How the shelter was created for Chernobyl nuclear power plant

How the shelter was  created for Chernobyl nuclear power plant

Dmitry Khazanov

The Shelter Object – an insulating structure over the fourth power unit of the Chernobyl nuclear power plant was put into operation 35 years ago, on November 30, 1986. The accident, which occurred on April 26 of the same year, is still the largest in the history of nuclear energy.
The explosion completely destroyed the fourth block of the reactor and all protective barriers – a huge amount of radioactive substances was released into the environment. The question arose about the conservation of the object, the responsibility for which, by a special resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR, was assigned to the Ministry of Medium Machine Building (Minsredmash) of the USSR. For the first time, the idea to cover the emergency block sounded from the lips of the vice-president of the USSR Academy of Sciences Yevgeny Velikhov back in early May 1986. However, the radiation situation did not allow to start large-scale work on the spot right away.
“Shelter” and additional measures
First of all, in order to reduce emissions from the destroyed reactor, the government commission decided to dump materials from helicopters into the reactor shaft, intended for localizing the source of emissions. On April 27, 45 flights were made, the next day – twice as many, by May the intensity of flights was increased by about 15 times. As follows from the documents, in just two weeks, more than 15 thousand tons of various materials were dropped onto the destroyed power unit – lead, sand, marble chips, rubber, dolomite and others.
The Leningrad All-Un-ion Scientific Research De-sign Institute of Energy Te-chnology (VNIPIET) beca-me the general designer of the disposal of the fourth unit of the Chernobyl nucl-ear power plant, radioactive waste and decontamination of equipment at the industrial site. At that time, he was the leading Soviet multidisciplinary organization, which had extensive experience in the design of facilities for a nuclear weapons complex, the nuclear industry and energy.
The project team consisted of 100 specialists from VNIPIET, with the involvement of various consultants from other institutes. However, the complexity of the Shelter project was still in the fact that there were no technical solutions for the burial of such objects in domestic and world practice at that time.
On May 21, 1986, a specialized construction department 605 was organized for the practical solution of problems (Major General Yevgeny Rygalov was appointed as the first head). US-605, first of all, had to install a water-cooled plate under the destroyed block – high-power channel-type uranium-graphite reactors (RBMK) installed at the Chernobyl nuclear power plant, unlike water-cooled power reactors (VVER), did not have rigid vessels.
Monolithic concrete was chosen as the main material at the facility – they were going to seal all the gaps with it so that “the radiation would sit inside.” Accordingly, it was required to prepare the territory and create a base for its processing and transportation. The difficulty lay in the fact that no one knew the true state of the block’s structures – many expeditions went inside, looking for fuel, studying the level of internal pollution, now another of their tasks was to inspect the elements of the object for integrity.
Already on May 25, the installation of equipment for three concrete plants began, 13 km from the Chernobyl nuclear power plant; five days later, work began to decontaminate the territory. For the intensity of the processes, it was also necessary to create intermediate barriers.
A total of 18 variants of the design of the main protective structure were developed, each of which required a huge expenditure of resources. As a result, it was decided to build the facility, making the most of the remnants of the surviving structures of the fourth power unit. The author and technical director of the “Shelter” was Vladimir Kurnosov, scientific director – Vladimir Asmolov.
It was necessary to develop extremely large structures allowing remote mounting; choosing such methods of work that would make it possible to shorten the construction time as much as possible and ensure the complete mechanization of the work performed with minimal participation of people of different professions.
The construction of the sarcophagus began with the so-called pioneer walls with a height of 5.75 m on the north side and 8.4 m in the west and south – in order to cut off highly radioactive debris from the place of constant work of people. Later, in the north, cascade walls with a height of 12 m were additionally erected, which made it possible to provide biological protection at the most contaminated part of the facility. The monolithic protective wall separating block 3 from the destroyed block 4 was the very first to be built. It was designed for 30 years of operation.
