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15 Intriguing Facts About Uranium | A Weak Radioactive Metal

[Estimated read time: 7 minutes]

Uranium is known to humanity since at least 79 AD when it was used in the ceramic industry (natural oxide form) in several parts of Europe. The chemical element was formally discovered only in 1789, when Martin Heinrich Klaproth, a German chemist stumbled upon a strange, unknown substance (oxide of uranium) during an experiment. Klaproth is also credited for discovering zirconium, cerium, and tellurium.

Uranium is a naturally occurring mineral found in small amount in the soil, water, and rocks and it is generally extracted from uraninite mineral for commercial use. It came into limelight at the world stage for the first time in the 1930s, when a team of researchers led by physicist Enrico Fermi and then Otto Hahn—Fritz Strassmann unearthed Uranium’s ability to break apart (fission) into lighter elements.

Subsequently, two of Uranium’s fundamental isotopes; uranium-235 and uranium-238 were discovered. These discoveries allowed different nations to develop nuclear weapons. The rest is history. Below, we have gathered some of the most interesting facts about uranium that you might not know.

Physical Properties

  • Density: 19.1 g/cm3
  • Atomic Number: 92
  • Melting Point: 1132 °C or 1405 K
  • Boiling point: 4131 °C or 4404 K

15. There is No Shortage of Uranium as A Power Source

A study conducted by MIT researchers in 2010 revealed that there are more than enough uranium reserves for the world’s nuclear energy for a foreseeable future. At the moment, all nuclear reactors use uranium as well as plutonium for the process. It is interesting to note that most of the plutonium in use is actually made from uranium isotopes since plutonium is only available in small traces in nature.

14. The First Ever Nuclear Reactor

After successfully discovering Uranium’s fission capability, another team led by Enrico Fermi, this time under the Manhattan Project, started working on world’s first nuclear reactor named Chicago Pile-1 (CP-1). On 2nd December 1942, the team was able to initiate the first ever self-sustaining nuclear chain reaction in CP-1.

Their initial plan was to use enriched uranium-235 as the fuel but was dropped due to its scarcity at that time. Instead, the reactor was fueled by 45 tonnes of uranium oxide and 5.4 tonnes of uranium metal. About 360 tonnes of granite was used as a neutron moderator. Unlike many contemporary nuclear reactors, CP-1 had no cooling system in place.

13. Uranium is Far More Important Than You Think

Thorium, uranium and potassium-40 decay is the main source of heat near the Earth’s mantle which drives the critical mantle convection and keeps the outer liquid contrary to the solid inner core. This heat also plays an important role in the plate tectonics. Furthermore, uranium-238’s long half-life (4.51×109 years) makes it perfect for all kinds of radiometric studies (radiocarbon dating) i.e uranium–uranium, uranium-thorium, and uranium-lead dating. It is also used for making high-energy X-rays.

uranium

12. It’s the Heaviest Naturally Occurring Element Known to Us

The heaviness of an element can be defined in two ways; in terms of its atomic weight and in terms of its density. With 92 protons in its nucleus and an atomic weight of about 238.0289 uranium is the heaviest naturally occurring element on Earth. The heaviest synthetic element known to date is ununoctium or oganesson (atomic number 118). On the other hand, the heaviest element in terms of density is Osmium (22.59 g/cm3).

11. Uranium is Highly Unstable

All the isotopes of uranium are highly unstable and it’s mostly due to its size. Tom Zoellner in his book Uranium: War, Energy, and the Rock described uranium something like this, “A uranium atom is so overloaded that it has begun to cast of pieces of itself, as a deluded man might tear off his clothes”.

10. Uranium was Isolated For the First Time in 1841

Becquerel's photographic plateBecquerel’s plate which has been fogged by radiation from uranium salt.

The first person to isolate uranium was Eugène Péligot, a chemistry professor at National Conservatory of Arts and Crafts (Conservatoire National des Arts et Métiers) in Paris. Péligot successfully demonstrated that the mysterious black powder discovered by Martin Heinrich Klaproth was not a pure substance but an oxide of uranium (UO2). He did that by treating uranium tetrachloride (the black powder) with potassium.

