Any global event remains in our memory for a long time, most often forever. Unfortunately, not all such events are joyful and expected. Sometimes it happens, therefore, when a particular country goes down in history “thanks to” a terrible incident that entails human casualties, destruction of the environment, devastation of an entire area, and the death of all living things around. One such event can accurately be called such a sad event as the accident at the Chernobyl nuclear power plant.

The accident at the Chernobyl nuclear power plant occurred on the territory of the former Ukrainian USSR (now an independent country - Ukraine), on April 26, 1986. The term most often used in the media is “Chernobyl disaster,” which became one of the largest nuclear tragedies in the history of mankind. When did the Chernobyl accident happen and what followed? Why did the accident happen at the Chernobyl nuclear power plant and who is to blame for it? When was Chernobyl, when did the Chernobyl accident happen? More about all this below.

The destruction that occurred during the accident at the Chernobyl nuclear power plant was in the nature of an explosion. was completely destroyed. A huge amount of radioactive substances were released into the environment.

As already mentioned, the accident at the Chernobyl nuclear power plant is regarded as the largest in the entire history of peaceful nuclear energy. Such conclusions can be drawn from the number of deaths, as well as those affected by the consequences. We cannot ignore the economic damage, which also affected the material condition of the Soviet Union.

Only within three months after the accident the number of victims reached 31 people. The first ones died within a few days. Further, radiation sickness claimed the lives of from sixty to eighty people, and this over the next fifteen years. Also, about one hundred and thirty-four people suffered radiation sickness, which had one degree or another of severity. More than 100 thousand people who lived in a 30-kilometer zone were immediately evacuated.

In order to eliminate such a phenomenon as the accident at the Chernobyl nuclear power plant, a force of 600 thousand people was deployed and a huge amount of resources was spent. However, even now we continue to feel the consequences of this terrible accident at the Chernobyl nuclear power plant, and it is safe to say that this atomic curse will weigh on humanity around the world for a long time.

No matter how you look at it, people will continue to ask such questions, since the date of the accident in Chernobyl has long been known: Chernobyl, as it all happened, the accident at the nuclear power plant in Chernobyl, or briefly, the emergency accident. All these questions remain largely open.

What did people do to deserve such a disaster and how did it happen? What is this, a human mistake or a curse from above? Probably, no one will say for sure, just as the true culprits will not be found. The Chernobyl accident became a good warning for those who believe that everything in this world is subject to human control, because sometimes the slightest mistake can lead to huge casualties. And we all tend to make mistakes...

Chernobyl and Hiroshima

Along with such grief as the Chernobyl accident, another world catastrophe is remembered, namely. But here you can find a difference. The explosion that resulted in the Chernobyl accident was more like a powerful “dirty bomb”, and the main damaging factor here can accurately be called radiation contamination.
The radioactive cloud formed from the burning reactor spread various radiation throughout almost all of Europe. Of course, the greatest consequences from this radiation were observed in large areas of the Soviet Union that were located near the reactor. Today these are lands that belong to the Republic of Belarus, Ukraine, and the Russian Federation.

The Chernobyl accident became an event of enormous social and political significance for the entire Soviet Union. And this, of course, left a significant imprint on the course of the investigation of the case. The interpretation of facts and their course were constantly changing, but there is still no exact designation or identification of the reasons that caused such a catastrophe as the Chernobyl accident.

The giant who buried the city. Characteristics of the Chernobyl Nuclear Power Plant

Chernobyl, the accident in which led to sad worldwide fame, is located on the territory of Ukraine, three kilometers from, 16 kilometers from Belarus, 110 kilometers from the capital of Ukraine, Kiev.

By the time the accident occurred, Chernobyl operated four power units based on RBMK-1000 reactors at the Chernobyl nuclear power plant. The total power of the station was already one of the highest in Europe at that time: the Chernobyl nuclear power plant produced one tenth of the electricity throughout the USSR. In the future, it was planned to increase the capacity of the Chernobyl nuclear power plant. There was simply no time to complete the two additional power units.

The Chernobyl nuclear power plant stopped forever on December 15, 2000. This date seemed to confirm that some things cannot be restored, they are now buried due to circumstances and, possibly, human omission.

Accident, Chernobyl - these two words can still inspire horror. For us, the current generation, it is impossible to imagine such a terrible thing happening again. And all we can do is draw the right conclusions and act in such a way as to protect ourselves and those around us.

Horror is coming. Accident

On April 26, 1986, at night, namely at 1:26 am, an explosion occurred at the fourth power unit, which led to the complete destruction of the reactor. The accident in Chernobyl began with the partial destruction of the power unit building, killing two people. Moreover, the body of one of them could not be found, since it was buried under the rubble of the building. The second person died in hospital from burns and other injuries incompatible with life. But that was only the beginning. The Chernobyl accident did not stop there, but continued to claim life after life and is still doing so.

The explosion at the Chernobyl nuclear power plant provoked the emergence of many fires. Fires broke out in various rooms of the station and on the roof, and as a result, the remains of the core melted. It seemed that the real end of the world had begun. Mixtures of sand, concrete, and fuel fragments began to spread throughout the sub-reactor rooms, destroying what was in their path.

Immediately the Chernobyl accident caused the release of radiation into the atmosphere. Among the radioactive substances there were plutonium, uranium and other substances terribly harmful to life, the half-life of which reaches several hundred and even thousands of years. The Chernobyl accident is something that will have consequences for centuries to come.

How it was. Chronology of the disaster

So, the Chernobyl nuclear power plant, the accident at which shocked the whole world, was once one of the largest systems that produced electricity. It would seem that it is indestructible, that there is no such phenomenon that can shake this powerful colossus.

The accident, the Chernobyl nuclear power plant, is something that is known to everyone, but not everyone knows how it all began. It's probably good to know the history of what remains in our memory forever. Let's talk about what caused what we feel even decades later.

Path to Death

When did the tragedy at the Chernobyl nuclear power plant occur? It all started on April 25, 1986. The plans were to shut down the fourth power unit in order to carry out regular preventive maintenance and at the same time conduct an experiment. As part of the experiment, “turbogenerator rotor run-out” tests were to take place. The project proposed by the general designer was seen as an effective and cost-effective way to obtain an additional power supply system.

It should be noted that this was already the fourth test of the regime that was carried out at the station. Therefore, if someone asks the question “when did the tragedy at the Chernobyl nuclear power plant occur,” we can say that the tragedy was approaching gradually. The station itself seemed to warn people about something terrible, and it happened when no one expected it.

