Chernobyl is located in northern Ukraine, about 80 miles north of Kiev. A small town, Pripyat, was constructed a few miles from the site of the nuclear plant to accommodate workers and their families.

Construction of the Chernobyl power plant began in 1977, when the country was still part of the Soviet Union. By 1983, four reactors had been completed, and the addition of two more reactors was planned in subsequent years.

A routine exercise to test whether an emergency water cooling system would work during a power loss started at 1:23 a.m. on April 26.

Within seconds, an uncontrolled reaction caused pressure to build up in Reactor No. 4 in the form of steam. The steam blasted the roof off the reactor, releasing plumes of radiation and chunks of burning, radioactive debris.

About two to three seconds later, a second explosion hurled out additional fuel. A fire started at the roof of Reactor No. 3, risking a breach at that facility. Automatic safety systems that would normally have kicked into action did not because they had been shut down prior to the test.

READ MORE: Chernobyl Disaster: The Meltdown by the Minute

Firefighters arrived at the scene within minutes and began to fight the blaze without gear to protect them from radiation. Many of them would soon number among the 28 killed by acute radiation exposure.

Eyewitness accounts of the firefighters who had helped battle the fires described the radiation as “tasting like metal,” and feeling pain like pins and needles on their faces, according to the CBC documentary series, Witness. Days later, many of those firefighters would be dead.

It wasn’t until 5 a.m. the following day that Reactor No. 3 was shut down. Some 24 hours later, Reactors No. 1 and 2 were also shut down.

By the afternoon of April 26, the Soviet government had mobilized troops to help fight the blaze. Some were dropped at the rooftop of the reactor to furiously shovel debris off the facility and spray water on the exposed reactor to keep it cool.

The workers were picked up within seconds to minimize their radiation exposure. It would take nearly two weeks to extinguish all the fires using sand, lead and nitrogen.

Meanwhile, life went on as usual for almost a day in the neighboring town of Pripyat. Aside from the sight of trucks cleaning the streets with foam, there were initially few signs of the disaster unfolding just miles away.

It wasn’t until the next day, April 27, when the government began evacuations of Pripyat’s 50,000 residents. Residents were told they would be away for just a few days, so they took very little with them. Most would never return to their homes.

It took days for Soviet leadership to inform the international community that the disaster had occurred. The Soviet government made no official statement about the global-scale accident until Swedish leaders demanded an explanation when operators of a nuclear power plant in Stockholm registered unusually high radiation levels near their plant.

Finally, on April 28, the Kremlin reported that there had been an accident at Chernobyl and that authorities were handling it. The statement was followed by a state broadcast detailing the U.S. nuclear accident at Three Mile Island and other nuclear incidents in western countries.

Three days later, Soviet May Day parades to celebrate workers went ahead as usual in Moscow, Kiev and Belarus’ capital Minsk—even as hazardous amounts of radiation were still streaming from the wrecked power plant.

Most people, even within the Ukraine, were still unaware of the accident, the deaths, and the hasty evacuations of Pripyat.

READ MORE: The Chernobyl Cover-Up: How Officials Botched Evacuating an Irradiated City

The damaged plant released a large quantity of radioactive substances, including iodine-131, cesium-137, plutonium and strontium-90, into the air for over a period of 10 days.

The radioactive cloud was deposited nearby as dust and debris, but was also carried by wind over the Ukraine, Belarus, Russia, Scandinavia and other parts of Europe.

In an attempt to contain the fallout, on May 14, Soviet leader Mikhail Gorbachev ordered the dispatch of hundreds of thousands of people, including firefighters, military reservists and miners, to the site to aid in clean-up. The corps worked steadily, often with inadequate protective gear, through 1989 to clear debris and contain the disaster.

Over a hurried construction period of 206 days, crews erected a steel and cement sarcophagus to entomb the damaged reactor and contain any further release of radiation.

As former liquidator, Yaroslav Melnik, told the BBC in January 2017, “We worked in three shifts, but only for five to seven minutes at a time because of the danger. After finishing, we’d throw our clothes in the garbage.”

Starting in 2010, an international consortium organized the building of a bigger, more secure sarcophagus for the site. The 35,000-ton New Safe Confinement was built on tracks and then slid over the damaged reactor and existing sarcophagus in November 2016.

After the installation of the new structure, radiation near the plant dropped to just one-tenth of previous levels, according to official figures. The structure was designed to contain the radioactive debris for 100 years.

Deep within the basement of Reactor 4 lies the Chernobyl Elephant’s Foot, a huge mass of melted concrete, sand and highly radioactive nuclear fuel.

