ACCIDENT At approximately 1:24 on April 26, 1986, an explosion occurred at the 4th power unit of the Chernobyl nuclear power plant, which completely destroyed the reactor. The reason for this was that safety tests were carried out at an ultra-low power of 200 MW, while the norm is 700 MW. When the power level dropped too low, pressing the emergency shutdown button triggered an uncontrollable increase in power, leading to the destruction of Unit 4. The power unit building partially collapsed. Subsequently, the remains of the core melted. A mixture of molten metal, sand, concrete and fuel particles 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).
Some facts: the reactor installation did not actually comply with applicable safety standards at the time of design and even had unsafe design features insufficient safety analysis insufficient attention to independent safety review operating regulations not adequately supported in the safety analysis insufficient and ineffective exchange of important safety information, both between operators, and between operators and designers, insufficient understanding by the personnel of aspects of their station related to safety, the use of COMBUSTIBLE materials in construction, in order to reduce the cost of construction, which affected the firefighting of the power unit building (the firefighting continued all night, many firefighters received lethal doses of radiation) Safety was in the background...
Disadvantages of the RBMK-1000 reactor The reactor becomes practically uncontrollable at ultra-low power, it is necessary to immediately shut it down, but the result was unexpected... A large number of pipelines and various auxiliary subsystems require a large number of highly qualified personnel; The need for channel-by-channel flow control, which may lead to accidents associated with the cessation of coolant flow through the channel; Higher load on operating personnel associated with a large number of components (for example, shut-off and control valves); Due to the large size of the core and the metal content of the RBMK, a larger amount of activated structural materials remains after decommissioning and requires disposal.
In the first hours after the accident, many did not realize how badly the reactor was damaged, so the mistaken decision was made to supply water to the reactor core to cool it. These efforts turned out to be futile, since both the pipelines and the core itself were destroyed, which required work in areas with high radiation. Other actions of the station personnel, such as extinguishing local fires in the premises of the station, measures aimed at preventing a possible explosion on the contrary, were necessary. They may have prevented even more serious consequences. While performing this work, many station employees received large doses of radiation, some even fatal. The release led to the death of trees near the nuclear power plant on an area of about 10 km²
Firefighters did not allow the fire to spread to the third unit (the 3rd and 4th power units have single transitions). The only protective equipment the firefighters had was a combat jacket (a canvas robe), a helmet and mittens. It was impossible to work in gas masks due to the high combustion temperature; firefighters took them off within the first 10 minutes. Instead of a fire-resistant coating, as required by the instructions, the roof of the turbine room was filled with ordinary flammable bitumen. At about 2 a.m., the first injured firefighters appeared. They began to experience weakness, vomiting, “nuclear tanning,” and after removing the mittens, the skin from their hands was removed. They were provided with assistance on the spot, at the station’s first aid post, after which they were transported to the Pripyat city hospital. On April 27, the first group of victims of 28 people was sent by plane to Moscow, to the 6th Radiological Hospital. The drivers of the fire trucks were practically unharmed.
The first official announcement was made on television on April 28. A rather dry message reported the fact of the accident and two deaths; the true scale of the disaster began to be reported later. After assessing the scale of radioactive contamination, it became clear that the evacuation of the city of Pripyat would be required, which was carried out on April 27. In the first days after the accident, the population of the 10-kilometer zone was evacuated. In the following days, the population of other settlements within the 30-kilometer zone was evacuated. It was forbidden to take things with you; many were evacuated in home clothes. To avoid fanning panic, it was reported that the evacuees would return home in three days. Safe routes for the movement of columns of the evacuated population were determined taking into account the radiation reconnaissance data already received. Despite this, neither on April 26 nor 27 were residents warned of the existing danger or given any recommendations on how to behave in order to reduce the impact of radioactive contamination.
Specialists sent to carry out work on and around the emergency unit, as well as military units, both regular and made up of urgently called up reservists, began to arrive in the 30-kilometer zone around the Chernobyl nuclear power plant. They all later began to be called “liquidators”. The liquidators worked in the dangerous zone in shifts: those who received the maximum permissible dose of radiation left, and others came to take their place. The bulk of the work was carried out in 1986 - 1987, involving approximately 240,000 people. The total number of liquidators (including subsequent years) was about 600,000. HAPPY MEMORY TO THEM...
Chernobyl, a city in Ukraine, on the Pripyat River, at its confluence with the Kiev Reservoir. Regional center with developed industry: iron foundry and cheese-making factories, fleet repair and maintenance base; workshop of the production and artistic association, medical school.