IT IS IMPORTANT TO KNOW:

Deadly experiment

The tests in question were to take place on April 25, 1986. About a day before such an event as the accident at Chernobyl, the power of the reactor was reduced by half. Reducing power was a mandatory condition of the experiment. For the same reason, the emergency cooling system was turned off. A further reduction in reactor power was prohibited by the Kievenergo dispatcher. At 23:10 the ban was lifted.

Although the date of the accident at the Chernobyl nuclear power plant is precise - April 26, 1986, the tragedy took place even earlier, since all huge events have their introductions. Due to prolonged unstable operation of the reactor, non-stationary xenon poisoning occurred.

Within 24 hours on April 25, the peak of poisonings had passed, and it seemed that the problem had been solved. But, as the date of the accident at the Chernobyl nuclear power plant confirms, the worst was yet to come. On the same day, the process of poisoning the reactor began at the Chernobyl nuclear power plant. But since the power of poisoning began to decrease again, the poisoning process gained momentum again. If the question “in what year was the accident at Chernobyl” can be answered precisely - 1986, then even scientists do not dare to give an exact answer to the question of when its consequences will pass.

If anyone wants to see what the accident at the Chernobyl nuclear power plant looks like, photos on the Internet are at your service. However, it is unlikely that photographs will be able to convey all the horror that actually happened there. No books or documentary stories will allow you to feel all the horror that is happening in the eighties of the twentieth century. The date of the Chernobyl accident will forever go down in history as one of the most terrible events that is unlikely to be corrected.

Signs from above?

Within about two hours, the reactor power was reduced to the level that was provided for by the program, but then, for unknown reasons, the reactor power could not be maintained at the required level and got out of control.

The shift manager decided to restore the rector's power. After a certain time, the station operators achieved the restoration of the reactor's power, but after a few minutes it began to grow again. Only after an hour of work did the operators finally manage to stabilize the reactor. The manual control rods continued to be removed.

After a certain thermal power was achieved, additional circulation pumps were put into use, the number of which was increased to eight. As the test program states, four pumps, together with two additional ones, were supposed to serve as a load for the generator of the “running down” turbine, which also participated in the experiment.

You already know that the tragedy in Chernobyl began with an experiment that started at 1:23 am. Due to the fact that the speed of the pumps connected to the run-down generator decreased, the reactor experienced a trend that entailed an increase in power. But at the same time, for almost the entire time of the process, the reactor power did not inspire concern. The tragedy in Chernobyl occurred a little later, and continues to this day. But then there was still no sign of trouble.

Seconds before the tragedy

Due to the fact that there was an additional increase in coolant flow through the reactor, and the cooling system was turned off, excessive amounts of steam were generated. As a result, when the coolant entered the core, the temperature in the reactor approached the boiling point. The situation began to become unmanageable.

Sensing something was wrong, the shift supervisor gave the command to stop the experiment. The operator pressed the emergency protection button, but the Chernobyl NPP system did not respond as it should. After just a few seconds, various signals were deciphered and recorded. They indicated that the reactor's power was growing, then the recording system simply failed.

The emergency protection system also did not work. Due to the large amount of steam in the reactor, the uranium rods, which were supposed to stop the fission of atoms, lingered at a height of 2 out of 7 meters. Dangerous processes continued to occur. Less than a minute after the “successful” start of the experiment, an explosion occurred, the consequences of which are shown in photographs of the Chernobyl accident to this day.

One way or another, the date of the Chernobyl accident is forever etched in the history of the former USSR. The consequences of the Chernobyl accident can be felt through the years, and then on that fateful day, it was impossible to imagine such a thing. But it is the consequences of the Chernobyl accident that make us think about how fragile and unreliable everything in this world is.

The accident at the Chernobyl nuclear power plant - what did the investigation show?

As mentioned above, the Chernobyl accident, the photo of which eloquently tells us about those terrible events, does not give an accurate idea of ​​the reasons for what happened. The investigation into this accident has been ongoing for many years. Not only Soviet, Ukrainian and Russian specialists tried to understand why the accident happened at the Chernobyl nuclear power plant, and whether it could have been avoided. The history of the disaster interests many scientists around the world. After all, as already mentioned, we continue to feel the consequences of the accident at the Chernobyl nuclear power plant even now, although enough time has passed.

Today, there are two different approaches that lead to explaining the causes of the Chernobyl accident. The consequences of the accident at the Chernobyl nuclear power plant arose as a result of an explosion, the causes of which have been trying to find out for many years in a row. These versions can be called official, in addition, there are several alternative versions, and their degree of reliability also varies.

A state commission was formed in the USSR in order to investigate such an event as the Chernobyl tragedy. The State Commission placed responsibility for this on the personnel of the Chernobyl plant, as well as on its management. But are these people really to blame for the Chernobyl tragedy?

Soviet experts, based on some of their research, confirm this point of view. There are allegations that the accident occurred due to a number of violations of the rules, that is, discipline was simply not observed, operating regulations were violated by personnel. The consequences at the Chernobyl nuclear power plant, photos may somewhere show that all this happened due to the fact that the reactor was not used in a regulated condition.

Probably, if you want to ask Google “Chernobyl accident, date,” it will also answer you clearly and precisely when it happened. But the errors given here cannot be considered reliable, since, as mentioned above, there is no evidence, one can only speculate.

Causes of the accident

The accident at the Chernobyl nuclear power plant, the date of which is known to everyone, could have occurred due to gross violations of established rules:

1. The experiment had to be carried out “at any cost,” despite the fact that changes in the state of the reactor were too obvious and indicated danger. The Chernobyl accident, the date of which is included in the list of the worst disasters, became inevitable due to the fact that human life was not valued.
2. The causes of the Chernobyl accident were that plant employees turned off manual safety mechanisms that were able to stop the reactor in a timely manner.
3. The causes of the Chernobyl accident could also have occurred due to the hushing up of the scale of the accident in the early days by the management at the nuclear power plant. All this was a gross violation of the rules, which led to the disaster.

Is this why the Chernobyl tragedy happened? After all, already in the nineties, namely in 1991, all this was reviewed anew by the USSR Gosatomnadzor. And as a result, they came to the conclusion that all these statements are not substantiated, that, they say, this is all quite doubtful. In addition, the commission carried out special analyzes regarding the regulatory documents at that time, and there was no confirmation of the accusations against the station personnel.

Also in 1993, a report of additional content was published, where a lot of attention was paid to the reasons that led to such a terrible event as the accident at the Chernobyl nuclear power plant. Questions regarding reactor malfunction were also addressed. All this was obtained from the old archive and new reports that were formed over many years.

