Accidents at nuclear facilities. Statistics of radiation accidents in the world

30.09.2019

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

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

Chernobyl Chernobyl accident level 7

At about 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, with the deaths of 2 people - the MCP operator (the main circulation pump) Valery Khodemchuk (the body was not found, heaped under the rubble of two 130-ton separator drums) and an employee of the commissioning enterprise Vladimir Shashenok (died of a spinal fracture and numerous burns at 6:00 in the Pripyat medical unit, on the morning of April 26). A fire broke out 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 over 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 about 1000 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 gray (Gy) and were found to be fatal in some cases.
There were 134 cases of acute radiation sickness among people performing emergency work on the fourth block. In many cases, radiation sickness was complicated by radiation burns of the skin caused by β-radiation. During 1986, 28 people died from radiation sickness. Two more people died in the accident for reasons 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 inconsistency of the official information about the disaster gave rise to many independent interpretations. Sometimes the victims of the tragedy are considered not only citizens who died immediately after the accident, but also residents of the adjacent 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 withdrawn from 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 nuclear power industry suffered a serious blow as a result of the Chernobyl accident. 1986 to 2002 in North America and Western Europe not a single new nuclear power plant was built, which is due both to the pressure of public opinion and to the fact that insurance premiums and the profitability of nuclear power has declined.

In the USSR, the construction and design of 10 new nuclear power plants was mothballed or stopped, the construction of dozens of new power units at operating nuclear power plants in different regions and republics was frozen.
Large areas of contaminated territories remained outside the 30-kilometer zone, and since the 1990s, a gradual resettlement of settlements in the Polesskiy region, in which the pre-emergency level of radionuclide contamination exceeded the norms established by law, was carried out. So, by 1996, the township was 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 control of the Ministry of Emergencies and included in the security perimeter.
The exclusion zone of the Chernobyl nuclear power plant is a territory prohibited for free access, which has been intensively contaminated with 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 is located, the cities of Chernobyl and Pripyat, the north of the Polessky district of the Kiev region (including the village of Polesskoye 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 technogenic 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 because the city of Ozersk was classified and was absent on maps until 1990. Kyshtym is the nearest town to it.

On September 29, 1957, at 16:22, due to the failure of the cooling system, an explosion occurred in a container with a volume of 300 cubic meters, which contained about 80 m³ of highly radioactive nuclear waste. An explosion, estimated at tens of tons in TNT equivalent, destroyed the container, concrete floor 1 meter thick and weighing 160 tons were thrown aside, about 20 million curies of radioactive substances were released into the atmosphere.
Some of the radioactive substances were lifted 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 out over a distance of 300-350 km in the northeast direction from the explosion site (in the direction of the wind). The territory of several enterprises of the Mayak plant, a military town, a fire station, a prisoner colony and then an area of 23,000 square kilometers were found in the zone of radiation contamination. with a population of 270,000 people in 217 settlements in three regions: Chelyabinsk, Sverdlovsk and Tyumen. Chelyabinsk-40 itself was not injured. 90 percent of radiation contamination fell on the territory of ZATO (closed administrative-territorial unit of the Mayak chemical plant), and the rest dispersed further.

During the liquidation of the consequences of the accident, 23 villages from the most polluted 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 a government decision, a sanitary protection zone was created on the most contaminated part of the radioactive trace, where any 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 who received significant doses of radiation were involved.

Accident at the Three Mile Island nuclear power plant level 5

The Three Mile Island accident is one of the largest accidents in the history of nuclear power, 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 power and is still considered the most severe nuclear accident in the United States, during which the reactor core was seriously damaged, part of the nuclear fuel melted.
The accident at the Three Mile Island nuclear power plant occurred a few days after the release of the movie China Syndrome, the plot of which is based on an investigation of problems with the reliability of a nuclear power plant, conducted by a TV journalist and an employee of the station. One of the episodes shows an incident very similar to what actually happened on Three Mile Island: an operator, deceived by a faulty sensor, turns off the emergency water supply to the core and this almost leads to its melting (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 was partially melted, it did not burn through the reactor vessel and the radioactive material remained mostly inside. According to various estimates, the radioactivity of noble gases released into the atmosphere was from 2.5 to 13 million curies (480 × 1015 Bq), but the release of hazardous nuclides, such as iodine-131, was insignificant. The territory of the station was also contaminated with radioactive water flowing out 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 children to leave the five-mile (8 km) zone. preschool age
The work to eliminate the consequences of the accident began in August 1979 and was officially completed in December 1993. They cost US $ 975 million. Decontamination of the station territory was carried out, fuel was unloaded from the reactor. However, part of the radioactive water has been absorbed into the concrete of the containment and this radioactivity is almost impossible to remove.

The plant's other reactor (TMI-1) was reopened in 1985.

Accident at the plant "Krasnoe Sormovo" level 5

A radiation accident at the Krasnoye Sormovo plant - occurred at the Krasnoye Sormovo plant on January 18, 1970 during the construction of the nuclear submarine K-320 of project 670 Skat.
During the construction of the nuclear submarine K-320, when it was on the slipway, an unauthorized launch of the reactor took place, which worked at prohibitive power for about 15 seconds. At the same time, there was a significant radioactive contamination of the territory of the workshop in which the ship was being built. There were about 1000 workers in the shop. Radioactive contamination of the area was avoided due to the closed nature of the workshop. On that day, many went home without receiving the necessary decontamination treatment and medical assistance. Six of the 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 taken to a non-disclosure agreement for 25 years. Only the next day the workers began to be washed with special solutions. On the same day, 450 people, having learned about the incident, quit their jobs, 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.

