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Where was the Chernobyl accident. Chronology of the accident at the chaes. Chronology of events of the explosion at chaes

It was the first nuclear power plant on the territory of the Ukrainian SSR, its location is north of Kiev, 11 km from the border with Belarus, in the Pripyat River valley. The eponymous city of Pripyat was located 3 km west of the nuclear power plant zone, and 18 km east of the station - the regional center of the city of Chernobyl. Both of these cities are currently abandoned (popularly called "ghost towns"). The first block of the nuclear power plant was put into operation on September 27, 1977.

Chronology of events

Staff Chernobyl nuclear power plant prepared for the shutdown of the fourth power unit for scheduled maintenance and research to remove additional energy during the operation of the main nuclear reactor. Due to dispatch restrictions, the shutdown of the nuclear reactor was postponed several times, which led to difficulties in controlling the reactor's power.
13:00-13:05
The power of the reactor began to decrease (from 3200 megawatts to 1600), turbine No. 7 was shut down, and the power supply of the electrical systems was transferred to turbine No. 8.
14:00
The emergency shutdown system of the reactor was blocked, and the dispatcher gave an order to delay the shutdown of Unit 4. The reactor itself was operating at half power (1600 megawatts).
23:10
It was allowed to start reducing the reactor power (up to 500 megawatts).

0:38
The reactor power dropped to 30 megawatts, and the xenon "poisoning" of the reactor began (the reactor acquired negative reactivity due to the accumulation of the xenon isotope and could not reach high power). Instead of shutting down the reactor (as prescribed by the instructions), the NPP employee removed the absorbing rods from the core.
1:00
The power of the reactor was only raised to 200 megawatts due to the growing xenon poisoning.
01:03-01:07
The seventh and eighth pumps were connected to the six main circulating pumps, but the operation of so many pumps provoked a failure in the system due to lack of water.
01:19
Due to the lowering of the water level, the station operator increased the supply of condensate (feed water). In addition, in violation of the instructions, the reactor shutdown systems were blocked by signals of insufficient water level and steam pressure. The last manual control rods were removed from the core, which made it possible to manually control the processes taking place in the reactor.

01:22-01:23
The water level has stabilized. The station staff received a printout of the reactor's parameters, which showed that the reactivity margin was dangerously small (which, again, according to the instructions, meant that the reactor needed to be shut down). The NPP personnel decided that it was possible to continue working with the reactor and conduct research. At the same time, the thermal power began to increase.
01:23
It was decided to press the emergency shutdown button of the A3-5 reactor. At the signal of this button, emergency protection rods were to be introduced into the core, but they could not be lowered to the end - the steam pressure in the reactor delayed them at a height of 2 meters (reactor height -7 meters). The thermal power continued to grow (up to 530 megawatts), the self-acceleration of the reactor began, as a result, at 01:23:44, the power jumped 100 times. The pressure in the core of Unit 4 increased many times over, it forced the water back into the pipelines. There was an explosion. It became impossible to control the reactor. According to some reports, another explosion occurred at 01:23:46. The walls and ceilings of the turbine hall were destroyed, and fires appeared. Employees began to leave their jobs.

01:24
The reactor core partially collapsed, fission fragments left the zone.
02:10-02:30
The centers of fire on the roof of the turbine hall and the reactor compartment of the station were suppressed.

By 5 o'clock the fire was completely extinguished.

At 8:00 In the evening, a fire broke out again in power unit No. 4, already of greater intensity, helicopters were involved in extinguishing.

CHERNOBYL.

He comes alive at night, of course,
our city, empty for centuries.
There our dreams wander like clouds
and the windows are lit by moonlight.
Trees live there with vigilant memory,
remembering hands touching.
How bitter it is for them to know
what's your shadow
they won't save anyone from the heat!
So they swing quietly on the branches
they are sick at night in our dreams ...
And the stars are torn down
on the pavements,
to stand here on the clock until the morning ...
But the blowjob is an hour.
Abandoned by dreams
orphaned houses will freeze,
and windows
crazy
once again
will say goodbye to us! ..

CHRONOLOGY OF EXPLOSION AT CHNPP

The Chernobyl Nuclear Power Plant is located in the north of Ukraine, at the confluence of the Pripyat River with the Dnieper. Construction began in 1976. In total, 4 units of 1000 MW each were built. The accident at the fourth unit of the Chernobyl nuclear power plant on April 26, 1986 did not occur during the normal operation of the reactor.

This happened during an experiment to study the safety reserves of the reactor in various situations. The experiment was planned to be carried out at a reduced reactor power. The experiment coincided with the planned shutdown of the reactor.

Typically, reactors not only generate electricity, but also consume it to operate the pumps in the cooling system. This energy is taken from a conventional electrical grid. If the normal power supply is disrupted, then it is possible to switch part of the electricity generated by the nuclear reactor for the needs of the reactor cooling system. However, if the operating reactor does not generate electricity, this happens during the extinguishing of the reactor, then an external autonomous power source is required - a generator. It takes some time to start up the generator, so it cannot provide the reactor with the necessary electricity immediately. During the experiment at the fourth unit of the Chernobyl nuclear power plant, they intended to show that the power electric current generated by the turbines rotating by inertia after the reactor is shut down is sufficient to power the cooling pumps before the diesel generators are turned on. The pumps were expected to provide sufficient coolant circulation to ensure the safety of the reactor.

Since then, many different reports have been published explaining the causes of the accident. But there are many inconsistencies in these reports. Many researchers have interpreted some of the data in their own way. As time went on, there were even more different interpretations... In addition, several authors were personally interested in this case. However, in most reports, the sequence of events that led to the accident is similar.

25.04.1986.
01:06 The planned shutdown of the reactor began. A gradual decrease in the thermal power of the reactor. (In normal operation, the thermal power of the reactor is 3200 MW).
03:47 Reduction of the reactor power was interrupted by 1600 MW.
14:00 The emergency cooling system has been disabled. This was part of the experiment program. This was done to prevent interruption of the experiment. This action did not directly lead to the accident, but if the emergency cooling system had not been turned off, the consequences might not have been as dire.
14:00 A further reduction in power was planned. However, the Kiev power grid dispatcher asked the reactor operator to continue generating electricity to meet the city's electricity needs. Therefore, the reactor power was left at 1600 MW. The experiment was delayed, and at first it was intended to be carried out within one shift.
23:10 It was recommended to continue the power reduction.
24:00 End of shift.
26.04.1986.
00:05 The reactor power was reduced to 720 MW. The decrease in power continued. Now it has been proven that the safe control of the reactor in that situation was possible at 700 MW, since otherwise, the "void" coefficient of the reactor becomes positive.
00:28 The reactor power was reduced to 500 MW. The control was switched to an auto-adjusting system. But then either the operator did not give a signal to hold the reactor at a given power, or the system did not respond to this signal, but suddenly the reactor power dropped to 30 MW.
00:32 (approximately) In response, the operator began to raise the control rods, trying to restore the reactor power. The Safety Requirements required the operator to coordinate with the chief engineer if the effective number of rods to be lifted was greater than 26. Today's calculations show that fewer control rods were required to be lifted at that time.

01:00 The reactor power increased to 200 MW.
01:03 An additional pump was connected to the left loop of the cooling system to increase the circulation of water through the reactor. This was part of the plans for the experiment.
01:07 An additional pump was connected to the right cycle of the cooling system (also according to the experiment plan). The connection of additional pumps caused an acceleration in the cooling of the reactor. This also led to a decrease in the water level in the steam separator.
01:15 The automatic steam separator control system was shut down by the operator to continue operating the reactor.
01:18 The operator increased the flow of water in an attempt to fix problems in the cooling system.
01:19 Several more control rods are extended to increase the reactor power and raise the temperature and pressure in the steam separator. The operating rules required that at least 15 control rods remain in the reactor core at all times. It is assumed that at that moment in the core there were already only 8 control rods. However, the automatically controlled rods remained in the core, which made it possible to increase the effective number of control rods in the reactor core.
01:21:40 The operator reduced the flow of water through the reactor to normal in order to restore the water level in the steam separator, thereby reducing the cooling of the reactor core.
01:22:10 Steam began to form in the core (water cooling the reactor boiled).
01:22:45 The data received by the operator signaled danger, but gave the impression that the reactor was still in a steady state.
01:23:04 The turbine valves were closed. The turbines were still spinning by inertia. This, in fact, was the beginning of the experiment.
01:23:10 The automatically controlled rods were removed from the core. The rods were lifted for about 10 seconds. This was a normal response to compensate for the decrease in reactivity following the closing of the turbine valves. Typically, a decrease in reactivity is caused by an increase in pressure in the refrigeration system. This should have led to a decrease in steam in the core. However, the expected decrease in the pair did not follow, because the water flow through the core was small.
01:23:21 Vaporization has reached a point where, due to its own positive "void" coefficient, further vaporization leads to a rapid increase in the thermal power of the reactor.
01:23:35 Uncontrolled steam generation began in the core.
01:23:40 The operator pressed the "Emergency" button (AZ-5). The control rods began to enter from the top of the core. In this case, the center of reactivity moved down the core.
01:23:44 The power of the reactor increased dramatically and exceeded the design one by about 100 times.
01:23:45 Fuel rods began to collapse. High pressure has built up in the fuel lines.
01:23:49 The fuel channels began to collapse.

01:24 Two explosions followed. The first is due to the explosive mixture formed as a result of the decomposition of water vapor. The second was caused by the expansion of fuel vapors. The explosions threw out the piles of the roof of the fourth block. Air has entered the reactor. The air reacted with the graphite rods to form carbon monoxide II (carbon monoxide). This gas flared up and a fire started. The roof of the turbine hall is made of materials that are highly flammable. (These are the same materials that were used at a weaving factory in Bukhara, which completely burned down in the early 70s. And although some workers were brought to justice after the incident in Bukhara, the same materials were used in the construction of the nuclear power plant.)

Eight out of 140 tons of nuclear fuel containing plutonium and other extremely radioactive materials (fission products), as well as fragments of a graphite moderator, also radioactive, were thrown into the atmosphere by the explosion. In addition, vapors of radioactive isotopes of iodine and cesium were emitted not only during the explosion, but also spread during the fire. As a result of the accident, the reactor core was completely destroyed, the reactor compartment, the deaerator stack, the turbine hall and a number of other structures were damaged.
The barriers and safety systems protecting the environment from the radionuclides contained in the irradiated fuel were destroyed and activity was released from the reactor. This release at the level of millions of curies per day lasted for 10 days from 26.04.86. until 06/05/86, after which it fell thousands of times and subsequently gradually decreased. By the nature of the processes of destruction of the 4th unit and by the scale of the consequences, the indicated accident had the category beyond design basis and belonged to the 7th level (severe accidents) according to the international scale of nuclear events INES.

