On the 26th anniversary of the Chernobyl disaster, Ukraine launched the construction of a new and improved shelter to permanently secure the traumatized plant.

Ukrainian President Viktor Yanukovych pressed the symbolic button at the construction site, while workers and ambassadors from countries including China and Japan watched on.

The president also spoke during the ceremony, which inaugurated the initial assembly of an enormous arch-shaped building that will essentially cover the remnants of the infamous exploded reactor.

The structure, which weighs an estimated 20,000 tons and is said to be big enough to house New York's State of Liberty, is due to be completed in 2015, allowing the delicate and dangerous job of dismantling the reactor and cleaning vast amounts of radioactive waste still around it to begin.

In the name of Ukraine, I express my deep thanks to all the donor countries to the Chernobyl Shelter Fund for their understanding and effective aid to our country in overcoming the consequences of the worst man-made disaster in human history, Yanukovych said, as cranes loomed over the site.

The project, which is expected to cost contributors around 1.5 billion euros, is intended to repair the damage from an explosion that occurred during testing at the power plant in the early hours of April 26, 1986.

The explosion resulted in radioactive fallout in the atmosphere which eventually spread across Europe, particularly contaminating Belarus, Ukraine and Russia.

The catastrophic event is widely considered to be the worst nuclear plant accident in history, and is one of only two events classified as a level 7 event on the International Nuclear Event Scale.

While a shelter called the sarcophagus was quickly built over the damaged reactor, in recent years it has reportedly been crumbling and leaking radiation.

Yanukovych said at the site that an estimated 2 million people have been hurt by the tragedy and it is the government's obligation to protect and treat them.

Regardless of his willingness to fix the problem at hand, About 2,000 protesters staged an angry rally outside parliament in Kiev, demanding an increase in compensations and pensions.

The demonstration was in response to benefits cuts of workers who were reportedly ordered to take part in the clean-up in Ukraine following the Chernobyl accident, working without adequate protection.

Yanukovych also thanked international donors for pledging $980 million to build the new shelter and a nuclear-fuel waste facility.

Among the biggest donors are the Group of Eight industrial nations, including Japan, which itself is still recovering from last year's Fukushima nuclear disaster.

In light of the construction of the Chernobyl shelter, here are the top 10 worst nuclear disasters

Chernobyl
The Chernobyl Disaster was a catastrophic nuclear accident that occurred on April 26,1986, at the Chernobyl Nuclear Power Plant in Ukraine. An explosion and fire released large quantities of radioactive contamination into the atmosphere, which spread over much of Western USSR and Europe. It is widely considered to have been the worst nuclear power plant accident in history, and is one of only two classified as a level 7 event on the International Nuclear Event Scale. REUTERS/Gleb Garanich
Fukushima Daichi Disaster
An 8.9 magnitude earthquake and subsequent tsunami on March 11, 2011, overwhelmed the cooling systems of an aging reactor along Japan's northeast coastline. The accident triggered explosions at several reactors at the complex, forcing a widespread evacuation in the area around the plant. http://en.wikipedia.org/wiki/F
Tomsk-7 Explosion
The accident in the Siberian city of Tomsk took place on April 6, 1993, after a tank exploded while being cleaned with nitric acid. The explosion released a cloud of radioactive gas drifting from the Tomsk-7 Reprocessing Complex. http://en.wikipedia.org/wiki/F
Goiania Accident
The Goiania accident was a radioactive contamination accident that occurred on September 13, 1987, at Goiania, in the Brazilian State of Goias after an old radiotherapy source was stolen from an abandoned hospital site in the city. It was subsequently handled by many people, resulting in four deaths. http://en.wikipedia.org/wiki/F
Three Mile Island Accident
The partial meltdown of the Three Mile Island Unit 2 nuclear power plant on March 28, 1979, was the most serious accident in the history of U.S. nuclear power plant operating history, despite the fact that it led to no deaths or injuries. http://en.wikipedia.org/wiki/F
Yucca Flat
On Dec. 8, 1970, After the Baneberry test, involving the detonation of a 10 kiloton nuclear device underneath Yucca Flat in Nevada, the plug sealing the shaft from the surface failed and radioactive debris vented into the atmosphere. Eighty six workers at the site were exposed to radiation. http://en.wikipedia.org/wiki/F
Windscale Fire
The Windscale Fire incident occurred on October 10, 1957, when the graphite core of a British nuclear reactor caught fire near Cumberland. The fire resulted in a release of a significant amount of radioactive contamination. It would come to be known as the worst reactor accident until Three Mile Island. http://en.wikipedia.org/wiki/F
K-431 Chazhma Bay
During refuelling in Vladivostok, Russia, on Aug. 10 1985, the Echo II class submarine (like the one seen above) suffered an explosion, sending a radioactive cloud of gas into the air. Ten sailors were killed in the incident and 49 people were observed to have radiation injuries. http://en.wikipedia.org/wiki/F
Russia China Japan Disasters