A radioactivity sign outside the fourth nuclear reactor at the former Chernobyl Nuclear power plant, site of the world's worst nuclear disaster, is pictured on April 4, 2011. SERGEI SUPINSKY/AFP/Getty Images
The worst nuclear catastrophe the world has ever seen marks its 30th anniversary this year.
On April 26, 1986, at 1:23 a.m., technicians at the Chernobyl nuclear power plant conducting a test inadvertently caused reactor Number Four to explode.
Ukrainian President Petro Poroshenko pays his respects after laying flowers at the memorial near the Chernobyl Nuclear Power plant on April 26, 2016. GENYA SAVILOV/AFP/Getty Images
The reactor—in then-USSR controlled Ukraine—contained over 200 tons of uranium. The explosion of the radioactive element flipped the 1,200 ton lid of the reactor into the air.
A plume of deadly, radioactive gas covered most of the Northern Hemisphere.
Two Soviet technicians control the level of water radioactivity in front of a group of Soviet and foreign newsmen who have been permitted to enter the Kiev area, on May 09, 1986, in the 30 km (18.6 mile) forbidden zone. AFP/Getty Images
Within a days of the disaster 32 people, many of them firemen sent to extinguish the blaze, died. Since then, estimates vary from 4,000 to 200,000 deaths that are attributed to illnesses resulting from the radioactive contamination.
Over 2.5 million Ukrainians suffer from health problems related to the blast, with 80,000 of them receiving a pension.
A policeman checks the level of radioactivity on vehicles leaving the 30 km (18.6 mile) forbidden area around Chernobyl on May 10, 1986. STF/AFP/Getty Images
An aerial view of the Chernobyl nuclear power plant, the site of the world's worst nuclear accident, is seen in April 1986, taken two to three days after the explosion. To the left of the chimney is the destroyed fourth reactor. AP Photo
This Oct. 13, 1991, file picture shows part of the collapsed roof at the Chernobyl, Ukraine, nuclear power plant during a media tour of the facility. Only a few photographers were allowed to cover the destroyed reactor and desperate cleanup efforts, and all of them paid for it with their health. AP Photo/Efrem Lukatsky, File
Photographs of victims of the 1986 Chernobyl nuclear accident are displayed at the site of a memorial service to commemorate the anniversary on April 25, 2014, in Donetsk, Ukraine. Brendan Hoffman/Getty Images
Chernobyl. Google maps/screenshot
Authorities evacuated approximately 43,000 people from Pripyat in the days following the disaster. The city—with its high-rise apartment buildings, hospital, shops, schools, restaurants, cultural center and sports facilities—has remained a ghost-town ever since.
It lies only a few kilometers from the power plant, within the inner Exclusion Zone.
Taken November 10, 2000, this photo displays the shattered remains of the control room for Reactor number four at the Chernobyl nuclear power plant. AP Photo/Efrem Lukatsky, File
Small dosimeters that measure radiation dosage and used by emergency workers following the disaster lie scattered on the ground outside on April 9, 2016 in Pripyat, Ukraine. Sean Gallup/Getty Images
A restricted zone contaminated by radiation from the meltdown—the inner zone being 30 km (18.6 mile), the outer zone 2,600 square km (1,000 square mile)—is called the Chernobyl Exclusion Zone.
The town of Pripyat was built in the 1970s as a model Soviet city to house the workers and families of the Chernobyl power plant.
General view of Chernobyl Nuclear Power Plant taken from the ghost city of Prypyat on April 8, 2016. SERGEI SUPINSKY/AFP/Getty Images
The picture shows a general view to Chernobyl Nuclear Power Plant from ghost city of Prypyat on April 8, 2016. SERGEI SUPINSKY/AFP/Getty Images
A photo taken on January 22, 2016, shows a ferris wheel between abandoned buildings in the ghost city Pripyat near to Chernobyl Power Plant. GENYA SAVILOV/AFP/Getty Images
Authorities evacuated approximately 43,000 people from Pripyat in the days following the disaster and the city, with its high-rise apartment buildings, hospital, shops, schools, restaurants, cultural center and sports facilities, has remained a ghost-town ever since.
It lies only a few kilometers from the power plant, within the inner Exclusion Zone.
A photo taken on January 22, 2016, shows a coat of arms of the former Soviet Union on the roof of an apartment building in the ghost city Pripyat. GENYA SAVILOV/AFP/Getty Images
Abandoned gas masks lay on the floor in a classroom in a school May 26, 2003, of the deserted town of Prypyat. SERGEI SUPINSKY/AFP/Getty Images
In this November 10, 2000, photo, radioactive contaminated vehicles lay dormant near the power plant. Some 1,350 Soviet military helicopters, buses, bulldozers, tankers, transporters, fire engines and ambulances were used while fighting against nuclear accident. All were irradiated during the clean-up operation. AP Photo/Efrem Lukatsky
Taken on January 22, 2016, this photo shows a crucifix and a radiation sign in front of apartment buildings in the ghost city Pripyat. GENYA SAVILOV/AFP/Getty Images
The remnants of an abandoned class room is seen in a pre-school in the deserted town of Pripyat on January 25, 2006. Daniel Berehulak/Getty Images
Large portions of the inner and outer Chernobyl Exclusion Zone remain contaminated. A consortium of western companies is building a movable enclosure called the New Safe Confinement that will cover the reactor remains and its fragile sarcophagus in order to prevent further contamination.
Pripyat and the surrounding area will not be safe for human habitation for several centuries. Scientists estimate that the most dangerous radioactive elements will take up to 900 years to decay sufficiently to render the area safe.
The former Chernobyl nuclear power plant, including destroyed reactor four (center), as well as the New Safe Confinement structure (right) that will one day enclose the remains of reactor four, stand behind the abandoned city of Pripyat on September 30, 2015. Sean Gallup/Getty Images
On October 2, 1989, in the Chernobyl area, a woman holds a disabled newly-born pig, victim of the radioactivity fall-out of the Chernobyl power plant accident in 1986. LARS GRANSTRAND/AFP/Getty Images
Stray dogs run in front of the Chernobyl nuclear power plant during a drill organized by Ukraine's Emergency Ministry, November 8, 2006. SERGEI SUPINSKY/AFP/Getty Images
A photo taken on January 22, 2016, shows wild Przewalski's horses on a snow covered field in the exclusion zone. In 1990, a handful of endangered Przewalski's (Dzungarian) horses were brought in the exclusions zone to see if they would take root. They did so with relish, and about a hundred of them now graze there. GENYA SAVILOV/AFP/Getty Images
A man walks past a mural on the wall of a museum commemorating the Chernobyl nuclear disaster with an exploding reactor core and images of storks, the Ukrainian national bird, shackled with bits of barbed wire on September 29, 2015, in Chernobyl, Ukraine. Sean Gallup/Getty Images
A photo taken on January 22, 2016, shows snow covered ride at the amusement park in the ghost city Pripyat near the Chernobyl Power Plant. GENYA SAVILOV/AFP/Getty Images
Tourists on a guided tour snap photos of one another outside an abandoned shop and apartment building on April 9, 2016, in Pripyat, Ukraine. Tour operators bring tourists in small groups to explore certain portions of the exclusion zone. Sean Gallup/Getty Images
A man walks through the "ghost town" of Pripyat on April 22, 2016. GENYA SAVILOV/AFP/Getty Images
Ukrainian President Petro Poroshenko speaks on the 30th anniversary of the Chernobyl nuclear in front of the sarcophagus that encloses stricken reactor number four at the Chernobyl nuclear power plant on April 26, 2016, near Chornobyl, Ukraine. Sean Gallup/Getty Images