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

Accident in the Chazhma bay level 5

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

When the reactor lid was blown up (lifted), an uncontrolled spontaneous chain reaction of uranium fission of the left side reactor occurred at the moment of passing by the 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. In 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 who were 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 out of the boat. Eyewitnesses who extinguished the fire spoke of large tongues of flame and puffs 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 shipyard and the crews of neighboring boats. At the same time, there was no work clothes or special equipment. It took about two and a half hours to put out the fire. Specialists of the emergency fleet 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 o'clock in the morning, waiting for a new set of clothes to replace the infected one.

An information blockade was set at the scene of the accident, the plant was cordoned off, and the plant's access control 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 and explanatory work with the population was carried out, as a result of which the population received a dose of radiation exposure.

It is known that as a result of the accident 290 people were injured. Of these, ten died at the time of the accident, ten had acute radiation sickness, and thirty-nine had a radiation reaction. Since the enterprise is a secure one, it was mainly servicemen who suffered, who were among the first to start eliminating the consequences of the disaster.

Radioactive contamination in Goiania level 5

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

In 1987, a part from a radiotherapy installation containing the radioactive isotope cesium-137 in the form of cesium chloride was stolen from an abandoned hospital by looters, 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 house and invited neighbors, relatives and friends to look at the powder glowing with blue light. Small fragments of the source were taken in hands, rubbed with them on the skin, passed on to other people as gifts, and as a result, the spread of radioactive contamination began. For more than two weeks, more and more people came into contact with powdered cesium chloride, and none of them knew about the danger associated with it.

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

The Goiânia accident has attracted international attention. Prior to the 1987 accident, regulations governing the control of the spread and movement of radioactive substances used in medicine and industry around the world were relatively weak. But after the incident in Goiânia, the attitude to these issues was overhauled. Subsequently, the revised and amended standards and concepts began to be really implemented at the household level, and stricter control was established over their observance. The IAEA has introduced strict safety standards for radioactive sources, namely International Basic Safety Standards No. 115, the development of which was co-sponsored by several international organizations. Today in Brazil there is a licensing requirement for each source, which allows its life cycle to be traced back to final disposal.

Windscale Graphite Fire Level 5

The Windscale fire is a major radiation accident that occurred on October 10, 1957, at one of the two reactors of the Sellafield nuclear complex in Cumbria in the North West of 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 is 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 the execution of the scheduled annealing of the graphite stack. During normal operation of the reactor, neutrons bombarding the graphite lead to a change in its crystal structure.
The consequences of the accident were studied by the National Commission on Radiological Protection. According to the assessment made by the commission, about 30 additional deaths from cancer could occur among the population (0.0015% increase in deaths from cancer), that is, during the time during which these 30 deaths can occur, among exposed people, according to statistics, 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 the time, it was the most serious incident in Japan involving the peaceful use of nuclear energy. The accident happened at a small JCO radiochemical plant, a division of Sumitomo Metal Mining, in Tokai Village, Naka County, Ibaraki Prefecture
As a result of the workers' actions at 10:45 am, about 40 liters of a mixture containing about 16 kg of uranium were found in the sump. Although the theoretical value of the critical mass of even pure uranium-235 is 45 kg, in solution the real critical mass is much lower compared to solid fuel due to the fact that the water in the solution acts as a neutron moderator; in addition, the water jacket around the sump 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 sump and partially hanging over it saw a blue flash of Cherenkov radiation. He and another worker near the sump 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 result of the nuclear reaction was intense gamma and neutron radiation from the sump, which triggered the alarm, after which actions began to localize the accident. In particular, 161 people out of 39 were evacuated. residential buildings within a radius of 350 meters from the enterprise (they were allowed to return to their homes in two days). Eleven hours after the start of the accident, an area outside the plant recorded gamma radiation levels of 0.5 millisieverts per hour, about 1,000 times 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 sump, and boric acid(boron is a good absorber of neutrons); 27 workers took part in this operation, who also received some dose of radiation. The breaks in the chain reaction were caused by the liquid boiling up, the amount of water becoming insufficient to reach criticality, and the chain reaction was dying out. After cooling and condensation of water, the reaction was resumed.

However, some of the radioactive noble gases and iodine-131 still got into the atmosphere.
Three workers who directly worked with the solution were heavily irradiated, having received doses: one from 10 to 20 sievert, another from 6 to 10 sievert, the third from 1 to 5 sievert (despite the fact that in 50% of cases, a dose of about 3-5 sievert is fatal ). The first died after 12 weeks, the second after 7 months. In total, 667 people were exposed to radiation (including plant workers, firefighters and rescuers, 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 sump was subsequently estimated in the 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 serious disregard for safety principles."

At the very end of the 18th century, radioactive radiation was discovered, after which an active study of this phenomenon began. Already in 1901, radiation was first used for medical purposes. Thirty years later, they began to think about the development of nuclear weapons. The first plutonium production plants started operating in 1944. The waste material was initially simply dumped into the environment like regular garbage. The surrounding area suffered significant damage. This is how the statistics of radiation accidents in the world were born. The era of radioactive contamination of the environment by humans has begun.

