Chernobyl’s blast was nuclear after all
Isotope analysis concludes plant’s first disastrous explosion was not steam.
The explosion of the Chernobyl nuclear power plant in April 1986 remains the most catastrophic nuclear power accident in history. To contain radiation, its ruptured No. 4 reactor was encased in thick concrete. Today the facility, 130 km north of Kiev in Ukraine, is still a no-go zone, at the centre of a 2,600 squarekilometre exclusion zone.
Past investigations into the failure of Chernobyl’s No. 4 reactor concluded it was caused by a steam explosion – an explanation supporting the case often put forward by nuclear power proponents that at least there has never been a nuclear explosion at a nuclear reactor.
That standard narrative has now been contradicted by researchers from the Swedish Defence Research Agency, the Swedish Meteorological and Hydrological Institute, and Stockholm University. The Chernobyl 4 reactor was destroyed by a nuclear explosion, not a steam one, they report in research published in the journal Nuclear Technology.
Based on analysing the distribution and composition of xenon isotopes in the days after the catastrophe, the team, led by LarsErik De Geer, concludes the first of two explosions reported by eyewitnesses was in fact a nuclear one – followed seconds later by a secondary steam explosion.
The nuclear explosion sent a jet of debris very high into the sky. The steam explosion ruptured the reactor and sent still more debris into the atmosphere, but at lower altitudes.
The Swedish team also looked at the physical evidence to support their case. Analysing damage to the reactor after the explosion, they noted the first blast had generated temperatures hot enough to melt through a two-metre-thick plate beneath the core – an outcome compatible with a nuclear blast. A steam explosion, they calculate, would not have had sufficient energy.
“We believe that thermal neutron mediated nuclear explosions at the bottom of a number of fuel channels in the reactor caused a jet of debris to shoot upwards through the refuelling tubes,” De Geer says. “The steam explosion which ruptured the reactor vessel occurred some 2.7 seconds later.”