The Chernobyl Nuclear Accident

The Chernobly nuclear power station, in Ukraine, was the site of possibly the worst nuclear accident ever. The day before the disaster, plant operators were preparing for ashutdown to perform routine maintenance on one of the four reactors. As part of the shutdown, they disabled the automatic shutdown mechanism.

At 1:23 a.m. on April 26, when extremely hot nuclear fuel rods were lowered into cooling water, an immense amount of steam was created, which, because of design flaws, created more reactivity in the nuclear core of reactor number 4. This created a power surge and an explosion that detached the roof of the reactor core, releasing radioactive material into the atmosphere.

A few seconds later, a second explosion blew the reactor building and core and started a number o f fires.

Most of the radiation released was from iodine-131, cesium-134 and cesium-137. Iodine-131 has a relatively short half-life of eight days, but is rapidly ingested through the air and concentrated in the thyroid gland. Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years). Lthe presence of longer lived nuclei, the area won't be safe for human habitation for at least 20,000 years.

On April 27, the residents of the local town, Pripyat were evacuated. By that time, many were already complaining about vomiting, headaches and other signs of radiation sickness. Officials eventually closed off an 18-mile (30 km) area around the plant; residents were told they would be able to return after a few days, so many left their personal belongings and valuables behind.

Twenty-eight of the workers at Chernobyl died in the four months following the accident, including some who knowingly exposed themselves to radiation while making the plant safe. Winds blew the radioactive fallout over Belarus and Sweden, and when it was detected there, Soviet officiials were forced to release more information about the disaster.

Shortly after the accident, trees in the woodlands surrounding the plant started to die. The dead trees turned red and became know as the 'Red Forest'. They were eventually bulldozed and buried in trenches.

The damaged reactor was hastily sealed in concrete designed to prevent any further release of radiation.

Despite the contamination of the site, the Chernobyl nuclear plant continued operation until its last reactor was shut down in December 2000.

The region today is widely known as one of the world's most unique wildlife sanctuaries. Thriving populations of wolves, deer, lynx, beaver, eagles, boar, elk, bears and other animals have been documented.

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