Peaceful "atom"

From the middle of the 20th century, the development of the engine began for its use in the transport industry. As this direction developed, they tried to develop an atomic-jet, an atomic-engine, an atomic-powered ship. The most successful was the idea to create nuclear powered ships. In the civilian sphere, these are nuclear icebreakers,.

In medicine, radiation began to serve the good almost immediately after its discovery. Today, radioactive radiation is effectively used in the field of neurology, oncology, cardiology, as well as complex diagnostics.

Statistics of radiation accidents in the world in the field of the national economy:

Years	Ejection type, conventional* qty
Years	Unorganized dumping of nuclear waste	Industrial accidents and other leaks	Civil incidents
1944–1949	2	4	–
1950–1959	1	15	–
1960–1969	1	11	–
1970–1979	1	10	–
1980–1989	1	28	1
1990–1999	2	31	15
2000–2009	2	10	9

* - the table contains conditional quantitative values. So, for example, only at the "Mayak" enterprise (Chelyabinsk region, Russia), about 32 incidents of varying severity are known over the entire period of operation, and only 15 of them were included in the summary statistics.

From the table, you can see that since the 90s, incidents began to occur among citizens. Cases of theft of nuclear materials and attempts to sell them have become more frequent (the culprits, in most cases, are soon from the radiation received). In particular, medical radioactive sources were stolen and disassembled and sold as scrap metal. In general, various materials “contaminated” with radiation have more than once got to the enterprises for the remelting of scrap metal.

Nuclear disasters

After the discovery of the chain reaction of decay in 1941, they thought about using the nuclear resource for generating electricity. In 1954, the world's first nuclear power plant was completed (Obninsk, USSR). Nowadays, there are about 200 power plants on the planet. However, it is difficult to ensure the trouble-free operation of such facilities.

In order to assess the degree of danger of data from statistics of radiation accidents in the world in 1990, INES was developed - international classification nuclear events in the civilian sphere. According to this scale, major radiation accidents in the world are accidents rated above 4 points. In the entire history of nuclear power, there are about 20 such cases.

INES 4. Events leading to the release into the environment of insignificant doses of radiation, equivalent to 10–100 TBq 131 I. In such accidents, isolated deaths from radiation are recorded. In the incident area, only food control is required. Examples of accidents:

Fleurus, Belgium (2006).
Tokaimura, Japan (1999).
Seversk, Russia (1993).
Saint Laurent, France (1980 and 1969).
Bohunice, Czechoslovakia (1977).

INES 5. Accidents resulting in a radiation release equivalent to 100–1000 TBq 131 I and causing several deaths. Local evacuation may be required in such areas. Examples:

Goiânia, Brazil (1987). An orphaned object was found, which turned out to be destroyed by a highly radioactive source of Cesium-137. Strong doses of radiation were received by 10 people, 4 of them died.
Chazhma Bay, USSR (1985).
Three Mile Island, USA (1979).
Idaho, USA (1961).
Santa Susana, USA (1959).
Windscale Pile, UK (1957).
Choke River, Canada (1952).

INES 6. Accidents in which the release of radioactive material into the environment is equivalent to 1000–10000 TBq 131 I. Evacuation of the population or shelter is required. One example is known. This is the very first radiation accident in the world of this scale - Kyshtym, USSR (1957).

Mayak is a nuclear fuel storage and processing facility in the Chelyabinsk Region. In 1957, an explosion occurred in a container containing 70–80 tons of nuclear waste. A radioactive cloud formed, which carried hazardous substances over a territory of more than 23 thousand km 2 per head of 272 thousand people. For the first 10 days, about 200 people died from radiation.

INES 7. This score is assigned to the largest radiation accidents and disasters in the world. They are characterized by extensive radiation exposure to people and the environment, equivalent to a release of 10,000 TBq 131 I and more. They have colossal consequences for human health and the state of nature. There is an urgent need to implement planned and long-term countermeasures designed for such cases. This rating is assigned to two of the largest radiation accidents in the world:

Fukushima (2011)... Succession tragic events hit Japan that year. Fukushima-1 NPP could not resist them either. and the subsequent three reactors were left without power supply, and therefore without a cooling system. The explosion was inevitable. They were contaminated with radiation, vast territories turned out to be, the ocean waters suffered the most in the accident. The exclusion zone has become a 30-kilometer territory around the nuclear power plant. In the first year, approximately 1,000 people died from radiation sickness.
Chernobyl (1986)... The disaster at the Chernobyl nuclear power plant occurred on April 26. In the fourth power unit, which contained about 190 tons of nuclear fuel, an explosion thundered. The accident that began due to erroneous actions of the personnel acquired inadequate proportions due to (as it later turned out) violations committed during the construction of the reactor.

As a result, about 50 thousand km 2 of agricultural land became unsuitable for cultivation. The city of Pripyat, whose population at that time was 50 thousand people, fell into the 30-kilometer exclusion zone. As well as other settlements.

The statistics of radiation accidents show that in the next twenty years about 4 thousand people died from radiation.

Military "atom"

They began to think about the development of nuclear weapons since 1938. In 1945, for the first time in the world, the United States tested a nuclear bomb on its territory, and then dropped two more on the cities of Japan: Hiroshima and Nagasaki. More than 210 thousand people were killed.

