Uranium: Useful for Atom Bombs & Dinner Parties

Today's Please Explain is about radiation. We present for you a primer on uranium, the radioactive rock:

Uranium is one of the heaviest and certainly one of the most volatile elements in nature. It’s also fairly abundant in the universe and can be found in the Earth's crust at a rate nearly 40 times that of silver. It's nucleus is so densely packed that uranium atoms can only be produced through the extreme force and pressure of a supernova. >>>


With 92 protons jammed into its nucleus, uranium is an element that is almost too large for its own good. As a result, the nucleus is constantly shedding parts of itself, producing radiation. Uranium has a half-life of about 4.5 billion years and will eventually decay into lead. It's kind of like an inverse form of alchemy.

You don’t have to look far —either the atom bomb or the unfolding crisis at the Fukushima Daiichi reactors-- to see the enormous power of uranium, but if you held it in your hand it would seem like a fairly innocuous yellow rock. It can even be shined to a nice polish. There are two main isotopes of uranium; U-238 and U-235, the latter being much more volatile. This is the kind of uranium most commonly used for bombs and reactors. Fortunately, U-235 only is about 0.7% of all uranium on the planet, so acquiring it requires making it yourself through a complicated enrichment process.

In the 16th century silver miners in Bohemia encountered so much uranium that they often called it the “bad luck rock.” Scores of miners perished from inhaling uranium dust. Piles of leftover radioactive rocks throughout what is now the Czech Republic were eventually harvested by the Soviet Union during the Cold War.

Uranium also has a unique ability to bind with oxygen in a way that creates colorful patterns and has been used a dye for centuries.  Stained glass containing uranium has been found dating to 1st Century AD. It has even been detected as a color additive in Roman glassware. As recently as the 1950’s uranium was used to color a line of highly radioactive dishes called “Fiesta Ware.” Those must have been some wild dinner parties.