40. Zirconium: Burning Up, Melting Down

Today, we reach the last element on the periodic table — but only alphabetically speaking.

Featured above: A cluster of fuel rods, of the type used to supply power on board a nuclear-powered ship.

Show Notes

Show notes are going to be a bit light until later today. Same with the works cited, I’m afraid. I spent my weekend with visiting family, which takes priority over the podcast! By Wednesday, everything should be in place.

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Episode Script

Some of the most ancient scriptures of Hinduism, Judaism, and Buddhism make prominent mention of a gem we know as “zircon.” It’s variously called jargon, gomeda, hyacinth, and more, but they all refer to the same lightly colored precious stone.

In Hinduism, it’s mentioned as one of the nine most precious gemstones that exists, alongside diamonds, rubies, and others. A Buddhist account describes the Exalted One’s bodhi tree as being adorned with a garland of zircon. 1 2 3 4

Modern times have taken the shine off zirconium-based gemstones. It’s popularly known in its form called “cubic zirconia,” a brilliant stone that looks similar to diamond, and is sometimes used to make jewelry that’s not so expensive. It’s a strange loop that’s responsible for cubic zirconia’s poor reputation: It’s an inexpensive gemstone, so people don’t value it — and people don’t value it because it’s inexpensive.

It’s unfortunate that element 40 is known as “the one that’s pretty and cheap,” because there’s so much more going on. Zirconium is an element at the heart of some of the most intensely hot, turbulent, and radioactive environments we have ever seen.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re getting steamed over zirconium.

Those holy texts are ancient, sure, but compared to some of the zircon on Earth, they’re still hot off the presses. The oldest scriptures were written around four thousand years ago, but the oldest zircons we’ve found are 4.4 billion years old.5 6 That’s almost as old as the Earth itself, minerals that formed just as the ocean of lava that covered the globe was starting to cool.

Zircon is so durable and resilient that these stones have remained internally unchanged for as long as they’ve existed. This sturdiness becomes less surprising when you glance upward — just above element 40 on the periodic table is the similarly strong titanium.

Zircon is also a stone that naturally includes a fair amount of uranium in its lattice. With a half-life around 4.5 billion years, conveniently, scientists can date samples of zircon by cracking them open and checking how much of that uranium has decayed into lead. It’s very similar to the carbon dating we discussed in episode 6, but on a much longer time scale.

Coincidentally, the German chemist Martin Heinrich Klaproth discovered both zirconium and uranium in 1789, from two entirely different mineral samples.7 There’s no way he could have known, but the special relationship between these two elements would only grow stronger over time.

Most of the pure zirconium metal that gets produced today, you see, winds up as uniquely valuable infrastructure coursing through nuclear power plants.

The properties that allow zircon stones to weather 4 billion years of geology are the same that make zirconium the metal of choice for the pipes that carry liquid coolant through a nuclear reactor: namely, its extreme resistance to corrosion.

But zirconium has another benefit that makes it uniquely suited to the task: it is practically impervious to the onslaught of neutron radiation that is a necessary byproduct of the fission of uranium. We have discovered no other material, yet, that acts as such effective armor against neutron radiation.

And that is why zirconium metal is also used to clad the outside of the all-important fuel rods inside a nuclear reactor.8 9The fuel rods are basically long containers stuffed full of uranium oxide pellets, which heat up, boiling steam that in turn drives the turbines that generate electricity. But it’s really important that the fuel rods don’t get too hot. The radiation-proof, corrosion resistant zirconium piping allows coolant to keep the fuel rods at a finely controlled temperature.10

But while element 40 excels in this high-heat, highly radioactive environment, it’s not indestructible. A violent natural disaster could easily cause things to break down — especially at a plant that had been poorly maintained for years.11

Such was the case on March 11, 2011, when one of the most powerful earthquakes ever recorded struck at 2:46pm local time just off the coast of Japan.12 So strong was this earthquake that it measurably caused the planet to wobble on its axis, and thrust the island of Honshu 2.4 meters eastward.13

That would qualify as a catastrophe at any point in human history. An earthquake such as this doesn’t just cause direct damage to people and structures on land. It also generates a series of tremendously powerful waves called a tsunami.

