April 9, 2024 | Allison Robertson

Chernobyl's Elephant Foot

A Deadly Discovery

In 1986, eight months after the catastrophic nuclear accident at Chernobyl, workers discovered a startling phenomenon that has since been named one of the most dangerous discoveries in the world.

Nearly four decades later, the extremely hazardous discovery remains just as deadly as when it was first discovered.

toxic sign and chernobyl elephant foot split image

What is it?

“The Elephant's Foot” is the nickname given to a large mass of corium and other materials formed underneath the Chernobyl Nuclear Power Plant, near Pripyat, Ukraine.

Chernobyl's Elephant FootUniversal History Archive, Getty Images

When was it formed?

It was formed during the Chernobyl disaster of April 1986, when a nuclear power plant reactor exploded—causing the worst nuclear disaster in history.
image of Chernobyl Exclusion Zone, UkraineEight Photo, Shutterstock

Why is it called an Elephant’s Foot?

Chernobyl’s Elephant’s Foot is named for its wrinkly appearance, reminiscent of the foot of a large elephant.


What does it look like?

The Elephant's Foot is a mass of black corium—a lava-like mixture of molten core material—with many layers, that looks like tree bark and glass.

Tree bark textureMikadun, Shutterstock

How big was it?

The Elephant Foot was estimated to weight 2.2 tons (2 metric tons). It also contains materials from the reactor itself, and components of the plant such as concrete and metal.

weights for the two-pan balanceRedRumStudio, Shutterstock

What is it made of?

The Elephant's Foot is a solidified corium glass composed primarily of silicon dioxide, with traces of dissolved uranium, titanium, zirconium, magnesium and graphite.

Image of Corium descriptionGraphic_TMI-2_Core_End-State_Configuration.jpg, Wikimedia commons

What is corium?

Corium is a rare substance which is produced in a a nuclear accident when nuclear fuel and parts of the reactor core structures overheat and melt, forming a mixture.

Close up image of Lava textureMichelle Fehler, Flickr

Is corium common?

No. Corium has only formed naturally five times in history — once during the Three Mile Island accident in Pennsylvania in 1979, once at Chernobyl and three times at the Fukushima Daiichi plant disaster in Japan in 2011.

image of Fukushima Nuclear PlantSantiherllor, Shutterstock

Where is it located?

The Elephant's Foot is located below the remains of the reactor, in the maintenance room (Room 217/2), 15 meters (49 ft) to the southeast of the ruined reactor and 6 meters (20 ft) below ground level.

image of Chernobyl Nuclear Power PlantIAEA Imagebank, Flickr

How did it form?

During the Chernobyl disaster, the lava-like mixture escaped the reactor enclosure. The black lava flowed from the reactor core, similar to a human-made volcano.

Image of Lava textureKelly Hudson, Picryl

What damage did it do?

The material making up the Elephant's Foot had burned through at least 2 meters (6.6 ft) of reinforced concrete, then flowed through pipes and fissures and down a hallway to reach its current location.

Chernobyl nuclear power plant.DimaSid, Shutterstock

Is it radioactive?

Yes. Despite the distribution of uranium-bearing particles not being uniform, the radioactivity of the mass is evenly distributed.

Scientist checks the level of radioactive radiationPRESSLAB, Shutterstock

How reactive was it?

At the time of its discovery, it was about 8,000-10,000 roentgens (a unit of measurement for the exposure of x-rays and gamma rays) or 80-100 grays per hour (the unit of ionizing radiation).

The sign of radiation danger in ChernobylKravets Misha, Shutterstock

How does it give off radiation?

The Elephant's Foot gives off radiation mainly in the form of alpha particles. As of 2015, measurements of a piece taken from the Elephant's Foot indicated radioactivity levels of roughly 2,500 Bq (.0675 µCi).

Diagram demonstrates different kinds of ionizing radiationFile:Alfa beta gamma radiation penetration.svg, Wikimedia Commons

Is the radioactivity lethal?

At the time of the discovery, the Elephant’s Foot was delivering a 50-50 lethal dose of radiation (4.5 grays) within five minutes of exposure.

A doll in a gas mask in abandoned cityOndrej Bucek, Shutterstock

Does the radioactivity reduce over time?

Yes. Over time the radiation intensity declined significantly, and in 1996 Artur Korneyev, the deputy director of the New Safe Confinement Project, was able to visit the Elephant Foot briefly and take photographs.