Within an hour, the radiation situation in the city was clear. There were no measures in case of an emergency: people did not know what to do. According to all the instructions and orders that have existed for 25 years, the decision to withdraw the population from the danger zone was to be made by local leaders. By the time the Government Commission arrived, it was possible to take all people out of the zone even on foot. But no one took responsibility (the Swedes first took people out of the zone of their station, and only then began to find out that the release did not occur from them).

At work in hazardous areas (including 800 meters from the reactor), there were soldiers without individual funds protection, in particular when unloading lead. Then it turned out that they did not have such clothes. The helicopter pilots found themselves in a similar position. AND officers, including the marshals and generals, flaunting in vain, appearing near the reactor in their usual form. In this case, intelligence was needed, not a false notion of courage. During the evacuation of Pripyat and during the embankment of the river, the drivers also worked without personal protective equipment. It cannot be used as an excuse that the radiation dose was an annual norm - they were mainly young people, and therefore, this will affect the offspring. Similarly, the adoption of combat norms for army units is a last resort in the event of hostilities and when passing through the affected area from nuclear weapons... Such an order was caused precisely by the absence of this moment personal protective equipment, which at the first stage of the accident were only in the special forces. The entire civil defense system was completely paralyzed. There were not even working dosimeters. We can only admire the work and courage of the fire department. They prevented the development of the accident at the first stage. But even the units located in Pripyat did not have the appropriate uniforms for work in the zone of increased radiation. As always, achieving the goal came at the cost of many, many lives.

On May 15, 1986, the Resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR was adopted, in which the main work on eliminating the consequences of the accident was entrusted to the Ministry of Medium Machine Building. The main task was the construction of the Shelter (Sarcophagus) facility of the fourth power unit of the Chernobyl NPP. Literally in a matter of days, practically from scratch, a powerful organization US-605 appeared, which includes six construction districts that erected various elements of the Shelter, an assembly and concrete plant, mechanization, motor transport, power supply, production and technical equipment, sanitary consumer services, work supplies (including canteens), as well as servicing the personnel residence bases. As part of US-605, a dosimetric control department (ODK) was organized. Units US-605 were stationed directly on the territory of the Chernobyl nuclear power plant, in the city of Chernobyl, in the city of Ivanpol and at the Teterev station in the Kiev region. Accommodation bases and support services were located at a distance of 50 - 100 km from the work site. Taking into account the difficult radiation situation and the need to comply with the requirements, norms and rules of radiation safety, a rotational work method was established for personnel with a shift duration of 2 months. The number of one watch reached 10,000 people. The personnel on the territory of the Chernobyl NPP worked around the clock in 4 shifts. All US-605 personnel were recruited from specialists from enterprises and organizations of the Ministry of Medium Machine Building, as well as military personnel (soldiers, sergeants, officers) called up from the reserve for military training and sent to Chernobyl (the so-called "partisans"). The task of burying the destroyed power unit facing the US-605 was complex and unique, since it had no analogues in the world engineering practice. The complexity of creating such a structure, in addition to significant destruction, was significantly aggravated by the severe radiation situation in the area of ​​the destroyed block, which made it difficult to access and extremely limited the use of conventional engineering solutions. During the construction of the Shelter, the implementation of design solutions in such a complex radiation environment became possible thanks to a set of specially developed organizational and technical activities, including the use of special equipment with remote control. However, the lack of experience affected. One expensive robot remained on the wall of the Sarcophagus, failing to complete its task: the electronics went out of order due to radiation.

In November 1986, the Shelter was built, and the US-605 was disbanded. The construction of the Shelter was carried out in a record short term... However, the gain in time and cost of construction entailed a number of significant difficulties.
This is the absence of any complete information about the strength of old structures, on which the new ones were based, the need to use remote concreting methods, the impossibility in some cases to use welding, etc. All difficulties arise due to the huge radiation fields near the destroyed block. Hundreds of tons of nuclear fuel remained under the concrete layer. Now no one knows what is happening to him. There are suggestions that a chain reaction may occur there, then a thermal explosion is possible. As always, there is no money for researching the ongoing processes. In addition, some of the information is still being withheld.

The Ministry of Health of Ukraine summed up the results: over 125 thousand deaths by 1994, last year alone, 532 deaths of liquidators were associated with the impact of the Chernobyl accident; thousand sq. km. contaminated land. Thirteen years after the accident, the impact of the effects of radiation appears, which is superimposed on the general deterioration of the demographic situation and the state of health of the population of the affected states. Already today, over 60% of people who were children and adolescents at that time and lived in the contaminated area are at risk of contracting thyroid cancer. The effect of complex factors characteristic of the Chernobyl disaster has led to an increase in the incidence of children, especially diseases of the blood, nervous system, digestive tract and respiratory tract. The persons who were directly involved in the liquidation of the accident now require close attention. Today there are over 432 thousand of them. Over the years of observation, their overall incidence increased to 1400%. The only consolation is that the results of the impact of the accident on the population could have been much worse if not for the active work of scientists and specialists. Recently, about a hundred methodological, regulatory and instructive documents have been developed. But there are not enough funds for their implementation ...

Exclusion zone: radioactive contamination

After the accident at the Chernobyl nuclear power plant, all components the environment experienced a powerful Nuclear pollution... The most polluted are the sections of the near zone of the Chernobyl NPP (up to 3-5 kilometers to the west and north east of the station).

Surface contamination of the zone with radionuclides

The most radiation hazardous area is the industrial site of the Chernobyl nuclear power plant. The exposure dose rate levels reach tens of mR / hour. High levels of ionizing radiation are caused by the contamination of this area with fragments of nuclear fuel that were ejected from the reactor by the explosion. Soil contamination levels of an industrial site Chernobyl reach 400 MBq per square meter.
It should be noted that over twenty years the radiation situation in the territory of the exclusion zone has significantly improved. The dose rate on the soil surface has decreased hundreds of times. In the areas where decontamination work (removal of the upper soil layer) was carried out, the radiation background decreased by two to three orders of magnitude.

Map of contamination of the territory of Ukraine with cesium-137. As of 1996. Scale 1: 350000. Compiled by A. Tabachny and others. Published by the Ministry of Chernobyl of Ukraine. 1996 year. The map was compiled based on the materials of aerospectrometric and field surveys.

The main source of gamma radiation is cesium-137, which is overwhelmingly found in soils (in the upper 5-10 cm soil layer).
The radiation conditions of the exclusion zone are quite diverse and change (decrease) depending on the distance to the emission source. Generally speaking, for territories that are within a 10-km exclusion zone, the exposure dose rate levels are in the range of 0.1-2.0 mR / h, and the density of soil contamination with radionuclides ranges from 800 to 8000 kBq / m2 ( may exceed these values).
In the territories that are within the 10-km exclusion zone, the radiation dose rate is from 20 to 200 μR / hour, and the soil contamination density is 20-4000 kBq / m2.
Most of the radioactivity is concentrated in the upper soil layer (5-10 cm) and litter (in forest ecosystems). There are areas where the intensity of vertical migration of radionuclides in the soil is higher than in other areas of the exclusion zone. These are places that are periodically flooded. Floodplains of rivers.
According to scientists, at the moment, on the territory of the Chernobyl exclusion zone, the total activity of radioactive substances is about 220 kCurie. The bulk of this activity is cesium-137 and strontium-90. The specific activity of these radionuclides, over the past 15 years, has decreased by more than 40%. In this case, the activity of cesium-137 is 97-158 kCurie, and the activity of strontium-90 is 70-80 kCurie. The total activity of alpha-emitting radionuclides does not exceed 2 kCi.
It should be noted that as a result of the beta decay of plutonium-241, the content of americium-241 increases. Per last years the activity of this radionuclide increased from 0.7 kCi to 1 kCi.
Special attention, from the problems of the radiation hazard of the territory of the exclusion zone, deserves the points of temporary localization of radioactive waste (STLRO), which are the places of burial of radioactive materials (mainly the highly active upper layer of the soil). Burials were carried out in extremely short lines, which led to the fact that there was no reliable isolation of materials containing radionuclides from the environment (soil water, etc.). On the territory of the Chernobyl exclusion zone, there are about 800 such sites, in which more than 1 million cubic meters of radioactive waste are buried, the activity of which (according to preliminary data) is about 60 kcurie.
In the Chernobyl exclusion zone, the disposal of radioactive waste, which is formed as a result of the activities of enterprises and the Chernobyl nuclear power plant, is carried out. Burial is carried out in accordance with all safety standards and requirements. At present, about 160 kCi of activity have been accumulated in the disposal facilities for radioactive waste.
The Shelter Object, which is a temporary storage site for unorganized radioactive waste, contains up to 20 MCurie of activity (the sum of cesium-137 and strontium-90). The activity of alpha-emitting radionuclides of the Shelter object is about 270 kCurie.

Exclusion zone: radionuclides in environmental components

The presence of radioactive substances in the soils of the exclusion zone causes contamination of groundwater, open water bodies, as well as the surface layer of the atmosphere. The pollution parameters of these environmental components are constantly monitored.
At the moment, the air pollution of the Chernobyl Exclusion Zone by radioactive substances is significantly below the established limits. For example, for the ChNPP industrial site, pollution is 0.2-16 mBq per m3, and in the far part of the exclusion zone it is 0.01-0.67 mBq per m3. It should be noted that the content of radionuclides varies depending on the season - during the warm period of the year, the specific activity of the air is one and a half to two times higher than during the cold one.
Sometimes there are sharp increases in air activity in the Chernobyl zone. This is often associated with economic (anthropogenic) activities, meteorological conditions, and fires. The reason for the increase in air activity is also the work on the creation of fire strips, production activities in the central part of the exclusion zone (construction, decontamination, etc.). For example, in the summer of 1992, there were many fires in the exclusion zone, which caused a sharp increase in the content of cesium-137 in the air. At that time, the levels of specific air activity reached 17 mBq / m3. In such conditions, increased exposure of the human body is possible due to inhalation of radioactive aerosols. This leads to inhalation (internal) exposure of a person. Read about the ways to protect the body in such conditions on the page "Rules of conduct in the alienated territories".
Radionuclide contamination of water bodies occurs due to their washout from the soil surface, which occurs both at the time of flooding of floodplain areas, and during intense precipitation. At this time, the content of cesium-137 in the water of the Pripyat River is 150 Bq / m 3, and strontium-90 is 300-350 Bq / m 3. The content of transuranic elements is quite low and amounts to several Becquerel units per m3. This is several orders of magnitude less than the norms that regulate the levels of pollution in the water of rivers and other open bodies of water.

______________________________________________________________________________________________

REPORT FROM THERE ...

In the first days after the accident on April 26, 1986 at 10 am A.Ya. Kramerov, head of the laboratory in charge of the RBMK reactor. I was glad that I was at home (day off, many went to rest). Asked to call A.P. Aleksandrov (AP, as his colleagues at the Kurchatov Institute of Atomic Energy called him). When asked what happened, he answered: "There is a major accident at the Chernobyl nuclear power plant at the 4th unit." "Anything with a separator?" I asked. “It seems worse,” said Kramerov.

