On 26th April 1986, a routine safety test went catastrophically wrong and triggered the worst nuclear accident of all time. The incident at the Chernobyl Nuclear Power Plant near Pripyat, Ukraine led to the release of 400 times more radiation than the atomic bomb dropped on Hiroshima during WW2.
31 people died in the immediate aftermath, whilst the long-term health effects caused by Chernobyl are still a hotly debated subject. Approximately 60,000 square miles around the plant were contaminated and an area nearly twice the city of London remains an exclusion zone to this day.
Background of Chernobyl
Lying just 10 miles from the Belarus-Ukraine border and around 62 miles north of the Ukrainian capital Kyiv, the Chernobyl Nuclear Power Plant was commissioned in 1977 as part of the old Soviet Union, with the first reactor supplying power to the grid later that year. By 1984, four reactors had entered commercial operation, each capable of producing 1,000 megawatts of electrical power.
Just under two miles from the plant was the city of Pripyat, founded in 1970 and named after the nearby river. It was built to serve the power plant and at the time of the disaster, its total population was just shy of 50,000.
Nuclear disaster unfolds
Throughout Friday, 25th April 1986, Chernobyl's engineers lowered power at Reactor No. 4 in preparation for a safety test to be conducted later that evening. The test was supposed to check whether the reactor turbines could continue powering emergency water coolant pumps in the event of a power failure.
Ironically, the safety test was anything but safe as human error and substandard reactor design led to a partial meltdown of the core.
The experiment was poorly conceived and equally badly executed. Firstly, the less-experienced night shift crew carried out the safety test and later claimed they had not received full instructions from the day shift crew on how to properly conduct it. Secondly, the emergency core cooling system for Reactor 4 was disabled along with the emergency shutdown system.
Finally, the reactor’s power level dropped to a dangerously unstable level at which point the engineers removed most of the control rods in violation of safety guidelines. Although power began to return, it was far from under control.
Explosion in Reactor 4
At 1:23am on 26th April, the safety test was given the all-clear by plant supervisors. Almost immediately a power surge occurred, triggering the engineers to re-insert all 211 control rods. The control rods were graphite tipped, a design flaw that would prove fatal as they increased the reaction in the core, instead of lowering it.
The subsequent steam explosions blew off the steel and concrete lid of the reactor as the core suffered a partial meltdown. Two engineers were killed instantly whilst two more suffered severe burns. The explosion, along with the resulting fires, released at least 5% of the radioactive reactor core into the atmosphere. Blown by the wind, radioactive materials were spread to many parts of Europe over the coming days.
Emergency response begins
Firefighters quickly arrived on the scene but without proper protective clothing, many perished in the coming months from acute radiation syndrome. By dawn, all the fires were suppressed except for the one in the reactor core.
The other three reactors were shut down a short while later. The following day officials ordered helicopters to begin dumping more than 5,000 tonnes of sand, lead, clay, and boron onto the burning reactor to help extinguish the core fire.
A Soviet cover-up
It took nearly 36 hours for Soviet officials to begin evacuating nearby Pripyat. The city’s residents were unaware of the true dangers presented by the previous day’s events. Advised to pack only necessities, the people of Pripyat were loaded onto buses believing their evacuation to be temporary. Little did they know, they would never return to their homes again.
Two days after the catastrophic explosion the rest of the world remained in the dark as the Soviets attempted to cover up the event. However, on 28th April, Swedish radiation monitoring stations 800 miles away began detecting high levels of radiation. With their backs to the wall, the Soviets finally made a statement, with the Kremlin admitting an accident had occurred at Chernobyl, but assuring the world that officials had it under control.
Heroism on display
In the days that followed, hundreds of workers risked their lives to contain radiation leaking from the reactor core.
On 4th May, three divers made their way through the dark flooded basement of Reactor 4 to turn valves and drain the ‘bubbler pools’ sitting below the core. Had they not succeeded in their mission, molten nuclear material would have eventually melted its way down to the pools.
This would have triggered a radiation-contaminated steam explosion and destroyed the entire plant along with its three other reactors, causing unimaginable damage and nuclear fallout that the world would have struggled to recover from.
Radioactive debris also needed to be removed from the roof of the reactor. After robots failed to do the job, workers equipped with heavy protective gear were sent in.
Nicknamed ‘Bio-robots’, these workers were unable to spend more than 90 seconds on the roof due to the extreme levels of radiation. In the end, 5,000 men went up on the irradiated rooftop to successfully clear the radioactive material from it.
By mid-May, Soviet leader Mikhail Gorbachev had ordered thousands of firefighters, miners, and soldiers to begin the long and arduous task of cleaning up. Known as ‘Liquidators’, 600,000 - 800,000 of them began burying radioactive debris and topsoil, as well as shooting all wildlife (both domestic and wild) within the 19-mile exclusion zone surrounding the power plant.
By the end of the year, an enormous concrete and steel structure known as ‘The Sarcophagus’ covered Reactor 4, limiting the radioactive contamination of the environment. A new structure was put in place in 2017, confining the radioactive remains of Reactor 4 for the next 100 years.
The Chernobyl Exclusion Zone was eventually extended to cover approximately 1,000 square miles, whereby it was declared uninhabitable for over 20,000 years. The other three reactors at Chernobyl remained active until their individual shutdowns in 1991, 1996, and 2000. Gorbachev later wrote that he believed the incident at Chernobyl was the ‘real cause of the collapse of the Soviet Union’.
Whilst the lasting health effects of the disaster remain unclear and much debated, various sources have estimated that thousands of cancer deaths can be linked back to Chernobyl.