Horror hides beneath reactor 4 of the infamous Chernobyl power plant. A huge mass of corium, a kind of already solidified radioactive lava, known as “elephant’s foot” for its wrinkled shape. For years it has been known as the most radioactive point of Chernobyland therefore one of the most dangerous in the world. It turns out that there is another one even worse, its name is “The China Syndrome.”
The chorio did not stop at the elephant’s foot
First of all, let’s see what corio is. The Spanish Nuclear Society defines it as a “mass, melted or solidified, formed by nuclear fuel, structural or control materials and reaction products thereof, which is produced by the total or partial melting of the core of a reactor, as a consequence of an accident with loss of cooling.”
While still burning, the Chernobyl core reached temperatures of 2,600 degrees, more than twice as much as volcanic lava which is usually between 850 and 1,200 degrees.
After the accident, corium accumulated in room 305/2, which is located just below reactor 4. From here, some flowed to the east, which is where the famous “elephant’s foot” is located. This formation was discovered in 1986, about eight months after the accident, and the radiation it emitted at that time was 10,000 roentgens per hour. To put it in context, according to the United States nuclear commission, between 400 and 500 roentgens per hour are lethal for 50% of the population.
The radiation of the elephant’s foot has decreased radically over the years. There is no data on current radiation, but in 1996 radiation specialist Artur Korneyev took a selfie with her and survived that exposure for a long time, finally dying in 2022 at the age of 73.

The corium is the red mass seen at the bottom. Image: Shredmash
But the chorio did not stop there, it continued descending and went through the ground of this room. It continued through the refrigeration piping system and exited through the steam ducts. This enormous mass is what is known among some Chernobyl fans as “The China Syndrome.”
The China Syndrome
It is a huge chorio mass that extends through the corridors of the steam distribution system. According to an amateur who posted the story on Reddit, in 1997 the most radioactive part of this mass was emitting 3,460 roentgens per hour, while the elephant’s foot was emitting only about 700 roentgens at that time. We have not found data about current measurements, but we have found references that indicate that the mass is much larger than the so-called elephant’s foot.
Reddit user ppitm was the first to call this mass of corium this way and the name has become popular since then. But why that name? It is a concept that was coined by William K. Ergen, a German theoretical physicist and later popularized by Ralph Lapp, a physicist participating in the Manhattan Project, who mentioned it in an article on nuclear plumbing.
‘The China Syndrome’ is a hyperbolic idea, as a warning, about what could happen if a nuclear reactor melts down and the resulting material ends up burning the concrete that contains it. The name comes from the idea (obviously exaggerated) that this mass could continue advancing for years, cross the Earth and end up in China.
To better understand this exaggeration, it must be taken into account that Ergen’s report was published in 1967, when no fusion accident had yet occurred in a reactor. His prediction was that, in the worst case, a high-temperature mass would form that would sink into the earth and increase in size for approximately two years, potentially reaching 30 meters in diameter and that would persist for a decade. Thank goodness he was wrong.
Imagen de portada | Chernobyl Chernobyl, Facebook
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