The accident at the Chernobyl nuclear power plant still worries the minds of those who study it. As this report states, the most obvious reason is that there was an error in the design of the rector structure. Design features could have had a major influence on the course of the accident and, as a result, led to such a catastrophe as the Chernobyl accident, while Chernobyl became the most famous place in the world, unfortunately notorious.

Causes of the accident considered today

So, if the question is asked “in what year was the Chernobyl accident,” we can answer clearly, but we are also interested in the liquidation of the Chernobyl accident and its main factors of occurrence. The main versions of the disaster that are being considered today are:

1. Failure to comply with safety regulations. It is believed that the reactor did not meet the required safety standards.
2. Low quality of regulations. The quality of the regulations was very low, therefore safety was also at zero.
3. Lack of information among staff. The exchange of information was not effective, it was impossible to properly convey danger signals.

The liquidation of the Chernobyl accident is still ongoing, because it is probably not possible to completely destroy the terrible phenomenon. The Chernobyl accident is of interest year after year for its gloom and mystery, interests in what happened in Chernobyl, how the seconds passed before the disaster at the Chernobyl nuclear power plant, how the accident occurred at the Chernobyl nuclear power plant, when there was an accident at the Chernobyl nuclear power plant, when there was an accident in Chernobyl, and the main question , this is probably “Chernobyl nuclear power plant photo after the accident”, because it will allow you to see how it once was and how it is happening now.

Characteristics of accidents at nuclear power plants

Radiation accident - loss of control of a source of ionizing radiation caused by a malfunction, damage to equipment, improper actions of employees (personnel), natural phenomena or other reasons that could lead or have led to the irradiation of people or radioactive contamination of the environment in excess of established standards.

The main sources of environmental pollution with radioactive substances include industrial enterprises that extract and process raw materials containing radioactive substances, nuclear facilities (NF), radiochemical plants, research institutes and other facilities.

The most dangerous sources of ionizing radiation and radioactive contamination of the environment are accidents at nuclear facilities. Radiation accidents at nuclear facilities mean a violation of their safe operation, in which there was a release of radioactive products and (or) ionizing radiation beyond the boundaries provided for by the design for normal operation in quantities exceeding the established values. Radiation accidents are characterized by the initiating event, the nature of its occurrence, and the radiation consequences.

In 1988, the International Atomic Energy Agency (IAEA) developed the International Nuclear Event Scale (INES, abbreviated as International Nuclear Event Scale). Already since 1990, this scale has been used for the purpose of uniform assessment of emergency cases associated with the civil nuclear industry.

The scale is applicable to any event involving the transport, storage and use of radioactive materials and radiation sources and covers a wide range of practical activities, including radiography, the use of radiation sources in hospitals, in any civil nuclear installations, etc. It also includes the loss and theft of radiation sources and the detection of orphan sources.

According to the INES scale, nuclear and radiological accidents and incidents are classified into 8 levels (Appendix 1):

Level 7. Major accident

Level 6. Serious accident

Level 5: Widespread accident

Level 4. Accident with local consequences

Level 3: Serious Incident

Level 2. Incident

Level 1. Abnormal situation

Level 0. Below scale event.

Chronology of accidents and disasters at nuclear power plants

The full chronology of events is described in an environmental blog post dated April 17, 2011. The world's first serious accident occurred on December 12, 1952 in Canada, Ontario, Chalk River at the NRX nuclear power plant. A technical error by personnel led to overheating and partial melting of the core. Thousands of curies of fission products were released into the external environment, and about 3,800 cubic meters of radioactively contaminated water were dumped directly onto the ground, into shallow trenches near the Ottawa River.

Almost 14 years later, on October 5, 1966, in the USA at the Enrico Fermi nuclear power plant, an accident occurred in the cooling system of an experimental nuclear reactor, which caused a partial meltdown of the core. The staff managed to manually stop it. It took a year and a half to get the reactor back up to full power.

Three years later, in France, on October 17, 1969, at the Saint Laurent nuclear power plant, during fuel refueling at an operating reactor, the operator mistakenly loaded into the fuel channel not a fuel assembly, but a device for regulating gas flow. As a result of the melting of five fuel elements, about 50 kilograms of molten fuel fell inside the reactor vessel. There was a release of radioactive products into the environment. The reactor was shut down for one year.

On March 20, 1975, a fire started at the Brown Ferry nuclear power plant in the United States, lasting 7 hours and causing direct material damage of $10 million. Two reactor units were out of action for more than a year, which brought additional losses of another 10 million dollars. The cause of the fire was non-compliance with safety measures during work on sealing cable entries passing through the wall of the reactor hall. This work was verified in the most primitive way; by the deflection of the flame of a burning stearine candle. As a result, the insulation materials of the cable openings ignited, and then the fire entered the reactor hall. It took a lot of effort to bring the reactor into trouble-free mode and put out the fire.

On January 5, 1976, an accident involving fuel overloading occurred at the Bohunice nuclear power plant in Czechoslovakia. A massive leak of “hot” radioactive gas killed two station workers. The emergency exit through which they could leave the emergency site was blocked (to “prevent frequent incidents of theft”). The population was not warned about the emergency release of radioactivity.

The worst accident in US nuclear power history occurred on March 28, 1979, at the Three Mile Island nuclear power plant. As a result of a series of equipment failures and operator errors, 53 percent of the reactor core melted at the second power unit of the nuclear power plant. What happened was like a domino effect. First the water pump went bad. Then, due to the interruption of the supply of cooling water, the uranium fuel melted and escaped beyond the cladding of the fuel assemblies. The resulting radioactive mass destroyed most of the core and almost burned through the reactor vessel. If this happened, the consequences would be catastrophic. However, the station staff managed to restore the water supply and reduce the temperature. During the accident, about 70 percent of the radioactive fission products accumulated in the core passed into the primary coolant. The exposure dose rate inside the vessel, which contained the reactor and the primary circuit system, reached 80 R/h. There was a release into the atmosphere of an inert radioactive gas - xenon, as well as iodine. In addition, 185 cubic meters of slightly radioactive water were discharged into the Saskugang River. 200 thousand people were evacuated from the area exposed to radiation. Residents of Dauphin County who lived near the nuclear power plant were most affected. The two-day delay in the decision to evacuate children and pregnant women from the 10-kilometer zone around the nuclear power plant had serious negative consequences. Work to clean up the second power unit, almost completely destroyed as a result of the accident, took 12 years and cost $1 billion, which effectively bankrupted the owner company.

On March 8, 1981, at the Tsugura Nuclear Power Plant in Japan, about 4 thousand gallons of highly radioactive water leaked through a crack in the bottom of the building where spent fuel assemblies were stored. 56 workers were exposed to radioactive radiation. A total of four such leaks occurred between January 10 and March 8, 1981. During emergency restoration work, 278 nuclear power plant workers received increased exposure.