Tsunamis don’t just look like big versions of your regular ocean surf. In the deep ocean, a tsunami can travel swiftly — over 800 kilometers per hour — yet silently, passing beneath seafaring vessels completely undetected.

It’s only when the tsunami approaches shallow water that the situation turns ugly. Right before it makes landfall, the water at the shore can recede by hundreds of meters, turning the shallows into dry land. Meanwhile the wave slows down, but grows taller as it approaches the shore. within a few minutes, it comes rushing back toward land as an unstoppable wall of water.

This particular tsunami may have brought waves as tall as 40 meters high, which traveled as far as ten kilometers inland. Already weakened by the quake, this surge of water caused hundreds of thousands of buildings to collapse — and then, the force of that massive amount of water quickly retreating back to the ocean did even further damage.

The damage was unspeakable. Thousands of people died, and millions of homes were left without electricity or water.14 15 And at the Fukushima Daiichi nuclear power plant, the disaster was just beginning.

Immediately following the earthquake, the power plant’s walls began to crack, gas tanks exploded, and pipes began to burst.16 Suffice to say, things were not working as intended. The coolant could no longer moderate the fuel rods, and as the temperature climbed higher, both the zirconium coolant pipes and the fuel rod cladding began to swell. Above 1,200 degrees Celsius, the zircaloy began to burn, reacting with the water to produce highly flammable hydrogen gas.17 18

Multiple explosions wreaked havoc across several buildings, and the uranium fuel began to liquefy. It was literally a meltdown.19

The scene took days to unfold, days that were full of confusion and fright. It was the worst nuclear accident since the Chernobyl disaster in 1986. Between the earthquake, the tsunami, and the nuclear meltdown, nearly half a million people needed to evacuate the area.

Years later, the site is still disastrously radioactive, and hundreds of millions of dollars have been spent attempting to mitigate the contamination of groundwater.20 21Many of the evacuees have not and probably never will return to their homes.22 And deep inside the ruins of the Fukushima Daiichi power plant, hundreds of tons of uranium fuel are cautiously probed by experimental robots. Experts with an optimistic bent estimate that the full cleanup will require decades of effort.23 24

Yet it could have been far worse. While it’s an environmental catastrophe, fewer than 18 casualties have been attributed to the nuclear meltdown, and only one death. Wherever the government was unable to provide assistance to the survivors, civilians stepped in to help — including a surprisingly dedicated contingent of the Yakuza, Japan’s most infamous organized criminals.25 Tokyo remained safe, avoiding the citywide evacuation of 13 million people.26 And critically, the reactor cores at Fukushima remained relatively protected from fire and explosions, which means far less radioactive material was released.27 28

So much went wrong at Fukushima. A lack of oversight, poor maintenance, incompetence, and lies meant to protect the company in charge illuminate part of the story. By contrast, the zirconium in chemical pipelines and fuel rod cladding lasted as long as possible, only failing after the disaster was well underway.

That may have been element 40’s finest hour, but it pops up in all kinds of extreme environments. Its high durability gives it jobs in jet engines and spaceships’ heat shields. The U.S. military researched the possibility of manufacturing internal combustion engines made entirely of zirconia ceramics, which would require neither lubricants nor coolants. That never came to fruition, but did result in new materials that can be stronger and sharper than steel.29Now the element is used in scissors, power tools, and golf clubs. (It turns out that the companies that manufacture golf clubs love incorporating obscure elements in their product. Rarely does that make for a better club, but it does make it sound like it’s worth a lot of money.)

Any of those would make a fine addition to your element collection — or you could instead choose to startle with a bright, expertly cut stone of zircon or cubic zirconia. They’re truly inexpensive, but lovely. Besides, you’re not trying to convince anyone that they’re diamonds — carbon is so trivially easy to acquire, anyway.

If you’re the jet setting type, though, you might want to fetch some of that ancient Australian crust for yourself. A sample from the Jack Hills, dating back to the Earth ‘s first days, would certainly make for a notable sample.30 But it’s also worth mentioning that nearby, on Australia’s Eastern coasts, there are a few beaches with sands composed almost entirely of zirconium oxides. After spending the past few weeks traipsing about tiny towns in northern Europe, that might be just the kind of vacation you need.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel.

