It’s hard for those of us in the modern era to grasp the true horror of the Chernobyl disaster. Even a deep dive into the Chernobyl meltdown timeline can only reveal so much about the very real, visceral consequences of the event. Putting the sequence of events that led to Chernobyl into context takes an event that American history books casually summarize as a horrible accident and paints the incident for what it really was: a series of compounding mistakes that produced one of the greatest environmental tragedies in human history.
The Chernobyl disaster occurred in the early morning hours of April 26, 1986, in a nuclear power plant next to the Ukrainian city of Pripyat. Multiple detonations spewed out vast quantities of toxic nuclear material and produced ongoing leaks that caused radiation levels to spike around the globe. At least 30 people lost their lives as a direct result of Chernobyl - but the true toll of the event, including increased rates of cancer and other illnesses along with environmental concerns, is impossible to measure. What is possible to track, however, are the series of unfortunate decisions that led to the tragedy in the first place.
Engineers Shut Down The Turbine Engine, Which Left The Water Pumps Under-Powered
Part of the experiment called for the turbine engines feeding the reactor with cooling water to be shut down. After struggling to increase power in the reactor, the operators also reduced the flow of feedwater. Combined, these two factors increased the temperature within the reactor and thus the amount of steam.
This steam may have led directly to the first detonation, though theories differ on that. Still, it made an unstable reactor all the more unbalanced. Before any actual disastrous events had occurred, the stage was set for something horrible.
A Power Surge Ruptured The Plant's Fuel Elements
After struggling to increase the power level of Chernobyl’s Unit 4 reactor, the operators were suddenly faced with the opposite problem: an unexpected power surge. There are a few possible explanations for why the megawatts suddenly started to increase, but it’s absolutely certain this surge ruptured the reactor’s fuel cells.
This rupture raised pressure in the reactor to preposterous levels, generating even more steam, which in turn increased the pressure in an uncontrollable cycle. The force ruptured the fuel elements and depressurization of the reactor’s cooling circuit - all but ensuring the first of multiple detonations that rocked the power plant.
The Graphite Control Rods May Have Caused The Power Surge
As the power levels within the reactor suddenly started surging out of nowhere, the operators hurriedly tried to insert more control rods - but this too-late precaution may have actually been a fatal mistake.
The Chernobyl control rods contained graphite displacers, and there’s a compelling theory that the graphite caused a nuclear reaction with the rupturing fuel cells. This would explain the severity of the first detonation, which blew the two-meter-thick lid right off the reactor.
Hydrogen Built Up In the Reactor And Ignited, Which Caused The Second Detonation
Once the initial detonation occurred at Chernobyl, it set off a devastating chain reaction. A second detonation happened seconds later, likely caused by a build-up of hydrogen due to all that steam reacting with zirconium.
While the first blast simply blew the lid off the reactor, the second blew it sky-high - along with large quantities of fuel, moderator, and the body of the reactor itself.
The release of these caustic materials was certainly disastrous within itself, but the detonation also left the core of the reactor exposed. Radiation started to seep from Chernobyl and spread around the world.