New Safe Confinement arch to seal what remains of Chornobyl reactor

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

On April 26, 1986, a botched test at the nuclear plant sent clouds of smouldering nuclear material across large swathes of Europe, led to the evacuation of Pripyat, a town of over 50,000 people, and poisoned unknown numbers of workers involved in its cleanup.

• Chornobyl, 30 years later: A 360 tour of a ghost town
• Chornobyl's troubled cleanup detailed in Nature

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 late 2010.

Easily visible from kilometres away, the New Safe Confinement arch will be pulled slowly over the site later this year to create a steel-clad casement to block radiation. This will allow the remains of the reactor to then be dismantled safely. The process is expected to be finalized next year.

The arch, reportedly weighing from about 27,216 tonnes to about 32,650 tonnes, is now at its full height (108 metres), width (250 metres) and length (150 metres).

David Driscoll, safety and environment manager on the project, told Reuters it will act as a "safe confinement" over reactor four.

He said it's designed to last "for 100 years," creating a leak-tight barrier to contain radioactive substances, to give Ukraine the opportunity to dismantle the damaged reactor.

"We plan to move the arch at the end of November this year, to place it over the [existing] arch, the tilting panels you can see in the background will be raised and then lowered and sealed around the reactor. And then we will commission all systems to make sure it is active," he said.

The European Bank for Reconstruction and Development (EBRD) has managed the funding of the arch, which has cost around 1.5 billion euros (more than $2.1 billion Cdn) and involved donations from more than 40 governments.

Even with the new structure, the surrounding zone, which at 2,600 square kilometres is roughly the size of Luxembourg, will remain largely uninhabitable and closed to unsanctioned visitors.

Nature has been quick to reclaim the area's abandoned infrastructure. Trees sprout from the rusted roofs of apartment blocks in the ghost town of Pripyat, built to house Chornobyl power plant workers.

The 30th anniversary of the disaster has shone a new light on the long-term human impact of the worst nuclear meltdown in history.

The official short-term death toll from the accident was 31 but many more people died of radiation-related illnesses such as cancer. The total death toll and long-term health effects remain a subject of intense debate.

It's a CBC News language policy to spell the city's name Chornobyl, not Chernobyl. Both are transliterations, and Chornobyl more accurately reflects the Ukrainian pronunciation, while Chernobyl is more Russian-influenced.