Chernobyl accident causes and consequences briefly. Chernobyl

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

A whole generation has grown up without this terrible tragedy, but on this day we traditionally remember Chernobyl. After all, only by remembering the mistakes of the past can we hope not to repeat them in the future.

In 1986, an explosion occurred at Chernobyl reactor No. 4, and several hundred workers and firefighters tried to put out the fire, which burned for 10 days. The world was enveloped in a cloud of radiation. 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 people’s health - only from 4 to 200 thousand people died from cancer that developed as a result of the received dose of radiation. Pripyat and the surrounding areas will remain unsafe for human habitation for several centuries.

This 1986 aerial photo of the Chernobyl nuclear power plant in Chernobyl, Ukraine, shows the damage from the explosion and fire of reactor No. 4 on April 26, 1986. As a result of the explosion and fire that followed it, a huge amount of radioactive substances were released into the atmosphere. Ten years after the world's worst nuclear disaster, the power plant continued to operate due to severe power shortages in Ukraine. The final shutdown of the power plant occurred only in 2000. (AP Photo/Volodymyr Repik)

On October 11, 1991, when the speed of turbogenerator No. 4 of the second power unit was reduced for its subsequent shutdown and removal of the SPP-44 steam separator-superheater for repair, an accident and fire occurred. This photo, taken during a journalists' visit to the plant 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 human history. The photo was taken three days after the explosion at the nuclear power plant in 1986. In front of the chimney is the destroyed 4th reactor. (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 acknowledged that there was an accident at the power plant, but did not provide additional information. (AP Photo)

A Swedish farmer removes straw contaminated by radiation a few months after the Chernobyl nuclear power plant explosion 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 photo was taken during a trip organized by Soviet authorities to show how they were coping 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 management of the nuclear power plant on February 23, 1989. This was the first visit of the Soviet leader to the station since the accident in April 1986. (AFP PHOTO/TASS)

Kiev residents queue for forms before being tested for radiation contamination after the accident at the Chernobyl nuclear power plant, in Kyiv on May 9, 1986. (AP Photo/Boris Yurchenko)

A boy reads a notice on the closed gate of a playground in Wiesbaden on May 5, 1986, which reads: “This playground is temporarily closed.” A week after the Chernobyl nuclear reactor explosion on April 26, 1986, the Wiesbaden municipal council closed all playgrounds after detecting radioactivity levels of 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 are tagging train 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 nuclear power plant accident and was contaminated by 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 Chernobyl explosion, all meat began to be subject to radiation control. (AP Photo/Kurt Strumpf/stf)

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

In the photo, which was taken on April 14, 1998, you can see 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 the cement sarcophagus covering the Chernobyl reactor are pictured in a memorable photo from 1986 next to the unfinished construction site. According to the Chernobyl Union 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, 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 No. 3, Tuesday, June 20, 2000. Andrei Shauman angrily pointed at a switch hidden under a sealed metal cover on the control panel of the reactor at 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 $2,000, I’ll let anyone push that button when the time comes,” Schauman, acting chief engineer, said at the time. When that time came on December 15, 2000, environmental activists, governments and ordinary people around the world breathed a sigh of relief. However, for the 5,800 workers at Chernobyl, it was a day of mourning. (AP Photo/Efrem Lukatsky)

17-year-old Oksana Gaibon (right) and 15-year-old Alla Kozimerka, victims of the 1986 Chernobyl disaster, are 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, were treated for free 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 to further assist the victims of the Chernobyl accident. (VIKTOR DRACHEV/AFP/Getty Images)

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

A Ferris wheel and carousel in 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 occurred at 1:23 a.m. on April 26, 1986. The resulting radioactive cloud damaged much of Europe. According to various estimates, from 15 to 30 thousand people subsequently died as a result of radiation exposure. Over 2.5 million residents of 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 from 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)

In the 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 from May 26, 2003: a TV case in a hotel room in the city of Pripyat, which is located near the Chernobyl nuclear power plant. (AFP PHOTO/ SERGEI SUPINSKY)

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

Photo from January 25, 2006: an abandoned classroom in one of the schools in 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 one of the schools 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 a former elementary school in the abandoned city of Pripyat on January 25, 2006. (Daniel Berehulak/Getty Images)

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

What remains of the 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 the 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 a photo taken on 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 the 30-kilometer zone around the Chernobyl nuclear power plant. (VIKTOR DRACHEV/AFP/Getty Images)

