| Chernobyl disaster |
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 Sarcophagus over reactor No. 4 in 2013 |
TheElephant's Foot (Ukrainian:Слонова нога,romanized: Slonova noha,Russian:Слоновья нога,romanized: Slonovya noga) is the nickname given to the large mass ofcorium beneath Reactor 4 of theChernobyl Nuclear Power Plant, nearPripyat,Ukraine. The mass formed during the 1986Chernobyl disaster from materials such as molten concrete, sand, steel,uranium, andzirconium. It is named for its wrinkled appearance and large size, evocative of the foot of anelephant.
Discovered in December 1986, the "foot" is located in a maintenance corridor below the remains of Reactor No. 4, though the often-photographed formation is only a small portion of several larger corium masses in the area. It has a popular reputation as one of the mostradioactive objects in history, though the danger has decreased over time due to thedecay of its radioactive components.[1][2]
The Elephant's Foot is a mass of blackcorium with many layers, resembling tree bark and glass. It was formed during theChernobyl disaster of April 1986 from a lava-like mixture of molten core material that had escaped the reactor enclosure, materials from the reactor itself, and structural components of the plant such as concrete and metal.[3] The Foot was discovered in December 1986 in Room 217/2, 15 metres (49 feet) to the southeast of the ruined reactor and 6 metres (20 feet) above ground level.[4][5] The material making up the Elephant's Foot had melted through at least 2 metres (6.6 feet) ofreinforced concrete, then flowed through pipes and fissures and down a hallway to reach its current location.[5]
The Elephant's Foot is a black ceramic composed primarily ofsilicon dioxide, with smaller amounts of other oxides, primarilyuranium,calcium,iron,zirconium,aluminum,magnesium, andpotassium.[1][2][6][7] Over time,zircon crystals have started to form slowly within the mass as it cools, and crystallineuranium dioxidedendrites are growing quickly and breaking down repeatedly.[3] Despite the distribution of uranium-bearing particles not being uniform, the radioactivity of the mass is evenly distributed.[3] The mass was quite dense and unyielding to efforts to collect samples for analysis via a drill mounted on a remote-controlled trolley, and armor-piercing rounds fired from anAK-47 rifle were necessary to break off usable chunks.[5][1][2] By June 1998, the outer layers had started turning to dust and the mass had started to crack, as the radioactive components were starting todisintegrate to a point where the structural integrity of the glass was failing.[3] In 2021, the mass was described as having a consistency similar to sand.[8]
At the time of its discovery, about eight months after formation, radioactivity near the Elephant's Foot was approximately 8,000 to 10,000[9]roentgens per hour, or 80 to 100grays per hour,[2] delivering a50/50 lethal dose of radiation (4.5 grays)[10] within 3 minutes.[2][4] Since that time, the radiation intensity has declined significantly, and in 1996, the Elephant's Foot was briefly visited by the deputy director of theNew Safe Confinement Project, Artur Korneyev,[a] who took photographs using an automatic camera and a flashlight to illuminate the otherwise dark room.[12]
The Elephant's Foot is roughly 10% uranium by mass, which is analpha emitter.[3] While alpha radiation is ordinarily unable to penetrate theskin, it is the most damaging form of radiation when radioactive particles are inhaled or ingested. This renewed concerns as samples of material from the meltdown (including the Elephant's Foot) turn to dust.[8] Nevertheless, the corium still poses an externalgamma radiation hazard due to the presence of fission products, mainlycaesium-137.
The substance proved too hard for a drill mounted on a motorized trolley, ... Finally, a police marksman arrived and shot a fragment of the surface away with a rifle. The sample revealed that the Elephant's Foot was a solidified mass of silicon dioxide, titanium, zirconium, magnesium, and uranium ...
The radiation level near it was approximately 8,000 roentgens per hour in 1986. Even five minutes spent near the 'foot' would have killed a man ... the substance failed to yield to a drill mounted on a special remote-controlled truck ... A skilled marksman ... fired armor-piercing bullets into it ... Analysis of the fragments obtained in this way showed that they consisted of 70–90% silicon dioxide (fused sand), 2–10% fuel particles, and, in addition, contained graphite (hence the black color), metal alloys, and so on ...
51°23′21″N30°05′54″E / 51.3892°N 30.09833°E /51.3892; 30.09833