According to Wikipedia, the city of Hiroshima was completely rebuilt in 1960. During the period from 1945 to 2009, 62 nuclear weapons tests and 33 accidents of military equipment using nuclear power plants as an engine or with nuclear weapons on board are known.

Years	Ejection type, qty..
Years	Weapon Test	Accidents military equipment
1945–1949	2	–
1950–1959	13	1
1960–1969	28	9
1970–1979	12	3
1980–1989	7	7
1990–1999	–	2
2000–2009	–	11

Since the 90s, weapon testing has ceased. Since in 1996, most countries signed a nuclear test ban treaty.

Statistics of radiation accidents in the world: expert opinion

There are two opinions about the dangers of radiation. Some scientists carry out scrupulous calculations, and argue that the share of man-made radiation accidents in the world and nuclear weapons tests account for only 1% of the total radiation background. That the nuclear industry is an inexhaustible resource with the future.

According to others, the statistics of radiation accidents in the world show that, in economic terms, there are no advantages from nuclear energy. Therefore, experts call for abandoning the nuclear industry, leaving it in the past. Technologies are expensive at the design and construction stage, and the damage in the event of an accident outweighs all possible benefits. Not to mention the loss of life and the negative impact of radiation on the health of many generations to come.

With horror, humanity realizes how much evil it is doing on the planet that gave it shelter, and the biggest of them is nuclear disasters. We don't seem to think about the harm caused by huge industrial corporations with a high level of danger in their activities, because they strive only for profit, and material well-being is a priority for mankind today. And it, humanity, having broken into conflicting parts, is trying to defend its gains, forgetting that almost all nuclear catastrophes occur when weapons are tested. This article will list the worst of them in terms of the amount of damage caused.

1954

The nuclear disaster in the United States occurred as a result of a test explosion in the area of the Marshall Islands, which turned out to be more than a thousand times more powerful than the explosions of Hiroshima and Nagasaki together. The US government decided to conduct an experiment in Bikini Atoll. And this explosion is only part of a monstrous experiment.

What happened? All nuclear disasters, without exception, bring irreversible consequences, but in this case the events developed unprecedented. There was a monstrous disaster that destroyed all life on an area of 11,265.41 square meters. km. Nuclear disasters of this magnitude did not occur on Earth until March 1954. 655 representatives of the fauna have completely disappeared. Until now, water and bottom soil samples do not show positive results, it is extremely dangerous to be in these areas.

1979

Another nuclear disaster in the United States occurred on Three Mile Island in Pennsylvania. An unknown amount of radioactive iodine and radioactive gases were released into the environment. This happened due to the fault of the staff, who committed whole line errors, resulting in mechanical problems. The general public was not admitted to information about this disaster, the official bodies withheld specific figures in order to prevent panic.

It was impossible even to argue about the scale of pollution, since the country's leadership immediately began to assert that the emission was insignificant. However, the fauna and flora were so damaged that it was impossible not to notice. People who were exposed to radiation in neighboring areas suffered from leukemia and cancer 10 times more than in other places. In 1997, the data was rediscovered and re-examined. In terms of irreversible consequences, this accident is included in the world's nuclear catastrophes of an especially large scale.

First in the world

The very first thundered nuclear explosion in July 1945 in the United States, New Mexico. He supervised the tests of yet unknown weapons of which the first was considered to be plutonium, and the creators gave her the affectionate name "Little Thing". The next one was named "Fat Man", and it was "Fat Man" that fell three weeks later on the heads of innocent people. The sixth day of August 1945 was an unforgettable mournful milestone in the history of mankind.

The American military used an atomic bomb, dropping it on Hiroshima, a densely populated Japanese city that was literally wiped off the face of the earth. The Fat Man's capacity is eighteen thousand tons of TNT. More than eighty thousand people died at one point, another one hundred and forty thousand died a little later. But the deaths did not end there either, they continued for years from both wounds and radiation. And three days later, the same fate befell the city of Nagasaki, where there were the same number of victims. Thus, the United States forced Japan to surrender in World War II.

Nuclear disaster of 1957

The Windscale accident was the largest in British history. The complex was built to produce plutonium, but later it was decided to convert it to the production of tritium - the basis for hydrogen and atomic bombs. As a result, the reactor could not withstand the load, and a fire began in it.

The workers, without hesitation, flooded the reactor with water. The fire was eventually extinguished. But the whole area was contaminated - all rivers, all lakes. Why did the nuclear reaction process get out of control? Because there was no normal test equipment and the staff made a lot of mistakes.

Consequences

The energy release was too great, and the uranium metal in the fuel channel reacted with air. As a result, the fuel rods of the fuel channels were heated to almost one and a half thousand degrees Celsius, they increased in volume and jammed in the channels, so it was impossible to unload them. The fire spread to one hundred and fifty channels with eight tons of uranium. Carbon dioxide could not cool the core. Therefore, on October 11, 1957, the reactor was flooded with water. The radioactive release was approximately twenty thousand curies, and long-term contamination with cesium-137 contained up to eight hundred curies.

Now metallic fuel is not used in modern reactors. In total, more than eleven tons of radioactive uranium burned there. The result was that the release of radionuclides began. Huge areas in Ireland and England were contaminated, and the radioactive cloud visited Germany, Denmark, Belgium. In England itself, cases of leukemia have increased significantly. The contaminated water used by the locals has led to numerous cancers.