What could be worse than an explosion of a BS - a separator drum, a bulky 30-meter barrel? And there are four such barrels, two on each side of the reactor. Each is pierced by almost five hundred pipes, and above - steam lines, below - downpipes. The possibility of a BS explosion was sometimes discussed when discussing emergencies at RBMK. It seemed that this was the worst accident that could happen at a reactor. After all, BS explosions happened at thermal power plants with boilers on natural circulation - with terrible destruction.

I'm calling A.P. Nina Vasilievna, his secretary, connects.

A.P. reported the accident. What it is is not clear. Go, he says, to Kitaygorodsky passage to Soyuzatomenergo, you will be a representative of the Institute. The chapter will bring together all those interested and involved. Call me in the evening and tell me what and how. Valery Alekseevich Legasov is already leaving for the Chernobyl nuclear power plant.

So I ended up in G.A.'s office. Veretennikov in a large group of people yearning for information. Information was scarce: something had exploded, the reactor was being cooled down, and water was being fed into the core.

Only in the evening did K.K. Polushkin (from the Chief Designer - NIKIET): the reactor is blown up, the core is destroyed, graphite is burning. The reactor shop is in ruins (he flew around the reactor in a helicopter, filmed it).

Everyone is shocked. S.P. wanders along the corridor under a strong degree. Kuznetsov (head of the laboratory of thermal engineering calculations of RBMK at NIKIET) repeats endlessly: "The Ukrainians blew up the reactor ...".

At about 12 o'clock in the morning I returned home, called Nina Vasilievna. I connected with A.P. The conversation is short: “Tomorrow (today) at 8 am to be in the head office. In the morning a plane will take off for Kiev. You will be in the working group of V.A. Legasov with A.K. Kalugin. The decision has just been made to evacuate the city of Pripyat. Try to understand what happened. Valery Alekseevich is not a reactor engineer. You will become his help and advisor. " Such was the parting words of A.P.

A briefcase with a travel kit is always ready. There were frequent trips to industrial reactors, sometimes to accidents, but mostly for information and business purposes. On the RBMK accident - the third (December 1975 - Leningrad NPP; September 1982 - Chernobyl NPP, and now April 1986). He took with him two respirator petals, which he once brought from a business trip to Tomsk. I thought it would come in handy. This was all preparation for the trip to the accident. Without paperwork.

In the morning of 04/27/1986 we were already in Bykovo. By 12 o'clock the ministerial special plane landed at an airfield near Kiev (I think, Borispol). We drove on a "rafik" along the outskirts of Kiev. Peaceful city, calm, knowing nothing. We rushed along the highway to Pripyat. On the sides of the road there are blooming gardens, calm people. Sometimes household plots are plowed on horses. Villages and villages are clean, spring, in white-pink cherry-apple blossoms.

We stopped twice on the way. Dosimetrists from the G8 (NIKIET) uncovered the instruments and measured the background. It was felt that the background was increased, but not catastrophic (at that time the wind was blowing not in our direction). About 10 kilometers before Pripyat we stopped in a village. At the side of the road and in a small square there are several buses with crying women and children. Understood - the evacuees. There are a lot of people near the buses, probably locals. They talk with those sitting on the buses. The conversations are quiet, without loud emotions, but there is anxiety in the eyes and behavior.

At the entrance to Pripyat we met a column of empty buses. It was about 3 pm. This means that everyone was evacuated, there were even empty buses. There are a lot of traffic cops. We drove into the city. Empty, quiet. On the streets - not a soul. We drove up to the hill. Near the hotel. There are many people in the city committee, in the lobby there is a crying woman with a boy of about ten. For some reason, they did not leave with everyone.

Found V.A. Legasov. He sent us to the hotel. Parting words: we will start working tomorrow. Until then, rest.

We settled down in a hotel. I met my roommate. Kievite, doctor. He said that yesterday there was a light glow over the destroyed block. Small soaring in the morning and afternoon. The upper parts of the station blocks are visible from the corridor window (on the 3rd or 4th floor). Soaring is not visible. Gathered in the room of the G8 dosimetrists. The background on the street is about one X-ray per hour (~ 300 μR / s). It is better not to go out into the street. This is advice. True, I felt hungry. The dining room is almost next door. We went with Kalugin (head of the RBC department at the Kurchatov Institute). We sat down at a table. It turns out that the canteen is communism, self-service. Dinner is free. The dining room is being liquidated. Take whatever you can and want in the buffet. Young guys (station workers) stocked up with blocks of BT cigarettes. We were picking up full shopping bags. I don’t actually smoke, but I took one block.
On the street, fine drizzle, fog, deep twilight. I thought: the head will be "dirty", there is no cap or cap. On the way to the hotel we met a friend. He scolded us: "Why wander, there are three X-rays per hour on the street!"

Gathered at the hotel in K.K.'s room. Polushkin. He showed the filmed videotape. We saw the collapse of the station, the crater of the central hall, littered with pipes, construction fittings. In one place, at the edge of the reactor shaft, there is a red spot in the form of a blurred crescent. This means that the scheme "E" ("Elena", the upper biological shielding of the reactor) has been shifted so that it exited the shaft, red-hot graphite is visible. However, almost the entire mine is closed by "Elena", which is still kept in a horizontal position on a picket fence of steel sections of canals. Zirconium pipes, most likely, have burnt out, "Elena" is supported by steel cuts of pipes, which, apparently, rest against graphite. There is no smoke and steam in the mine. So we discussed what we saw and went to sleep. Yu.E. came. Khandamirov (a dosimetric engineer from the G8) and advised to move the beds away from the window (there is a strong background from the window). And it's better to move with the beds to the corridor altogether. Showed the scale of the dosage device. At the window, the readings had to be moved two clicks higher. Here for the first time the spleen skipped a beat, something pinched in the stomach. The owner of the dosage device reassured me: it's okay. We fell asleep, never dreamed of nightmares.

04/28/1986 in the morning we went to the regional executive committee, to the headquarters. We had breakfast in dry bread with boiled sausage, drank a glass of tea. All this on the go, on the windowsill. They forgot about the background from the window. They gave us another handful of pills with iodine. How to swallow, what to drink - no one knows. Then it turned out that we swallowed the pills too late, the thyroid gland was already filled with iodine from the reactor.

Valery Alekseevich Legasov (VAL) on the move, in a hurry met with us, asked to visit the unit, see the documentation that should have been retrieved from the 15th room (control room of the unit's operators). View the memorandums of the operators, who are all already in Moscow, in the 6th clinical hospital.

VAL supplied us with thick, shiny pencil dosimeters. I put the dosimeter in my pocket and forgot about it. As it turned out later, the dosimeters were not charged, not prepared for use.

We arrived at the unit, placed ourselves with the documentation and tapes of the DREG program (DREG tapes - huge sheets of paper with information on diagnostics and recording the parameters and state of the reactor plant systems before and at the time of the reactor accident) in a large basement room. We read the memorandums, talked with a few of the local engineers - personnel who remained with us. I was struck by the story of A.L. Gobov, head of the reactor safety laboratory. He was familiar to me from the Tomsk industrial reactors. Alexander Lvovich showed photographs of pieces of graphite lying near the walls of the 4th block, along with the remains of pipes of technological channels, and in them - pieces of fuel elements! The first impression cannot be. How? Where from! Only then the scale of the accidental explosion began to become clear! The graphite blocks flew out of the reactor shaft! How he was filming, he did not begin to tell in detail, but he “rolled” around the site near the destroyed block on an armored personnel carrier.

Examining the DREG tapes, Kalugin discovered a record of the operational reactivity margin before the explosion: only 2 rods. This is a catastrophic, gross violation of the Technological Regulations: when the reactivity margin drops to 15 rods, the reactor must be shut down immediately. And before the explosion, he worked with 2 rods.

At about three in the afternoon, Valery Alekseevich called. I asked to come to the headquarters. Gathered, went to the site in front of the entrance to the administrative building. The destroyed block is several hundred meters away, but it is not visible. The walls are covered with whole blocks, there are three of them. Young guys (shift) on the site smoke, chat. The helicopter flew by. On a suspension net with a load. The height is small, you can see everything. Hovering over a destroyed block. I dropped the load. Flew away. The crowd in the open air is calm. The faces are cheerful, none of them even has a "petal". Then I felt my "petals" in my pocket, I remembered! It's somehow awkward to put on, everyone's faces are open.

A bus came up, Lviv. We filled the bus completely. We ride standing. We pass by the destroyed block on the north side, where the road is less polluted, but all broken up and terribly dusty. In the cabin - dust (the bus is old, full of holes), and also fumes from exhaust gases. I remembered about the "petal". Pulled out. He covered his mouth and nose with his hand with an open “petal”. I don’t remember if I gave the second “petal” to Kalugin. In any case, I later threw out mine, and the second did not come across to me anymore.

Passing the destroyed block, we saw with our own eyes the scale of the disaster from a distance of no more than 100 m (maybe less). It seemed so. The bus was going very slowly, the collapse at a glance: the blue housings of vertical pumps, some kind of vertical containers, pipelines. Above - the bare "ribs" of the separator drum, black rags of thermal protection. The walls were destroyed into small pieces and approach the pump casings with an inclined hill.

Suddenly, attention turned to a helicopter that appeared above the block. Again I threw sandbags (as it turned out later) into the collapse of the reactor shaft. A second later, a black mushroom of dust and burning (just like a mushroom of an atomic explosion, only miniature) rose above the destroyed block. The hat of the black ominous mushroom for 3-4 seconds reached the height of about two-thirds of the ventilation pipe and slowly began to sink down in black shaggy, heavy streams, like rain from a cloud against a gray sky. After 10-12 seconds, the mushroom disappeared, the sky cleared. The wind blew the cloud-mushroom not in our direction. Lucky: the bus was directed along the safest route. This picture with a swirling black mushroom above a destroyed reactor in my head and before my eyes for 20 years.

We met with V.A. Legasov. The task is new, and the reason for the explosion of the reactor is later. The main thing is what to do now, what to prepare for? How will the destroyed reactor behave, how to extinguish the graphite, will there not be a new chain reaction?

A high government commission made a decision - to throw sand into the reactor shaft from a helicopter (to stop the burning of graphite), throw boric acid(to exclude the occurrence of a new chain reaction), throw lead (to reduce the temperature of the burning graphite). Tomorrow they will bring a water cannon to fill the mine with water from a distance of about 100 m. to the "Chinese syndrome", that is, to the ingress of molten fuel into the subsoil water through the melted foundation slab. It was decided to build a heat exchanger under the reactor in order to catch and cool the melt. There was also talk about liquid nitrogen. The idea was completely incomprehensible: there was already a lot of nitrogen in the air, the main thing was the supply of oxygen, you couldn't take it away from the masonry. V.A. Legasov. He asked me to immediately comment on the planned measures, and in the next hours and days to think over them and evaluate them, if there is enough ingenuity.