Residents of the village of Ilintsy in the closed zone around the Chernobyl nuclear power plant, about 100 km from Kyiv, pass by rescuers from the Ukrainian Ministry of Emergency Situations who are rehearsing before a concert on April 5, 2006. Rescuers organized an amateur concert on the 20th anniversary of the Chernobyl disaster for more than three hundred people (mostly elderly people) who returned to live illegally 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 of Tulgovichi, located in the 30-kilometer exclusion zone around the Chernobyl nuclear power plant, celebrate the Orthodox holiday of the Annunciation of the Virgin Mary on April 7, 2006. Before the accident, about 2,000 people lived in the village, but now only eight remain. (AFP PHOTO / VIKTOR DRACHEV)

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

A construction crew wearing masks and special protective suits on 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 high radiation levels, crews only work for a few minutes at a time. (GENIA SAVILOV/AFP/Getty Images)

The Chernobyl disaster is gradually being forgotten, although it seemed that the most grandiose man-made disaster in the history of mankind in terms of its scale and consequences - the accident at the Chernobyl nuclear power plant - will forever be etched in human memory and will serve as a menacing warning to people living today and their descendants that the nucleus of an atom must always be dealt with talk to YOU ​​about the frivolous, self-confident attitude towards nuclear energy,

The article examines the technical side of this huge tragedy. I tell specialists in advance that much is given here in an extremely simplified form, in some places even to the detriment of scientific accuracy. This was done so that even a person very far from physics and nuclear energy would understand what happened and why on the night of April 25-26, 1986.

Although this disaster is not directly related to military science and history, it was the “stupid and illiterate, rude and stupid” army that had to use the lives and health of its soldiers and officers to correct the mistakes of the “intelligent geniuses of science, the concentration of all the best that is in our society ".
It was highly educated and technically competent nuclear scientists, all these “Promstroykompleks”, “Atomstroy”, Dontekhenergo”, all the venerable academicians, doctors of sciences who managed to arrange this disaster, but were unable to either organize work to eliminate the consequences or manage all the material resources provided at their disposal.

It turned out that they simply did not know what to do now, they did not know the processes occurring in the reactor. You should have seen their shaking hands, confused faces, and pitiful babble of self-justification in those days.

Orders and decisions were either made or cancelled, but nothing was done. And radioactive dust rained down on the heads of Kiev residents.

And only when the head of the chemical forces of the Ministry of Defense got down to work and troops began to gather at the site of the tragedy; When at least some concrete work began, these “scientists” breathed a sigh of relief. Now you can again intelligently argue about the scientific aspects of the problem, give interviews, criticize the mistakes of the military, and tell tales about your scientific foresight.

Physical processes occurring in a nuclear reactor

A nuclear power plant is not much different from a thermal power plant. The whole difference is that in a thermal power plant, steam for turbines driving electric generators is obtained by heating water from the combustion of coal, fuel oil, gas in the furnaces of steam boilers, and in a nuclear power plant, steam is obtained in a nuclear reactor from the same water.

When the atomic nucleus of heavy elements decays, several neutrons are released from it. The absorption of such a free neutron by another atomic nucleus causes excitation and decay of this nucleus. At the same time, several neutrons are also released from it, which in turn... The so-called nuclear chain reaction begins, accompanied by the release of thermal energy.

Attention! First term! Multiplication factor - K. If at a given stage of the process the number of free neutrons formed is equal to the number of neutrons that caused nuclear fission, then K = 1 and each unit of time the same amount of energy is released, but if the number of free neutrons formed is greater than the number of neutrons that caused nuclear fission , then K>1 and at each subsequent moment of time the energy release will increase. And if the number of free neutrons produced is less than the number of neutrons that caused nuclear fission, then K<1 и в каждый следующий момент времени выделение энергии будет уменьшаться.
The task of the power plant duty shift personnel is precisely to keep K approximately equal to 1. If K<1, то реакция будет затухать, количество вырабатываемого пара уменьшаться, пока реактор не остановится. Если К>1 and it cannot be made equal to 1, then what happened at the Chernbyl nuclear power plant will happen.

It seems easy to come to the conclusion that the nuclear fission reaction will increase all the time, because One free neutron during the splitting of an atomic nucleus releases 2-3 neutrons and the number of free neutrons should increase all the time.
To prevent this from happening, tubes containing a substance that absorbs neutrons well (cadmium or boron) are placed between the tubes containing nuclear fuel. By moving such tubes out of the reactor core, or vice versa, introducing such tubes into the zone, they can be used to capture some of the free neutrons, thus regulating their number in the reactor core and maintaining the K coefficient close to unity.

