According to the International Atomic Energy Agency, which is headquartered in Vienna, Austria, only the Chernobyl disaster attained its highest level—Level 7—on its International Nuclear Event Scale (pdf file), what is considered a “Major Accident: Maximum Credible Accident,” or an event that causes a severe nuclear meltdown.

At 1:23:40 a.m. local time (Coordinated Universal Time plus three hours [UTC+3]), the number four nuclear reactor at the Chernobyl Nuclear Power Plant in the Soviet Union (near Pripyat in the northern section of the Ukraine) exploded.

The plant was named after the city of Chernobyl, which was located about eighteen kilometers northwest of the nuclear power planet site.

Afterwards, the explosion, which sent up a huge mushroom-shaped cloud of radioactive materials into the atmosphere, was considered thirty to forty times more deadly that the fallout from the atomic bomb dropped by the United States onto Hiroshima, Japan, at the end of World War II (1939-45).

Hundreds of thousands of people were forced to resettle because of the nuclear disaster.

The deadly fallout spread over parts of western Soviet Union, along with parts of Western, Eastern, and Northern Europe. It even made it to the eastern seacoast of the United States.

Radiation experts estimated that sixty percent of its deadly contents fell on the former U.S.S.R. satellite country of Belarus, along with also dropping large amounts on the Ukraine and Russia. These areas within the three countries were directly contaminated, an area half the size of the country of Italy.

More information about the old structure and the New Safe Confinement structure follows on the next page.

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After the disaster the Soviets constructed an iron-and-concrete structure, called a "sarcophagus," to cover the number four nuclear reactor.

However, it was poorly constructed in just six months and, consequently deadly radioactivity continues to spew out of it and it is rapidly becoming structurally unsound.

With the breakup of the Soviet Union, the disaster site is now located in the country of the Ukraine.

Experts contend that a natural disaster, such as an earthquake, could destroy the shelter, re-releasing deadly radiation back into the atmosphere.

The $505 million project, which is managed by the European Bank for Reconstruction and Development (ERBD), is part of a larger $1.4 billion project that has been operational since 1997. The project is funded by the Chernobyl Shelter Fund (pdf file), which has received approximately 810 million Euros since 1997 from international donors.

The massive cleanup project has been working for the last nine years at monitoring the radiation leaking out of the shelter (along with the amount of radiation still inside), strengthening the current shelter (which is in poor condition due to weakening effects of the radiation), and other activities associated with the Chernobyl nuclear plant.

The new steel arched structure—called a New Safe Confinement structure—will be designed and built by Novarka, a European-Ukrainian consortium led by French construction and engineering firm VINCI Companies. It will be constructed next to the old shelter.

When completed (scheduled completion is 2012), it will be transported on railroad tracks over top the old shelter. The new 20,000-ton shelter will be 345 feet (105 meters) in height, 840 feet (256 meters) in width, and 490 feet (149 meters) in length.

It will cover nuclear reactor unit number four and the old shelter structure.

The construction is scheduled to begin in 2009. The designers state that the structure will last one hundred years.

The United Nations Chernobyl website is: “The United Nations and Chernobyl.”

Historical information about the Chernobyl accident is found at the Nuclear Energy Agency’s website: “Chernobyl: Assessment of Radiological and Health Impacts.”