The mass was named for its wrinkled appearance, which reminded some observers of the wrinkled skin of an elephant’s leg and foot.

In the 1980s, the Elephant’s Foot gave off an estimated 10,000 roentgens of radiation each hour, enough to kill a person three feet away in less than two minutes. By 2001, that rate had dropped to roughly 800 roentgens per hour.

Ukraine’s government declared in 1995 that 125,000 people had died from the effects of Chernobyl radiation. A 2005 report from the United Nations Chernobyl Forum estimated that while fewer than 50 people were killed in the months following the accident, up to 9,000 people could eventually die from excess cancer deaths linked to radiation exposure from Chernobyl.

As of 2005, according to the Union of Concerned Scientists, some 6,000 thyroid cancers and 15 thyroid cancer deaths had been attributed to Chernobyl.

Health effects from the Chernobyl disaster remain unclear, apart from the initial 30 people the Soviet government confirmed killed from the explosions and acute radiation exposure. No official government studies were conducted following the explosion to assess its effects on workers, the liquidators and nearby populations.

A 2011 study by the U.S. National Institutes of Health concluded that exposure to radioactive iodine-131 from Chernobyl fallout was likely responsible for thyroid cancers that were still being reported among people who were children or adolescents at the time of the accident.

Apart from the ever-unfolding human toll from the disaster, the Chernobyl accident also left behind a huge area of radiation-tainted land.

A 770-mile-wide Chernobyl Exclusion Zone around the site isn’t considered safe for human habitation and can’t be used for logging or agriculture due to contaminated plants and soil. By 2017, however, entrepreneurs found a new use for the territory.

In December 2017, a Ukrainian-German company, Solar Chernobyl, announced construction of a massive solar power plant in the abandoned territory. The one-megawatt power plant, built just a few hundred feet from the damaged Reactor 4, was fitted with 3,800 photovoltaic panels. The Ukrainian government said that a collection of companies planned to eventually develop up to 99 more megawatts of solar power at the site.

That’s a lot of power, but still not close to the former output of the ruined nuclear power plant. At the time of the accident Chernobyl’s four reactors could generate 1,000 megawatts each.

Meanwhile, wildlife, including boars, wolves, beavers and bison, showed signs of flourishing at the Chernobyl site, according to an April 2016 study.

The researchers pointed out that while radiation exposure couldn’t be good for the animals, the benefits of the absence of humans outweighed radiation risk.

Humans, on the other hand, aren’t expected to repopulate the area any time soon. Ukrainian authorities have said it will not be safe for people to live in the Chernobyl Exclusion Zone for more than 24,000 years.

Today tourists can visit the site, which appears frozen in time, apart from signs of looting, natural weathering and the encroachment of nature.

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Chernobyl Accident 1986, updated November 2016, World Nuclear Association
“Health Effects of the Chernobyl Accident: An Overview,” April 2006, World Health Organization.
“Chernobyl’s Legacy 30 Years On,” by Tom Burridge, April 26, 2016, BBC News
“Higher Cancer Risk Continues After Chernobyl,” March 17, 2011, National Institutes of Health.
“How Many Cancer Deaths Did Chernobyl Really Cause?” by Lisbeth Gronlund, Union of Concerned Scientists.
“Animals Rule Chernobyl Three Decades After Nuclear Disaster,” by John Wendle, April 18, 2016, National Geographic.
“A Nuclear Disaster That Brought Down an Empire,” April 26, 2016, The Economist.
“World’s Largest Moveable Steel Structure Shelters Sarcophagus at Chernobyl,” April 27, 2017, PhysOrg/Pacific Northwest National Laboratory.
“Pictures: ‘Liquidators’ Endured Chernobyl 25 Years Ago,” by Marianne Lavelle, April 27, 2011, National Geographic.
“Chernobyl: Timeline of a Nuclear Nightmare,” by Kim Hjelmgaard, USA Today.
“A Vast New Tomb for the Most Dangerous Disaster Site in the World,” by Christian Borys, January 3, 2017, BBC Future Now.
“The Lessons of Chernobyl May Be Different Than We Thought,” by Ryan Faith, April 26, 2016, Vice News.
“25 Years After Chernobyl, We Don’t Know How Many Died,” by Roger Highfield, April 21, 2011, New Scientist.
“Chernobyl’s Transformation Into a Massive Solar Plant Is Almost Complete,” by David Nield, January 13, 2018, Science Alert.
“The Famous Photo of Chernobyl’s Most Dangerous Radioactive Material Was a Selfie.” January 24, 2016, Atlas Obscura.