When uranium nuclei fission, nuclei of lighter elements are formed from their fragments. Among them is tellurium-135, which turns into iodine-135, and iodine in turn quickly turns into xenon-135. This xenon is very active in capturing free neutrons. If the reactor operates in a stable mode, then the xenon-135 atoms burn out quite quickly and do not affect the operation of the reactor. However, if there is a sharp and rapid decrease in reactor power for some reason, xenon does not have time to burn out and begins to accumulate in the reactor, significantly reducing K, i.e. helping to reduce reactor power. The phenomenon of so-called (Attention! Second term!) xenon poisoning of the reactor is growing. At the same time, the iodine-135 accumulated in the reactor begins to turn into xenon even more actively. This phenomenon is called (Attention! Third term!) iodine pit.
Under such conditions, the reactor does not respond well to the extension of control rods (tubes with boron or cadmium), because neutrons are actively absorbed by xenon. However, in the end, with a sufficiently significant extension of the control rods from the core, the power of the reactor begins to increase, heat generation increases, and xenon begins to burn out very quickly. It no longer captures free neutrons and their number is rapidly increasing. The reactor gives a sharp jump in power. The control rods lowered at this moment do not have time to absorb the neutrons quickly enough. The reactor may escape the operator's control.

The instructions require that when there is a certain amount of xenon in the core, do not try to increase the power of the reactor, but by lowering the control rods, finally stop the reactor. But the natural removal of xenon from the reactor core takes up to several days. All this time, no electricity is generated by this energy unit.

There is another term - reactor reactivity, i.e. how the reactor responds to operator actions. This coefficient is determined by the formula p=(K-1)/K. At p>0 the reactor accelerates, at p=0 the reactor operates in a stable mode, at p< 0 идет затухание реактора.

Principles of reactor design

Nuclear fuel is black tablets with a diameter of about 1 cm and a height of about 1.5 cm. They contain 2% uranium dioxide 235, and 98% uranium 238, 236, 239. In all cases, with any amount of nuclear fuel, a nuclear explosion cannot develop , because for an avalanche-like rapid fission reaction characteristic of a nuclear explosion, a concentration of uranium 235 of more than 60% is required.

Two hundred nuclear fuel pellets are loaded into a tube made of zirconium metal. The length of this tube is 3.5m. diameter 1.35 cm. This tube is called (Attention! Fifth term!) Fuel element - fuel element.

36 fuel rods are assembled into a cassette (another name is “assembly”).

The RBMK-1000 brand reactor (high-power channel reactorchernob-5.jpg (7563 bytes) with an electric power of 1000 megawatts) is a cylinder with a diameter of 11.8 m and a height of 7 meters, made of graphite blocks (the size of each block is 25x25x60cm. Through each The block passes through a hole - a channel. There are a total of 1872 such holes - channels in this cylinder. 1661 channels are intended for cartridges with nuclear fuel, and 211 for control rods containing a neutron absorber (cadmium or boron).
This cylinder is surrounded by a 1 meter thick wall made of the same graphite blocks, but without holes. The whole thing is surrounded by a steel tank filled with water. This entire structure lies on a metal plate and is covered on top with another plate (lid). The total weight of the reactor is 1850 tons. The total mass of nuclear fuel in the reactor is 190 tons.

In the figure on the left is an assembly with fuel rods in the reactor channel, on the right is a control rod in the reactor channel.

Each reactor supplies steam to two turbines. Each turbine has an electrical power of 500 megawatts. The thermal power of the reactor is 3200 megawatts.

The operating principle of the reactor is as follows:

Water under pressure of 70 atmospheres by main circulation pumps
The main circulation pump is supplied through pipelines to the lower part of the reactor, from where it is pressed through the channels into the upper part of the reactor, washing the assemblies with fuel rods.

In fuel rods, under the influence of neutrons, a nuclear chain reaction occurs with the release of a large amount of heat. The water heats up to a temperature of 248 degrees and boils. A mixture of 14% steam and 86% water is supplied through pipelines to separator drums, where steam is separated from water. Steam is supplied through a pipeline to the turbine.

From the turbine, through a pipeline, steam, which has already turned into water with a temperature of 165 degrees, returns to the separator drum, where it mixes with hot water coming from the reactor and cools it to 270 degrees. This water is again supplied through the pipeline to the pumps. The cycle is complete. Additional water can be supplied to the separator from outside through the pipeline (6).

There are only eight main circulation pumps. Six of them are in operation, and two are in reserve. There are only four separator drums. The dimensions of each are 2.6 m in diameter, 30 meters long. They work simultaneously.

Prerequisites for disaster

The reactor is not only a source of electricity, but also its consumer. Until nuclear fuel is unloaded from the reactor core, water must be continuously pumped through it so that the fuel rods do not overheat.

