On November 29, 2016, an epoch-making event, albeit not noticed by everyone, took place: the infamous fourth power unit of the Chernobyl nuclear power plant was closed with an arch-shaped stainless steel shell, blocking the spread of harmful radio emissions. Prior to that, over the past ten years, the first “shelter” installed after the accident was on the verge of collapse. It was rather primitive: made of concrete and metal structures - it was erected in record time, from May to November 1986. Then, immediately after the explosion, speed and efficiency were the main ones: the structure, which immediately received the nickname "sarcophagus", was designed for a maximum of twenty years.
Only in 2007, after the formal "shelf life" of the old structure expired, the newly created Novarka company - a consortium of French firms Vinci and Bouygues - signed a contract for the construction of a "New Safe Confinement": this name was at the meeting of the "Big Seven" in 1997 year gave the "Plan for the implementation of measures at the Shelter to ensure its environmental safety."
The history of the project of the new sarcophagus for Chernobyl is one of those when the thoughtfulness of engineering structures and the highest quality of materials become the key to success.
The word "confinement" (English "confinement") was not chosen by chance: it emphasizes that the new sarcophagus cuts off from the outside world and "keeps" not only radiation radiation, but also those negative effects that solid radioactive waste: there are thousands of tons of them inside the Shelter. This was the main requirement in the terms of reference for the project. In addition, it was necessary to reduce the rate of degradation of the existing reinforced concrete shell under the influence of atmospheric influences; to strengthen its structures in order to prevent collapses, which would inevitably entail the formation of radioactive dust; provide the ability to remotely dismantle the most unstable elements. And while they were looking for funding, a special European commission, having carefully studied the work of the finalists of the previously held architectural competition, found out that among them there is a project that is suitable in all respects - and even superior.
The moveable arch was proposed by the Englishman David Haslwood from the Manchester bureau of Design Group Partnership. The original design invented by David allowed not only remote dismantling: the arch itself could be mounted remotely, minimizing the risks of workers' contact with the contaminated site. The arch had to be assembled at a safe distance, and then simply "move", completely covering the old sarcophagus. Moreover, after the installation and adjustment of the equipment, it would gradually be possible to completely disassemble both the old Shelter and what was left of the fourth power unit.
Novarka reworked this idea into a finished working project, and in 2008 the preparatory phase began. The territory at a distance of about 30 meters from the existing sarcophagus - the site for the installation of the arch - was cleared, 400 concrete and 400 steel piles were driven into the ground, trenches were prepared for moving the arch, and the entire area was poured with concrete. On February 13, 2012, the construction of the main structure began.
Many companies participated in the tender for the construction of the roof of the sarcophagus, but after all the tests passed and the technical solutions for the coating presented, a German company was declared the winner.
KALZIP®, a world renowned firm headquartered in Koblenz, known for its exclusive projects around the world, as well as in Russia, Kazakhstan and Belarus. KALZIP® Is a seam system of profiled sheets with a thoroughly developed manufacturing technology, including the necessary calculations of the bearing capacity of structures, computer-aided development of drawings and specifications.
For the outer shell of the sarcophagus, the KALZIP seam system was used®, for the interior - a panel system. The outer shell is made of alloyed stainless steel EN 1.4404, the inner one is made of EN 1.4301. However, stainless steel compositions were developed specifically for this project.
Profiled sheets and panels according to KALZIP systems® were manufactured directly at the construction site on mobile KALZIP roll forming machines®delivered to the site from Germany. In total, the employees of the company completed the profiling of 86,000 m2 of metal for the outer shell and 80,000 m2 for the inner one.
The fact that this is the first project of the KALZIP company is evidence of the exceptional nature of the object and the responsibility of the company - the supplier of material and technology.® made of stainless steel (before that she always worked with aluminum), and therefore, for the profiling of steel, the KALZIP designers® developed special machines: their tests with profiling of a trial batch of sheets were carried out in England in the presence of the customer of the sarcophagus.
High requirements were imposed on the project and the shell itself, especially with regard to the structural stability of the entire structure as a whole and the fire resistance of the materials used. After all, after the final installation of the containment over the reactor, repair work is excluded. Therefore, potential suppliers were required to test the system for all kinds of weather events. For example, testing the roofing of a class 3 tornado (and these are loads of 11kN / m² - like a tornado with a speed of up to 332 km / h).
In the folded KALZIP system® profiled sheets snap together - and to meet the tornado condition, the company's designers invented a new type of connecting clip, which, during the pull-off test, withstood the load twice as much - 22 kN / m²!
A unique arched structure with a total weight of 29 thousand tons, a width of 257 meters, a length of 150 meters and a height of 109 meters is truly an engineering miracle. And the point is not only that it has become the largest movable metal structure in history. The technology of its assembly and installation deserves special mention, during which, in fact, not a single builder approached the Shelter closer than 30 meters.
The arch was assembled in two steps from prefabricated modular metal structures, which are connected to each other using clips and hinges. That is why, when at the very beginning they assembled the top of the first half of the arch, added a number of modules on both sides to it and lifted the entire structure up with cranes - the side modules took an almost vertical position, continuing the radius bend. After that, the frame was covered with stainless steel sheets - and it was time to attach the next modules.
Some of them were pre-assembled with electromechanical, ventilation and climatic equipment: a certain humidity and temperature will be maintained inside the arch in order to “preserve” the old sarcophagus. And an electromechanic will be needed for remote access to everything that is locked inside the "confinement".
After half of the arch was ready, the moment of "shift" came: the cranes moved it even closer to the sarcophagus, to the "waiting area". In the vacant space, they began to mount the second part of the arch, in order to then "roll back" the first and finally connect both halves, revealing the voids with stainless steel sheets.
Video from the site
novarka.com
Debugging of the equipment is predicted to take about another year. However, the solemn movement has taken place, the arch is already standing in the place allotted to it - and will stand for at least a hundred years.
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