Mystery of crucial first moments of Chernobyl disaster solved

Saturday 26 April 1986 was a day that shook the world. At 1.23 am, the number 4 reactor at the Chernobyl nuclear power plant near Pripyat, Ukraine, leapt to more than 100 times its usual operating power. As a result, high pressure steam in the reactor vessel exploded and parts of the reactor shot through the roof of the building, igniting fires that ejected highly radioactive nuclides over much of the western Soviet Union and Europe.

At least, that’s the sequence of events many experts have agreed on. Now, scientists in Sweden have reanalysed data from the event, and concluded that the first explosion in the Chernobyl disaster was due not to steam, but to a runaway nuclear reaction.

The new conclusions do not revise the underlying cause of the disaster. That is widely believed to be the operators’ decision, less than an hour earlier, to proceed with a long-awaited experiment to see how the reactor would cope under a power outage, despite a series of operational failures leaving it in a potentially unstable state. After the recovery did not go to plan, witnesses reported two major explosions just a few seconds apart. […]

The rest of this article is available here.