Typically, part of the electrical power of turbines is selected for the reactor's own needs. If the reactor is shut down (fuel replacement, preventive maintenance, emergency shutdown), then the reactor is powered from neighboring units or an external power grid.

In case of extreme emergency, power is provided from backup diesel generators. However, in the best case scenario, they will be able to start producing electricity no sooner than in one to three minutes.

The question arises: how to power the pumps until the diesel generators reach operating mode? It was necessary to find out how long from the moment the steam supply to the turbines is turned off, they, rotating by inertia, will generate a current sufficient for emergency power supply to the main reactor systems. The first tests showed that the turbines cannot provide electricity to the main systems in the inertial rotation mode (coasting mode).

Dontekhenergo specialists proposed their own system for controlling the magnetic field of the turbine, which promised to solve the problem of power supply to the reactor in the event of an emergency shutdown of the steam supply to the turbine.
On April 25, it was planned to test this system in operation, because... The 4th power unit was still planned to be shut down for repair work that day.

However, it was necessary, firstly, to use something as a ballast load so that measurements could be taken on a running-out turbine. Secondly, it was known that if the thermal power of the reactor dropped to 700-1000 megawatts, the reactor emergency shutdown system (ERS) would be triggered, the reactor would be shut down and it would be impossible to repeat the experiment several times, because xenon poisoning will occur.

It was decided to block the ECCS system and use backup main circulation pumps as a ballast load.
(main central pump)

These were the FIRST and SECOND tragic mistakes that led to everything else.

Firstly, there was absolutely no need to block the ECCS.
Secondly, anything could be used as a ballast load, but not circulation pumps.

It was they who connected the completely distant electrical processes and processes occurring in the reactor.

Chronicle of the disaster

13.05. The reactor power was reduced from 3200 megawatts to 1600. Turbine No. 7 was stopped. Power supply to the reactor electrical systems was transferred to turbine No. 8.

14.00. The emergency shutdown system of the ECCS reactor is blocked. At this time, the Kievenergo dispatcher ordered to delay the shutdown of the unit (end of the week, afternoon, energy consumption is growing). The reactor is operating at half power, and the ECCS has not been reconnected. This was a gross mistake by the staff, but it did not affect the development of events.

23.10. The dispatcher lifts the ban. The personnel begins to reduce the power of the reactor.

April 26, 1986 0.28. The reactor power has decreased to a level where the system for controlling the movement of the control rods must be transferred from local to general (in normal mode, groups of rods can be moved independently of each other - this is more convenient, but at low power all rods must be controlled from one place and move simultaneously).

This was not done. This was the THIRD tragic mistake. At the same time, the operator makes a FOURTH tragic mistake. It does not command the car to "hold power". As a result, the reactor power is rapidly reduced to 30 megawatts. Boiling in the channels decreased sharply, and xenon poisoning of the reactor began.

The shift staff makes the FIFTH tragic mistake (I would give a different assessment to the actions of the shift at this moment. This is no longer a mistake, but a crime. All instructions require shutting down the reactor in such a situation). The operator removes all control rods from the core.

1.00. The reactor power was raised to 200 megawatts against the 700-1000 prescribed by the test program. This was the second criminal act of the shift. Due to the growing xenon poisoning of the reactor, the power cannot be raised higher.

1.03. The experiment began. The seventh pump is connected to the six operating main circulation pumps as a ballast load.

1.07. The eighth pump is connected as a ballast load. The system is not designed to operate such a number of pumps. The cavitation failure of the main circulation pump began (they simply do not have enough water). They suck water out of the separator drums and its level in them drops dangerously. The huge flow of fairly cold water through the reactor reduced steam generation to a critical level. The machine completely removed the automatic control rods from the core.

1.19. Due to the dangerously low water level in the separator drums, the operator increases the supply of feed water (condensate) to them. At the same time, the staff makes the SIXTH tragic mistake (I would say the second criminal act). It blocks reactor shutdown systems based on signals of insufficient water level and steam pressure.

1.19.30 The water level in the separator drums began to rise, but due to a decrease in the temperature of the water entering the reactor core and its large quantity, boiling there stopped.

The last automatic control rods left the core. The operator makes his SEVENTH tragic mistake. He completely removes the last manual control rods from the core, thereby depriving himself of the ability to control the processes occurring in the reactor.

The fact is that the height of the reactor is 7 meters and it responds well to the movement of the control rods when they move in the middle part of the core, and as they move away from the center, controllability deteriorates. The speed of movement of the rods is 40 cm. per second

1.21.50 The water level in the separator drums has slightly exceeded the norm and the operator turns off some of the pumps.

1.22.10 The water level in the separator drums has stabilized. Much less water now enters the core than before. Boiling begins again in the core.

