The exterior of Primo Autobody Repair shop.

90. Thorium: Bright Lights, Big City

Sure, thorium could provide practically limitless clean energy, but then we couldn’t build weapons of mass destruction.

Featured above: The most radioactive site in New York City.

Show Notes

Many thanks again to all of you who so kindly wished me well, and for waiting so patiently for a new episode. It means the world to me.

I’d love to get back to the every-other-week schedule if possible, but for now I’m planning on going a little slower than that.

Non-Lead-Based Plumbing: In Salt: A World History, Mark Kurlansky relates how Chinese well diggers discovered and employed natural gas a very long time ago:

By A.D. 100, the well workers, understanding that the disturbances were caused by an invisible substance, found the holes where it came out of the ground, lit them, and started placing pots close by. They could cook with it. Soon they learned to insulate bamboo tubes with mud and brine and pipe the invisible force to boiling houses. These boiling houses were open sheds where pots of brine cooked until the water evaporated and left salt crystals. By A.D. 200, the boiling houses had iron pots heated by gas flames. This is the first known use of natural gas in the world.”

Episode Script

Jons Jakob Berzelius was apparently a big fan of Norse mythology. He’s the one who named element 23 “vanadium,” after the goddess Vanadis, and when he thought he discovered a new element in 1815, he named it “thorium,” after the god of thunder.

Only one problem: he hadn’t actually discovered a new element. T’was naught but yttrium phosphate. But he really liked the name. So when he actually did find a new element 13 years later, he used it again. That time it stuck.1 2

On the one hand, it’s rather inappropriate to name element 90 after a god of war, because the only way it can be used as a weapon is if you throw it hard enough. But as an homage to the god of lightning, it’s quite fitting, because thorium is absolutely crackling with potential as a source of electrical energy.

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 collecting issues of the mighty thorium.

It’s hard to imagine now, but there once was a time when we had more elements lying around than we knew what to do with. Not just ephemeral laboratory curiosities — relatively stable, naturally occurring elements that could be found as sand on a beach. For decades, thorium was one of them.

There wasn’t anything wrong with it. Its properties are similar to lead — it’s easy to hammer, weld, and work, it’s silvery-white in color, it’s heavy, and it’s even pretty abundant. But lead is way easier to find, so there was no good reason to use thorium instead. Or at least, it took a long time for anyone to find a good reason.

The person who did was Carl Auer von Welsbach, whose name might sound familiar. He was a scientist of many accomplishments, but most notably, he discovered neodymium and praseodymium.3 4

He had other claims to fame, though. In his own time, he was appreciated for his innovations in artificial lighting.5

In the 19th century, gas lighting was all the rage. The technology was a significant improvement over lamps and wax candles, and electrical infrastructure didn’t yet exist on any wide scale. But gas lamps were far from perfect. Notably, the light they produced was pretty dim.

von Welsbach was in the lab one day working with rare earth metals when he stumbled upon something brilliant. When he held those elements within the flame of a Bunsen burner, they glowed brightly — much more brightly than the flame itself. It’s a phenomenon called “candoluminescence.” That would provide the solution to the problem of dim streetlights.

There was a pretty clever method to hold the metals within the flame of a gas lamp: A bit of cotton is saturated with those rare earths and placed in the part of the lamp where the flame appears. The first time the lamp is used, the cotton burns away, leaving behind a delicate mesh of metals that greatly amplifies the light produced.6

von Welsbach experimented with various mixtures of metals. He tried oxides of magnesium, lanthanum, yttrium, and more, but the most effective — as you probably guessed — was thorium (with just a dash of cerium). Not only was its light more intense, but also a more pleasing color than the sickly green glow provided by earlier mixtures.

The use of thorium mantles declined by the 1900s, when electric lights became more common. The fact that thorium is radioactive had very little to do with it.

Every element after lead is radioactive, of course, but that can describe everything from protactinium-219’s explosive half-life of 53 nanoseconds to bismuth lazily emitting a few alpha particles every day. Thorium is squarely between those two extremes, acting an awful lot like uranium.

So it was rather worrisome when the world’s thorium reserves started getting snatched up by the Nazis.

