The “Elephant’s Foot” is a dangerous mass of corium located beneath Reactor 4 of the Chernobyl Nuclear Power Plant in Ukraine. This solidified, lava-like material formed during the 1986 nuclear disaster’s catastrophic meltdown. It represents a highly hazardous object, drawing interest due to its origins and ongoing threat within the Chernobyl Exclusion Zone.
Formation of the Elephant’s Foot
The Elephant’s Foot was created during the Chernobyl disaster on April 26, 1986. A power surge during a test caused the reactor core to rapidly overheat, leading to a massive explosion that blew apart the reactor assembly. Extreme temperatures melted nuclear fuel rods, control rods, and other reactor components.
This molten material, resembling hot lava, combined with structural elements like concrete, sand, and steel, forming corium. This mixture flowed out of the damaged reactor, melting through at least two meters of reinforced concrete. It continued to ooze through pipes and fissures, eventually solidifying in a maintenance corridor in the basement of Reactor 4.
Its Material Composition
The Elephant’s Foot is a type of corium, specifically referred to as a “fuel-containing material” (FCM). It is a black ceramic-like substance, characterized by a wrinkled texture and multiple layers, resembling tree bark and glass. Its primary components include melted nuclear fuel, primarily uranium dioxide, and oxidized zirconium from the fuel rod cladding.
It also contains graphite from the reactor core, along with various melted structural materials. These include silicon dioxide, derived from concrete and sand, and other oxides such as calcium, iron, aluminum, magnesium, and potassium. While it contains only a small percentage of the original nuclear fuel, it is a complex, heterogeneous mixture of these highly radioactive materials.
The Extreme Radiological Hazard
The Elephant’s Foot poses an extreme radiological hazard due to its highly radioactive nature. At the time of its discovery in December 1986, approximately eight months after the disaster, radiation levels near the mass were 8,000 to 10,000 roentgens per hour. Exposure to such levels meant a lethal dose could be received within minutes; five minutes could lead to death within two days.
The mass emits various types of radiation, including alpha, beta, and gamma radiation. While alpha radiation cannot penetrate the skin, it becomes highly damaging if radioactive particles are inhaled or ingested. The presence of fission products, particularly cesium-137, contributes to its external gamma radiation hazard. Decades later, the site remains dangerous, with direct contact or prolonged proximity still posing severe health risks like acute radiation sickness, organ damage, and increased cancer risk.
Current State and Monitoring
Decades after its formation, the Elephant’s Foot has undergone physical changes. While initially extremely hot, its temperature has significantly decreased over time due to the decay of shorter-lived radioisotopes. This cooling has led to changes in its structural integrity; once dense and unyielding, it has become brittle and is reportedly cracking. By 2021, its consistency was described as similar to sand.
Despite the decrease in its radiation intensity, the Elephant’s Foot remains lethally radioactive. Scientists and engineers continuously monitor its stability and radiation levels using remote cameras and dosimeters. These ongoing efforts help understand the long-term behavior of this unique and hazardous material, especially within the New Safe Confinement structure that now encases Reactor 4.