1.22.30 Due to the inaccuracy of the control systems, which were not designed for such an operating mode, it turned out that the water supply to the reactor was about 2/3 of what was required. At this moment, the station computer issues a printout of the reactor parameters indicating that the reactivity margin is dangerously low. However, the staff simply ignored this data (this was the third criminal act that day). The instructions prescribe in such a situation to immediately shut down the reactor in an emergency manner.

1.22.45 The water level in the separators has stabilized, and the amount of water entering the reactor has been brought back to normal.

The thermal power of the reactor slowly began to increase. The staff assumed that the operation of the reactor had been stabilized and it was decided to continue the experiment.

This was the EIGHTH tragic mistake. After all, practically all the control rods were in the raised position, the reactivity margin was unacceptably small, the ECCS was disabled, and the systems for automatically shutting down the reactor due to abnormal steam pressure and water level were blocked.

1.23.04 Personnel blocks the reactor emergency shutdown system, which is triggered in the event of a loss of steam supply to the second turbine, if the first one has already been turned off. Let me remind you that turbine No. 7 was turned off at 13.05 on 25.04 and now only turbine No. 8 was working.

This was the NINTH tragic mistake. (and the fourth criminal act this day). The instructions prohibit disabling this reactor emergency shutdown system in all cases. At the same time, the personnel shuts off the steam supply to turbine No. 8. This is an experiment to measure the electrical characteristics of the turbine in run-down mode. The turbine begins to lose speed, the voltage in the network decreases and the main circulation pump powered by this turbine begins to reduce speed.

The investigation established that if the emergency shutdown system of the reactor had not been turned off by a signal that the steam supply to the last turbine had been stopped, the disaster would not have occurred. Automation would have shut down the reactor.
But the staff intended to repeat the experiment several times using different parameters for controlling the magnetic field of the generator. Shutting down the reactor excluded this possibility.

1.23.30 The main circulation pumps significantly reduced their speed and the flow of water through the reactor core decreased significantly. Steam formation began to rapidly increase. Three groups of automatic control rods went down, but they could not stop the increase in the thermal power of the reactor, because there weren't enough of them anymore. Because The steam supply to the turbine was turned off, its speed continued to decrease, and the pumps supplied less and less water to the reactor.

1.23.40 The shift supervisor, realizing what is happening, orders to press the AZ-5 button. At this command, the control rods move down at maximum speed. Such a massive introduction of neutron absorbers into the reactor core is intended to completely stop nuclear fission processes in a short time.

This was the last TENTH tragic personnel error and the last direct cause of the disaster. Although it should be said that if this last mistake had not been made, then the catastrophe would have been inevitable.

And this is what happened - at a distance of 1.5 meters under each rod
the so-called “displacer” is suspended
This is an aluminum cylinder 4.5 m long, filled with graphite. Its task is to ensure that when the control rod is lowered, the increase in neutron absorption does not occur abruptly, but more smoothly. Graphite also absorbs neutrons, but somewhat weaker. than boron or cadmium.

When the control rods are raised to their maximum limit, the lower ends of the displacers are 1.25 m above the lower boundary of the core. In this space there is water that is not yet boiling. When all the rods sharply went down the AZ-5 singal, the rods themselves with boron and cadmium had not yet actually entered the active zone, and the displacer cylinders, acting like pistons, displaced this water from the active zone. The fuel rods were exposed.

There was a sharp jump in vaporization. The steam pressure in the reactor increased sharply and this pressure did not allow the rods to fall down. They hovered after walking only 2 meters. The operator turns off the power to the rod couplings.
Pressing this button turns off the electromagnets that keep the control rods attached to the valve. After such a signal is given, absolutely all the rods (both manual and automatic control) are disconnected from their reinforcement and freely fall down under the influence of their own weight. But they were already hanging, supported by steam, and did not move.

1.23.43 Self-acceleration of the reactor began. Thermal power reached 530 megawatts and continued to grow rapidly. The last two emergency protection systems were activated - by power level and by the rate of power growth. But both of these systems control the issuance of the AZ-5 signal, and it was given manually 3 seconds ago.

1.23.44 In a split second, the thermal power of the reactor increased 100 times and continued to increase. The fuel rods became hot, and the swelling fuel particles tore the shells of the fuel rods. The pressure in the core increased many times over. This pressure, overcoming the pressure of the pumps, forced the water back into the supply pipelines.
Further, the steam pressure destroyed part of the channels and steam pipelines above them.

This was the moment of the first explosion.

The reactor ceased to exist as a controlled system.

After the destruction of the channels and steam lines, the pressure in the reactor began to drop and water again flowed into the reactor core.