Then in 1896, physicist Henri Becquerel unearthed the radioactive properties of uranium along with radioactivity itself. In order to do this, he used multiple phosphorescent materials which glow in dark after being exposed to light. He covered a photographic plate with black paper and placed different phosphorescent salts one by one. He hypothesized that the glow produced in CRTs (cathode ray tunes) by X-rays might be due to phosphorescence.

The results were unexpected as uranium salt was the only substance that caused a significant blackening of the plate. The study made it clear that phosphorescence was not behind fogging of the plate (uranium salts is non-phosphorescent) and that some form of invisible radiation was there which was penetrating the black paper and making it look like as the plate was exposed to light.

Read: Scientists Extract 5 Grams Of Uranium From Seawater

9. Nature’s Own Nuclear Fission Reactor

In 1972, Francis Perrin discovered more than a dozen ancient natural nuclear reactors located in three separate ore deposits at the Oklo mine in Gabon (a nation in the west coast of central Africa). Those fission reactors are inactive. Subsequent studies have revealed that they are nearly 2 billion years old, ages before the first man-made nuclear reactor were built.

You might be wondering, how it is possible? Well, in order to get a grasp of this you should first know that uranium-235, which makes just about 0.72% of natural uranium today, can sustain a fission chain reaction, unlike uranium-238. It also decays at a much faster rate than uranium-238. This means that uranium-235 has depleted much more than uranium-238 since the Earth was born.

If we project this backward (2 billion years ago) there would have been about 3%-3.6% uranium-235 present in uranium ore which would be enough to sustain a nuclear fission chain reaction. So theoretically, it is viable for an ancient, natural nuclear reactor to exist.

Some Quick Facts

8. Apart from being used as a nuclear fuel, depleted uranium is also used in high-density armor piercing ammo. An armor piercing shell is a type of ammunition specially made for penetrating armored glasses, cars, tanks, and even warships. Theoretically, a kilo of uranium 235 could produce ~80 terajoules of energy. It would take more than 3000 tonnes of coal to generate the same amount of energy.

uranium bulletMilitary grade depleted uranium high-density penetrators

7. In 2017, the global uranium production stood at 59,531 tonnes, slightly less than the 2015 and 2016 levels. Kazakhstan is the largest producer of uranium in the world followed by Canada, Australia, Niger, Russia, and Namibia. The United States is currently in the ninth position, responsible for about 2% of the world’s annual uranium production.

6. Australia has the largest uranium ore reserves in the world, about 29% (in 2015). The Olympic Dam Mine in South Australia is the largest known single uranium deposit. Another significant uranium reserve is in Bakouma, a sub-prefecture in the Central African Republic (central Africa). Uranium reserves are simply recoverable uranium, irrespective of its isotope.

5. After mining, uranium ores are generally crushed into regular pieces and then treated by chemical leaching to extract the uranium. The resulted product is a dry powder material known as  U3O8 and is marketed as “yellowcake”.

4. Uranium miners are more likely to develop lung cancer and other long-term health issues than an average person. A well-documented study conducted between the period of 1969-1993 found out that Uranium mining was the biggest factor leading to lung cancer among Navajo (tribe) people (after uranium mining was ended in Navajo Nation).

3. Health problems associated with the element is mostly due to its high toxicity rather than radioactivity since uranium is weakly radioactive (alpha particles emitted by uranium cannot penetrate the human skin). However, direct ingestion of the substance can cause serious damage to multiple organs, cancer, and long-term neurological disorders. While ingestion of high amounts of uranium is certainly deadly, kidneys can cope with the low amount of uranium exposure.

Read: Researchers Discover New Uranium Compounds With Unique Properties

2. Uranium’s density (19.1 g/cm3) is about 70% more than lead and slightly below than that of gold and tungsten, though it has the second-highest weight of naturally occurring elements.

Little Boy designLittle Boy ‘Gun’ assembly method. A nuclear explosion occurs when the hollow uranium projectile hit the target cylinder 

1. During World War II, the US military developed two types of nuclear bombs. The first was “Little Boy,” a uranium-based device which was detonated over the city of Hiroshima. The second nuclear device was nicknamed the “Fat Man,” an implosion-type nuclear weapon with a plutonium core (its plutonium was derived from uranium-235). The “Fat Man” was dropped on Nagasaki on 9 August 1945.

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