Facts So Romantic

Chernobyl’s Hot Mess, “the Elephant’s Foot,” Is Still Lethal

Chernobyl glowing
US Department of Energy

300 seconds will produce a relatively quick death, which is better than many alternatives. 

After just 30 seconds of exposure, dizziness and fatigue will find you a week later. Two minutes of exposure and your cells will soon begin to hemorrhage; four minutes: vomiting, diarrhea, and fever. 300 seconds and you have two days to live. 

By the fall of 1986, the emergency crews fighting to contain the nuclear disaster at Chernobyl made it into a steam corridor beneath failed reactor Number 4. Inside this chamber they found black lava that had oozed straight from the core. The most famous formation was a solid flow that their radiation sensors firmly told them not to approach. With cameras pushed in from around a corner, the workers dubbed the dimly lit mass “the Elephant’s Foot.” According to readings taken at the time, the still hot portion of molten core put out enough radiation to give a lethal dose in 300 seconds.

The Elephant’s Foot could be the most dangerous piece of waste in the world.

Hot Zone

During a routine test on April 26, 1986, reactor Number 4 at the Chernobyl Nuclear Power Plant experienced a power surge that triggered an emergency shutdown. It did not work. The attempt to manage the surge in power and the alarming increase in the core’s temperature caused an even larger power surge. Control rods that are used to manage core temperature were inserted too late. Their insertion into the hot core caused the rods themselves to crack and fracture, locking them in place. Heat and power output continued to rise until the water that was used to cool the entire reactor vaporized, generating massive amounts of pressure. The first explosion from the steam inside the reactor was enough to send the 4-million-pound lid of the reactor assembly through the roof of the building. Now catastrophically damaged, the remaining cooling water from broken channels seeped into the reactor as well, turning directly into steam as it touched the increasingly hot nuclear fuel rods. A second, even more massive explosion followed shortly after the first, belching broken core material into the air, spreading fire and radioactive detritus.

With a glowing heart no longer shielded by tons of steel and concrete, the core could no longer be cooled. It began to melt.

When we say that a nuclear reactor “melts down,” it’s not simply illustrative language. The radioactive materials used as fuel get hotter and hotter, due to their unstinting emission of high-energy particles, until they literally melt, turning into something like lava. At Chernobyl, the loss of coolant caused a meltdown of the fuel, some of which was scattered into the atmosphere. Much of it however, flowed into the bottom of the reactor vessel and eventually melted through it. Oozing through pipes and eating through concrete, the radioactive lava flow from reactor Number 4 eventually cooled enough to solidfy. The result was a collection of stalactites and stalagmites, steam valves clogged with hardened lava, and the large black mass that would later be dubbed the Elephant’s Foot.

A Deadly Game of Red Rover

Radioactive atoms are unstable atoms. While something like hydrogen is just fine with a nucleus consisting of one solitary proton, radioactive elements like uranium (the most common flavor, or isotope, contains 92 protons and 146 neutrons) is not so happy. Electrons, protons, and neutrons are emitted from the nuclei of these large atoms, transforming them, until something like plutonium degrades, over time, into a stable element like lead.

Particles emitted from radioactive atoms are a form of ionizing radiation—they have enough energy to scramble atoms and molecules they crash into. (This is different from non-ionizing radiation, like the kind emitted by your cell phone, which does not have enough energy to break bonds.)

The reason that radiation can increase the risk of cancer is because destructive particles are playing a deadly game of red rover in our bodies. Our DNA is held in chromosomes—packets of billions of genetic building blocks holding hands in a chain, with astonishingly precise sequences. But radiation can break up the clasped hands, destroying or altering the bonds that hold DNA (and other important molecules) together. With enough damage to key components, cells start to function irregularly, leading to potentially lethal effects. For instance, the damage can make cells start reproducing uncontrollably, causing cancer.

The more radiation released from a mass of atoms, the more dangerous it is. Reports from Chernobyl estimated that the Elephant’s Foot was practically off the charts, putting out nearly 10,000 roentgens per hour. It takes about 1/10th of that to kill a person. In one hour, the Elephant’s Foot would expose you to the radiation of over four and a half million chest x-rays. That dose is almost 1,000 times stronger than exposures that have been clearly linked to increased cancer risk. Because of the way radiation damages human cells—by knocking atoms and molecules out of place—death by radiation is a relatively slow one. Up to a point, treatment helps. But high doses, like the kind delivered by close contact with the Elephant’s Foot, can’t be tolerated.

Quickly after the Chernobyl meltdown, nearly 600,000 workers descended on the site to help contain the escaping radiation. Knowingly or not, many of these workers were making the greatest sacrifice. More than 30 of them died within months following the incident, with many thousands more getting a full lifetime’s dose of radiation, which is sure to cause a significant increase in cancer rates.

Overexposed

After the nuclear fires were finally controlled, workers scrambled to contain the invisible dangers of the failed Chernobyl core. In May of 1986, construction began on the sarcophagus—a gigantic concrete enclosure built to seal off the radiation from the outside world. But it’s not entirely sealed: The Chernobyl sarcophagus was outfitted with access points allowing researchers to observe the core and workers to enter.

That December, researchers discovered the Elephant’s Foot. It was a couple of meters across, and it put out enough radiation to prevent anyone from getting near it for more than a few seconds. But despite the dangers, we have pictures of the deadly mass. How?

From a safe distance, workers—or “liquidators” as they were called—rigged up a crude wheeled camera contraption and pushed it towards the Elephant’s Foot. Careful examination determined that it wasn’t all nuclear fuel. In fact, the mass was comprised of only a small percentage of fuel; the rest was melted concrete, sand, and core shielding that all melted and flowed together. The material was dubbed “corium,” after the part of the reactor that spawned it. Over time, the Elephant’s Foot decomposed. It puffed dust and its surface cracked. But for years it remained too dangerous to approach.

We don’t know what happened to the photographers of the Elephant’s Foot, but we do know that not every attempt to study it was as safe as wheeling in a camera from around a corner. In some photos, we see a worker directly interacting with the mass. Samples had to be taken; more information about the foot was needed.

US Department of Energy

When this photo was taken, 10 years after the disaster, the Elephant’s Foot was only emitting one-tenth of the radiation it once had. Still, merely 500 seconds of exposure at this level would bring on mild radiation sickness, and a little over an hour of exposure would prove fatal. The Elephant’s Foot is still dangerous, but human curiosity and attempts to contain our mistakes keep us coming back to it.

Though the Chernobyl sarcophagus was constructed with enough concrete to fill more than a third of the Empire State building, the structure has since deteriorated and crumbled, threatening to re-expose the surrounding areas. Plans are underway to try make sure that by 2015, the Elephant’s Foot will be fully contained once again.

300 Seconds, 100 Years

Born of human error, continually generating copious heat, the Elephant’s Foot is still melting into the base of the Chernobyl nuclear power plant. If it hits ground water, it could trigger another catastrophic explosion or leach radioactive material into the water nearby residents drink. Long after bleeding from the core, this unique piece of waste continues to be a testament to the potential dangers of nuclear power. The Elephant’s Foot will be there for centuries, sitting in the dark basement of a concrete and steel sarcophagus, a symbol of one of humankind’s most powerful tools gone awry.


Kyle Hill is a freelance science writer and blogger for Scientific American who has contributed toSlateWiredPopular ScienceSkeptical Inquirer, and io9. He is a research fellow with the James Randi Educational Foundation, and you can follow him on Twitter under @Sci_Phile.

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