Gigantic radiation-blocking shield slides into place at Chernobyl

In the middle of a vast exclusion zone in northern Ukraine, the world's largest land-based moving structure has been slid over the Chernobyl nuclear disaster site to prevent deadly radiation spewing from the stricken reactor for the next 100 years.

On April 26, 1986, a botched test at the Soviet nuclear plant sent clouds of smoldering nuclear material across large swathes of Europe, forced over 50,000 people to evacuate and poisoned unknown numbers of workers involved in its clean-up.

A concrete sarcophagus was hastily built over the site of the stricken reactor to contain the worst of the radiation, but a more permanent solution has been in the works since 2001.

Easily visible from kilometers away, the 36,000-metric-ton "New Safe Confinement arch has been slowly pulled over the site over the past four days to create a casement to block radiation and allow the remains of the reactor to be dismantled safely.

On Tuesday, a ceremony was held at Chernobyl to mark this major milestone in the decades of work to secure the site that has been funded by donations amounting to more than 2 billion euros ($2.1 billion) from more than 40 countries and organizations.

"Let the whole world see today what Ukraine and the world can do when they unite, how we are able to protect the world from nuclear contamination and nuclear threats," Ukrainian President Petro Poroshenko said.

The structure, which resembles a vast aircraft hangar, has been designed to withstand extreme temperatures, corrosion, and tornadoes.

The European Bank for Reconstruction and Development which has managed the funding for the clean-up said the program to transform Chernobyl into an environmentally safe and secure condition by November 2017 was on track.

Even with the new arch, the surrounding zone, which at 2,600 square kilometers (1,000 square miles) is roughly the size of Luxembourg, will remain largely uninhabitable and closed to unsanctioned visitors.

More than thirty years after the disaster, nature has reclaimed much of the area's abandoned infrastructure. Trees sprout from the rusted roofs of apartment blocks in the ghost town of Prypyat, while some animal populations are booming in the absence of humans.

As The Christian Science Monitor reported in April:

Thirty years after the worst nuclear accident in history, land once blanketed in radioactive fallout is now home to a stable wildlife population.

A new study on the Chernobyl Exclusion Zone (CEZ), the 1,000-square-mile area surrounding the Chernobyl Nuclear Power Station in Pripyat, Ukraine, found that animals are living normally in the exclusion area despite persistent radiation across the region.

"When humans are removed, nature flourishes – even in the wake of the world's worst nuclear accident," said Jim Smith, an environmental scientist at the University of Portsmouth in England, in an October interview with Reuters, following the release of another study pointing to the natural resurgence in the abandoned area.

"It's very likely that wildlife numbers at Chernobyl are now much higher than they were before the accident," he said.

It will likely be a very long time before people, however, can return to the region to live. By some estimates, it could be 3,000 years before the area is once again suitable for human habitation.