On December 9, 1986, as a result of a break in the secondary circuit pipeline at the Surry Nuclear Power Plant in the United States, 120 cubic meters of superheated radioactive water and steam were released. Eight nuclear power plant workers were caught in a boiling stream. Four of them died from their burns. The cause of the accident was corrosive wear of the pipeline, which led to a decrease in the thickness of the pipe walls (from 12 to 1.6 mm).

The largest accident in the history of nuclear power in Spain (a level three event on the INES scale) occurred at the Vandellos nuclear power plant on October 19, 1989. Fire at the first power unit of the nuclear power plant. Due to the sudden shutdown of one of the turbines, overheating and decomposition of the lubricating oil occurred. The resulting hydrogen exploded, which caused the turbine to catch fire. Since the automatic fire extinguishing system at the station did not work, fire departments of neighboring cities were called, including those located at a distance of up to 100 kilometers from the nuclear power plant. The fight against the fire lasted more than 4 hours. During this time, the turbine power supply and reactor cooling systems were seriously damaged. The firefighters working at the station risked their lives. They did not know the location and functions of its facilities, and were not familiar with the emergency action plan at the nuclear power plant. They used water instead of foam to extinguish electrical systems, which could lead to electric shock. In addition, people were not warned about the risk of working in areas with high levels of radiation. So three years after Chernobyl, firefighters, already in another country, became hostages of a dangerous situation at a nuclear power plant. Fortunately, this time none of them were seriously injured.

In Japan, on February 9, 1991, there was an accident at the Mihama nuclear power plant, 320 kilometers northwest of Tokyo. Due to a pipe rupture, 55 tons of radioactive water leaked from the cooling system of the reactor of the second power unit. There was no radioactive contamination of personnel or the area, but the incident was considered at that time the most serious accident at Japanese nuclear power plants.

A level three accident on the INES scale was recorded at the Khmelnitsky NPP in Ukraine on July 25, 1996. There was a release of radioactive products into the station premises. One person died.

During scheduled repair work on April 10, 2003, at the second power unit of the Paks NPP (Hungary), inert radioactive gases and radioactive iodine were released into the atmosphere. The reason is damage to the fuel assemblies during chemical cleaning of their surface in a special container. Level 3 accident on the INES scale.

On July 4, 2003, an explosion occurred at the radioactive waste processing plant of the Fugen nuclear complex, 350 kilometers west of Tokyo, resulting in a fire. The 165 MW experimental nuclear reactor, shut down in March 2003, was not affected by this incident.

The accident at the Mihama nuclear power plant on August 9, 2004. A jet of steam with a temperature of 270° escaped from a burst pipe in the second circuit of the cooling system of the third power unit and scalded the workers who were in the turbine hall. Four people were killed and 18 were seriously injured.

On August 25, 2004, a large leak of radioactive water occurred from the reactor cooling system of the second power unit of the Vandellos Nuclear Power Plant (Spain). The Spanish Radiation Safety Council said it was the most serious accident at the plant since a fire in 1989.

On March 11, 2011, the most powerful earthquake in the country's history occurred in Japan. As a result, a turbine at the Onagawa nuclear power plant was destroyed and a fire broke out, which was quickly extinguished. At the Fukushima-1 nuclear power plant, the situation was very serious - as a result of the shutdown of the cooling system, nuclear fuel melted in the reactor of unit No. 1, a radiation leak was detected outside the unit, and an evacuation was carried out in the 10-kilometer zone around the nuclear power plant. The next day, March 12, the media reported an explosion at the nuclear power plant.

On March 19, 2012, Canadian authorities reported a leak of radioactive water into Lake Ontario from a nuclear power plant owned by Ontario Power. According to MIGnews, the nuclear power plant is located in the city of Pickering, 35 km from Toronto. In a statement, the company said that 73 thousand liters of radioactive water got into the lake. This fact was confirmed by representatives of the Canadian Nuclear Safety Commission.

At the French nuclear power plant Flamanville, located in the northwestern department of Manche, a radiation leak occurred on October 26, 2012, as a result of which the first reactor was placed in a cold shutdown state. Over the past year, this is not the first case of accidents at French nuclear power plants, which is forcing opponents of this type of energy to increasingly demand the abandonment of nuclear energy.

NPP is nuclear equipment for generating electricity that operates under specified conditions and mode. It is a nuclear reactor connected to various systems necessary for its full and safe operation. Accidents at nuclear power plants are large-scale man-made disasters. Despite the fact that they generate electricity in an environmentally friendly way, the consequences of the failure are felt around the world.

Why are nuclear power plants dangerous?

World map of nuclear power plant locations

An accident at a power plant occurs due to errors in system maintenance, wear and tear of equipment, or due to natural disasters. Failures due to design errors occur in the initial stages of starting up a nuclear power plant and are much less common. The most common human factor in the occurrence of emergency incidents. Equipment malfunctions are accompanied by the release of radioactive particles into the environment.

The power of the emission and the degree of contamination of the surrounding area depend on the type of breakdown and the time to eliminate the fault. The most dangerous situations are those associated with overheating of reactors due to a malfunction of the cooling system and depressurization of the fuel rod casing. In this case, radioactive vapors are released through the ventilation pipe into the external environment. Accidents at power plants in Russia do not go beyond hazard class 3 and are minor incidents.

Radiation disasters in Russia

The largest accident occurred in the Chelyabinsk region in 1948 at the Mayak plant during the process of commissioning a nuclear reactor using plutonium fuel to the capacity specified by the design. Due to poor cooling of the reactor, several blocks of uranium combined with the graphite located around them. Elimination of the incident lasted 9 days. Later, in 1949, hazardous liquid contents were discharged into the Techa River. The population of 41 nearby villages was affected. In 1957, a man-made disaster called “Kushtymskaya” occurred at the same plant.

UKRAINE. Chernobyl exclusion zone.

In 1970, in Nizhny Novgorod, during the production of a nuclear vessel at the Krasnoye Sormovo plant, a prohibited launch of a nuclear reactor occurred, which began to operate at prohibitive power. The fifteen-second failure caused contamination of the closed area of ​​the workshop; the radioactive contents did not enter the territory of the plant. Elimination of the consequences lasted 4 months, most of the liquidators died due to excess radiation.