In addition, there were fears that, due to the residual heat release of the fuel remaining in the reactor, its core would melt and the composition would penetrate into the soil and water. To prevent this, the miners dug a 136-meter tunnel under the reactor within a month. To exclude the pollution of the Dnieper waters, a protective wall was erected around the station, the depth of which in some places reached 30 m. Also, within ten days, engineering troops dumped dams on the Pripyat River.
Own experience
Specialists of the Specialized Scientific Research Institute of Instrument Engineering (to which I belonged), SNIIP, like miners, builders, military men, worked on a rotational basis.
At first, SNIIP employees were solving current tasks related to measuring various indicators in air, water, earth, and so on; conducted reconnaissance on the ground, issued recommendations. Radiation levels by the summer of 1986 had slightly decreased: in the area of the Chernobyl NPP in different places – from 50 to 500 mR / h, and in the city of nuclear scientists Pripyat – from units to 10 mR / h (for comparison: the normal background in Moscow is 12-14 µR / h). For measurements, mass army dosimeters of the DP-5 type were usually used.
As the front of activity grew, it was decided to start deploying an automated system for radiation reconnaissance of the terrain (SRRM-2) in the area of the destroyed reactor. The assembly and adjustment of the equipment of this system also involved the organization of the transmission of information to the central console by radio channel in the automatic mode of operational data, so that the operator, and then the shift leader, could monitor the situation in the area of the third and fourth power units of the ChNPP, as well as in the control building. The second stage organized the work of SRRM-2 to control the situation in the storage of liquid and solid waste, fire station, garage and so on. The SNIIP group that solved this problem usually included about 20 qualified specialists.
After July 25, 1986, a commission chaired by the Deputy Director of the Institute of Atomic Energy named after V.I. I.V. Kurchatov, academician Spartak Belyaev (the government commission created it in order to coordinate and scientific and methodological guidance of the work of various organizations on long-term systematic monitoring of the radiation situation in the Chernobyl nuclear power plant zone and adjacent areas).
Working on site, we quickly got used to the terminology generally accepted there. So, everyone called the lid of the reactor that flew up from the explosion tens of meters, and then fell and crushed the upper part of the core, everyone called Elena, the bizarre and highly deformed beams – Octopus and Mammoth (the latter weighed 147 tons).
Work in the NPP area allowed us to see many wonderful people who are rightfully proud of the nuclear industry. One of them is Alexander Usanov, Deputy Minister of Medium Machine Building of the USSR.
He was appointed the general contractor for the mothballing of the fourth power unit and spent more than 100 days at the scene of the accident. Usanov personally made his way into many dangerous zones, trying to understand the scale of what happened as accurately as possible.
For courage, selfless actions and labor heroism at the end of 1986 he was awarded the title of Hero of Socialist Labor, and six years later the 63-year-old nuclear specialist, who had previously been distinguished by excellent health, passed away.
I was also able to see in action the most new and advanced technology at that time, including specialized Japanese robots. True, not all of them coped. For example, the fully radio-controlled Komatsu amphibious bulldozer, capable of clearing debris even on the seabed, collapsed very quickly due to high radiation fields.
There were also problems of a different nature. The cranes of the German company Demag, which had previously been purchased for the construction of the Rostov nuclear power plant, were delivered to a 30-kilometer zone near Pripyat on July 8 – with their help, it was possible to significantly speed up the construction. Units and parts of each crane occupied 32 railway platforms during transportation. German specialists were supposed to supervise the installation, but when they learned that the assembly would be carried out near the fourth block, they refused. At that time, Soviet specialists did not have experience in assembling and adjusting this equipment, but already on July 21, the first supercrane moved to the emergency block in a self-propelled manner. The complete assembly of two more took 26 days, while according to German regulations it took 90 days. And this despite the fact that at the assembly site, where the assembly was carried out, the radiation background was up to 200 mR / hour.
