The Chernobyl disaster, which occurred on April 26, 1986, was the most catastrophic nuclear accident in history, claiming dozens of lives in its immediate aftermath and thousands more to extended radiation exposure.
Given its devastating human toll and cultural impact, which included the reignition of intense concern over nuclear power risks, the leadup to Chernobyl’s reactor 4 failure has been exhaustively examined over the past 31 years. The prevailing consensus is that the meltdown, which was triggered by a safety test gone wrong, resulted in two explosions in quick succession: First, a steam eruption, and a few seconds later, a nuclear blast.
But a study published in Nuclear Technology on Thursday makes a compelling case to reverse this conventional timeline. Led by Lars-Erik De Geer, a retired nuclear physicist from the Swedish Defence Research Agency, the authors propose that the steam explosion came on the heels of a nuclear explosion, not the other way around.
The hypothesis’ smoking gun lies in the Russian city of Cherepovets, which is about 230 miles north of Moscow. Four days after the explosions in Chernobyl, scientists based at the V.G. Khlopin Radium Institute in Saint Petersburg (then, Leningrad) detected fresh xenon signatures in this municipal region, suggesting it lay within the trajectory of radiation debris from the disaster.
But Cherepovets is off the path of known Chernobyl contamination that reached throughout central Europe and Scandinavia. To explain this inconsistency, De Geer and his colleagues propose that an initial nuclear explosion shot a nasty jet of reactor debris about two miles into the skies.
This high-flying fallout could have been picked up by a different weather pattern at its elevated altitude, guiding it northeast towards Cherepovets, in contrast to the subsequent steam explosion that ruptured the reactor, which spewed debris northwest.
To back up this origin story for the Cherepovets xenon readings, the team point to a local fisherman’s account of a “blue flash” over the reactor, which could be consistent with an initial nuclear blast rather than a steam explosion.
Seismic readings taken 62 miles (100 kilometers) west of the explosion site could also be evidence of a large initial nuclear blast, the authors said, while the pattern of damage dealt to the reactor, which included the melting of a two-meter-thick core plate, may have been caused by a nuclear explosion preceding the steam blast.
Over email, I asked De Geer if he had any further studies in the works about the reimagined meltdown sequence, but he told me this is just one of many post-retirement projects in his “bag of ideas,” and next up, he’ll be researching nuclear tests, rather than accidents.
Other nuclear scientists, however, may follow-up on this possible twist to one of the most investigated technological disasters in history. It will be up to them to find out if there is evidence to either further substantiate the new chronology, or poke holes in it. Either way, Chernobyl is still full of mystery, both macabre and fascinating, over three decades after the region was changed forever.
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