Another man-made accident was hidden from the public. In 1967, the largest ALVZ-67 disaster occurred, as a result of which the population of the Tyumen and Sverdlovsk regions suffered. Details were kept secret and little is known about what happened to date. The territory was contaminated unevenly; pockets appeared in which the coating density exceeded 50 curies per 100 km. Accidents at power plants in Russia are local in nature and do not pose a danger to the population, these include:

• a fire at the Beloyarsk Nuclear Power Plant in 1978 due to a fall of the ceiling on the oil tank of a turbogenerator, in 1992 due to the negligence of employees when pumping radioactive components for subsequent specialized cleaning;
• pipeline rupture in 1984 at the Balakovo nuclear power plant;
• when the power supply sources of the Kola Nuclear Power Plant are de-energized due to a hurricane;
• failures in the operation of the reactor in 1987 at the Leningrad Nuclear Power Plant with the release of radiation outside the station, minor failures in 2004 and 2015. without global environmental consequences.

In 1986, a global power plant accident occurred in Ukraine. Part of the active reaction zone was destroyed, as a result of a global catastrophe, the Western part of Ukraine, 19 western regions of Russia and Belarus were contaminated with radioactive substances, and the 30-kilometer zone became uninhabitable. The releases of active content lasted almost two weeks. No explosions have been recorded at nuclear power plants in Russia over the entire period of the existence of nuclear energy.

The risk of breakdowns at nuclear power plants is calculated according to the IAEA International Scale. Conventionally, man-made disasters can be divided into two levels of danger:

• lower level (class 1-3) - minor failures that are classified as incidents;
• medium level (grades 4-7) - significant malfunctions, which are called accidents.

Extensive consequences cause incidents of hazard class 5-7. Failures below the third class are most often dangerous only for plant personnel due to contamination of the internal premises and exposure of employees. The probability of a global catastrophe occurring is 1 in 1-10 thousand years. The most dangerous accidents at nuclear power plants are classified as class 5-7; they cause negative consequences for the environment and the population. Modern nuclear power plants have four degrees of protection:

• a fuel matrix that does not allow decay products to leave the radioactive shell;
• a radiator shell that protects the entry of hazardous substances into the circulation circuit;
• the circulation circuit does not allow radioactive contents to leak out under the containment shell;
• a complex of shells called containment.

The outer dome protects the room from the release of radiation outside the station; this dome can withstand a shock wave of 30 kPa, so an explosion of a nuclear power plant with emissions on a global scale is unlikely. At which nuclear power plants are explosions most dangerous? The most dangerous incidents are considered to be those when ionizing radiation is emitted outside the reactor safety system in quantities exceeding the parameters provided for in the design documentation. They are called:

• the lack of control over the nuclear reaction inside the unit and the inability to control it;
• failure of the fuel cell cooling system;
• the appearance of a critical mass due to overloading, transportation and storage of used components.

The grin of atomic energy

Despite the fact that nuclear energy actually provides people with carbon-free energy at reasonable prices, it also shows its dangerous side in the form of radiation and other disasters. The International Atomic Energy Agency evaluates accidents at nuclear facilities on a special 7-point scale. The most serious events are classified into the highest category, level seven, while level 1 is considered minor. Based on this system for assessing nuclear disasters, we offer a list of the five most dangerous accidents at nuclear facilities in the world.

1 place. Chernobyl. USSR (now Ukraine). Rating: 7 (major accident)

The accident at the Chernobyl nuclear facility is recognized by all experts as the worst disaster in the history of nuclear energy. This is the only nuclear accident that has been classified as a worst-case accident by the International Atomic Energy Agency. The largest man-made disaster occurred on April 26, 1986, at the 4th block of the Chernobyl nuclear power plant, located in the small town of Pripyat. The destruction was explosive, the reactor was completely destroyed, and a large amount of radioactive substances was released into the environment. At the time of the accident, the Chernobyl nuclear power plant was the most powerful in the USSR. 31 people died within the first three months after the accident; long-term effects of radiation, identified over the next 15 years, caused the death of 60 to 80 people. 134 people suffered radiation sickness of varying severity, more than 115 thousand people were evacuated from the 30-kilometer zone. More than 600 thousand people took part in eliminating the consequences of the accident. The radioactive cloud from the accident passed over the European part of the USSR, Eastern Europe and Scandinavia. The station ceased operation forever only on December 15, 2000.

Chernobyl

The “Kyshtym accident” is a very serious radiation man-made accident at the Mayak chemical plant, located in the closed city of Chelyabinsk-40 (since the 1990s - Ozersk). The accident got its name Kyshtymskaya for the reason that Ozyorsk was classified and was absent on maps until 1990, and Kyshtym was the closest city to it. On September 29, 1957, due to the failure of the cooling system, an explosion occurred in a tank with a volume of 300 cubic meters, which contained about 80 m³ of highly radioactive nuclear waste. The explosion, estimated at tens of tons of TNT equivalent, destroyed the tank, a 1-meter-thick concrete floor weighing 160 tons was thrown aside, and about 20 million curies of radiation were released into the atmosphere. Some of the radioactive substances were raised by the explosion to a height of 1-2 km and formed a cloud consisting of liquid and solid aerosols. Within 10-11 hours, radioactive substances fell over a distance of 300-350 km in the northeast direction from the explosion site (in the direction of the wind). More than 23 thousand square kilometers were in the zone contaminated with radionuclides. In this territory there were 217 settlements with more than 280 thousand inhabitants; the closest to the epicenter of the disaster were several factories of the Mayak plant, a military town and a prison colony. To eliminate the consequences of the accident, hundreds of thousands of military personnel and civilians were involved, receiving significant doses of radiation. The territory that was exposed to radioactive contamination as a result of an explosion at a chemical plant was called the “East Ural Radioactive Trace.” The total length was approximately 300 km, with a width of 5-10 km.

From memories from the website oykumena.org: “Mom began to get sick (there were frequent fainting spells, anemia)... I was born in 1959, I had the same health problems... We left Kyshtym when I was 10 years old. I'm a bit of an unusual person. Strange things have happened throughout my life... I foresaw the disaster of the Estonian airliner. And she even talked about the plane collision with her friend, a flight attendant... She died.”

3rd place. Windscale Fire, UK. Rating: 5 (accident with environmental risk)

On October 10, 1957, Windscale plant operators noticed that the temperature of the reactor was steadily increasing, while the opposite should be happening. The first thing everyone thought about was a malfunction of the reactor equipment, which two station workers went to inspect. When they got to the reactor itself, they saw to their horror that it was on fire. At first, workers did not use water because plant operators expressed concerns that the fire was so hot that the water would disintegrate instantly, and as is known, hydrogen in water can cause an explosion. All the methods tried did not help, and then the station staff opened the hoses. Thank God, the water was able to stop the fire without any explosion. It is estimated that 200 people in the UK developed cancer due to Windscale, half of whom died. The exact number of victims is unknown, as British authorities tried to cover up the disaster. Prime Minister Harold Macmillan feared that the incident could undermine public support for nuclear projects. The problem of counting the victims of this disaster is further aggravated by the fact that radiation from Windscale spread hundreds of kilometers throughout northern Europe.