I will not talk in detail about Kalugin's reaction. Alexander Konstantinovich immediately said that a chain reaction is out of the question, the fuel rods are destroyed, and only graphite is burning.

See my answers in more detail.

VMF: It is impossible to stop the burning of graphite with sand and lead, since the reactor shaft was opened, but closed by "Elena". Throwing sand and lead is useless, they won't get on graphite. It is even harmful and very: each throw-portion causes the movement of radioactive dust, the remains of dispersed fuel, all this flies out with hot gases after the discharge of a portion of sand. We were witnesses of this. Nitrogen will not stop the flow of oxygen into the masonry. At that time they did not talk about the contamination of the surroundings with lead.

VMF: But the Swedes do not know the real picture of the destruction and the situation with the reactor shaft.

Legasov: Yes, after the start of the dumping of sand and other things, the activity went up sharply. But, most likely, this is temporary.

VMF: The action of a water cannon is useless and even harmful. Water will intensify, activate the combustion of graphite. It is not for nothing that coal in the old wartime was moistened with water in "stoves" for better combustion. And in industrial technology, steam is used to activate the combustion of coal and coke. The flow of water in the form of scattered raindrops will turn into steam on the hot surfaces of structures and graphite, the removal of activity with steam will significantly increase. It's like pouring water into an incompletely burnt fire. Of course, over time, the fire will go out, but how much ash will fly away with the steam?

Legasov: This proposal was made in a radio broadcast from the British. They suggest flooding the core with plenty of water.

VMF: It is unlikely that the British correctly represent the scale of our "fire" and the capabilities of the "gun".

(The next day, Valery Alekseevich said that the high commission refused to use the "gun" after discussion and categorical "against" the firefighters).

VMF: There is no need to dig under the reactor and build a heat exchanger under it. There will be no melting of the OP circuit. Why? The OP scheme has now become the grate of the forge. The lower water communications were torn off by the explosion (the "rolls" of the canals were torn off). The upper sections of the channels are also torn off (the "E" scheme is noticeably shifted up and to the side, it was visible on the videotape). The zirconium pipes of the channels burned out. The walls of the main rooms circulation pumps(RCP) destroyed. The blast wave has reached the MCP, which means that the "rolls" are torn off, air access through the openings in the "OP" scheme to the burning graphite from below is open, and the outflow of gases is also free from above. So the graphite will burn unhindered until the whole thing burns out, and the "OP" scheme - the grate remains intact, as it is cooled by the air flow from below.

Legasov: Where is the guarantee of such a representation of the consequences of the explosion?

VMF: There is no guarantee. This is the first thing that comes to mind when you mentally replay the entire picture of the rate of rise of a black column of dust above the reactor shaft after a portion of sand has been dumped. The air clearly passes through the "OP" and the masonry and the hot air comes out.

Then it turned out that I was right, but not quite. The OP scheme actually turned into a grate of the forge, did not melt, only the steam explosion of the core sank several meters down, as the "C" scheme cross, on which the OP scheme was held, was crushed. Air access was still free, otherwise the burning of graphite would have lasted much longer.

I realized that the decisions of the high commission cannot be changed; there, in the commission, there were more weighty advisers when I heard the final phrase of our meeting: “They will not understand us if we don’t do anything ...”.

That is why there was an anecdote (or maybe it was true): an active movement of equipment (armored personnel carriers) began around the destroyed block, clouds of dust rose when American spy satellites flew over the Chernobyl nuclear power plant. They were supposed to capture the stormy activities to eliminate the consequences of the accident.

We parted with Valery Alekseevich after receiving a new assignment: to estimate how long the graphite will burn.

I went to the window on the stairs. Near the building (in the courtyard), a pyramid of green boxes of clearly military origin was erected. I asked what it was. A guy standing next to him replied that the military had brought lead shot in boxes. Somehow I could not believe it: it would hurt the boxes to be heavy, but from such a weight they themselves would fall apart. Curiosity got the better, went to look. One box was broken, the lid was knocked down. Green military respirators are tightly packed inside. I put about five in my pockets. I thought it would come in handy. I will share with Kalugin.

04/29/1986 at the headquarters in the morning we met and discussed Melnichenko's report. He was responsible for the experiment on running out of the MCP from Donetskenergo. I read the program of the experiment. I drew attention to the phrase (not literally): "During the experiment, the work is carried out in accordance with the current technological regulations of the reactor." Had I come across this program earlier, I would have signed it, although it did not contain a serious justification for the safety of the experiment, analysis of the operation of the reactor itself during the experiment. And it couldn't be. The experiment was considered ordinary. But the reactor operators violated several requirements of the Regulations when they carried out the experiment. But now we are not talking about that.

At about 12 o'clock, our entire working committee was put on a bus and taken away from the radioactive volcano - the burning interior of the reactor. Destination - pioneer camp "Fabulous". On the way, we stopped near a place where paper bags were stuffed with sand to be thrown into the reactor shaft of Unit 4. The work supervisors were talking about something. I was struck by the picture, which will be before our eyes for a long time: against the background of the foggy bulk of the station, the houses of a small village a kilometer away. A plowman walks behind a fence for a plow with a horse. Processes a personal plot. Rural idyll on a radioactive field.

Once again we stopped on the way to the pioneer camp. Why we drove for so long was somehow forgotten. We sat on last year's and young grass. Fit A.K. Kalugin with E.P. Sirotkin (a physicist from NIKITET). They sat down. Aleksandr Konstantinovich quietly says: “But the reactor exploded when the emergency protection rods were dropped. Do you remember Sasha Krayushkin's report? 10 power ratings after dropping of the A3 rods, if all of them are in the upper position before dropping. "

The pioneer camp estimated how long the graphite would burn. Compiled a memorandum to V.A. Legasov, According to the estimate - it will burn for 10-15 days, The assessment was based on the observation of a radioactive "mushroom" over the reactor shaft (it seems that he was a little mistaken in time). By the end of the first ten days of May, “Elena”, loaded with sand and lead, turned over and stood almost upright in an empty shaft. The graphite is almost completely burnt out. The pipes of the channels were burnt so that only cinders stick out from the bottom of the scheme "E".

The Elena's coup was mistaken for an explosion. It was unclear for what reason it happened. There was a lot of radioactive dust and talk that the reactor was "breathing" again. Analysis of emissions showed that this is not the case.

In the pioneer camp we were first dressed in overalls. In the dining room were plates full of iodine pills.

When we returned home at the end of the first decade of May, I was already wearing the 4th set of work clothes. As we moved away from the station, we had to change clothes. The last change was at the airport. We waited a long time to board the plane. We sat on the bus with the door open. The bus attracted attention: all the passengers were in gray overalls. They came up and asked about the accident. Listened to the conversations. We were silent.

In Bykovo, right on the plane, we were met by a group of our dosimetrists led by the staff of the Kurchatov Institute E.O. Adamov and A.E. Borokhovich. A portable dosimeter in Adamov's hands crackled briskly when the sensor was brought to his boots and overalls. The fountain pen crackled faster in my pocket. Head - crackle like a machine-gun shot. The spleen jumped again when the sensor was brought to the throat. The machine-gun shot turned into a continuous, uniform squealing. Dosimetrists, perhaps, will laugh at my assessment of the situation, but after the bath in the sanitary inspection room I washed my head for a long time and hopelessly. I had to cut my hair.

In August 1986, I was returning from a business trip to the Chernobyl nuclear power plant together with the head of the safety group, Chernyshev. I remembered my surname, because on the maternal side I am Chernyshev.In the plane and in my apartment they talked for a long time about the reasons for the explosion of the reactor. My interlocutor was terribly surprised when he learned that the RBMK-1000 reactor at the Chernobyl nuclear power plant could explode at any time, if the Regulations were violated, the operational reactivity margin was allowed to decrease to a state when all the control rods were in the upper position, the power was reduced, and the water temperature at the inlet into the channels is maximum. If at this moment the emergency protection of the reactor is triggered, an explosion is inevitable. And we, - he said, - went to power several times a year after short-term shutdowns in such a state of the reactor. They did not have time to get up in time and lost their reactivity reserve, they were afraid to get into the "iodine pit". The dispatcher demanded an increase in the reactor power (for him - "samovar") at any cost. Usually this situation occurred in winter, when energy was especially needed. Lucky. Such was the reactor ...

Explaining the reasons for the explosion of the reactor is not an easy task, since there is still no single point of view.

As you know, the prototype of the RBMK reactor was an industrial reactor producing weapons-grade plutonium. Two such reactors near Tomsk and one near Krasnoyarsk still work reliably (for more than 40 years now) and produce heat and electricity. They will be stopped, most likely, after the launch of replacement heating capacities, otherwise the satellite cities Seversk and Zheleznogorsk will be left without communal heat.

So, in the technical specifications for an industrial reactor, it was written that the emergency protection rods should stop the reactor in 2-3 seconds. This requirement is fulfilled in industrial reactors from the moment of their construction, the emergency protection rods are fully inserted into the core in about 5-6 s, and the reactor is "muted" by the 3rd second, when the rods are about half of its core.

The same requirement was written down in the technical specifications for the RBMK-1000. However, in the process of working on the reactor design, it turned out that it is difficult to quickly insert the control rods into the core. In industrial reactors, the cooling circuit of the control rods is open, the cooling water, after passing through the reactor, does not return back to the circuit; therefore, it is relatively easy to organize cooling of the control rods in it by the so-called film cooling, in which the rods “fall” under their own weight into an almost empty channel. In the RBMK reactor, the loop is closed, the CPS channels are filled with water, film cooling is difficult to organize, so the control rods are forced in and at a lower speed. The designers chose a simplified path: the physical "weight" of the rods, i.e. the ability to absorb neutrons was increased, and the injection rate was reduced so that the rods were inserted into the core in 18 s, i.e. almost three times slower than in industrial reactors. When the Americans heard about this feature of the reactor in Vienna at the IAEA in 1986 from V.A. Legasov (he talked about the Chernobyl disaster, Chernobyl.), Then they were very surprised, saying that back in 1953 they had put forward a categorical requirement for the speed of insertion of emergency rods in 2-3 s. in order to exclude any possibility of uncontrolled acceleration of the reactor on prompt neutrons (this requirement has been implemented in industrial reactors from the moment of their start-up.

