Prior to a routine shutdown of Reactor #4, the crew disabled automatic shutdown mechanisms, leaving the reactor in an extremely unstable condition. Because of a design flaw, when the graphite control rods began to be inserted, a dramatic power surge occurred. The contact of the hot fuel with its cooling waters lead to a dramatic increase in steam. The intense pressure caused a massive explosion, blowing the roof off the containment building, releasing radioactive particles and gas into the atmosphere.
Three seconds later, a second explosion blew out fragments from the reactor core itself.
Two workers died instantly in the explosions. They were the lucky ones. Thirty one deaths are attributed to the two explosions and the attempts to put out the fire. The casualties included the firefighters who fought the fires on the roof of the turbine building.
Most of the radioactivity was deposited within a few kilometers as dust and debris. But the radioactive plume went on to drift over large parts of the Ukraine, Belarus, Russia and Eastern Europe. Only after drifting radiation set off alarms in Sweden, over 1000 km away, did the Soviet Union publicly admit that an accident had occurred. Only after evacuating the nearby city of Pripyat, was a warning message was read on Soviet state TV:
Pripyat was built in 1970, 4 km away, to house the employees of Chernobyl and had grown to a population of 50,000. The city however was not immediately evacuated after the explosion. The majority were unaware of the disaster and went about their usual business. Children played outside and gardeners worked on their plants. The black smoke rising from the Power Plant was explained away as a routine steam discharge. Residents gathered on rooftops to watch the burning reactor and exposed themselves to fatal doses of radiation.
Within hours of the explosion, scores of people began to fall ill, reporting headaches, nausea, coughing and vomiting. By Sunday morning 1200 buses began arriving in Pripyat in preparation for evacuation. The order was finally announced at Noon. Residents were asked to carry with them only what would be needed for 2-3 days away, some food and a change of clothing. Employee dosimeters were confiscated. By nightfall, the city was empty. No one would live in Pripyat ever again. It now lies within the Exclusion zone and remains abandoned to this day.
The Chernobyl disaster caused the largest uncontrolled radioactive release ever recorded.
Large quantities of radioactive materials were released into the air for the next 10 days. A massive concrete and metal shell was hastily constructed to encase the remains of Unit 4, both as a means to halt the release of radiation and to allow continuing operation of the other 3 functional reactors. About 200 tons of highly radioactive material remains buried within.
The “Chernobyl Nuclear Zone of Alienation” is the officially designated exclusion area around the site. Established by the Russian military, it covers the areas worst affected by contamination, an area of 30 km radius evacuated and placed under military control. By May, 116,000 people had been evacuated. The Exclusion Zone remains one of the most radioactively contaminated areas in the world and oddly draws an increased tourist crowd.
The effort to contain the contamination and repair the site eventually involved over 500,000 workers, known as ‘Liquidators’ and cost 18 billion Rubles. Unit 2 was shut down in 1991, and unit 1 in 1997. Energy shortages necessitated the continued operation of unit 3 until 2000. Almost 6000 people continued to work at the plant every day.
A Russian publication concluded that 985,000 premature cancer deaths occurred across Europe and Asia between 1986 and 2004 as a result of radioactive contamination from Chernobyl. Nearly 5 million people, including more than 1 million children, still live near dangerous levels of radioactive contamination in Belarus and Ukraine.
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