Windscale

4th place. Three Mile Island, USA. Rating: 5 (accident with environmental risk)

Until the Chernobyl accident, which occurred seven years later, the accident at the Three Mile Island nuclear power plant was considered the largest in the history of global nuclear power and is still considered the worst nuclear accident in the United States. On March 28, 1979, early in the morning, a major accident occurred in reactor unit No. 2 with a capacity of 880 MW (electric) at the Three Mile Island nuclear power plant, located twenty kilometers from the city of Harrisburg (Pennsylvania) and owned by the Metropolitan Edison company. Unit 2 at the Three Mile Island nuclear power plant did not appear to be equipped with an additional safety system, although similar systems are available at some of the plant's units. Despite the fact that the nuclear fuel partially melted, it did not burn through the reactor vessel and the radioactive substances mainly remained inside. According to various estimates, the radioactivity of noble gases released into the atmosphere ranged from 2.5 to 13 million curies, but the release of dangerous nuclides such as iodine-131 was insignificant. The station area was also contaminated with radioactive water leaking from the primary circuit. It was decided that there was no need to evacuate the population living near the station, but authorities advised pregnant women and preschool children to leave the 8-kilometer zone. Work to eliminate the consequences of the accident was officially completed in December 1993. The station area was decontaminated and fuel was unloaded from the reactor. However, some of the radioactive water has been absorbed into the concrete of the containment shell and this radioactivity is almost impossible to remove. Operation of the plant's other reactor (TMI-1) was resumed in 1985.

Three Mile Island

5th place. Tokaimura, Japan. Rating: 4 (accident without significant risk to the environment)

On September 30, 1999, the worst nuclear tragedy for the Land of the Rising Sun occurred. Japan's worst nuclear accident occurred more than a decade ago, although it was outside of Tokyo. A batch of highly enriched uranium was prepared for a nuclear reactor that had not been used for more than three years. The plant's operators were not trained in how to handle such highly enriched uranium. Without understanding what they were doing in terms of possible consequences, the “experts” placed much more uranium in the tank than was necessary. Moreover, the reactor tank was not designed for this type of uranium. ...But the critical reaction cannot be stopped and two out of three operators who worked with uranium then die from radiation. After the disaster, about a hundred workers and those who lived nearby were hospitalized with a diagnosis of radiation exposure, and 161 people who lived a few hundred meters from the nuclear power plant were subject to evacuation.

According to the International Nuclear Event Scale, all nuclear incidents are rated on an 8-level system. For 2011, 2 accidents were rated at level 7 Chernobyl and Fukushima One at level 6 (Kyshtym accident)

The accident at the Fukushima-1 nuclear power plant is a major radiation accident (according to Japanese officials - level 7 on the INES scale), which occurred on March 11, 2011 as a result of a powerful earthquake in Japan and the subsequent tsunami

Chernobyl Chernobyl accident level 7

At approximately 1:24 am on April 26, 1986, an explosion occurred at the 4th power unit of the Chernobyl nuclear power plant, which completely destroyed the reactor. The building of the power unit partially collapsed, killing 2 people - MCP (main circulation pump) operator Valery Khodemchuk (body was not found, buried under the rubble of two 130-ton separator drums) and commissioning plant employee Vladimir Shashenok (died from a broken spine and numerous burns at 6:00 at the Pripyat Medical Unit, on the morning of April 26th). A fire started in various rooms and on the roof. Subsequently, the remains of the core melted. A mixture of molten metal, sand, concrete and fuel fragments spread throughout the sub-reactor rooms. As a result of the accident, radioactive substances were released into the environment, including isotopes of uranium, plutonium, iodine-131 (half-life 8 days), cesium-134 (half-life 2 years), cesium-137 (half-life 33 years), strontium -90 (half-life 28 years).

The highest doses were received by approximately 1,000 people who were near the reactor at the time of the explosion and who took part in emergency work in the first days after it. These doses ranged from 2 to 20 grays (Gy) and were fatal in some cases.
134 cases of acute radiation sickness were recorded among people performing emergency work at the fourth unit. In many cases, radiation sickness was complicated by radiation skin burns caused by β-radiation. During 1986, 28 people died from radiation sickness. Two more people died during the accident from causes unrelated to radiation, and one died, presumably from coronary thrombosis. During 1987-2004, another 19 people died, but their deaths were not necessarily caused by radiation sickness.
The untimeliness, incompleteness and contradictory nature of official information about the disaster gave rise to many independent interpretations. Sometimes the victims of the tragedy are considered not only the citizens who died immediately after the accident, but also the residents of the surrounding regions who went to the May Day demonstration, not knowing about the accident. With this calculation, the Chernobyl disaster significantly exceeds the atomic bombing of Hiroshima in terms of the number of victims
As a result of the accident, about 5 million hectares of land were taken out of agricultural use, a 30-kilometer exclusion zone was created around the nuclear power plant, hundreds of small settlements were destroyed and buried (buried with heavy equipment).
The world's nuclear energy industry suffered a serious blow as a result of the Chernobyl accident. From 1986 to 2002, not a single new nuclear power plant was built in North America and Western Europe, which is due both to the pressure of public opinion and to the fact that insurance premiums have increased significantly and the profitability of nuclear power has decreased.

In the USSR, the construction and design of 10 new nuclear power plants was mothballed or stopped, and the construction of dozens of new power units at existing nuclear power plants in different regions and republics was frozen.
Large areas of contaminated areas remained outside the 30-kilometer zone, and starting from the 1990s, a gradual resettlement of settlements in the Polesie region was carried out, in which the pre-accident level of radionuclide contamination exceeded the legal norms. So, by 1996 the towns were finally resettled. Polesskoe, town. Vilcha, s. Dibrova, s. New World and many others. Since 1997, this territory became part of the Chernobyl zone, was transferred under the management of the Ministry of Emergency Situations and included in the security perimeter.
The exclusion zone of the Chernobyl nuclear power plant is a territory prohibited for free access, subject to intense contamination by long-lived radionuclides as a result of the accident at the Chernobyl nuclear power plant.

The Chernobyl zone includes the north of the Ivankovsky district of the Kiev region, where the power plant itself, the cities of Chernobyl and Pripyat are located, the north of the Polessky district of the Kiev region (including the village of Polesskoe and the village of Vilcha), as well as part of the Zhytomyr region up to the border with Belarus.