One more fatal feature of the reactor emergency protection. Once, in the mid-70s, the building structures of the Chernobyl nuclear power plant were discussed at the Kurchatov Institute. They talked about the concrete structures of the under-reactor room: it seemed too deep. As a result of the discussion, a proposal was accepted to save concrete and reduce its depth by almost 2 meters. As a result, it was necessary to reduce the length of the displacers of the CPS rods to 4.5 m, since their full length (7 m) was already placed in the sub-reactor space if the CPS rods were introduced into the core along their entire length. In general, the decision was justified: the displacers of the CPS rods were introduced into the design to save neutrons, and their efficiency is optimal if the displacers (in the case of removing the absorbing rods completely from the core) are located in its central part. The upper and lower edges of the displacers, located at the periphery, are practically useless, since there are few neutrons. Let us explain that the displacers are made of graphite in an aluminum alloy shell. Graphite absorbs neutrons much less than water; therefore, the propellers are designed to remove water from the CPS channels when the absorbing rods are brought to the upper position and do not participate in the regulation of the reactor power. This decision led to the fact that in the lower part of the core in the CPS channels there was a water column about 1.2 m high when the absorbing part of the rods was removed from the core. This situation often occurs in transient conditions, especially after short-term shutdowns or the transfer of the reactor from a higher power to a lower one. At this time, the reactivity margin decreases due to the "poisoning" of the core with xenon, the rods from the reactor are removed to the upper position. To maintain the power at a lower level or bring it to the required level during start-up, it is necessary to reduce the “useless” absorption of thermal neutrons, which is done by removing the control rods from the core.

And the third feature of RBMK. During the design of the reactor and even in subsequent years, they did not know with sufficient certainty (there were no calculation programs and conditions for reliable reactor experiments) what the changes in reactivity would be if the amount of steam in the working channels increased in the event of an increase in power, i.e. the amount of "dense" water will decrease, the absorption capacity of which is much higher than that of steam (this effect is called the "density effect of reactivity"). Then it was believed that the density (or steam) effect of reactivity, if positive, then only at the stage of the average change in the density of the coolant, and when the water in the channel is completely replaced by steam, the effect is negative, i.e. the reactor power should be reduced. With a positive density effect of reactivity, the reactor power increases with an increase in the amount of steam, and, accordingly, the growth of the reactor power is also "whipped up".

As it turned out later, as a result of calculations under the new programs, the replacement of water with steam caused a sharp jump in reactivity, and of such magnitude that the reactor power had to increase on "prompt" neutrons in a few seconds to values ​​exceeding the initial value by tens and hundreds of times.

There is one more effect, the significance of which for the stable operation of the reactor was not sufficiently understood - this is the “double hump” distribution of the energy release over the height of the core, which is associated with a large burnup of fuel in the center of the zone as compared to the upper and lower periphery (under the conditions of a stationary refueling ).

Here are four effects that led to the explosion of a reactor of such a scale, the possibility of which the developers of that time practically did not know and did not know.

Here it should be said that they still knew something from calculations and experiments. Three years before the accident, the calculation showed: if all the control rods located in the upper position, i.e. when the absorbing (active) part of them is removed from the core, will be introduced into the core, then in the first seconds of the operation of the rods due to the displacement of water from the bottom of the control and safety channels by graphite displacers, a short-term surge in the reactor power up to ten times of the initial power is possible.

A possible increase in reactivity due to the replacement of water in the channel by steam with an increase in power was not considered in this calculation. In this regard, and for other reasons due to the stability of the reactor operation, there was a point in the technological regulations that categorically required to "shut down" the reactor power if the number of control rods in the core reaches fifteen. In this case, the absorbing part of the control rods located inside the core, as they were further introduced into the core, reduced the reactivity of the reactor and led to its shutdown.

Three years before the accident, decisions were made to rework the control rods in order to eliminate the "displacement effect". However, nothing was done.

Our working commission immediately noticed a violation of the Regulations in the actions of the operators: there were only 2 CPS rods in the core instead of the more than fifteen required to continue the work. But could dropping the control rods under the conditions of an experiment with turbine run-out lead to such an explosion?

It was seen from the recorder tapes that a few (1-2) seconds before the pressure in the separators grew, and after the growth (and hence the explosion), the flow rate at all 8 pumps dropped sharply to almost zero. An idea appeared: at low power and with their unstable operation, all the pumps were coiled, since steam appeared there, their work and water supply to the reactor were interrupted. That is why there was an overheating of the fuel rods and pipes of the fuel complex, which led to their rupture and further development of the accident. (At the time of the experiment with the run-out of a part of the pumps, all the pumps did not operate in the nominal mode with a noticeable excess of the flow rate, which increased the likelihood of their failure).

Almost everyone liked the idea, especially the representatives of the Chief Designer of the reactor. Subsequent computational analysis using more advanced programs showed that the reason for the explosion of the reactor was different. This is how events developed, in my opinion.

During the experiment with turning off turbines and running out of pumps, the power of the reactor was hardly maintained at a low level (~ 20% of the nominal value). The reactivity margin was falling due to "poisoning" with xenon. To maintain the power and bring the experiment to its logical conclusion, the operators removed practically all the control rods from the core (in accordance with the records on the DREG tapes, only 2 rods remained). This violated an important safety provision in the Regulation. The experiment was almost completed, the reactor was unstable. A noise was heard in the pumping room - a cavitation rumble, which the operating personnel are familiar with in case of violation of the optimal operating conditions of the pumps. Apparently at this moment the reactor operator noticed a slight increase in the reactor power associated with an increase in the amount of steam in the channels. The situation is tense, the automatic power control rods are inactive. He made a quite reasonable decision to "shut down" the reactor with the "button" of emergency protection. In two or three seconds, water was displaced from all CPS channels, and positive reactivity was introduced, sufficient to increase the power of the lower part of the core. The upper part of the core decreases its power, since absorbing rods are introduced into it. However, the lower part of it continues to accelerate, since the reactor is to some extent divided into two parts that are little connected to each other due to the double hump of the energy release curve along the height of the reactor. The acceleration of the reactor power on prompt neutrons began due to the displacement of water from the lower part of the CPS channels and the positive effect of reactivity due to an increase in the amount of steam in the lower part of the working channels. The appearance of steam in the lower part of the working channels (to start boiling big stature power was not required, tk. the water was practically at the saturation temperature) led to the complete expulsion of water from the technological channels. By this time, the absorbing part of the control rods had entered the core by only 1.5-2 meters and did not prevent the growth of reactivity in the lower 5-meter part of the core. The acceleration of the power on prompt neutrons by a factor of hundreds of times from the nominal value in the first 2-3 seconds "blew up" the fuel elements. The pumps stopped supplying water due to a sharp increase in the hydraulic resistance of the core. The incandescent fuel “dust” with steam (against the background of an increase in pressure in the core and in the separator up to 80-85 atmospheres and complete cessation of the flow rate in the pumps) overheated, mainly by radiation, the pipes of the process channels to temperatures at which they ruptured. It was at this time that noise and roar were heard from the central hall, which were mistaken for the first explosion in the central hall. Water and steam with overheated fuel "dust" filled the reactor space, got on hot graphite, the temperature of which by that time was about 350-400 ° C. The pressure in the reactor space increased to the values ​​at which the upper biological protection (scheme "E", "Elena") was torn off, the channels at the top were torn, the lower pipes-rolls supplying water to the working channels were cut off. Under pressure in the RP, the lower "cross" (scheme "C") sank, on which the lower biological protection (scheme "OP") rests.

The thermal explosion of the reactor was the second explosion heard by the personnel. At that moment, the upper and lower communications were destroyed, diverting the steam-water mixture and supplying water to the technological channel, the premises of pumps and separator drums. Together with steam, graphite blocks with pieces of zirconium pipes and fuel assemblies were thrown out into the hole after lifting and shifting of the "E" scheme. The personnel outside the reactor building (according to the memorandum) saw sparks and red-hot pieces of something resembling "burning rags".

The first, initial phase of the Chernobyl tragedy, as I see it, is over. Most of the fuel and graphite remaining in the reactor shaft began to warm up due to the residual energy release of fission products in the fuel. Cooling water, in principle, could no longer get into the core, since all communications were torn. The graphite heated up to 700-800 ° C and began to burn itself. The temperature of the burning graphite could rise to 1500 ° C. Within a few days, graphite, zirconium pipes, and zirconium cladding of fuel elements were almost completely burned out. Heavy fuel fractions remained in the reactor shaft (some experts claim that there was nothing left there), volatile and gaseous uranium fission fragments were thrown into the atmosphere.

How can you finish? Here are a few IF. If the reactor had been designed soundly, without the above-mentioned shortcomings in the protection control system (CPS) and in the characteristics of the core, and even if the CPS were modernized in time, if there were trained, disciplined and qualified personnel ... conducted a study of possible emergencies and communicated their results to the operating personnel ... If PSA of RBMK reactors were carried out in the early 80s ...

PSA - Probabilistic Safety Analysis. In the United States, its basic principles were developed after the 1979 Trimile Island nuclear power plant accident in Pennsylvania. The PSA considers the most probable and improbable, possible and impossible emergency events and their combinations and overlaps. The possibility of this accident would be carefully considered, and its probability would be minimized.

By the way, sabotage in the form of meaningful bringing the reactor to an emergency state in conditions of violation of the regulations, most likely, would be considered in the PSA too. But all are clever thoughts on the stairs.

And I want to end with a well-known expression: do not look for malice where everything is explained by stupidity. Or do not look for otherworldly forces where everything is explained by earthly forces (about fantasies like an earthquake under a reactor).

Chernobyl

The Chernobyl accident. Chronology of events. April 26, which divides the history of Ukraine into two periods - before and after the crash.

Here is a brief chronology of the most important dates associated with the Vladimir Ilyich Lenin Nuclear Power Plant in Chernobyl.

The Chernobyl accident per minute, the years of events from 1970 to 2016 are also included.

1966

The Council of Ministers of the USSR issues a resolution of June 29, 1966, which approves the plan for the commissioning of nuclear power plants throughout the USSR.

According to preliminary calculations, the commissioned nuclear power plants were supposed to generate 8000 MW, which would compensate for the shortage of electricity in the central region of the southern part.

1967

From 1966 to 1967, work was carried out to find suitable territories. The work was carried out by the Kiev branch of the Teploelektroproekt design institute. As part of the research, sixteen territories were studied, mainly in the Kiev, Vinnitsa and Zhytomyr regions.

Territory exploration continued until January 1967. As a result, it was decided to stay on the territory in the Chernobyl region, on January 18, 1967, the territory was officially approved by the Board of the State Planning Committee of the Ukrainian SSR.

On February 2, 1967, the Board of the State Planning Committee of the Ukrainian SSR approved the project for the construction of the Chernobyl Nuclear Power Plant.

On September 29, 1967, the reactors were approved to be installed at the Chernobyl Nuclear Power Plant.

In total, there are three approved:

• graphite-water reactor RBMK-1000;
• graphite-gas reactor RK-1000;
• pressurized water reactor VVER.
• Based on the results of the options considered, a decision was made to select the RBMK-1000 graphite-water reactor.

1970

The ChNPP Directorate was formed. Projects and urban planning plans for the city of Pripyat have been approved, and its construction has begun.

May 1970 marked the first pit for the first power unit of the Chernobyl NPP.

