Chernobyl nuclear distaster - a reactor explosion at the nuclear power plant in Pripyat, Ukraine, releases dangerous radiation and prompts a desperate scramble to contain the fallout
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.
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,
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. 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.
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.
World Nuclear - Chernobyl Accident 1986
The Chernobyl Gallery - Liquidators
BBC - The True Toll of the Chernobyl Disaster
Challenger disaster - the NASA space shuttle breaks apart 73 seconds into its flight, killing all seven crew members
Challenger, NASA’s second space shuttle to enter service, embarked on its maiden voyage on April 4, 1983, and made a total of nine voyages prior to 1986.
That year, it was scheduled to launch on January 22 carrying a seven-member crew that included Christa McAuliffe, a 37-year-old high school social studies instructor from New Hampshire who had earned a spot on the mission through NASA’s Teacher in Space Program. After undergoing months of training, she was set to become the first ordinary American citizen to travel into space.
The mission’s launch from Kennedy Space Center at Cape Canaveral, Florida, was delayed for six days due to weather and technical problems.
The morning of January 28 was unusually cold, and engineers warned their superiors that certain components—particularly the rubber O-rings that sealed the joints of the shuttle’s solid rocket boosters—were vulnerable to failure at low temperatures. However, these warnings went unheeded, and at 11:39 a.m. Challenger lifted off.
Seventy-three seconds later, hundreds on the ground, including the families of McAuliffe and the other astronauts on board, stared in disbelief as the shuttle broke up in a plume of smoke and fire. Millions more watched the wrenching tragedy unfold on live television.
Within seconds, the spacecraft broke apart and plunged into the ocean, killing its entire crew, traumatizing the nation and throwing NASA’s shuttle program into turmoil.
A special commission's investigation revealed that the O-ring seal on Challenger’s solid rocket booster, which had become brittle in the cold temperatures, failed. Flames then broke out of the booster and damaged the external fuel tank, causing the spacecraft to explode and disintegrate.
After the accident, NASA refrained from sending astronauts into space for more than two years as it redesigned a number of the shuttle’s features.
Space.com - Challenger: The Shuttle Disaster That Changed NASA
Popular Mechanics - The Oral History of the Space Shuttle Challenger Disaster