Not all the news that came out of Nazi Germany could be taken seriously, like their claims that they had trained dogs to salute and say “Mein Fuhrer!”7

But the conversation necessarily turned quite serious whenever Hitler declared that Germany possessed “secret weapons.” They had some kind of nuclear program, and the very real possibility that they would eventually manufacture atomic bombs made the Allies very anxious. 8

A team was assembled to gather intelligence on the German nuclear program, named “Alsos.” (That was taken from the Greek for “Grove” as a little wink toward our old friend General Leslie Groves, head of the Manhattan Project.)9 10

In 1944, the Alsos team made a chilling discovery: The Nazis had taken over a French manufacturer and shipped its entire, substantial supply of thorium back to Germany. It had fallen into the possession of Auergesellschaft, an industrial conglomerate with deep ties to the German government.

(Incidentally, that’s “Auer” as in Carl Auer von Welsbach — he founded the company in 1892, and it became wildly successful.)

It seemed obvious that the Nazis would use the radioactive material in their pursuit of the bomb — and this could indicate that their atomic program was far more mature than the Allies had previously thought.

There were two Germans in charge of that thorium reclamation effort, and agents of Alsos tracked them down to a border town in Belgium. Alsos was simply a division of the Manhattan Project, not some kind of officially backed foreign intelligence agency. They really had no authority to arrest, well, anyone, especially in another country — but that didn’t stop them. They apprehended the two Germans of interest, along with a jackpot of secret documents.

That intelligence revealed exactly what happened to the stolen stockpile of thorium. The Alsos team was quite surprised to learn that it was not fuel for the Nazi’s nuclear program. No, Auergesellschaft was going to use it for Doramad.

What was Doramad, you ask? Some kind of nefarious chemical weapon? Perhaps a poison employed by skulking assassins? Or maybe a new and powerful source of electrical energy?

No, Doramad was none of those things. Of course it wasn’t.

Doramad was toothpaste. Radioactive toothpaste! Auergesellschaft was just as active in the commercial space as in the military-industrial complex, and they were all aboard the radioactive hype wagon, just like William Bailey or the many cosmetics companies offering radium-infused makeup. “Its radioactivity increases the defense of the teeth and gums,” read the packaging. “The cells are loaded with new life energy, the bacteria are hindered in their destroying effect.”11 12

Truly, this Nazi toothpaste was meant for the whitest of whites.

You probably don’t need me to tell you that, at best, thorium does absolutely nothing for your dental health. But neither would it be as detrimental as those products infused with radium. Thorium’s radioactivity is quite mild in comparison. Its most common isotope has a half-life around 14 billion years.13

Don’t let that fool you, though. Thorium has the potential to be a radioactive superstar, with some calling  it the green energy source of the future.

Thorium has a lot of qualities that make it appealing as a nuclear fuel. For starters, it’s an awful lot cheaper than uranium, and a thorium-based nuclear reactor needs much less fuel than a typical uranium plant. For example, one ton of thorium could produce as much energy as 200 tons of uranium or 3.5 million tons of coal. It produces less waste, waste that’s much less radioactive than what we use today, waste that cannot be used to create weapons. In fact, a thorium plant can even consume the hazardous plutonium waste produced by today’s reactors. Thorium reactors are designed to fail safe and prevent a meltdown from ever occurring.14 15 16 17 18 19

The technology does have some drawbacks, but scientists have found ways to circumvent most of them in the past few decades.

So why doesn’t the world enjoy limitless clean(-ish) energy from thorium reactors dotting the landscape? Well, because… reasons.

You can’t blame Alvin Weinberg. He was director of Oak Ridge National Labs from 1955 to 1973, and he spent years campaigning for thorium power plants. But he met powerful resistance at every turn.

Most innocuously, there was already significant momentum behind uranium plants. A lot of time, money, and labor had been invested in their creation, and no one was too keen on switching horses.

Even the greater safety offered by thorium reactors couldn’t sway some people. One Congressman told him point-blank, “Alvin, if you are concerned about the safety of reactors, then I think it may be time for you to leave nuclear energy.”

It wasn’t just about the money. There was a more critical reason the government preferred uranium-based reactors. Remember that plutonium waste that’s a byproduct of the uranium plants? That’s not a bug, that’s a feature — depending on who you are and what you’re trying to do.