Kyshtym Kyshtym accident level 6

The “Kyshtym accident” is a major radiation man-made accident that occurred on September 29, 1957 at the Mayak chemical plant, located in the closed city of Chelyabinsk-40. Now this city is called Ozersk. The accident is called Kyshtym due to the fact that the city of Ozyorsk was classified and was not on maps until 1990. Kyshtym is the closest city to it.

On September 29, 1957 at 16:22, due to the failure of the cooling system, an explosion occurred in a 300 cubic meter tank containing about 80 m³ of highly radioactive nuclear waste. The explosion, estimated at tens of tons of TNT equivalent, destroyed the tank, a 1-meter-thick concrete floor weighing 160 tons was thrown aside, and about 20 million curies of radioactive substances were released into the atmosphere.
Some of the radioactive substances were raised by the explosion to a height of 1-2 km and formed a cloud consisting of liquid and solid aerosols. Within 10-11 hours, radioactive substances fell over a distance of 300-350 km in the northeast direction from the explosion site (in the direction of the wind). The area of ​​radiation contamination included the territory of several enterprises of the Mayak plant, a military camp, a fire station, a prison colony, and then an area of ​​23,000 sq. km. with a population of 270,000 people in 217 settlements in three regions: Chelyabinsk, Sverdlovsk and Tyumen. Chelyabinsk-40 itself was not damaged. 90 percent of the radiation contamination fell on the territory of the closed administrative-territorial entity of the Mayak chemical plant, and the rest dispersed further.

During the liquidation of the consequences of the accident, 23 villages from the most contaminated areas with a population of 10 to 12 thousand people were resettled, and buildings, property and livestock were destroyed. To prevent the spread of radiation, in 1959, by government decision, a sanitary protection zone was formed on the most contaminated part of the radioactive trace, where all economic activity was prohibited, and since 1968, the East Ural State Reserve was formed on this territory. Now the contamination zone is called the East Ural Radioactive Trace (EURT).

To eliminate the consequences of the accident, hundreds of thousands of military personnel and civilians were involved, receiving significant doses of radiation.

Three Mile Island nuclear power plant accident level 5

The accident at the Three Mile Island nuclear power plant (Eng. Three Mile Island accident) is one of the largest accidents in the history of nuclear energy, which occurred on March 28, 1979 at the Three Mile Island nuclear power plant, located on the Susquehanna River, near Harrisburg (Pennsylvania). , USA).

Before the Chernobyl accident, which happened seven years later, the accident at the Three Mile Island nuclear power plant was considered the largest in the history of world nuclear energy and is still considered the worst nuclear accident in the United States, during which the reactor core and part of the nuclear fuel were seriously damaged melted.
The accident at the Three Mile Island nuclear power plant occurred a few days after the release of the movie “The China Syndrome,” the plot of which is built around an investigation into problems with the reliability of a nuclear power plant conducted by a television journalist and a plant employee. One episode depicts an incident very similar to what actually happened at Three Mile Island: an operator, misled by a faulty sensor, turns off the emergency water supply to the core and this almost leads to a meltdown (to " Chinese syndrome"). In another coincidence, one of the characters in the film says that such an accident could lead to the evacuation of people from an area “the size of Pennsylvania.”

Although the nuclear fuel partially melted, it did not burn through the reactor vessel and the radioactive substances largely remained inside. According to various estimates, the radioactivity of the noble gases released into the atmosphere ranged from 2.5 to 13 million curies (480 × 1015 Bq), but the release of dangerous nuclides such as iodine-131 was insignificant. The station area was also contaminated with radioactive water leaking from the primary circuit. It was decided that there was no need to evacuate the population living near the station, but the governor of Pennsylvania advised pregnant women and preschool children to leave the five-mile (8 km) zone
Work to eliminate the consequences of the accident began in August 1979 and was officially completed in December 1993. They cost 975 million US dollars. The station area was decontaminated and fuel was unloaded from the reactor. However, some of the radioactive water has been absorbed into the concrete of the containment shell and this radioactivity is almost impossible to remove.

Operation of the plant's other reactor (TMI-1) was resumed in 1985.

Accident at the Krasnoye Sormovo plant, level 5

Radiation accident at the Krasnoye Sormovo plant - occurred at the Krasnoye Sormovo plant on January 18, 1970 during the construction of the Project 670 Skat nuclear submarine K-320.
During the construction of the nuclear submarine K-320, while it was on the slipway, an unauthorized launch of the reactor occurred, which operated at extreme power for about 15 seconds. At the same time, significant radioactive contamination occurred on the territory of the workshop in which the ship was built. There were about 1000 workers in the workshop. Radioactive contamination of the area was avoided due to the closed nature of the workshop. That day, many went home without receiving the necessary decontamination treatment and medical care. Six victims were taken to a hospital in Moscow, three of them died a week later with a diagnosis of acute radiation sickness, the rest were required to sign a non-disclosure agreement for 25 years. Only the next day they began to wash the workers with special solutions. On the same day, 450 people, having learned about what had happened, quit the plant, the rest had to take part in eliminating the consequences of the accident. The main work to eliminate the accident continued until April 24, 1970. More than a thousand people took part in them.

None of them received government awards for their participation in the liquidation of the accident.
By January 2005, out of more than a thousand participants, 380 people remained alive. Of the benefits, they only have a small allowance from the regional authorities (330 rubles per month until January 1, 2010, 750 rubles - from January 1, 2010). They cannot receive a higher status as employees of a high-risk unit due to the lack of a law. The new owner of the Krasnoye Sormovo plant de jure does not bear any responsibility for the accident that occurred.

Accident in Chazhma Bay Level 5

The radiation accident in Chazhma Bay is an accident of a nuclear power plant on a nuclear submarine of the Pacific Fleet, resulting in human casualties and radioactive contamination of the environment.
On August 10, 1985, on the K-431 nuclear submarine of Project 675, located at pier No. 2 of the Navy ship repair plant in Chazhma Bay (Shkotovo-22 village), the reactor cores were being recharged. The work was carried out in violation of nuclear safety and technology requirements: non-standard lifting devices were used. The starboard reactor was recharged normally.

When the reactor lid was blown up (lifted), an uncontrollable spontaneous chain reaction of fission of uranium nuclei of the port side reactor occurred at the moment of passing by a torpedo boat, which exceeded the permissible speed in the port.

As a result, a thermal explosion of the reactor occurred, killing 8 officers and 2 sailors. At the center of the explosion, the radiation level, according to scientists, was 90,000 roentgens per hour, which led to the instant death of those there. A fire started on the submarine, which was accompanied by powerful emissions of radioactive dust and steam. According to expert Alexei Mityunin, the entire active part of the reactor was eventually thrown outside the boat. Eyewitnesses who extinguished the fire spoke of large tongues of flame and clouds of brown smoke that escaped from a technological hole in the boat's hull.