Kyshtym

Then, in 1957, an accident occurred in the USSR in the closed city of Chelyabinsk-40, where the Mayak chemical plant is located. It was a very large nuclear disaster in Russia. Lake Kyshtym is located nearby, and this serious emergency was called the Kyshtym tragedy. At the end of September, the cooling system at the plant went out of order, because of this, a container with highly radioactive nuclear waste exploded.

More than twelve thousand people were evacuated from the disaster zone, twenty-three villages ceased to exist. The accident was eliminated by the military. In general, two hundred seventy thousand residents of the Tyumen, Sverdlovsk and Chelyabinsk regions were found in the pollution zone. Information about the tragedy was also carefully concealed, the truth was officially told only in 1989. In terms of the damage done, this is also a very large nuclear disaster.

At the Chernobyl nuclear power plant

In Ukraine in Pripyat there was an explosion of a nuclear reactor, which until recently was considered the largest world man-made accident. The Chernobyl nuclear disaster (1986) was so severe that atmospheric emissions exceeded four hundred times the consequences of a nuclear attack on Hiroshima and Nagasaki.

But there the main damage happened from the shock wave, and here the radioactive contamination became much more terrible. Since the accident, more than thirty people have died from radiation sickness in three months. More than one hundred thousand were evacuated. Why the explosion occurred is still not entirely clear, because the opinions of scientists are fundamentally different from each other.

Consequences

And the consequences were dire. The release of uranium dioxide into the environment was very large. Before the accident, the reactor at the fourth block had about one hundred and eighty tons of nuclear fuel, up to thirty percent of which was in the release. The rest melted and flowed into the fractures of the reactor vessel. But, in addition to fuel, there were fission products, transuranic elements, that is, radioactive isotopes that accumulate while the reactor is running. The greatest radiation hazard is from them. Volatiles were ejected from the reactor.

And these are aerosols of tellurium and cesium, more than fifty percent of iodine - a mixture of solid particles and steam, as well as organic compounds, all the gases that were contained in the reactor. In total, the activity of the ejected substances turned out to be enormous. Iodine-131, cesium-137, strontium-90, plutonium isotopes and much more. The 1986 nuclear disaster in Ukraine is still making itself felt. And people are still keenly interested in her. The most interesting series in the genre of fiction "Chernobyl. Exclusion Zone" was filmed. In the second season, the situation is transferred to the United States, where, allegedly, instead of the Ukrainian one, there was a nuclear disaster on August 7, 1986 in Maryland.

Outcomes

In fact, it was not there. All results are summarized here. And this is more than two hundred thousand hectares of contaminated soils, of which seventy percent - the territory of Ukraine, Russia, Belarus. The nature of the pollution was not uniform, everything depended on the direction of the wind after the accident. The regions directly close to the Chernobyl NPP were especially affected: Kievskaya, Zhitomirskaya, Gomelskaya, Bryanskaya. Radiation of an increased background was observed even in Chuvashia and Mordovia, radioactive fallout fell in the Leningrad region. Most of the plutonium and strontium fell out within a radius of one hundred kilometers, while cesium and iodine spread much more widely.

Tellurium and iodine posed a danger to the population in the first few weeks; they have a short half-life. But until now and for many more decades, the isotopes of strontium and cesium, which lie in a layer on the soil surface, will be killed in these territories. Cesium-137 in high concentration is found in all plants and fungi, all insects and animals are contaminated. And the isotopes of americium and plutonium are stored without losing radioactivity for hundreds and thousands of years. Their number is not so great, but americium-241 will also increase, because it is formed when plutonium-241 decays. However, the 1986 nuclear catastrophe in its consequences turned out to be not as terrible as the one that will be discussed below.

Fukushima

Today, the accident is not only the saddest event in the history of Japan, but also the most terrible for the entire existence of mankind on Earth. It happened on March 11 in 2011. First, the country was shocked by a powerful earthquake, after a few hours all of northern Japan was literally washed away by a huge tsunami wave. The earthquake disrupted energy connections, and this is what became the main reason a disaster that has no equal yet.

The tsunami wave disabled the reactors, chaos began, the installations heated up quickly, there was no way to cool down (without electricity, the pumps did not work). The radioactive vapor was simply released into the atmosphere, but still a day later the first unit of the nuclear power plant exploded. Two more power units exploded next. And today, the level of pollution around Fukushima is unusually high.

Situation today

The decontamination that is carried out there does not cleanse the earth, it is just that the radiation is transferred to other places. All nuclear power plants in northern Japan were shut down, and there is a whole chain of them - twenty-five nuclear reactors. Now they have been put back into operation despite public outcry. The area is too seismological and the risk is enormous. The same situation may well be repeated from any of the other stations.

Almost eight hundred thousand terabecquerels of radiation were released into the atmosphere, this is not so much, about fifteen percent of the release in Chernobyl. But here something else is much worse. Contaminated water continues to flow out of the already destroyed station even now, radioactive waste is still accumulating. The Pacific Ocean is getting more and more polluted every day. Fish, even far from the Japanese coast, should not be eaten.

Pacific Ocean

Three hundred twenty thousand people were evacuated from the disaster zone - a thirty-kilometer zone. According to experts, the zone should have been significantly expanded. Many times more radioactive substances were dumped into the Pacific Ocean than the releases from Chernobyl. For the seventh year now, three hundred tons of radioactive water has been supplied there from the reactor every day. Fukushima has infected the entire ocean, even North America finds Japanese radiation off its coast.

