splitting in February 1939 and named it 'nuclear fission'?

Frisch was Meitner's nephew; she had fled Nazi Germany the previous year.

On average, how many neutrons are released by each fission of uranium-235?

Enough of them hitting other nuclei is what sustains a chain reaction, confirmed in 1939.

Fermi's team at first mistook uranium fission products for new elements 93 and 94. What were they named?

Orso Mario Corbino, dean at Rome's Sapienza University, coined the names; the real elements 93 and 94 were identified a few years later.

Who separated the world's first sample of uranium-235, on 29 February 1940?

He used an instrument he built himself at the University of Minnesota; John Dunning confirmed its fissility with Columbia's cyclotron the next day.

Where was Chicago Pile-1, the first self-sustaining artificial chain reaction, built in 1942?

Fermi's team stacked 360 tonnes of graphite, 53 tonnes of uranium oxide and 5.5 tonnes of uranium metal.

Which nuclear weapon, dropped on Hiroshima, relied on uranium fission?

The Trinity test device and Fat Man, dropped on Nagasaki, used a different fissile element.

What is the smallest amount of uranium-235 said to be enough for an atomic bomb?

The Hiroshima bomb exploded with the force of about 12,500 tonnes of TNT.

What was the name of Germany's wartime nuclear research project?

The 'uranium club' was hampered by infighting, exiled scientists and a mistake about impurities in graphite that ruled it out as a moderator.

Which installation first generated nuclear electricity, lighting four bulbs on 20 December 1951?

The nearby town of Arco later became the first anywhere to run entirely on nuclear electricity, from BORAX-III.

The world's first commercial-scale nuclear power station began generating in June 1954. Where?

Calder Hall followed in 1956 and Shippingport in 1958; the submarine USS Nautilus went nuclear in 1954 too.

Natural nuclear reactors that ran 1.7 billion years ago were discovered in 1972 at which mine?

Back then uranium-235 made up about 3% of uranium, enough for a chain reaction with groundwater as moderator.

Commercial nuclear power plants typically use fuel enriched to roughly what level of uranium-235?

Only the CANDU and Magnox designs can run on unenriched uranium; US Navy reactors use highly enriched fuel.

One kilogram of uranium-235, fully fissioned, releases as much energy as roughly how much coal?

That is about 20 terajoules from a single kilogram.

What was the cheapest and leading method of enriching uranium in the 2020s?

They exploit the tiny mass difference between the isotopes; gaseous diffusion was the Manhattan Project's method.

Which white, easily sublimed compound of the metal is used in enrichment because its vapour behaves like a gas?

UF6 is the most volatile uranium compound known.

What is 'yellowcake'?

It contains at least 75% U3O8 and is calcined before refining and conversion.

Which country mined 39% of the world's uranium in 2024?

It has dominated the market since 2010; Canada and Namibia came next in 2024.

Which country holds 28% of known uranium reserves and the largest deposit, at Olympic Dam?

There is also a significant reserve at Bakouma in the Central African Republic.

High-grade ores in which Canadian basin can average up to 23% uranium oxides?

Typical low-grade ore holds only 0.01 to 0.25%.

In 2021, most of the world's uranium was produced not by conventional mining but how?

It accounted for 66% of production in 2021 versus 29% from underground mining.

Roughly how much uranium is estimated to be dissolved in the world's seawater?

Japanese scientists showed extraction with ion exchangers was feasible in the 1980s, but carbonate in the water keeps yields low.

Before radioactivity was discovered, uranium's main use was for what?

Uranium glass and Fiestaware are the best-known examples; the Romans were adding it to glazes by 79 AD.

Yellow glass with 1% uranium oxide was found in a Roman villa on which cape near Naples?

R. T. Gunther of Oxford found it in 1912, pushing uranium's use back to at least 79 AD.

In the early 1800s, the world's only known uranium ore came from silver mines in which Bohemian town?

Ore from the Habsburg mines had been used to colour local glass since the late Middle Ages.

Marie Curie's discovery of which element in uranium ore sparked mining that left uranium as a waste product?

It took three tonnes of uranium to extract one gram of radium, so cheap uranium waste flooded the tile-glazing trade.

In WWI the Central Powers substituted ferrouranium for which scarce metal in gun barrels?

When the practice became known in 1916, the US government asked universities to study uranium in metalwork.

What is the main military use of depleted uranium?

Its density, hardness and pyrophoricity make it devastating against armour; it also hardens tank plating.

What is the main health risk from depleted uranium?

Uranium is only a weak alpha emitter, and alpha particles cannot penetrate the skin.

To count as 'depleted', uranium must contain no more than what fraction of uranium-235?

Enriched fuel sits between 3% and 5%; the price rise since 2001 has made re-enriching some tailings worthwhile.

Uranium bioaccumulates for years in which body tissue because of its affinity for phosphates?

Uranyl ions also gather in the liver, kidney and reproductive tissues; the metal is toxic quite apart from its radioactivity.

Under Megatons to Megawatts, Russia supplied the US with 15,000 tonnes of what?

Weapons-grade uranium is diluted with uranium-238 and burned as ordinary reactor fuel.

Which US law of 1990 required $100,000 'compassion payments' to uranium miners diagnosed with cancer?

Excess lung cancer among Navajo uranium miners had been documented and linked to their work.

Like all elements heavier than iron, uranium is naturally forged only by what?

Rapid neutron capture is needed because the slow s-process cannot jump the instability gap after bismuth.

Radioactive decay of uranium, thorium and potassium-40 deep inside Earth is thought to drive what?

That heat is also what keeps the outer core liquid.

Uranium can be transmuted in a reactor into which fissile element?

Uranium-238 absorbs a neutron and beta-decays through neptunium-239 to plutonium-239 within days.

How does uranium's abundance in Earth's crust compare with silver's?

At 2 to 4 parts per million it is the 48th most abundant element, about as common as arsenic or molybdenum.

Which two commercial reactor designs can run on unenriched uranium fuel?

Most commercial plants use fuel enriched to around 3% uranium-235, while US Navy reactors use highly enriched fuel.

How many tonnes of uranium ore had to be processed to extract a single gram of radium?

The leftover uranium was so plentiful it was diverted to make cheap pottery and bathroom-tile glazes.

Which bacterium can encrust itself with nine grams of uranyl phosphate crystals per gram of cells in a day?

The ability raises hopes of using microbes to clean up uranium-polluted water; the lichen Trapelia involuta also concentrates the metal.