Chemical reactions of water with nuclear fuel, heated graphite, and zirconium began. During these reactions, rapid formation of hydrogen and carbon monoxide began. The gas pressure in the reactor rapidly increased. The reactor cover, weighing about 1,000 tons, lifted, breaking all the pipelines.

1.23.46 The gases in the reactor combined with atmospheric oxygen, forming an explosive gas, which instantly exploded due to the high temperature.

This was the second explosion.

The reactor lid flew up, turned 90 degrees and fell back down again. The walls and ceiling of the reactor hall collapsed. A quarter of the graphite located there and fragments of hot fuel rods flew out of the reactor. These debris fell on the roof of the turbine hall and other places, creating about 30 fires.

The fission chain reaction has stopped.

The station staff began leaving their jobs at approximately 1.23.40. But from the moment the AZ-5 signal was issued until the moment of the second explosion, only 6 seconds passed. It is impossible to figure out what is happening during this time, and even more so to have time to do something to save yourself. The employees who survived the explosion left the hall after the explosion.

At 1.30 a.m. the first fire brigade, Lieutenant Pravik, arrived at the scene of the fire.

What happened next, who behaved how and what was done correctly and what was wrong is no longer the topic of this article.

author Yuri Veremeev

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3. O.F.Kabardin. Physics. Reference materials. Education. Moscow. 1991
4.A.G.Alenitsin, E.I.Butikov, A.S.Kondratiev. Brief physical and mathematical reference book. The science. Moscow. 1990
5. Report of the IAEA expert group “On the causes of the accident of the RBMK-1000 nuclear reactor at the Chernobyl power plant on April 26, 1986.” Uralurizdat. Ekaterinburg. 1996
6. Atlas of the USSR. Main Directorate of Geodesy and Cartography under the Council of Ministers of the USSR. Moscow. 1986

Thirty-two years ago, one of the power units of the Chernobyl nuclear power plant suddenly experienced a strong explosion. Since then, the history of these events began to become overgrown with myths and by now it has become so densely overgrown with them that few people today remember the causes and consequences of those events. Let's try to restore them using the documents.

Why did the reactor explode?

Most often, the cause of the explosion is called an “experiment.” They say that at a nuclear power plant they experimented with turning off the cooling, and so that the automatic protection would not interrupt the experiment, it was turned off. In fact, on April 26, 1986, scheduled maintenance was underway at the station. And each such repair for a reactor like RBMK included tests of operation in abnormal modes, and during these tests the automatic protection was always turned off. Since “experiments” were carried out often, and they led to a disaster only once, it is clear: the experiment was not the cause of the accident.

Photo: © RIA Novosti / Vitaly Ankov

The latter figure has been criticized on two sides. Greenpeace criticizes it for being too small and offers its own figure - 92,000 people. However, unfortunately, he never even tried to substantiate it or report by what method it was obtained. Because of this, no one takes her seriously. No studies could find traces of the congenital deformities of newborns repeatedly promised by the organization. When asked where Greenpeace gets information about such deformities, representatives of the organization bashfully remained silent.

However, scientists also criticize the figure. As they rightly point out, the estimate of 4000 may be greatly overestimated. She relies on hypothesis about the non-threshold harm of radiation- that even negligibly small doses increase the likelihood of cancer and other diseases. Critics of this hypothesis note, that it has never been proven by any factual data, that is, in fact, it is an unsupported assumption. They remind: in places of very high radioactive background - close to Pripyat in the first years after the accident - there is no evidence of an increased incidence of cancer. On the contrary, in the Iranian city of Ramsar, where the highest natural background level on Earth (radioactive water), cancer less common, than on the planet on average.

However, we would recommend ignoring such criticism. Yes, there is no scientific evidence for the idea of ​​no threshold harm from radiation. And perhaps it cannot be, since it is generally difficult to find confirmation of ideas that clearly contradict observations (in the same Ramsar). But still, 4,000 people are the only existing estimate of the potential number of victims (fortunately, no one takes Greenpeace’s version seriously, including its authors). Therefore, it is precisely this figure that is worth starting from.

Exclusion Zone

People tend to be afraid of everything big and incomprehensible. Everyone thinks they know how a car works, but not a very large part of the population can handle a correct explanation of why a plane flies. Therefore, there are few people who are afraid to ride in a car, but there are many aviophobes. And it is completely useless to tell them that the probability of dying in a car is an order of magnitude greater. The facts in such cases are subjectively unimportant, but what is subjectively important is that a person is afraid of everything big and incomprehensible.