The Canadians prove this by presenting the caught irradiated fish. The ichthyofauna has already decreased by ten percent, even the herring in the north of the Pacific Ocean has disappeared. The level of radioactive iodine twenty days after the accident in western Canada was raised by three hundred percent, and it is still increasing. In the United States, starfish began to lose legs and disintegrate, they have been dying en masse since 2013, when radioactive waters got there. The entire oceanic ecosystem of the region is under attack. The famous Oregon tuna has become radioactive. On the beaches of California, radiation has risen by five hundred percent.

Worldwide silence

But it wasn't just America's west coast that suffered. Scientists talk about the contamination of the entire world ocean: the Pacific Ocean is currently up to ten times more radioactive than after World War II, when the United States tested its nuclear submarines there. However, Western politicians prefer not to say anything about the impact of the Fukushima tragedy. And everyone knows why.

Japan's Tepco is a subsidiary, while Daddy here is General Electric, the world's largest company that controls both politicians and the media. O nuclear disaster Fukushima they cannot speak with their hands.

In normal operation, nuclear power plants are absolutely safe, but emergency situations with radiation emissions have a detrimental effect on the environment and public health. Despite the introduction of technologies and automatic systems monitoring, the threat of a potentially dangerous situation remains. Each tragedy in the history of nuclear energy has its own unique anatomy. Human factors, inattention, equipment failure, natural disasters and fatal circumstances can lead to fatal accidents.

What is called an accident in nuclear power

As in any technological facility, there are emergency situations at a nuclear power plant. Since accidents can affect the environment within a radius of up to 30 kilometers, in order to respond as quickly as possible to an incident and prevent consequences, the International Atomic Energy Agency (IAEA) has developed the International Nuclear Events Scale (INES). All events are rated on a 7-point scale.

0 points - emergency situations that did not affect the safety of the NPP. To eliminate them, it was not necessary to use additional systems, there was no threat of radiation leakage, but some mechanisms were malfunctioning. Zero-level situations occur periodically at every nuclear power plant.

1 point according to INES or anomaly - the work of the station is out of the established mode. This category includes, for example, the theft of low-level sources or exposure of a stranger to a dose that exceeds the annual dose, but does not pose a threat to the health of the victim.

2 points or incident - a situation that led to overexposure of plant workers or a significant spread of radiation outside the zones established by the design within the station. Two points are used to assess the increase in the level of radiation in working area up to 50 mSv / h (at an annual rate of 3 mSv), damage to the insulating package of high-level waste or sources.

3 points - the class of a serious incident is assigned to emergency situations that have led to an increase in radiation in the working area up to 1 Sv / h, minor radiation leakages outside the station are possible. Burns and other non-fatal effects may occur in the general population. The peculiarity of level 3 accidents is that workers manage to prevent the spread of radiation on their own, using all echelons of protection.

Such emergencies pose a threat primarily to plant workers. The fire at the Vandellos nuclear power plant (Spain) in 1989 or the accident at the Khmelnitsky nuclear power plant in 1996 with the release of radioactive products into the plant's premises resulted in casualties among employees. Another case is known that took place at the Rivne NPP in 2008. The personnel discovered a potentially dangerous defect in the equipment of the reactor plant. The reactor of the second power unit had to be transferred to a cold state during the repair work.

Abnormal situations from 4 to 8 points are called accidents.

What are the accidents at nuclear power plants

4 points - this is an accident that does not pose a significant risk outside the work site of the station, but death is possible among the population. The most common causes of such incidents are the melting or damage of fuel elements, accompanied by a small leak of radioactive material within the reactor, which can lead to a release to the outside.

In 1999, a 4-point accident occurred in Japan at the Tokaimura radio engineering plant. During the purification of uranium for the subsequent manufacture of nuclear fuel, employees violated the rules of the technical process and launched a self-sustaining nuclear reaction. 600 people were irradiated, 135 employees were evacuated from the plant.

5 points - an accident with wide consequences. It is characterized by damage to physical barriers between the reactor core and working rooms, critical operation and fire. The radiological equivalent of several hundred terabecquerels of iodine-131 is released into the environment. Evacuation of the population can be carried out.

It was the 5th level that was assigned to a major accident in the United States. It happened in March 1979 at the Three Mile Island nuclear power plant. At the second power unit too late, a coolant leak was detected (a vapor or liquid mixture that removes heat from the reactor). A failure occurred in the first circuit of the installation, this led to a halt in the cooling process of the fuel assemblies. Half of the reactor core suffered, it completely melted. The premises of the second power unit were heavily contaminated with radioactive products, but outside the nuclear power plant, the radiation level remained normal.

A significant accident corresponds to 6 points. We are talking about incidents associated with the release of significant amounts of radioactive substances into the environment. Evacuation and placement of people in shelters are being carried out. The premises of the station can be deadly.

The incident, known as the "Kyshtym accident", was assigned a level 6 hazard. An explosion of a container for radioactive waste occurred at the Mayak chemical plant. This happened due to a breakdown of the cooling system. The tank was completely destroyed, the concrete ceiling was torn off by an explosion, which was estimated at tens of tons in TNT equivalent. A radioactive cloud was formed, but up to 90% of radiation contamination fell out on the territory of the chemical plant. In the process of liquidating the accident, 12 thousand people were evacuated. The site of the incident is referred to as the East Ural Radioactive Trail.

