When it's completed, the New Safe Confinement, or NSC, will be the largest movable object built on land, according to the European Bank for Reconstruction and Development, or EBRD.
When an explosion tore through Chernobyl's No. 4 reactor on April 26, 1986, near Pripyat, Ukraine, more than 30 people died and countless others have died from radiation symptoms since, according to the International Atomic Energy Agency and the World Health Organization. The Ukraine government evacuated some 135,000 people from the area and the 19-mile exclusion zone around the plant will remain uninhabitable for decades.
In the months after the accident, a sarcophagus was built to cover Reactor 4 and contain the radioactive material. However, it has since deteriorated, resulting in radiation leaks.
Construction of the NSC, in the shadow of Reactor 4, started in late 2010 and is expected to be finished in late 2017. When completed, the NSC will rise 360 feet into the air and will be tall enough to house the Statue of Liberty. It will be over 540 feet long, have a span of 850 feet and a lifetime of at least 100 years. The entire structure will weigh more than 30,000 tons, according to the EBRD.
When the NSC is completed, it will be pushed over the damaged reactor. The arch-like structure is designed to prevent the release of contaminated material from the present sarcophagus and also protect the structure from external impacts, such as tornadoes or extreme thunderstorms.
Vince Novak, the director of nuclear safety for EBRD, called the Chernobyl disaster "the worst accident that ever happened in nuclear history."
"It's more than just a shed," Novak continued. "It is also a workshop. It has to provide an environment in which people will be able to carry out the waste management activities for a period of probably 100 years."
A project of this magnitude required a lot of financial help and cooperation from around the world. The Chernobyl Shelter Fund was set up at the EBRD in 1997 and over 40 countries and organizations have donated a collective $1.7 billion.
The contract for this unprecedented project was awarded to the Novarka consortium led by the French construction companies Bouygues and Vinci in 2007.
The consortium is working with local subcontractors and other entities from across the world to provide the materials to complete the project. For instance, the arch is made of elements prefabricated in Italy and transported to the site in Ukraine. The cranes were manufactured in the United States and shipped over, according to the EBRD.
The arch is being fitted with cranes and other equipment for dismantling the damaged reactor and waste management tasks ahead of them, before it is eventually slid over Reactor 4.
Moving things into place
The target date for sliding of the arch into its final position is November 2016, and the sealing operations will be complete a year later. This is a unique task in which a total of more than 35,000 tons will be pushed nearly 1,000 feet on a rail system by 116 remote-controlled synchronized jacks. The sliding operation, at a speed of 10 mph, is expected to take two days.
The move will require 33 hours of uninterrupted operations. Just like a space launch, the skidding process must take place within a selected 72 hour meteorological window. The additional time ensures a sufficient margin for contingencies.
Safety for workers is a priority
Building an arch in proximity to a nuclear leak has its fair share of challenges.
Before construction of the NSC began, workers helped decontaminate the area by removing the top layer of soil along with any potential radioactive material that might have been left behind. After that they poured a layer of concrete over a large area and erected a wall closest to the sarcophagus.
During peak construction times, there are around 1,200 employees at the site from over 27 nations. To ensure they are safe from radiation exposure, the millisievert (mSv), or the average accumulated background radiation exposure dose, is closely monitored. The average dental X-ray exposes someone to about 0.014 mSv. A worker in the New Safe Confinement arch is exposed to 0.0075 mSv's per hour.
A new, state-of-the-art changing facility with a capacity for 1,430 workers was built onsite and offers medical and radiation protection facilities. There also is an ambulance on duty, in case of emergencies. In addition, the Chernobyl Shelter Fund provides training facilities, radiation monitoring and medical equipment as well as a medical screening program for the workers, according to the EBRD.
All work on site is carried out under the strictest health and safety regulations by a specially trained workforce, according to Bouygues and Vinci.
So far there has not been a single case of exposure beyond permissible limits, according to the EBRD.