The same story happened with the nuclear power plant. Everyone thinks they know how a thermal power plant works, but far fewer people have an idea of ​​how a nuclear power plant works. Naturally, this does not include politicians. Therefore, the people who made the decision to evacuate had no idea that the radioactive contamination zone became relatively safe after the decay of the shortest-lived isotopes. And they had no time to delve into all this - the shock from the world’s first nuclear power plant accident was too great. But politicians, according to the stories of the military, very highly appreciated the power of nuclear weapons.

Therefore, the decision to evacuate was made with a large margin. As shown 2016 study, out of 336 thousand evacuees, only 31 thousand lived in the threatened zone, where evacuation was actually required - those who were closest to the emergency reactor.

Photo: © RIA Novosti / Igor Kostin

Chernobyl: nuclear power's gravedigger, nuclear power's justification

As you know, after the accident, the construction of nuclear power plants around the world began to decline and has not yet recovered to its previous level. And it will not recover - radiophobia is strong and, just like the fear of airplanes, is invincible by any reasonable arguments. You should just accept this and not try to change anything. The current virtual abandonment of nuclear energy by most developed countries of the world is not the first irrational decision in the history of mankind and certainly not the last.

However, from the point of view of a future historian, the Chernobyl accident is a very important marker. It shows how dangerous nuclear power really is. And these indications are quite unexpected. Taking into account Chernobyl, nuclear power plant give 90 deaths for every trillion kilowatt-hours produced. A country like Russia consumes a trillion kilowatt-hours per year.

There are also more dangerous types of energy. The most lethal radionuclides released from a reactor are very short-lived, their half-lives do not take very long. And these heavy elements settle with the first rain. But the micrometer-sized particles produced by the combustion of fossil fuels are too small for rain to quickly remove them from the atmosphere. A person passes 15 kilograms of air through his lungs per day - many times more than he eats and drinks. Therefore, thermal energy constantly and in large quantities saturates our lungs with such particles and they cause many diseases - the heart, blood vessels, lungs, and also cancer.

52,000 people are buried annually. A little more than one Chernobyl per month. No one, of course, is organizing demonstrations against this, because they don’t talk about the monthly Chernobyl on TV, but science articles Nobody reads about this topic.

Thus, nuclear energy is the safest of all existing ones, with the exception of large-scale solar generation. And if you choose from power plants with continuous controlled generation, it is generally the safest.

However, this is not at all a reason to run and protest against this or that country’s abandonment of nuclear power plants. That is, of course, you can protest, but there is no point. People make decisions the way the PR people of the 1996 election campaign in Russia recommended. So to speak, they “vote with their hearts.” It is useless to show numbers to the heart.

Almost 25 years have passed since the terrible event that shocked the whole world. The echoes of this catastrophe of the century will stir the souls of people for a long time, and its consequences will affect people more than once. The disaster at the Chernobyl nuclear power plant - why did it happen and what are its consequences for us?

Why did the Chernobyl disaster happen?

There is still no clear opinion about what caused the disaster at the Chernobyl nuclear power plant. Some argue that the reason is faulty equipment and gross mistakes during the construction of the nuclear power plant. Others see the cause of the explosion as a malfunction of the circulating water supply system, which provided cooling to the reactor. Still others are convinced that the permissible load experiments carried out at the station that ominous night were to blame, during which a gross violation of operating rules occurred. Still others are confident that if there had been a protective concrete cap over the reactor, the construction of which was neglected, such a spread of radiation that occurred as a result of the explosion would not have occurred.

Most likely, this terrible event occurred due to the combination of the listed factors - after all, each of them took place. Human irresponsibility, acting at random in matters relating to life and death, and the deliberate concealment of information about what happened on the part of the Soviet authorities led to consequences, the results of which will echo for a long time to more than one generation of people around the world.

Chernobyl disaster. Chronicle of events

The explosion at the Chernobyl nuclear power plant occurred in the dead of night on April 26, 1986. A fire brigade was called to the scene. Brave and courageous people, they were shocked by what they saw and, judging by the off-scale radiation meters, they immediately guessed what had happened. However, there was no time to think - and a team of 30 people rushed to fight the disaster. For protective clothing, they wore ordinary helmets and boots - of course, they in no way could protect the firefighters from huge doses of radiation. These people have been dead for a long time; they all died a painful death at different times from the cancer that struck them..

By morning the fire was extinguished. However, pieces of uranium and graphite emitting radiation were scattered throughout the territory of the nuclear power plant. The worst thing is that the Soviet people did not immediately learn about the disaster that occurred at the Chernobyl nuclear power plant. This made it possible to maintain calm and prevent panic - this is exactly what the authorities sought, turning a blind eye to the cost of their ignorance for people. The unaware population spent two whole days after the explosion calmly resting in the territory, which had become deadly dangerous, going out into nature, to the river; on a warm spring day, children spent a long time on the street. And everyone absorbed huge doses of radiation.