1972

The formation of a special water tank begins to cool the reactors. The reservoir was formed by changing the river channel and building a dam in this channel, as a result, in addition to the dam, the Pripyat River acquired a wide navigable canal.

1976

October 1976 the tank filling procedure began.

1977

May 1977 start-up and adjustment work began at the first power unit.

1978

1979

Pripyat receives city rights.

The Chernobyl nuclear power plant produced 10 billion kilowatt-hours of electricity.

1981

1982

On September 1, a malfunction of the reactor No. 1 was recorded. Slight contamination of some of the damaged evaporation fuel blocks.

On September 9, the destruction of the fuel assembly and an emergency rupture of the technological channel No. 62-44 occurred.

Due to the rupture, the graphite stack of the core was deformed; a significant amount of radioactive substances from the destroyed fuel assembly was thrown into the reactor space.

The reactor was repaired and restarted. Information about the accident was published only in 1985.

1983

The construction of reactor No. 4 has been completed.

1984

On August 21, the Chernobyl nuclear power plant produced 100 billion kilowatt-hours of electricity.

1986

“The probability of the destruction of the core occurs once every 10,000 years. The power plants are safe and reliable. They are protected from destruction by three security systems, ”said Vitaliy Sklyarov, Minister of Energy and Electrification of Ukraine.

Beginning of preparation for the test of the turbocharger of the reactor 4. The power of the reactor was reduced.

The reactor power was reduced to 1600 MW, which is half the nominal value.

Reduction of the power intended for the own needs of the reactor. Generator shutdown 2.

At this hour, the power of the reactor is expected to reach only 30 percent. The capacity, at the request of the dispatcher of the Kiev Energy District, was reduced for several hours. 23:00 the reactor was working at 50 percent. Rated power.

The reactor power was reduced to 1600 MW, at which the experiment was carried out. The operator Kyivenergo banned further power cuts.

The ban on power reduction has been lifted, and a new stage of power reduction has begun.

26 April

The night shift took over the reactor.

The reactor power dropped to the planned 700 MW.

The reactor power dropped to 500 MW. Due to the complexity of the steering, the xenon core was "poisoned", as a result of which the thermal power of the reactor decreased to 30 MW. To boost the reactor's power, the crew removed the control rods. There were only 18 rem in the core, but at least 30 rem is needed.

The reactor power was increased to 200 MW. To prevent the automatic shutdown of the reactor, the personnel blocked the safety system.

A sharp decrease in the reactivity of the reactor.

Start of testing the turbine generator. The turbine valves were cut. The power of the reactor began to grow uncontrollably.

The emergency braking of the control rods did not work because they jammed the channels (and reached a depth of 2-2.5 m instead of a full thrust of 7 m).

Rapid increase in steam power and reactor power (within a few seconds the power was about 100 times higher than the required value).

The fuel overheated, the surrounding zirconium dioxide burst and the molten fuel escaped, and then the pressure channels burst. This started to lead to an exothermic reaction.

Emergency signal given

The first explosion occurred

There was a second explosion - the first was water vapor, then hydrogen was released. The reactor and parts of the structure were destroyed.

As a result of the explosion, the 2000-ton plate was thrown back onto the reactor vessel. Waste graphite core and molten fuel are discarded.

The reactor is estimated to have leaked about 8 out of 140 tons of fuel.

The fire brigade accepted the call from the Chernobyl nuclear power plant and moved forward to extinguish the fire.

An additional fire brigade left the city of Pripyat.

A fire alarm was announced. The staff tried to start the reactor's cooling systems, hoping they were not damaged in the explosion.

Arriving firefighters of the first crew begin to extinguish the fire on the roof of the turbine hall.

The absence of a measuring device was established, the first device was damaged by an explosion. The second is in the area cut off by rubble. The second fire brigade arrived, some of the firemen are engaged in extinguishing the fire, the other part of the calculation is taking apart the rubble to access the measuring equipment.

Firefighters begin to vomit, the skin begins to burn under the clothes.

The Department of the Ministry of the Interior is in charge of the crisis personnel meeting.

It was decided to put blocks on the road. Firefighters and police brigades are called.

The officers are not sufficiently trained - they do not have dosimeters and protective clothing.

Viktor Bryukhanov, director of the plant, arrives at the crisis management center, located in a bunker under the administrative building of the gym.

The authorities notified the central authorities of the incident in Moscow.

The fire is blocked, the possibility of fire transfer to other rooms is excluded.

Other firefighters arrived from Polesie and Kiev.

The fire is completely extinguished.

188 firefighters were called to the scene of the accident.

The irradiated firefighters were evacuated to the 6th radiological hospital in Moscow. Air ambulance was used for evacuation.

The morning shift came to the power plant. Construction work began on the construction site of reactors 5 and 6. 286 people worked there.

A decision was made to supply water to the damaged reactor zone.

A status report was sent to the Chernobyl NPP

The government commission was headed by Valery Legasov. The specialists who arrived at the scene did not expect to see parts of the graphite fuel channels.

The data from the measuring devices were obtained, the level of pollution was established, and a decision was made to evacuate the population.

Requests were sent to neighboring districts and the city of Kiev for the allocation of transport for the evacuation of the population.

The transport department of the city of Kiev gives an order to remove from the routes of all buses of suburban communication and the direction of transport to the city of Chernobyl.

Checkpoints have been set up on roads within a radius of 30 kilometers to prevent the movement of civilians across the contaminated territory.

Reactors 1 and 2 are off.

The administration of the city of Pripyat collects all administrative personnel.

Instructing the administrative staff of hospitals, schools, kindergartens.

Processing of the city begins. Laundry soap and additional water tanks were placed in all toilets in the city. The processing of the premises had to be repeated every hour.

All schools started working, without fail all children were measured with a radiation device, medical personnel issued pills containing iodine.

The processing of the forest around the Chernobyl NPP has begun.

Militia officers were instructed. The precinct officers made a detour and count of residential buildings, taking into account the number of people living in them.

The first emissions of sand, boron and lead over the destroyed reactor No. 4 began.

Two thousand buses and more than one hundred units of military equipment have been assembled on the border of the city of Chernobyl.

The students were sent home with instructions to stay in their apartments. General briefing has begun in the city.

An instant drop in radioactivity around the power plant.

Instructions are conducted at the city police department. The city is divided into six sectors. A responsible person was assigned to each, two police officers were assigned to each entrance of a residential building.

The police officers arrived at their places and began instructing and gathering the residents.

An official announcement of the accident and the planned evacuation of the population was broadcast on the radio.

The evacuation of people from Pripyat began. Almost 50 thousand. People left their homes within 3.5 hours. 1,200 buses were used for this purpose.

Police officers examined the city of Pripyat, recorded the absence of the civilian population.

The radioactivity in the air around the Swedish nuclear power plant in Forsmark has increased.

Moscow television reported on the "incident" at the Chernobyl nuclear power plant.

The Danish Institute of Nuclear Physics reported that, most likely, the accident at the Chernobyl nuclear power plant completely melted the reactor.

The Soviet media reported the death of two people as a result of the accident, the destruction of the reactor block and the evacuation of the population.

At that time, American spy satellites took the first photographs of the destroyed reactor.

Analysts were shocked by what they saw - the damaged roof of the reactor and the glowing mass of the molten core of the reactor.

By that day, over 1,000 tons of material had been dropped from helicopters into the destroyed reactor block.

The wind changed direction, and the radioactive cloud began to move towards Kiev. Ceremonial processes took place on the occasion of the May 1 holiday.

May 2

The staff of the liquidation commission found that the core of the exploded reactor was still melting. At that time, the core contained 185 tons of nuclear fuel, and the nuclear reaction continued at an alarming rate.

Beneath 185 tons of molten nuclear material was a reservoir with five million gallons of water. This water was needed as a coolant, and a thick concrete slab separated the nuclear fuel and the water reservoir.

For molten nuclear fuel, a thick concrete slab was not a sufficient obstacle, the melting core burned through this slab, going down to the water.

In the event of contact of the incandescent core of the reactor with water, a massive, radiation-contaminated steam explosion will occur. The result could be radioactive contamination of much of Europe. In terms of the death toll, the first Chernobyl explosion would have looked like an insignificant incident.

The engineers have developed a plan according to which it is possible to avoid a steam explosion. To do this, you need to drain the water in the tank. To drain the water, it is necessary to open the valves located in the flooded radioactive zone.

Three people volunteered for the task:

• Alexey Ananenko senior engineer
• Valery Baspalov mid-level engineer
• Boris Baranov shift supervisor

They all understood that the dose of radiation substances that they would receive during a dive would be fatal for them.

It was about opening valves in a water tank, which was under the damaged reactor, to prevent another explosion - a mixture of graphite and other materials with a temperature of over 1200 degrees Celsius with water.

The scuba divers plunged into a dark reservoir and with difficulty found the necessary valves, manually opened them, after which the water was drained. After their return, they were taken to the hospital, by the time of hospitalization they had an acute stage of radiation sickness, they could not be saved.

Work has begun on the construction of a tunnel under reactor No. 4 in order to install a special cooling system there.

A 30-kilometer zone was created around the reactor, from which 90,000 people were evacuated.

A special embankment was built to protect it from pollution.

Reducing radioisotope emissions.

Firefighters pump water from the basement under the reactor core.

From radiation in Chernobyl, they began to give out Lugol's drug.

It was decided to start building a sarcophagus over the destroyed reactor block No. 4.

The Chernobyl Atomic Energy Council was fired, accusing it of "lack of responsibility and because of gaps in the supervision of the reactor."

Russia sent its first report after to the International Atomic Energy Agency.

There it was discovered that an extraordinary sequence of events, negligence, mismanagement and security breaches led to the disaster.

Reactor No. 1 was turned on again.

Work continued on the construction of reactors 5 and 6.

Reactor # 2 was switched on. Hans Blixa, Director of the International Atomic Energy Agency, visited Chernobyl.

The work on assembling the sarcophagi for reactor block 4 has been completed; they are designed for 30 years of radiation protection.

Used 400 thousand tons of concrete and more than 7 thousand tons of metal.

1987

Reactor # 3 started producing electricity again.

Work on the construction of reactors 5 and 6 was stopped.

1989

Closure of reactor No. 2 after a turbine fire. It is important to note that there was no risk of infection.

The final decision was made to stop the construction of reactors 5 and 6.

1991

Fire in the turbine hall of Reactor No. 2.

Power unit No. 2 was put into operation after overhaul... While reaching the set power level, one of the turbine generators of the power unit spontaneously turned on.

The reactor power was 50% of the thermal power - at that time, one turbine generator of the unit was operating (at 425 MW).

The spontaneously switched on second turbine generator worked in the "propulsion" mode for only 30 seconds.

As a result of work in the turbine generator, large axle loads arose, which led to the complete destruction of the bearings of the turbine generator shaft.

The destruction of the bearings led to the depressurization (desealing) of the generator, which led to the release of large amounts of oil and hydrogen. As a result, there was a big fire.