Nuclear radioactive danger sign in forest in ChernobylMilan Sommer, Shutterstock

How dangerous is this?

While alpha radiation is ordinarily unable to penetrate the skin, it is the most damaging form of radiation when radioactive particles are inhaled or ingested.

Danger Red Tape WarningPmmrd, Shutterstock

How does this affect people long after the initial formation?

This raised concerns as samples of material from the meltdown (including the Elephant's Foot) turn to dust and become aerosols (droplets in the air).

liquid droplets in the airJade ThaiCatwalk, Shutterstock

Was it scientifically tested?

The mass was quite dense and it was challenging to collect samples for analysis using a drill mounted on a remote-controlled trolley. Armor-piercing rounds fired from an AK-47 were necessary to break off usable chunks.

Two Scientists Working in labGorodenkoff, Shutterstock

What happens to it over time?

By 1998, the outer layers had started turning to dust and the mass had started to crack. The radioactive components were starting to break down to a point where the integrity of the mass was failing.

Old children's gas maskRoman Belogorodov, Shutterstock

What does it turn into?

Over time, the mass continued to disintegrate. By 2021, the mass was described as having a consistency similar to sand.

woman hand holding sandJade ThaiCatwalk, Shutterstock

How dangerous is the Elephant Foot?

The Elephant Foot is particularly dangerous because it is difficult to handle, package, and store. Generally, corium is more hazardous than undamaged spent fuel because of its unstable state.

caution information metal sign plate on the wire fenceNattawit Khomsanit, Shutterstock

Is it still dangerously radioactive today?

Yes. Corium retains highly radioactive fission products, plutonium, and core materials that have become radioactive, it will have a high dose rate and remain extremely hazardous many decades or even centuries later.

Radiation supervisor in glove with geiger counterEgoreichenkov Evgenii, Shutterstock

Can it be removed?

Very hard solidified corium would have to be broken up to remove it from damaged reactors. Breaking up the Elephant Foot will create radioactive dust and increase hazards to workers, as well as the environment.

Two people with gas masks and dramatic sky behindMarijus Auruskevicius, Shutterstock

What is known and unknown?

Scientists are unsure how corium might behave over long-term, if it is stored in a nuclear waste repository. What they do know is that it is cooling on its own, and will continue to cool over time—though is continued to remain highly radioactive.

view on cooling tower of Nuclear Power PlanFotokon, Shutterstock

What more could happen with the Elephant’s Foot?

The Elephant’s Foot is still melting into the base of the Chernobyl Nuclear Power Plant. It is said that if it hits ground water, it could trigger another catastrophic explosion or leach radioactive material into the water nearby—that residents drink.

Scientists in a protective suit and masknarai chal, Shutterstock

What preventions have been taken?

In 2016, the New Safe Confinement (NSC) was placed over Chernobyl to prevent any more radiation leaks from the nuclear power plant.

Another steel structure was built within the containment shield to support the decaying concrete sarcophagus in Chernobyl's reactor No. 4.

New construction intended to contain the nuclear reactorE.Kryzhanivskyi, Shutterstock

What is the New Safe Confinement?

Chernobyl’s New Safe Confinement (NSC) is a design and construction project unprecedented in the history of engineering. Never before has such a huge structure been constructed at a heavily contaminated site.

Confinement for old sarcophagus of nuclear reactorFotokon, Shutterstock

What was its purpose?

The New Safe Confinement was created to help prevent a massive cloud of uranium dust from dispersing into the air in case of an explosion in room 305/2—which was directly under the reactor core and had been showing signs of increased neutron emissions since 2016.

man dressed as chemical troops is examining the radioactive territoryAnelo, Shutterstock

Can people visit the Elephant Foot today?

Absolutely not. The Elephant Foot remains an extremely dangerous site, and is said to be one of the most dangerous objects in the world.

toys left behind in an abandoned building in Pripyat, UkraineSybille Reuter, Shutterstock

Final Thoughts

Long after the initial disaster, this unique piece of waste continues to be a testament to the potential dangers of nuclear power.

The Elephant’s Foot will remain untouchable in the dark basement of a concrete and steel structure for centuries to come.

Hotel and other building with radiation signDiego Grandi, Shutterstock

Sources:  1, 2, 3


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