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Thirty years ago, during a spring night in northern Ukraine, a group of men on the evening shift at a new nuclear plant prepared for a test of an emergency backup system.
But the emergency quickly became real. The engineers lowered too many control rods into the number four reactor’s core at the Chernobyl Power Plant. It began a chain of errors that would change nuclear power forever.
Within days, a city would be evacuated, a radioactive plume would spread across Europe, and the events of April 26, 1986 would become a cautionary tale.
“I went in there when everyone was fleeing, we were going right into the heat,” said Mykola Bludchiy, one of the 600,000 “liquidators” who responded to the emergency 30 years ago, at a commemoration in the Ukraine today. “And today everything is forgotten. It’s a disgrace.”
A midnight test
The Soviet team wanted to find out if the one-minute gap between power failure and the warming-up of the three backup diesel generators could be bridged by the rotational energy from the steam turbine. The tests had been undertaken in 1982, 1984 and 1985, and the results were unsuccessful – but there were no mishaps.
That night in 1986, the engineers lowered the control rods too far. It resulted in a nearly-complete shutdown of the power output, at 11 p.m. on April 25, according to timelines.
Ninety minutes later, the team decided to proceed with the experiments anyway. They wanted to see whether the cooling pump system could still function using power generated under a low-power situation.
The raising of the rods did not have an immediate effect. At 1 a.m., and at about seven percent of total power, more rods were raised – and the automatic shutdown system was disabled to allow the reactor to continue under the low-power conditions.
At 1:23 a.m., the power reached 12 percent, and the tests began.
Seconds later, power levels surged to dangerous levels.
Pushing the button
According to several accounts, all but six rods had been removed from the reactor core – but the minimum safe operating number was 30. The core overheated, and its water coolant turned to steam.
Somebody pushed the emergency shutdown button. The rods traveled about 0.4 meters per second, and usually took about 20 seconds to reach all the way to the bottom of the 7-meter core.
READ MORE: Chernobyl Wildlife Emerges Again on First Remote Cameras
But they never made it that far. The addition of all the rods at once displaced more coolant – and also concentrated all the radioactivity at the bottom of the core.
Fuel pellets in the core exploded, just a minute into the chain of events. The dome-shaped roof blew into the sky.
Air sucked into the exposed reactor ignited flammable carbon monoxide. The reactor fire burned for nine days.
Radioactive plume
Radioactivity surged into the atmosphere. Helicopters dumped sand and lead atop the smoldering wreckage to tamp down the radiation. The secretive Soviet Union only admitted to the disaster when the plume was detected by scientists in Scandinavia, thousands of miles away.
Fifty people, mostly emergency responders, died. (The World Health Organization estimates the overall death toll at 9,000 or more due to increased cancer rates in the region, while the environmental group Greenpeace places it at 90,000).
Some 135,000 people, including all of the adjoining town of Pripyat, were evacuated. Today the Chernobyl Exclusion Zone encompasses more than a thousand square miles around the sealed tomb of the melted-down core at reactor four.
Three of the staff were sentenced to lengthy prison terms in labor camps for their actions at Chernobyl. The first state explanation placed most of the blame for the disaster on them. However, subsequent reports in the 1990s placed greater emphasis on the flawed plant design’s role in the disaster. Of specific note were the graphite tips of the control rods, which actually boosted power output for the first few seconds of deployment, according to the later reports.
Today, a 2-billion euro shelter over the Chernobyl wreckage is underway – and could be completed later this year. The reactor and the melted-down core will have to then be cleaned – a job expected to take until the second half of this century.
Belarus has also reported elevated levels of radiation tainting its agriculture, as The Associated Press reported recently.
However, wildlife studies released as recently as this month have indicated animal population sizes have thrived in the irradiated area.
The Associated Press contributed to this report.
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