Plutonium provided the core for the first atomic bomb ever detonated, the Trinity test bomb, as well as the bomb detonated over Nagasaki. And it would provide the cores for thousands more. When given the choice between safe, abundant energy versus weapons that unleash hell on earth, officials found the choice to be obvious.

Poor element 90 languished for decades, occasionally being used to process petroleum and as a mantle in some camping lanterns, but not much else.

A few countries have tried to start up a thorium nuclear program, but none of them have really gotten off the ground — at least not yet. India has had an on-again off-again relationship with thorium for seventy years. It would make a lot of sense for the country. It’s home to only one or two percent of the world’s uranium, but nearly one quarter of all known thorium.

Sadly, ballooning costs and ongoing delays have hampered progress. India’s 22 nuclear power plants produce less energy than planned, and they’re all uranium-based. Supposedly their first thorium plant will come online in 2022, or 2023, but it’s already been delayed several times.

The future may look bright and clean thanks to thorium, but for now, the element’s lasting legacy is a little dirty.

New York’s hottest bar is Nowadays, a hipster hideaway that’s got everything: twinkle lights, graffiti, an autobody repair shop, and human ninja turtles. What are human ninja turtles? You know, it’s that thing where the building’s previous owners dumped so much radioactive sludge down the sewer that the EPA names it a Superfund site.

That’s not just the fever dream of some 2000s-era club kid, that’s all true. Nowadays shares a building with Primo Autobody Repair in Ridgewood, Queens. From the 1920s until 1954, the building was occupied by the Wolff-Alport chemical company, where sand was imported from Congo and processed to extract rare earths. For much of that time, thorium — which constitutes around 8% of that sand — was seen as useless, a waste byproduct, and simply poured down the drain or buried onsite.20 21 22 23

And for a long time, no one did anything about it. It was the most radioactive place in New York City, positively soaked in gamma rays, and people lived, worked, and ate sandwiches there, just like any other block in the city.

By 2014, the EPA installed concrete, steel, and lead shielding to insulate against the radiation emanating from underground. Remediation is still not complete, though. The official plan “includes relocation of all on-site tenants, demolition of all on-site buildings, … and off-site disposal of all contaminated soils, sediment, and building materials.”24

If that sounds like an ambitious plan, well, it might be. According to the agency’s website, “EPA is hopeful that tenant relocations will begin summer 2021 and be completed by the end of the calendar year.” At time of writing, it’s now February 2022, and Nowadays is advertising events at least through the end of March, so the EPA may not wield as much influence as Ghostbusters would have you believe.25

So for now, all of that thorium sludge is locked beneath industrial-strength cladding, and whenever they do finally dig it up, they probably won’t be terribly comfortable passing it out to the voracious hordes of interested element collectors. (There are dozens of us. Dozens!)

You’re better off finding a natural source of monazite sand close to home. Technically, not all monazite contains thorium, but a lot of it does — and there’s a lot of it located all around the world. You could get your hands on one of those thorium-laced lantern mantles, but those are getting harder to find as non-radioactive alternatives take their place.26

Applications for thorium being somewhat limited, the only other bulk sources are industrial in nature, subject to fairly tight regulation, and quite expensive.27 But that doesn’t make those sources impossible to acquire — they’re almost certainly easier to get your hands on than a tube of Nazi toothpaste.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To learn how gas lighting was actually invented a few thousand years ago, visit episodic table dot com slash T h.

Thank you all for waiting patiently for a new episode while I dealt with some drawn-out medical issues, and for the well-wishes so many of you offered. I’m doing much better now, and got to add gadolinium to my own collection as a consequence. It may take a little time for me to get back in the groove of releasing episodes, but the next one certainly shouldn’t take as long as this one did.

Next time, we’ll move up from the minors with protactinium.

Until then, this is T. R. Appleton, reminding you to be careful what you pour down the drain.