Accidents are classified separately as design basis and beyond design basis. Initiating events, elimination procedures and final states are defined for the design ones. Such accidents can usually be prevented with the help of automatic and manual safety systems. Beyond design basis incidents are spontaneous emergencies that either disable systems or are triggered by external catalysts. Such accidents can lead to the release of radiation.

Weaknesses of modern nuclear power plants

Since nuclear power began to develop in the last century, the first problem of modern nuclear facilities is the deterioration of equipment. Most of the European nuclear power plants were built in the 70s and 80s. Of course, when extending the operating life, the operator carefully analyzes the state of the NPP, changes the equipment. But the complete modernization of the technical process requires huge financial costs, therefore, the stations often operate on the basis of old methods. Such nuclear power plants do not have reliable systems for preventing accidents. Building a nuclear power plant from scratch is also expensive, so one country after another is extending the life of a nuclear power plant and even restarting after a downtime.

The second most frequent emergencies there are technical mistakes of the staff. Incorrect actions can lead to loss of control over the reactor. Most often, as a result of negligent actions, overheating occurs and the core is partially or completely melted. Under certain circumstances, a fire can occur in the core. This happened, for example, in Great Britain in 1957 in a reactor for the production of armed plutonium. The personnel did not keep track of the indicators of the few measuring instruments of the reactor and missed the moment when the uranium fuel reacted with the air and ignited. Another case of technical error of personnel is the accident at the St. Lawrence NPP. The operator inadvertently loaded the fuel assemblies into the reactor incorrectly.

There are very curious cases - at the Browns Ferry reactor in 1975, an employee's initiative to eliminate an air leak in a concrete wall led to a fire. He performed the work with a candle in his hands, the draft caught the fire and spread it along the cable channel. To eliminate the consequences of the accident at the nuclear power plant, they spent no less than 10 million dollars.

The largest accident at a nuclear facility in 1986 at the Chernobyl nuclear power plant, as well as the well-known major accident at the Fukushima nuclear power plant, also happened due to a number of errors of technical personnel. In the first case, fatal mistakes were made during the experiment; in the second, the reactor core overheated.

Unfortunately, the Fukushima nuclear power plant scenario is not uncommon for plants where the same boiling water reactors are installed. Potentially dangerous situations can arise because all processes, including the main cooling process, depend on the water circulation mode. If an industrial drain is clogged or a part is out of order, the reactor will start to overheat.

As the temperature rises, the nuclear fission reaction in the fuel assemblies is more intense, and an uncontrolled chain reaction can begin. Nuclear rods melt together with nuclear fuel (uranium or plutonium). An emergency situation arises, which can develop according to two scenarios: a) molten fuel burns through the body and protection, getting into groundwater; b) the pressure inside the case leads to an explosion.

TOP-5 accidents at nuclear power plants

1. For a long time, the only accident that the IAEA has assessed at 7 points (the worst that can happen) was the explosion at the nuclear facility in Chernobyl. More than 100 thousand people have suffered from radiation sickness of varying degrees, and the 30-kilometer zone has been deserted for 30 years.

The accident was investigated not only by Soviet physicists, but also by the IAEA. The main version remains a fatal coincidence and personnel mistakes. It is known that the reactor worked freelance and tests in such a situation should not have been carried out. But the staff decided to work according to the plan, the employees turned off the working technological protection systems (they could stop the reactor before entering a dangerous mode) and began testing. Later, experts came to the conclusion that the self-design of the reactor was imperfect, this also contributed to the explosion.

2. The accident at "Fukushima-1" led to the fact that territories within a radius of 20 kilometers from the station were recognized as an exclusion zone. For a long time, the cause of the incident was believed to be an earthquake and tsunami. But later, Japanese parliamentarians blamed the incident on the operator Tokyo Electric Power, which did not protect the nuclear power plant. As a result of the accident, the fuel rods in three reactors at once completely melted. 80 thousand people were evacuated from the station area. At the moment, in the premises of the station, which are examined exclusively by robots, tons of radioactive materials and fuel remain, as Pronedra previously wrote about.

3. In 1957, on the territory of the Soviet Union, an accident occurred at the Mayak chemical plant, known as Kyshtym. The reason for the incident was the failure of the cooling system of the container with high-level nuclear waste. The concrete floor was destroyed by a powerful explosion. The IAEA later assigned the 6th hazard level to the nuclear incident.

4. The fifth category was received by the Windscale fire at a station in the UK. The accident happened on October 10 of the same 1957 as the explosion at the Mayak chemical plant. The exact cause of the accident is unknown. At that time, the personnel did not have control devices, so it was more difficult to monitor the state of the reactor. At some point, the workers noticed that the temperature in the reactor was growing, although it should be falling. While inspecting the equipment, employees were horrified to find a fire in the reactor. They did not immediately dare to extinguish the fire with water due to fears that the water would instantly disintegrate, and hydrogen would lead to an explosion. Having tried all the available means, the staff nevertheless opened the taps. Fortunately, the explosion did not occur. According to official information, about 300 people received radiation.

