It is the world’s largest mobile metal structure and cost roughly €1.5 billion
On November 29th, the final placement of the massive shelter over reactor 4, which exploded in April 1986, was completed. Called the New Safe Confinement (NSC), the shelter was designed to cover the concrete sarcophagus which was hastily built over the site of the stricken reactor and prevent additional radioactive material leaking out over the next 100 years. The NSC was built in a clean area near reactor 4, as the radiation immediately above the reactor is still too intense. It was then slid over 327m to seal off the unit, using a system of 224 hydraulic jacks. Works started in 2010, and both its construction and the sliding operation was a challenge for the engineers.
The NSC has a span of 257m, and measures 162m in length and 108m in height, with a total weight of 36,200 tonnes. Due to the vast dimensions of the structure, it has been built in two halves that were lifted and joined together in 2015. It is equipped with double walls, guaranteed to prevent any radiological releases and to completely keep out rain and snow, providing a barrier against extreme hot or cold. The external cladding will be able to withstand a class 3 tornado or a 6.0 magnitude earthquake. The structure's internal wall is smooth to “minimize the risk of dust deposition and accumulation," according to the European Bank for Reconstruction and Development (EBRD), and it’s made of corrosion-resistant, fire-resistant, and non-magnetic steel.
The shelter is fitted with an overhead crane and now that placing is completed, works will begin to safely dismantle the existing concrete sarcophagus and the remains of the reactor, as well as to secure the radioactive material still inside. Throughout 2017, additional construction will make the shelter airtight. Despite all these actions, the surrounding zone, which at 2,600 km2 (1,000 miles2) is roughly the size of Luxembourg, will remain largely uninhabitable and closed to unsanctioned visitors.
For the realization of this international project, 40 countries raised money, with EBRD being the project’s leader and biggest single donor.
Construction work is being undertaken by Novarka, a joint venture formed by Vinci Construction and Bouygues Construction. Novarka started constructing the NSC in 2012 after extensive preparatory works on site, which included excavation of two trenches on either side of the reactor to prepare the ground for the longitudinal beams that serve as the arch foundations.
Ukraine's ecology minister, Ostap Semerak, said the start of the operation to cover the reactor was ‘the beginning of the end of a 30-year long fight with the consequences of the 1986 accident’. ‘The credit for construction of this one-of-a-kind technological structure goes to an expert team of engineers and builders. This is a historic step towards the improvement of environmental safety throughout the world, as well as in the Chernobyl exclusion zone’.
Igor Gramotkin, Director-General of the Chernobyl Nuclear Power Plant, said: ‘We were not building this arch for ourselves. We were building it for our children, for our grandchildren and for our great-grandchildren. This is our contribution to the future, in line with our responsibility for those who will come after us’.
The shelter under construction
Inside the shelter
The system of the hydraulic jacks