During the subsequent investigation of the causes of the accident, it was found that the turning on of the turbo generator was caused by the fact that the turbo generator was not protected from the mode of connection to the network on the freewheel of the rotor.

Spontaneous switching on occurred as a result of loss of insulation between the cable controlling the closing of the switch and the cable through which the signal about the disconnected state of the switch is transmitted.

There was a defect in the installation of cables - signal and control cables were placed in one tray.

This accident at the Chernobyl nuclear power plant did not lead to significant pollution of the territory of the exclusion zone. The specific activity of the emission is estimated at 3.6 * 10 -5 Ci.

1992

The Ukrainian authorities are announcing a competition for new construction, which will cover the hastily constructed sarcophagus on reactor building 4.

There were 394 proposals, but only one was considered worthwhile - the construction of a sliding installation.

Assembly tests of structures in Italy. Delivery of the first components for the construction of the sarcophagus.

The first eastern fragment of the dome was raised (5,300 t, 53 m)

2013

A fragment of the roof over reactor block 4 was destroyed under the pressure of snow. Fortunately, the construction was not compromised.

The second operation to raise the first eastern fragment (9,100 tons, 85.5 m)

The third operation to raise the first eastern fragment (11 516 t, 109 m)

October November

Construction of a new and dismantling of the old chimney for power unit No. 3.

2014

The first part of the construction was completed and moved to the parking lot (12,500 t, 112 m)

The first operation to raise the second western fragment of the sarcophagus (4,579 t, 23 m)

The second operation to raise the second western fragment (8 352 t, 85 m).

The third operation to raise the second western fragment of the dome (12,500 t, 112 m)

2015

The beginning of raising the inclined side walls of the sarcophagus.

Work began on the electrical and ventilation systems inside the dome.

Docking of the two parts of the new sarcophagus.

Commissioning of new equipment for the dome.

2016

Beginning of the ladle shift operation over Reactor Unit 4 and the old sarcophagus.

Ceremonial completion of work on the construction of a new dome over reactor block 4.

April 26, 1986 ... This date will be remembered by several more generations of Ukrainians, Belarusians and Russians as the day and year when the terrible happened. When all this happened, perhaps even the most experienced experts did not fully realize what awaited us all later.

The disaster on April 26, 1986 resulted in thousands of deaths and diseases, contaminated forests, poisoned water and soil, mutations of plants and animals. Among other things, a thirty-kilometer exclusion zone appeared on the map of Ukraine, passage into the territory of which is possible only with a special permitting document.

This article is aimed not only at reminding readers once again what happened on April 26, 1986, but also to look at what happened, as they say, from different angles. Now, it seems, it is not a secret for anyone that in modern world more and more often there are those who are ready to pay a lot of money to go on an excursion to these places, and some former residents, without settling in other regions, often return to their ghostly and abandoned cities.

Brief summary of events

Almost 30 years ago, namely on April 26, 1986, the largest atomic accident in the world happened on the territory of present-day Ukraine, the consequences of which are felt by the planet to this day.

At a power plant in the city of Chernobyl, the nuclear reactor of the fourth power unit exploded. A huge amount of deadly radioactive substances were simultaneously thrown into the air.

It has now been calculated that in the first three months alone, starting from April 26, 1986, 31 people literally died on the spot from radiation. Later, 134 people were sent to specialized clinics for intensive treatment for radiation sickness, and another 80 died in agony from infection of the skin, blood and respiratory tract.

The Chernobyl nuclear power plant (1986, April 26 and the following days) needed workers more than ever. More than 600 thousand people took part in the liquidation of the accident, most of whom were military personnel.

Perhaps the most dangerous consequence of the incident was a huge release into the environment of deadly radioactive substances, namely isotopes of plutonium, uranium, iodine and cesium, strontium and radioactive dust itself. The plume of radiation covered not only a huge part of the USSR, but also Eastern Europe, and the Scandinavian countries, but most of all on April 26, 1986 affected the Byelorussian and Ukrainian SSR.

A lot of international experts were engaged in the investigation of the causes of the accident, but even to this day no one knows for sure the true reasons for the incident.

Distribution area

After the accident around the Chernobyl nuclear power plant, it was necessary to designate the so-called "dead" zone of 30 km. Hundreds of settlements were destroyed almost to the ground or buried under tons of earth using heavy equipment. If we consider the sphere with confidence, we can say that Ukraine at that time lost five million hectares of fertile soil.

Before the accident, the reactor of the fourth power unit contained almost 190 tons of fuel, 30% of which was released into the environment during the explosion. In addition, at that time, various radioactive isotopes that had accumulated during the operation were in the active phase. It was they, according to experts, that represented the greatest danger.

More than 200,000 sq. km of the surrounding land was contaminated with radiation. The lethal radiation spread like an aerosol, gradually settling on the surface of the earth. Pollution of the territories at that time mainly depended only on the regions where it rained on April 26, 1986 and the next few weeks.

Who is to blame for what happened?

In April 1987, a court hearing took place in the city of Chernobyl. One of the main culprits at the Chernobyl NPP was the director of the plant, a certain V. Bryukhanov, who initially neglected the elementary safety rules. Subsequently, this person deliberately underestimated the data on the level of radiation, did not put into effect the plan for the evacuation of workers and the local population.

Also, in the course of the case, facts of gross neglect of their official duties on April 26, 1986 by the chief engineer of the Chernobyl NPP N. Fomin and his deputy A. Dyatlov were discovered. All of them were sentenced to 10 years in prison.

The head of the same shift where the accident happened (B. Rogozhkin) was sentenced to another five years, A. Kovalenko, his deputy, to three years, and Y. Laushkin, state inspector of Gosatomenergonadzor, to two years.

At first glance, it may seem that this is quite cruel, but if all these people had shown great caution in working at such a dangerous enterprise as the Chernobyl nuclear power plant, the catastrophe on April 26, 1986 would hardly have happened.

Notification and evacuation of the population

The expert commission claims that after the accident, the first thing to do was to immediately evacuate the population, but no one took responsibility to make the necessary decisions. If then the opposite happened, the number of human casualties could be tens, or even hundreds of times less.

In practice, it turned out that people all day did not know anything about what had happened. On April 26, 1986, someone was working on a personal plot, someone was preparing the city for the upcoming kindergarten kids were walking on the street, and schoolchildren, as if nothing had happened, did physical education in the fresh air, as it seemed to them.

The work to evacuate the population began only at night, when an official instruction was issued to prepare for the evacuation. On April 27, a directive was announced on the complete evacuation from the city, scheduled for 14.00.

So the Chernobyl nuclear power plant, the disaster of April 26, 1986, which deprived many thousands of Ukrainians of their homes, turned the modest satellite town of Pripyat into a terrible ghost with devastated parks and squares and dead, deserted streets.

Panic and provocations

When the first rumors about the accident passed, part of the population decided to leave the city on their own. Already on April 26, 1986, closer to the afternoon, many women in panic and despair, picking up babies in their arms, literally ran along the road away from the city.

Everything would be fine, but this was done through the forest, the dose of pollution of which, in fact, many times exceeded all permissible indicators. And the road ... According to eyewitnesses, the asphalt pavement glowed with some strange neon shade, although they tried to fill it abundantly with water mixed with some white solution unknown to ordinary people.

It is very disappointing that serious decisions on the rescue and evacuation of the population were not made in time.

And finally, only a few years later it turned out that the special services of the Soviet Union were aware of the procurement of three tons of meat and fifteen tons of butter in the territories directly affected by the Chernobyl tragedy on April 26, 1986. Despite this, they decided to recycle radioactive products by adding relatively pure components to them. In accordance with the decision taken, this radioactive meat and butter was transported to many large factories in the country.

The KGB also knew for sure that during the construction of the Chernobyl nuclear power plant, defective equipment from Yugoslavia was used, it was also familiarized with various kinds of miscalculations in the design of the station, the stratification of the foundation and the presence of cracks in the walls ...

What was done after all? Attempts to prevent more grief

At about half past one in the night in Chernobyl (1986, April 26), the local fire department received a signal about a fire. The guard on duty went to the call and almost immediately sent a signal about a fire of high complexity.

Upon arrival, the special team saw that the roof of the turbine hall and the huge reactor hall were on fire. By the way, to date, it has been established that when extinguishing that terrible fire, the guys who were involved in the reactor hall suffered most of all.

Only at 6 o'clock in the morning the fire was completely extinguished.

In total, 14 vehicles and 69 employees were involved. Of the overalls, people performing such an important mission had only a canvas robe, helmet and mittens. The men extinguished the fire without gas masks, since it was simply impossible to work in them at high temperatures.

At two o'clock in the morning, the first victims of radiation appeared. The people began to vomit severely and general weakness, as well as the so-called "nuclear sunburn" was observed. They say that some of them had the skin of their hands removed along with the mittens.

Desperate firefighters did their best to prevent the fire from reaching the third block and beyond. The staff of the station began to extinguish local foci in different rooms of the station and took all the necessary measures to prevent a hydrogen explosion. These actions helped to prevent an even greater man-made disaster.

Biological consequences for all mankind

Ionizing radiation, when it hits all living organisms, has a destructive biological effect.

Radiation radiation leads to the destruction of biological matter, mutations, changes in the structure of organ tissues. Such irradiation contributes to the development of various types of oncological disorders of the vital functions of the body, the change and decay of DNA and, as a result, leads to death.

A ghost town called Pripyat

Several years after the man-made disaster, this settlement aroused the interest of various kinds of specialists. They came here en masse, trying to measure and analyze the level of the contaminated area.

However, in the 90s. Pripyat began to attract more and more attention from scientists interested in environmental changes in the environment, as well as transformation issues natural area a city completely left without anthropogenic influence.

Many Ukrainian scientific centers carried out assessments of changes in flora and fauna in the city.

Stalkers of the Chernobyl zone

First of all, it is worth noting that stalkers are people who, by hook or by crook, penetrate the exclusion zone. Chernobyl extreme lovers are conventionally divided into two categories, differing in their appearance, used slang, photographs and prepared reports. The first are curious, the second are ideological.

Agree, now in the media you can really find a lot of information

April 26 - Day of Remembrance of those killed in radiation accidents and disasters. This year marks 27 years since the Chernobyl disaster - the largest ever nuclear power in the world.

A whole generation has grown up that has not seen this terrible tragedy, but on this day we traditionally remember Chernobyl. After all, only remembering the mistakes of the past can one hope not to repeat them in the future.

In 1986, an explosion occurred at the Chernobyl reactor No. 4, and several hundred workers and firefighters tried to extinguish the fire that burned for 10 days. The world was enveloped in a cloud of radiation. Then about 50 station employees were killed and hundreds of rescuers were injured. It is still difficult to determine the scale of the disaster and its impact on human health - from 4,000 to 200,000 people died from cancer, which developed as a result of the radiation dose received. Pripyat and the surrounding areas will remain unsafe for human habitation for several centuries.