“The main condition for the successful use of heavy equipment is a pre-planned method of work. It was necessary to know where to get [the materials], where the installation would take place, what conditions are necessary for successful operation… When working at the Chernobyl nuclear power plant, all these decisions had to be made on the spot and promptly. And only the presence in our country of a large number of highly qualified management and engineering personnel made it possible to organize the start of work quickly and without significant critical errors.” Andrey Lavretsky Trust engineer.
After years
In the 35 years that have passed since the Shelter was commissioned, no more than 60% of the NPP premises have been investigated (another 170 are still inaccessible due to extre-mely high radiation fields or barriers created by the e-xplosion and during the pouring of concrete by the builders). The unexplored area continues to form the main risks from the des-troyed fourth block of the Chernobyl nuclear power plant – due to the incomp-lete tightness of the sarco-phagus, moisture gets there in large quantities (during rain, melting snow). Hun-dreds of cubic meters of liquid radioactive waste are generated annually from the interaction of water with nuclear fuel residues.
In addition, a large amount of radioactive dust is formed with a high content of long-lived transuranic isotopes, including plutonium-239 (whose half-life is 24 thousand years). According to the most conservative estimates, at least 1.5 tons of such dust have already accumulated there (according to other estimates, from 20 to 30 tons). A volley release into the environment is not predicted, but it is impossible to completely exclude the spread of these particles by winds with the current protective barriers.
In 2007, the French company Vinci Construction Grand Projects, at the request of the Ukrainian leadership, began to create a new sarcophagus over the destroyed block.
At the end of November 2016, that is, exactly 30 years after the Shelter was commissioned, the Shelter-2 movable arch was successfully installed.
The completion of this project and its commissioning took place in July 2019.
90 thousand people were involved in the construction of the first Shelter structure; in 1986, approximately 345 thousand cubic met-ers were laid. m of concrete mix and installed about 7 thousand tons of metal structures. It took 206 days to build such a complex and unique facility in an extr-emely dangerous radiation environment – the work was carried out in three shifts, that is, around the clock.
Years later, the management of the state corporation “Rosatom” at one of the conferences emphasized that April 26 is the day of remembrance for all who sacrificed their health and life during the liquidation of the consequences of the Chernobyl accident, and November 30 is the day of pride of all employees of the industry, since they managed to solve an extremely difficult task in harsh radiation fields in a very short time.
Looking back, I would like to draw three conclusions. Firstly, very few of the industry leadership, and even more so ordinary employees, could have predicted such a devastating accident, did not expect that something similar was possible at all. The accidents at the American nuclear power plant Three Mile Island (March 1979) and at the Japanese nuclear power plant Fukushima (March 2011) were also not expected, although they had an extremely negative impact on the development of national energy and on all nuclear scientists on a global scale. The progress of work during the construction of the sarcophagus over the fourth block of the Chernobyl nuclear power plant showed that no original, reference plan existed, decisions were made on the spot in rooms near the destroyed block after short but heated discussions.
Secondly, experts in the field of nuclear energy safety believed that even if a severe accident happened (unlikely, but theoretically possible), the low population density in the USSR and the considerable distances from plants to large cities served as a moral basis for justifying insufficient attention to security issues in the 1970s and early 1980s.
If a similar sarcophagus had been foreseen and created over a RBMK-type reactor at the design and construction stage, which later came to be called containment in our country, this would not have excluded the development of an emergency in similar conditions, but would have significantly reduced the consequences, since part of the explosion energy would have been spent on destruction of the containment, and would change the nature of the release of radioactivity.
Thirdly, the extremely hard, well-coordinated and effective work of all involved people made it possible to solve a complex technical problem extremely quickly. What we today call the command-administrative system, in relation to the functioning of the management of human resour-ces and material resources in the Soviet Union, made it possible in the shortest possible time to mobilize thousands of qualified people who worked selflessly, responsibly, not for fear, but for conscience, constantly risking their health. Probably, analogies with the period of the Great Patriotic War are quite appropriate here.

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