In December of 1986, scientists at Chernobyl, searching for nuclear fuel from the destroyed Reactor #4, made a breakthrough.
Deep in the basement of Block 4, an enormous, radioactive mass was discovered. The radiation level on the surface of the mass was 10,000 roentgens per hour. To approach it directly would mean certain death, so a crude, wheeled camera was rigged up to take a look. The mass was two metres across, and several tons. Because of its shape, it was christened “The Elephant’s Foot.”
The mass appeared to be corium - a lava-like molten mixture of portions of nuclear reactor core, formed during a nuclear meltdown. It consists of many things: nuclear fuel, fission products, control rods, structural materials from the affected parts of the reactor, products of their chemical reaction with air, water and steam, and, in case the reactor vessel is breached, molten concrete from the floor of the reactor room. Analysis showed that sand from the reactor area had absorbed the hot nuclear fuel and fused into glass. The discovery of The Elephant’s Foot gave scientists, for the very first time, the idea that an enormous amount of nuclear fuel escaped the reactor in this form.