And on April 28, complete evacuation was announced. 1,100 buses in a convoy transported the population of Chernobyl, Pripyat and other nearby settlements. People abandoned their homes and everything in them - they were only allowed to take with them identity cards and food for a couple of days.

A zone with a radius of 30 km was recognized as an exclusion zone unsuitable for human life. The water, livestock and vegetation in this area were considered unfit for consumption and hazardous to health.

The temperature in the reactor in the first days reached 5000 degrees - it was impossible to approach it. A radioactive cloud hung over the nuclear power plant and circled the Earth three times. To nail it to the ground, the reactor was bombed from helicopters with sand and watered, but the effect of these actions was negligible. There was 77 kg of radiation in the air - as if a hundred atomic bombs had been dropped on Chernobyl at the same time.

A huge ditch was dug near the Chernobyl nuclear power plant. It was filled with the remains of the reactor, pieces of concrete walls, and the clothes of disaster relief workers. For a month and a half, the reactor was completely sealed with concrete (the so-called sarcophagus) to prevent radiation leakage.

In 2000, the Chernobyl nuclear power plant was closed. Work is still underway on the Shelter project. However, Ukraine, for which Chernobyl became a sad “inheritance” from the USSR, does not have the required money for it.

The tragedy of the century that they wanted to hide

Who knows how long the Soviet government would have hidden the “incident” if not for the weather. Strong winds and rains, which inappropriately passed through Europe, carried radiation throughout the world. Ukraine, Belarus and the southwestern regions of Russia, as well as Finland, Sweden, Germany, and Great Britain suffered the most.

For the first time, unprecedented numbers on radiation level meters were seen by employees of the nuclear power plant in Forsmark (Sweden). Unlike the Soviet government, they rushed to immediately evacuate all the people living in the surrounding area before determining that the problem was not their reactor, but the supposed source of the emanating threat was the USSR.

And exactly two days after Forsmark scientists declared a radioactive alert, US President Ronald Reagan held in his hands photographs of the Chernobyl nuclear power plant disaster site taken by a CIA artificial satellite. What was depicted on them would have horrified even a person with a very stable psyche.

While periodicals around the world trumpeted the dangers arising from the Chernobyl disaster, the Soviet press escaped with a modest statement that there had been an “accident” at the Chernobyl nuclear power plant.

Chernobyl disaster and its consequences

The consequences of the Chernobyl disaster made themselves felt in the very first months after the explosion. People living in the areas adjacent to the site of the tragedy died from hemorrhages and apoplexy.

The liquidators of the consequences of the accident suffered: out of a total number of liquidators of 600,000, about 100,000 people are no longer alive - they died from malignant tumors and destruction of the hematopoietic system. The existence of other liquidators cannot be called cloudless - they suffer from numerous diseases, including cancer, disorders of the nervous and endocrine systems. Many evacuees and affected populations in the surrounding areas have these same health problems.

The consequences of the Chernobyl disaster for children are terrible. Developmental delays, thyroid cancer, mental disorders and a decrease in the body's resistance to all types of diseases - this is what awaited children exposed to radiation.

However, the worst thing is that the consequences of the Chernobyl disaster affected not only people living at that time. Problems with pregnancy, frequent miscarriages, stillborn children, frequent births of children with genetic disorders (Down syndrome, etc.), weakened immunity, an astounding number of children with leukemia, an increase in the number of cancer patients - all these are echoes of the disaster at the Chernobyl nuclear power plant, the end of which will come yet not soon. If it comes...

Not only people suffered from the Chernobyl disaster - all life on Earth felt the deadly force of radiation. As a result of the Chernobyl disaster, mutants appeared - descendants of humans and animals born with various deformations. A foal with five legs, a calf with two heads, fish and birds of unnaturally huge sizes, giant mushrooms, newborns with deformities of the head and limbs - photos of the consequences of the Chernobyl disaster are terrifying evidence of human negligence.

The lesson taught to humanity by the Chernobyl disaster was not appreciated by people. We still treat our own lives with the same carelessness, we still strive to squeeze the maximum out of the riches given to us by nature, everything we need “here and now.” Who knows, maybe the disaster at the Chernobyl nuclear power plant became the beginning to which humanity is moving slowly but surely...

Film about the Chernobyl disaster
We advise everyone who is interested to watch the full-length documentary film “The Battle of Chernobyl”. This video can be watched right here online and for free. Enjoy watching!