The “Elephant’s Foot” is a unique and dangerous formation located beneath Reactor No. 4 of the Chernobyl Nuclear Power Plant, near Pripyat, Ukraine. This solidified mass symbolizes the extreme aftermath of the 1986 nuclear disaster. Discovered months after the event, it is situated in a maintenance corridor, approximately 15 meters southeast of the ruined reactor. Its nickname comes from its wrinkled appearance and large, imposing size, reminiscent of an elephant’s foot.
The Core Material: Corium
The primary substance comprising the Elephant’s Foot is corium. Corium is a lava-like material that forms during a nuclear reactor meltdown when the reactor core overheats and melts. This process combines the nuclear fuel with various structural materials from the reactor and its containment. This ceramic-like material results from the intense temperatures and pressures during a meltdown. Corium has only formed naturally in a few instances, including the Three Mile Island accident, Chernobyl, and the Fukushima Daiichi plant disaster.
Key Components and Elements
The Elephant’s Foot is a complex mixture of materials, reflecting the severe conditions of the meltdown. Its composition primarily includes uranium dioxide from the reactor’s nuclear fuel. Zirconium, a component of the fuel rod cladding, and graphite, used as a reactor moderator, are also significant constituents. The molten mass also incorporated concrete from the reactor’s structural components and steel as it flowed. Additionally, the Elephant’s Foot contains highly radioactive fission products and transuranic elements like plutonium and americium, generated during the nuclear reactions. Its exact composition can vary slightly, but silicon dioxide is a major component, often giving it a brownish or blackish hue.
Physical Properties and Appearance
The Elephant’s Foot presents as a solidified, dark, and wrinkled mass. Its appearance has been described as resembling tree bark or obsidian, and it also shares characteristics with glass. The material formed as molten corium flowed through pipes and concrete channels beneath the reactor before solidifying. The mass is notably dense and hard, making it difficult to sample or break apart. When first discovered, the material was searing hot. While its consistency has changed over decades, the material’s visual characteristics, including its color and texture, are influenced by the specific materials that melted and fused during the meltdown, such as silica-rich concrete.
Radioactivity and Hazard Level
The Elephant’s Foot is extremely radioactive, due to its composition of radioactive isotopes of uranium, fission products, and other activated materials. It emits various types of radiation, including alpha, beta, and gamma radiation. At its discovery, radiation levels were estimated to be around 8,000 to 10,000 roentgens per hour. Exposure to such high levels posed an immediate and lethal threat. Just 30 seconds of exposure could cause dizziness and fatigue, two minutes would lead to cell hemorrhaging, and five minutes could result in death within two days. While its radioactivity has decreased significantly over the decades due to natural decay, the Elephant’s Foot remains highly hazardous. It continues to generate heat and poses a long-term risk, with concerns about its potential interaction with groundwater, although such fears have proven unfounded to date.