5. The accident at the Three Mile Island nuclear power plant in the United States happened in 1979. It was considered the largest in the history of American nuclear power. The main reason for the incident was the breakdown of the pump in the second cooling circuit of the reactor. TO emergency all the same set of circumstances led to: breakdown of metering devices, failure of other pumps, gross violations of operating rules. Fortunately, there were no casualties. People living in the 16-kilometer zone received a small amount of radiation (slightly more than during a fluorography session).

Despite the fact that nuclear energy does provide 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 in the highest category - seventh, while the 1st level is regarded as 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.

Time will tell what category the accident at Fukushima-1 will assign to the rock. Photo: japantimes.co.jp

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

The accident at the nuclear facility in Chernobyl is recognized by all experts as the worst disaster in the history of nuclear power. It is the only nuclear accident that has been classified by the International Atomic Energy Agency as the worst it can be. The largest man-made disaster broke out on April 26, 1986, at the 4th block of the Chernobyl nuclear power plant, located in small town Pripyat. The destruction was explosive, the reactor was completely destroyed, and a large amount of radioactive substances were 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 in the first three months after the accident; the long-term consequences of radiation, revealed over the next 15 years, caused the death of 60 to 80 people. 134 people suffered from 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 the liquidation of 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 permanently ceased its work only on December 15, 2000.

The Kyshtym accident is a very serious radiation technogenic accident at the Mayak chemical plant located in the closed city of Chelyabinsk-40 (since the 1990s - Ozersk). The accident got its name Kyshtym for the reason that Ozersk was classified and was absent on maps until 1990, and Kyshtym is the city closest to it. On September 29, 1957, due to the failure of the cooling system, an explosion occurred in a container with a volume of 300 cubic meters, which contained about 80 m³ of highly radioactive nuclear waste. An explosion, estimated at tens of tons in TNT equivalent, destroyed the container, a 1-meter-thick concrete ceiling weighing 160 tons was thrown aside, about 20 million curies of radiation were thrown into the atmosphere. Some of the radioactive substances were lifted 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 out 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. On 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, who received significant doses of radiation. Territory that has undergone radioactive contamination as a result of an explosion at a chemical plant, it was named "East Ural radioactive trace". The total length was about 300 km, with a width of 5-10 km.

From the memoirs from the website oykumena.org: “Mom began to get sick (there were frequent fainting, anemia) ... I was born in 1959, there were the same health problems ... We left Kyshtym when I was 10 years old. I'm a little unusual person... During my life, strange things happened ... I foresaw the crash of the Estonian liner. And she even talked about the collision of planes with a friend of the flight attendant ... She died. "

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

On October 10, 1957, operators at Windscale Station noticed that the reactor temperature was steadily rising, while the opposite should be the case. First of all, everyone thought about the malfunction of the reactor equipment, which two workstations went to inspect. When they got to the reactor itself, they saw to their horror that it was on fire. At first, the workers did not use the water, because the plant operators expressed fears that the fire was so hot that the water would disintegrate instantly, and as you know, hydrogen in water could cause an explosion. All the means tried did not help, and then the station employees opened the hoses. Thank God the water was able to stop the fire without any explosion. According to some estimates, in the UK, Windscale has caused cancer in 200 people, half of whom have died. The exact number of victims is unknown as the British authorities tried to cover up this 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 aggravated by the fact that the radiation from Windscale has spread for hundreds of kilometers throughout northern Europe.

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

Before the Chernobyl accident, which happened seven years later, the Three Mile Island nuclear power plant accident was considered the largest in the history of world nuclear power and is still considered the worst nuclear accident in the United States. On March 28, 1979, early in the morning, there was a major accident at the 880 MW (electrical) reactor block 2 at the Trimile Island nuclear power plant, located twenty kilometers from Harrisburg, Pennsylvania and owned by the Metropolitan Edison company. Unit 2 at the Threemile Island NPP, as it turned out, was not equipped with an additional safety system, although such systems are available at some units of this NPP. Despite the fact that the nuclear fuel partially melted, it did not burn through the reactor vessel and radioactive substances, basically, remained inside. According to various estimates, the radioactivity of noble gases released into the atmosphere was from 2.5 to 13 million curies, but the release of hazardous nuclides, such as iodine-131, was insignificant. The territory of the station was also contaminated with radioactive water flowing out from the primary circuit. It was decided that there was no need to evacuate the population living near the station, but the authorities advised pregnant women and preschool children to leave the 8-kilometer zone. Officially, the work to eliminate the consequences of the accident was completed in December 1993. Decontamination of the station territory was carried out, fuel was unloaded from the reactor. However, part of the radioactive water has been absorbed into the concrete of the containment and this radioactivity is almost impossible to remove. The plant's other reactor (TMI-1) was reopened in 1985.

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

On September 30, 1999, the most terrible atomic tragedy for the Land of the Rising Sun took place. Japan's worst nuclear accident took place over a decade ago, though it was outside of Tokyo. For a nuclear reactor that has not been used for more than three years, a batch of highly enriched uranium was prepared. The plant operators were not trained in how to handle such highly enriched uranium. Not understanding what they were doing in terms of the possible consequences, the "specialists" put much more uranium in the tank than needed. Moreover, the reactor vessel 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 at that time die from radiation. After the disaster, about a hundred workers and those who lived nearby were hospitalized with a diagnosis of radiation exposure, 161 people who lived several hundred meters from the nuclear power plant were subject to evacuation.