A great article here from the New York Times on efforts to clean up and control damage caused by the Chernobyl catastrophe. One such project involves the construction of a giant shelter to cover the entombed remains of the reactor.
The Chernobyl accident can be likened to a huge dirty bomb, an explosion that spewed radioactive material in all directions. The blast was followed by a fire that sent even more contaminants into the atmosphere that were then carried by winds across the region and into Western Europe.
In this way the disaster differs from nuclear power’s two other major accidents, at Three Mile Island in Pennsylvania in 1979 and Fukushima in 2011. At both of those plants, reactor cores melted down, but the core material — the nuclear fuel — remained within protective containment structures.
The four reactors at the Chernobyl plant had no such containment. But that was only one aspect of their flawed design. The system for controlling the nuclear fission reaction was temperamental, and under certain conditions reactor power could quickly soar out of control.
That is what happened in the early hours of April 26, 1986, at Chernobyl’s Unit 4, during an ill-advised test of some of the reactor’s safety systems. In a matter of seconds, the reactor power rose exponentially and the core was blasted apart by steam.
A few workers died immediately, but most of the technicians in Unit 4, and the firefighters who initially responded, suffered agonizing deaths over the ensuing weeks from exposure to high levels of radiation.
Officially, several dozen people were killed, and many others became sick. The radiation also caused thousands of later cancers — though just how many is still the subject of much debate.