Thirty years after the Chernobyl nuclear disaster, engineers are giving the epicenter of the long-defunct facility a facelift. With financial assistance from more than 40 nations, including the United States, workers are constructing a colossal structure that will contain the destroyed reactor and the sarcophagus that was built immediately after the accident.

"This new structure is unprecedented and unique," said Najmedin Meshkati, a professor of civil and environmental engineering at the University of Southern California.

The enclosure, weighing more than 33,000 metric tons and expected to be completed next year, will be one of the largest movable structures ever constructed. Its base occupies an area larger than two football fields and at its crest the structure will rise to a height of about 32 stories.

In the months following the meltdown, a Soviet crew put in place the temporary structure in order to contain the radioactive debris as soon as possible. Workers who built the sarcophagus were exposed to high levels of radioactivity.

"It was built hastily, but heroically," Meshkati said.

Over the years the sarcophagus has deteriorated and become vulnerable to leaks during rain and snowstorms.

"The new safe confinement is a robust structure designed to withstand natural phenomenon such as tornadoes, heavy snow, earthquakes since it does not rely on the damaged structures for support and stability," Ron Hink of Bechtel, which is leading an international consortium responsible for the project and helped design the arch.

The skeleton of the new arch is made from carbon steel pipe and the skin is composed of a multilayered arrangement of stainless steel, a moisture barrier, and insulation. The structure has been designed not just to contain the radioactive debris but also allow for the safe dismantling of the older structure that is slowly disintegrating, mostly from corrosion.

Controlling humidity within the structure was a main task for the designers, Hick explained. Keeping humidity below 40 percent will prevent condensation and corrosion.

The new structure is expected to last for 100 years.

Apart from the engineering challenges of building a gargantuan structure at a radioactive site, Hink said that obtaining regulatory approvals, and the declining local economic conditions also posed a hurdle.

"Although fighting in eastern Ukraine did not directly impact the project," he said, "the decline in the local economy did worsen local living conditions and add to hardships being experienced by local residents."

The confinement structure costs about $1.3 billion, while the larger set up, known as the Shelter Implementation Plan, comes with a price tag of $2.7 billion. The funding for the project has come from more than 40 countries, including the United States, and is overseen by the European Bank for Reconstruction and Development.

The Chernobyl nuclear power plant is seen through the construction of a new protective shelter.(Photo by Roman Pilipey/EPA)

Despite radiation levels falling over the years, the exclusion zone of about 1,000 square miles carved out around the plant in the aftermath of the disaster remains mostly uninhabited, a testimony to the lasting effects of the disaster.

Chernobyl has left an enduring impact on public's perception of the safety of nuclear plants. It reinforced the old adage that a nuclear accident anywhere is a nuclear accident everywhere, Meshkati said, because major failures have spillover effects far beyond the localities where they take place.

The Chernobyl accident, in addition to the more recent Fukushima meltdown, are reminders of the consequences of breeches in safety culture at nuclear facilities.

"I hope that we have learnt enough lessons from Chernobyl and Fukushima," Meshkati said. "We don't need a third reminder."