On November 30, 1986, the Deed of the State Acceptance Commission on commissioning of a protective structure above the destroyed Unit 4 of Chornobyl NPP was signed, it was named the Shelter object (hereinafter - SO). And this year is the 34th anniversary of the completion of perhaps the most dangerous and complex construction process in the history of domestic nuclear energy. Here are some interesting facts about the features of this facility, which for 30 years, until New Safe Confinement sliding, has become a physical barrier from the destroyed as a result of the accident Unit.
1. 18 design concepts were considered, but most of them were not accepted due to significant cost for construction materials, significant construction time, huge labor costs and radiation doses, and some solutions could not be implemented due to lack of appropriate technologies.
2. The Shelter object is, in fact, a combination of "old" and "new" structures. Part of the SO power base are the support columns of the Unit 4, supporting the bearing constructions of beams B1, B2, "Mammoth" and "Octopus".
3. SO designing was performed using the aerial photography, then the photos were sent to design institutes in Moscow, St. Petersburg, Kiev and Dnipro.
4. The process of SO construction represents a colossal figures. 7,000 tons of metal structures and 345,000 cubic meters of concrete mixture were used. 90 thousand workers were involved, and the construction process itself was carried out day and night, which allowed the project to be completed in the shortest possible time - 206 days.
5. To achieve these very short terms, a huge construction base was created, which included a supply base, a base for equipment repair and maintenance, points of building structures acceptance and unloading, concrete plants and other facilities.
6. In order to optimize the construction, the method of enlarged assembly of structures at clean sites was used, which were then delivered directly to the assembly area.
7. In order to minimize the dose load for the builders, unique equipment was purchased - concrete pumps from Putzmeister, Schwing and Worthington, powerful crawler-mounted crane "Demagh" and wheel-mounted crane "Liebherr", as well as other technical equipment equipped with remote control and additional protection.
8. A special post was established to control the installation process, it was equipped with video cameras, which were installed on crane jibs and towers in the maximum visibility areas.
9. Within the first weeks after the Chоrnobyl NPP Unit 4 explosion, the processes of the reactor core melting occurred, as well as boron, sand, and lead, actively dumped to stop the chain reaction and reduce the temperature took place. The cooled down lava formed, in fact, a new mineral, which scientists studying the interior of the destroyed unit called "chornobilit". It was zirconium orthosilicate (ZrSiO4) with large inclusions of uranium in the form of dipyramidal crystals ranging in size from 5 to 500 microns in corium.
10. After completion of the accident consequences elimination stage, various high-tech equipment was installed in the Shelter object - dust suppression and dust fixation system, radiation monitoring system, liquid RAW removal system, etc.
11. Within 2004-2008, stabilization works were implemented at the Shelter object based on the Shelter implementation plan (SIP). Eight measures were realized to reinforce the Shelter. The most spectacular of them was construction of the external reinforcement structure, which relieved the load from the damaged frame and walls of the SO western fragment. The implemented work ensured that the existing structures of the facility would not collapse, and provided time for the successful implementation of the New Safe Confinement construction project.
12. Measures were also implemented to stabilize the second stage ventilation stack (VS-2). During the explosion the load-bearing frame of the stack was damaged, and the reactor core fragments remained on the inspection decks. Therefore, decontamination of desks along the stack perimeter was carried out in 1996-1998, and after that - repair work on the VS-2 frame beams. In 2011, a new ventilation stack (NVS) was built near the VS-2, and 2 years later, in the winter of 2013, the "old" one was dismantled.
13. After beginning of SO operation, the work was carried out both outside and inside SO. The Interdisciplinary Scientific and Technical Center "Shelter" was established under the sponsorship of the Academy of Technical Sciences of Ukraine, whose staff performed large-scale research jointly with the Kurchatov Institute. Thus, the locations and characteristics of fuel-containing masses were identified and dosimetric survey of the premises was carried out.
14. During the process of accident consequences elimination in 1986, robotics were used to reduce the dose loads for all those who worked at the site, as well as to avoid for some time additional labour resources involvement. Testing processes for new remotely controlled robot prototypes continued into the 90s. SCSD concept - remotely controlled self-driving devices was developed and "Magnitokhod" robot became an absolutely exotic robot, which was used during work on the SO walls and could carry considerable weight due to the use of samarium-cobalt magnets.
15. As for the state of fuel-containing materials, in the early 00's it was revealed that over the time, the structure of this so-called corium is destroyed due to its own activity in the submicron dust. This fact caused some concern with regard to the prospects for the Shelter transformation into an environmentally safe system, but in 2003-2005 Kurchatov Institute together with the Institute for NPPs Safety Problems of Ukraine performed a number of studies and came to the common conclusion that the rate of submicron dust generation during 30-50 years will not contribute to its release outside SO or New Safe Confinement.
16. Of course, work outside and inside the Shelter still requires Chornobyl personnel to be quite responsible for radiation safety. Therefore, international cooperation also consisted in implementation of various scientific and technical solutions aimed at monitoring the radiation situation, as well as personnel involved in the work. In July 1998, one of the first was STREAM software package developed by US specialists, which was used to control the radiation doses to the personnel. The United States also provided with equipment for air sampling and nuclear criticality control (namely, an electronic neutron burst control system).
17. Currently, the Shelter object is controlled by an integrated automated monitoring system, or IAMS, created as part of SIP project. It represents a distributed two-level information system with a number of control sensors installed along fifteen different routes, including Turbine Hall supports and roof.
18. Today, the Shelter object is hidden under the world's largest sliding arch structure, known as the New Safe Confinement or NSC.
19. More recently, in the immediate vicinity of the Shelter object, Boston University scientists, using the Spot robot manufactured by the American company Boston Dynamics, tested the equipment and generated deep interest from the international community.
20. We should not forget about a certain culturological impact of the very fact of man-made accident at Chornobyl NPP and Shelter object as its symbol. Hundreds of different written and musical compositions devoted to the accident were written, and release in 2007 S.T.A.L.K.E.R. computer trilogy caused a real explosion, creating a youth subculture that combined a book series, the S.T.A.L.K.E.R. Fest, cosplay contests, and with the social networks advent - virtual communities, united by the storyline of the game universe.