  1. The Royal Society Of Chemistry, Chemistry In Its Element – Thorium.
  2. Elementymology & Elements Multidict, Thorium. Peter Van der Krogt.
  3. Encyclopedia Britannica, Carl Auer, Freiherr von Welsbach. Last updated August 28, 2021.
  4. World Of Chemicals, Carl Auer von Welsbach — Discoverer Of Gas Mantle & Neodymium, Praseodymium Elements.
  5. Nature Chemistry In Your Element, Thorium Lends A Fiery Hand. John Arnold, Thomas L. Gianetti and Yannai Kashtan, May 21, 2014.
  6. The Chicago Tribune, Gaslight Era Left Radioactive Legacy In Chicago. Michael Hawthorne, April 17, 2014.
  7. The New York Times, Hitler’s Talking Dogs. Maureen Dowd, July 12, 2011.
  8. Manhattan: The Army And The Atomic Bomb, p. 280 (p. 304 of the PDF). Vincent C. Jones, 1985.
  9. Oak Ridge Associated Universities Museum Of Radiation And Radioactivity, Alsos And The Nazi Thorium. Samuel Goudsmit, 1996.
  10. ORAU Museum Of Radiation And Radioactivity, Alsos And The Nazi Thorium.
  11. Oak Ridge Associated Universities Museum Of Radiation And Radioactivity, Doramad Radioactive Toothpaste.
  12. Atlas Obscura, The Mysterious Case Of The Radioactive Toothpaste. Eric Grundhauser, May 5, 2017.
  13. JLab Science Education, The Element Thorium.
  14. Super-Fuel: Thorium, The Green Energy Source For The Future. Richard Martin, 2012.
  15. Wired, Uranium Is So Last Century — Enter Thorium, The New Green Nuke. Richard Martin, December 21, 2009.
  16. Chemical & Engineering News, Trying To Unleash The Power Of Thorium. Mitch Jacoby, July 6, 2015.
  17. The Baltimore Sun, Thor’s Nuclear-Powered Hammer. Dan Rodricks, May 9, 2011.
  18. Discover, Why Aren’t We Using Thorium In Nuclear Reactors? Adam Hadhazy, May 6, 2014.
  19. Science Focus, Why Isn’t Thorium Used For Nuclear Power? Helen Scales.
  20. Atlas Obscura, Primo Autobody Repair. Eric Grundhauser.
  21. Jalopnik, NYC’s Most Radioactive Spot Is An Auto Shop. Raphael Orlove, February 26, 2019.
  22. Curbed, Ridgewood’s Radioactive Superfund Site Worries Neighbors. Nathan Kensinger, July 3, 2014.
  23. Gothamist, The Most Radioactive Place In NYC Is In Ridgewood. Ben Yakas, May 7, 2014.
  24. United States Environmental Protection Agency, Wolff-Alport Chemical Company Radiological Site RV1.
  26. Gizmodo, The Thorium Lantern, Your Opportunity For Retail Radiation Exposure. Keith Veronese, March 2, 2012.
  27., Thorium. Theodore Gray.

19 Replies to “90. Thorium: Bright Lights, Big City”

    1. You tell us absolutely zero about dose rates, therefore your story is woefully incomplete. Radiation is not an “on or off” quality… there are degrees of hazard that can only be understood with dose rate info.

      1. Could we have a little respect? A tactful request to the provider of an excellent podcast? TR Appleton does not claim to present the encyclopedia on thorium. If you want to respectfully contribute your knowledge you are at liberty to do so. If you prefer angry criticism you can find plenty of better opportunities elsewhere.

        1. How much you have helped me, you couldn’t imagine. Chemistry was hard to understand. Glad I found this. Although I am now around half life (perhaps) its never too late. Chemistry is vast, but you put a human perspective to it. Thank you. And hope you feel a lot better and stronger. Life’s been a roller-coaster, but your podcasts helps every now and then.. 😉 see you around.

  1. Great to hear you’re back!
    I hope you are feeling well and wish you good health moving forward.
    Thank you for the excellent podcasts, fascinating, educational and amusing listening!
    Kind regards and best wishes from the UK.

      1. Thank you so much for making such an awesome podcast. I’m so happy to hear that you’re feeling better.

  2. I’ve enjoyed listening to episodes you start to thorium for the past 2 months at every opportunity. This is the best podcast I’ve ever listened to. I continue to look for alternates while I await the next release however it’s like comparing gold to lead on a regular basis. Thank you for setting the bar so high with quality and excellence. I hope you are well soon

  3. Trevor, I agree with your clever comparison. I also underscore your good wishes for TR Appleton. TRA, I have thought of you many times, hoping for your sound recovery.

  4. FYI, tungsten welding electrodes containing 2% thorium are still widely sold, and are relatively inexpensive. The thorium apparently enhanced arc properties.

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