Chernobyl: Reactor number 4 goes from operating at 7% of its maximum power to 100 times its maximum power in four seconds. The 2,000-ton concrete shield atop it, called the pyatachok (the five-kopeck coin), begins to boil and dance. Then two explosions within four seconds tear the reactor and the building apart. The first explosion lifts the pyatachok upward and vents onto the fiery red graphite below. The steam combines fiercely with the red-hot coal to form carbon monoxide, releasing hydrogen. This triggers the second explosion, toppling the pyatachok upright and projecting debris from the explosion almost 1 km into the air: six tons of highly irradiated uranium, radioactive graphite, and zirconium. About half of the ejected material falls within a 3 km radius of the reactor. About a ton of plutonium also remains in the reactor. There were 130 recorded deaths in the explosion, 500 deaths among rescuers, and more than 5,000 deaths in the following years (mostly from thyroid cancer, which stores iodine-131). The radiation released into the atmosphere was more than 500 times that of the Hiroshima bomb (which exploded 700 meters above the ground); approximately 50 tons of radioactive material was released into the atmosphere over an area populated by 5 million people. The explosion’s radioactive emissions are comparable to those of a 12-megaton H-bomb (2003 study).