The extinguishing was carried out by untrained employees - workers of the ship repair plant and crews of neighboring boats. At the same time, there was no special clothing or special equipment. Putting out the fire took about two and a half hours. Specialists from the naval emergency team arrived at the scene of the emergency three hours after the explosion. As a result of uncoordinated actions of the parties, the liquidators stayed in the contaminated area until two in the morning, waiting for a new set of clothes to replace the contaminated ones.

An information blockade was established at the scene of the accident, the plant was cordoned off, and the access control of the plant was strengthened. In the evening of the same day, the village’s communication with the outside world was cut off. At the same time, no preventive or explanatory work was carried out with the population, as a result of which the population received a dose of radiation exposure.

It is known that 290 people were injured as a result of the accident. Of these, ten died at the time of the accident, ten suffered from acute radiation sickness, and thirty-nine had a radiation reaction. Since the enterprise is sensitive, the main victims were military personnel, who were among the first to begin eliminating the consequences of the disaster.

Radioactive contamination in Goiania level 5

Radioactive contamination in Goiania is a case of radioactive contamination that occurred in the Brazilian city of Goiania.

In 1987, looters stole from an abandoned hospital a part from a radiotherapy unit containing the radioactive isotope cesium-137 in the form of cesium chloride, after which it was thrown away. But after some time it was discovered in a landfill and attracted the attention of the owner of the landfill, who then brought the found medical source of radioactive radiation to his home and invited neighbors, relatives and friends to look at the powder glowing blue. Small fragments of the source were picked up, rubbed on the skin, and given to other people as gifts, and as a result, radioactive contamination began to spread. Over the course of more than two weeks, more and more people came into contact with powdered cesium chloride, and none of them knew about the dangers associated with it.

As a result of the widespread distribution of highly radioactive powder and its active contact with various objects, a large amount of material contaminated with radiation accumulated, which was later buried on the hilly territory of one of the city’s outskirts, in the so-called near-surface storage facility. This area can only be used again after 300 years.

The Goiania accident attracted international attention. Before the 1987 accident, regulations governing the control of the distribution and movement of radioactive substances used in medicine and industry throughout the world were relatively weak. But after the incident in Goiania, the attitude towards these issues was completely revised. Subsequently, revised and supplemented standards and concepts began to be actually implemented at the household level, and stricter control was established over their compliance. The IAEA has established stringent safety standards for radioactive sources, namely International Basic Safety Standards No. 115, the development of which was jointly sponsored by several international organizations. Today, Brazil requires licensing of each source, allowing its life cycle to be traced back to final disposal.

Accident in Windscale with graphite fire level 5

The Windscale fire accident was a major radiation accident that occurred on October 10, 1957 at one of the two reactors at the Sellafield nuclear complex, in Cumbria in North-West England.

As a result of a fire in an air-cooled graphite reactor for the production of weapons-grade plutonium, a large (550-750 TBq) release of radioactive substances occurred. The accident corresponds to level 5 on the International Nuclear Event Scale (INES) and is the largest in the history of the UK nuclear industry
The accident occurred during a scheduled annealing program for graphite masonry. During normal operation of the reactor, neutrons bombarding graphite lead to a change in its crystal structure
The consequences of the accident were studied by the National Commission for Radiological Protection. According to the commission's estimate, about 30 additional deaths from cancer could have occurred among the population (0.0015% increase in cancer mortality), that is, during the time during which these 30 deaths could occur, about 1 million people

Accident at the Tokaimura nuclear facility level 4

The accident at the Tokaimura nuclear facility occurred on September 30, 1999 and resulted in the death of two people. At that time, it was the most serious incident in Japan related to the peaceful use of nuclear energy. The accident occurred at a small radiochemical plant of JCO, a division of Sumitomo Metal Mining, in the village of Tokai, Naka County, Ibaraki Prefecture.
As a result of the workers’ actions, at 10:45 a.m., about 40 liters of a mixture containing approximately 16 kg of uranium ended up in the settling tank. Although the theoretical value of the critical mass of even pure uranium-235 is 45 kg, in solution the actual critical mass is significantly lower compared to solid fuel due to the fact that the water present in the solution acted as a neutron moderator; In addition, the water jacket around the settling tank played the role of a neutron reflector. As a result, the critical mass was significantly exceeded and a self-sustaining chain reaction began.

A worker who was adding the seventh bucket of uranyl nitrate to the settling tank and partially hanging over it saw a blue flash of Cherenkov radiation. He and another worker in the vicinity of the septic tank immediately experienced pain, nausea, difficulty breathing and other symptoms; A few minutes later, already in the decontamination room, he vomited and lost consciousness.

There was no explosion, but the consequence of the nuclear reaction was intense gamma and neutron radiation from the settling tank, which triggered an alarm, after which actions began to localize the accident. In particular, 161 people were evacuated from 39 residential buildings within a radius of 350 meters from the enterprise (they were allowed to return to their homes after two days). Eleven hours after the accident began, a gamma radiation level of 0.5 millisieverts per hour was recorded at one site outside the plant, which is about 1,000 times higher than the natural background.

The chain reaction continued intermittently for about 20 hours, after which it stopped due to the fact that water, which played the role of a neutron reflector, was drained from the cooling jacket surrounding the settling tank, and boric acid was added to the settling tank itself (boron is a good neutron absorber); 27 workers took part in this operation and also received some radiation dose. Interruptions in the chain reaction were caused by the liquid boiling, the amount of water becoming insufficient to reach criticality and the chain reaction dying out. After cooling and condensing the water, the reaction resumed.

However, some of the radioactive noble gases and iodine-131 still entered the atmosphere
Three workers who directly worked with the solution were heavily irradiated, receiving doses: one from 10 to 20 sieverts, another from 6 to 10 sieverts, the third from 1 to 5 sieverts (despite the fact that a dose of about 3-5 sieverts is fatal in 50% of cases ). The first died after 12 weeks, the second after 7 months. In total, 667 people were exposed to radiation (including plant workers, firefighters and rescue workers, as well as local residents), but, with the exception of the three workers mentioned above, their radiation doses were insignificant (no more than 50 millisieverts).

The thermal power of the nuclear chain reaction in the settling tank was subsequently estimated to range from 5 to 30 kW. This incident was assigned level 4 on the International Nuclear Event Scale (INES). The IAEA concluded that the incident was caused by “human error and a serious disregard for safety principles.”