It’s that time of year again: listener nominations are open starting today for the people’s choice podcast awards. If you would like to help the Episodic Table of Elements on the slate of contenders, visit episodic table dot com, or the show notes for today’s episode at episodic table dot com slash z r.

Next time, sadly, we’ll turn to niobium.

Until then, this is T. R. Appleton, reminding you


  1. Jataka Parijata, Chapter 2, Sloka 21. See here for more.
  2. The Shiva Purana, Chapter 11, verses 10-12. Note that Hessonite is used interchangeably with Zircon, as they were presumed to be the same stone in ancient times.
  3. The Mahavastu, Chapter XXX: The Second Avalokita-Sutra. Ctrl-F for “gomedaka,” I am referring to the second instance.
  4. The Bible, New International Version, Exodus 28:18.
  5. Medium, The Oldest Scriptures In The World. Joshua Hehe, December 30, 2017.
  6. National Geographic, Earth’s Oldest Crust Dates To 4.4 Billion Years Ago. Dan Vergano, February 24, 2014.
  7. Academic Dictionaries And Encyclopedias, Timeline Of Chemical Element Discoveries.
  8. Springer International Publishing, Nuclear Fuel, Cladding, And The “Discovery” Of Zirconium. Thomas Filburn and Stephen Bullard, November 9, 2016.
  9. The New York Times, Zirconium: Covering For Fuel Rods. June 9, 1995.
  10. The Star, Explainer: What Is A Fuel Rod And How Does It Work? Leslie Ciarula Taylor, March 14, 2011.
  11. The Guardian, Fukushima Disaster Could Have Been Avoided, Nuclear Plant Operator Admits. Justin McCurry, October 15, 2012.
  12. LiveScience, Japan Earthquake & Tsunami Of 2011: Facts And Information. Becky Oskin, September 13, 2017.
  13. Deutsche Welle, Quake Shifted Japan By Over 2 Meters. Cyrus Farivar, March 14, 2011.
  14. Reconstruction Agency, Great East Japan Earthquake.
  15. NPR, Millions Of Stricken Japanese Lack Water, Food, Heat. March14, 2011.
  16. The Atlantic, Meltdown: What Really Happened At Fukushima? Jake Adelstein and David McNeill, July 2, 2011.
  17. World Nuclear Association, Fukushima Daiichi Accident. Updated October 2018.
  18. Harvard University Science In The News, Nuclear Chemistry: Lessons From The Fukushima Disaster. June 5, 2011.
  19. Scientific American, Partial Meltdowns Led To Hydrogen Explosions At Fukushima Nuclear Power Plant. David Biello, March 14, 2011.
  20. Wired, Fukushima’s Other Big Problem: A Million Tons Of Radioactive Water. Vince Beiser, April 27, 2018.
  21. CNET, Fukushima Dai-Ichi: The Latest Botch.
  22. Wired, The Robot Assault On Fukushima. Vince Beiser, April 26, 2018.
  23. The Guardian, Fukushima Operator May Have To Dump Contaminated Water Into Pacific. Justin McCurry, March 10, 2014.
  24. The Guardian, Dying Robots And Failing Hope: Fukushima Clean-Up Falters Six Years After Tsunami. Justin McCurry, March 8, 2017.
  25. Reuters, Yakuza Among First With Relief Supplies In Japan. Terril Yue Jones, March 25, 2011.
  26. The Independent, Safety Expert: Fukushima Nuclear Disaster Could Have Been Worse — And Nearly Was. Jeff Garberson, March 3, 2016.
  27. NPR, Fukushima Vs. Chernobyl: Still Not Equal. Eliza Barclay, April 12, 2011.
  28. Environmental Science And Technology, The Fukushima Disaster And Japan’s Nuclear Plant Vulnerability In Comparative Perspective. Phillip Y. Lipscy, Kenji E. Kushida, and Trevor Incerti, 2013. (PDF)
  29. Ultrahard Materials Limited, Why A Ceramic Engine?
  30. LiveScience, Confirmed: Oldest Fragment Of Early Earth Is 4.4 Billion Years Old. Becky Oskin, February 23, 2014.

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