This 1986 aerial view of the Chernobyl nuclear power plant in Chernobyl, Ukraine, shows the destruction from the explosion and fire of Reactor 4 on April 26, 1986. As a result of the explosion and the fire that followed, a huge amount of radioactive substances were released into the atmosphere. Ten years after the world's largest nuclear disaster, the power plant continued to operate due to an acute shortage of electricity in Ukraine. The final shutdown of the power plant took place only in 2000. (AP Photo / Volodymyr Repik)

On October 11, 1991, with a decrease in the speed of the turbine generator No. 4 of the second power unit for its subsequent shutdown and withdrawal of the SPP-44 separator-superheater for repair, an accident and a fire occurred. This photograph, taken during a visit by journalists to the station on October 13, 1991, shows part of the collapsed roof of the Chernobyl nuclear power plant, destroyed by fire. (AP Photo / Efrm Lucasky)

Aerial view of the Chernobyl nuclear power plant after the largest nuclear disaster in the history of mankind. The picture was taken three days after the explosion at the nuclear power plant in 1986. The destroyed 4th reactor is located in front of the chimney. (AP Photo)

Photo from the February issue of the magazine "Soviet Life": the main hall of the 1st power unit of the Chernobyl nuclear power plant on April 29, 1986 in Chernobyl (Ukraine). The Soviet Union admitted that an accident had occurred at the power plant, but did not provide additional information. (AP Photo)

A Swedish farmer removes the straw contaminated by rainfall a few months after the explosion at the Chernobyl nuclear power plant in June 1986. (STF / AFP / Getty Images)

A Soviet medical worker examines an unknown child who was evacuated from the nuclear disaster zone to the Kopelovo state farm near Kiev on May 11, 1986. The photograph was taken during a trip organized by the Soviet authorities to show how they dealt with the accident. (AP Photo / Boris Yurchenko)

Chairman of the Presidium of the Supreme Soviet of the USSR Mikhail Gorbachev (center) and his wife Raisa Gorbacheva during a conversation with the leadership of the nuclear power plant on February 23, 1989. This was the first visit by a Soviet leader to the station after the accident in April 1986. (AFP PHOTO / TASS)

People in Kiev queue up for forms before being checked for radiation contamination after the Chernobyl disaster, in Kiev on May 9, 1986. (AP Photo / Boris Yurchenko)

A boy reads an ad on the closed gate of a playground in Wiesbaden on May 5, 1986, which reads: "This playground is temporarily closed." A week after the explosion of a nuclear reactor in Chernobyl on April 26, 1986, the Wiesbaden municipal council closed all playgrounds after detecting radioactivity levels from 124 to 280 becquerels. (AP Photo / Frank Rumpenhorst)

One of the engineers who worked at the Chernobyl nuclear power plant undergoes a medical examination at the Lesnaya Polyana sanatorium on May 15, 1986, a few weeks after the explosion. (STF / AFP / Getty Images)

Environmental activists mark railroad cars containing radiation-contaminated whey powder. Photo taken in Bremen, northern Germany on February 6, 1987. The serum, which was delivered to Bremen for onward transport to Egypt, was produced after the Chernobyl accident and was contaminated with radioactive fallout. (AP Photo / Peter Meyer)

A slaughterhouse worker places fitness stamps on cow carcasses in Frankfurt am Main, West Germany, May 12, 1986. According to the decision of the Minister of Social Affairs of the federal state of Hesse, after the explosion at the Chernobyl nuclear power plant, all meat began to be subjected to radiation control. (AP Photo / Kurt Strumpf / stf)

Archive photo dated April 14, 1998. Workers of the Chernobyl nuclear power plant walk past the control panel of the destroyed 4th power unit of the plant. On April 26, 2006, Ukraine celebrated the 20th anniversary of the Chernobyl disaster, which affected the fate of millions of people, demanded astronomical costs from international funds and became an ominous symbol of the danger of atomic energy. (AFP PHOTO / GENIA SAVILOV)

The picture taken on April 14, 1998 shows the control panel of the 4th power unit of the Chernobyl nuclear power plant. (AFP PHOTO / GENIA SAVILOV)

Workers who took part in the construction of a cement sarcophagus covering the Chernobyl reactor, in a memorable photo in 1986, next to an unfinished construction site. According to the "Union of Chernobyl of Ukraine" thousands of people who took part in the liquidation of the consequences of the Chernobyl disaster, died from the consequences of radiation contamination, from which they suffered during their work. (AP Photo / Volodymyr Repik)

High-voltage towers near the Chernobyl nuclear power plant on June 20, 2000 in Chernobyl. (AP Photo / Efrem Lukatsky)

A nuclear reactor operator on duty records control readings at the site of the only operating reactor # 3 on Tuesday 20 June 2000. Andrei Shauman angrily poked in the direction of a switch hidden under a sealed metal cover on the control panel of a reactor in Chernobyl, a nuclear power plant whose name has become synonymous with nuclear disaster. “This is the same switch with which you can turn off the reactor. For 2 thousand dollars, I will allow anyone to press this button when the time comes, "- said then Shauman, acting chief engineer. When that very time came on December 15, 2000, environmental activists, governments and ordinary people around the world breathed a sigh of calm. However, for 5800 Chernobyl workers, it was a day of mourning. (AP Photo / Efrem Lukatsky)

17-year-old Oksana Gaibon (right) and 15-year-old Alla Kozimerka, injured in the 1986 Chernobyl disaster, are being treated with infrared rays at the Tarara Children's Hospital in the Cuban capital. Oksana and Alla, like hundreds of other Russian and Ukrainian teenagers who received a dose of radiation, received free treatment in Cuba as part of a humanitarian project. (ADALBERTO ROQUE / AFP)

Photo dated April 18, 2006. A child during treatment at the Center for Pediatric Oncology and Hematology, which was built in Minsk after the accident at the Chernobyl nuclear power plant. On the eve of the 20th anniversary of the Chernobyl disaster, representatives of the Red Cross reported that they were faced with a lack of funds for further assistance to the victims of the Chernobyl disaster. (VIKTOR DRACHEV / AFP / Getty Images)

View of the city of Pripyat and the fourth reactor of Chernobyl on December 15, 2000, the day of the complete shutdown of the Chernobyl nuclear power plant. (Photo by Yuri Kozyrev / Newsmakers)

A Ferris wheel and a merry-go-round at a deserted amusement park in the ghost town of Pripyat next to the Chernobyl nuclear power plant on May 26, 2003. The population of Pripyat, which in 1986 was 45,000 people, was completely evacuated within the first three days after the explosion of the 4th reactor No. 4. The explosion at the Chernobyl nuclear power plant thundered at 1:23 am on April 26, 1986. The resulting radioactive cloud damaged much of Europe. According to various estimates, from 15 to 30 thousand people later died as a result of radiation exposure. Over 2.5 million people in Ukraine suffer from diseases acquired as a result of radiation, and about 80 thousand of them receive benefits. (AFP PHOTO / SERGEI SUPINSKY)

In the photo dated May 26, 2003: an abandoned amusement park in the city of Pripyat, which is located next to the Chernobyl nuclear power plant. (AFP PHOTO / SERGEI SUPINSKY)

Photo from May 26, 2003: gas masks on the floor of a classroom in one of the schools in the ghost town of Pripyat, which is located near the Chernobyl nuclear power plant. (AFP PHOTO / SERGEI SUPINSKY)

In the photo dated May 26, 2003: a TV case in the room of one of the hotels in the city of Pripyat, which is located not far from the Chernobyl nuclear power plant. (AFP PHOTO / SERGEI SUPINSKY)

View of the ghost town of Pripyat in the vicinity of the Chernobyl nuclear power plant. (AFP PHOTO / SERGEI SUPINSKY)

Photo from January 25, 2006: an abandoned classroom in one of the schools of the deserted city of Pripyat near Chernobyl, Ukraine. Pripyat and the surrounding areas will remain unsafe for human habitation for several centuries. Scientists estimate that the complete decomposition of the most dangerous radioactive elements will take about 900 years. (Photo by Daniel Berehulak / Getty Images)

Textbooks and notebooks on the floor of a school in the ghost town of Pripyat on January 25, 2006. (Photo by Daniel Berehulak / Getty Images)

Toys and a gas mask in the dust in the former primary school the abandoned city of Pripyat on January 25, 2006. (Daniel Berehulak / Getty Images)

In the photo on January 25, 2006: an abandoned gymnasium of one of the schools of the deserted city of Pripyat. (Photo by Daniel Berehulak / Getty Images)

What's left of a school gym in the abandoned city of Pripyat. January 25, 2006. (Daniel Berehulak / Getty Images)

A woman with piglets in the deserted Belarusian village of Tulgovichi, 370 km southeast of Minsk, April 7, 2006. This village is located within a 30-kilometer zone around the Chernobyl nuclear power plant. (AFP PHOTO / VIKTOR DRACHEV)

A resident of the Belarusian village of Novoselki, located just outside the 30-kilometer exclusion zone around the Chernobyl nuclear power plant, in the photo from April 7, 2006. (AFP PHOTO / VIKTOR DRACHEV)

On April 6, 2006, an employee of the Belarusian radiation-ecological reserve measures the level of radiation in the Belarusian village of Vorotets, which is located within a 30-kilometer zone around the Chernobyl nuclear power plant. (VIKTOR DRACHEV / AFP / Getty Images)

Residents of the village of Ilyintsy in a closed area around the Chernobyl nuclear power plant, about 100 km from Kiev, walk past the rescuers of the Ministry of Emergencies of Ukraine, who are rehearsing before a concert on April 5, 2006. Rescuers organized an amateur concert dedicated to the 20th anniversary of the Chernobyl disaster for more than three hundred people (mostly elderly people) who returned to illegal residence in villages located in the exclusion zone around the Chernobyl nuclear power plant. (SERGEI SUPINSKY / AFP / Getty Images)

The remaining residents of the abandoned Belarusian village Tulgovichi, located in a 30-kilometer exclusion zone around the Chernobyl nuclear power plant, on April 7, 2006, celebrate Orthodox holiday Annunciation of the Virgin. Before the accident, about 2,000 people lived in the village, but now there are only eight left. (AFP PHOTO / VIKTOR DRACHEV)

A worker at the Chernobyl nuclear power plant measures the level of radiation using a stationary radiation monitoring system at the exit from the power plant building after office hours on April 12, 2006. (AFP PHOTO / GENIA SAVILOV)

Construction team in masks and special protective suits April 12, 2006 during work to strengthen the sarcophagus covering the destroyed 4th reactor of the Chernobyl nuclear power plant. (AFP PHOTO / GENIA SAVILOV)

On April 12, 2006, workers sweep away radioactive dust in front of the sarcophagus covering the damaged 4th reactor of the Chernobyl nuclear power plant. Due to the high level of radiation, the brigades only work for a few minutes. (GENIA SAVILOV / AFP / Getty Images)