On April 25, 1986, a shutdown of the 4th power unit of the Chernobyl nuclear power plant was planned for the next scheduled maintenance. During such shutdowns, various routine procedures and equipment tests are usually carried out.
At approximately 1:24 am on April 26, 1986, a release occurred at the 4th power unit of the Chernobyl nuclear power plant, which completely destroyed the reactor. The power unit building partially collapsed, killing 2 people.
A fire started in various rooms and on the roof. Subsequently, the remains of the core melted. As a result of the accident, radioactive substances were released into the environment.
The accident is regarded as the largest of its kind in the entire history of nuclear energy, both in terms of the estimated number of people killed and affected by its consequences, and in terms of economic damage. At the time of the accident, the Chernobyl nuclear power plant was the most powerful in the USSR. The actual death toll during the first 3 months is estimated at 31; long-term effects of radiation, identified over the next 15 years, caused the death of 60 to 80 people.
Unlike the bombings of Hiroshima and Nagasaki, the explosion resembled a very powerful “dirty bomb” - the main damaging factor was radioactive contamination. The radioactive cloud from the accident passed over the European part of the USSR, Eastern Europe and Scandinavia. Approximately 60% of the radioactive fallout fell on the territory of Belarus. About 200,000 people were evacuated from contaminated areas.
evacuation
About 50,000 people were evacuated from the city of Pripyat alone in one day.
In the first days after the accident, the population of the 10-kilometer zone was evacuated. In the following days, the population of other settlements within the 30-kilometer zone was evacuated. It was forbidden to take things with you; many were evacuated in home clothes. To avoid fanning panic, it was reported that the evacuees would return home in three days. They were not allowed to take pets with them (they were subsequently shot).
While all foreign media were talking about the threat to people's lives, and a map of air flows in Central and Eastern Europe was shown on TV screens, festive demonstrations and celebrations dedicated to May Day were held in Kiev and other cities of Ukraine and Belarus. Those responsible for concealing information subsequently explained their decision by the need to prevent panic among the population
Elimination of consequences of the accident
Target:
1. Consideration of the problem of using the atom for peaceful purposes and overcoming possible crisis moments.
2. Demonstration using the example of Chernobyl that man-made disasters are caused not only by failures in equipment and mechanisms, but also by incorrect actions of personnel and other employees of the nuclear power plant
3. Developing in students a sense of responsibility for the fate of their country, their compatriots, the understanding that each person must approach the performance of their work efficiently and seriously.
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GOU secondary school 1981 Moscow 25 years of the accident at the Chernobyl nuclear power plant Physics teacher Elena Anatolyevna Alikueva 2011
Chernobyl Nuclear Power Plant Complete destruction of the Chernobyl reactor, Pripyat, Ukrainian SSR A radioactive cloud passed over the USSR, Eastern Europe, Scandinavia Chernobyl accident - April 26, 1986
Release into the environment Uranium isotopes Plutonium Iodine – 131 (half-life – 8 days) Cesium – 134 (half-life – 2 years) Cesium – 137 (half-life – 33 years) Strontium – 190 (half-life – 28 years)
Chronology of events At 1:23:39 - emergency protection signal (AZ-5) Then a signal about a rapid increase in power Recording systems fail Emergency protection rods stopped 1:23:47 - 1:23:50 (3 seconds!) - explosion , the reactor is completely destroyed
Presumable causes were suggested: Hydrogen explosion - chemical nature of the explosion Thermal explosion - nuclear nature Steam explosion INSAG “... the accident was the result of an unlikely coincidence of a number of violations of rules and regulations by the operating personnel; the accident acquired catastrophic consequences due to the fact that the reactor was brought into an unregulated state. » Causes of the accident
Disadvantages of the reactor As of April 1986, the RBMK reactor had dozens of violations and deviations from the safety rules in force at that time. Due to the incorrectly chosen physical and design parameters of the core by its developers, the reactor was a system dynamically unstable with respect to disturbances both in power and steam content.
Operator errors Thus, the most significant errors of operational personnel should be called: interpretation of the proposed tests as electrical; improper preparation of the test program, including in terms of regulation of safety measures; significant deviations from the program at the stage of preparation for the experiment and its conduct; disabling safety systems, including emergency reactor protection
Consequences of the accident
Informing the population
Elimination of consequences of the accident
Impact of the accident on human health
Radiation doses
Oncological diseases The thyroid gland is one of the organs most at risk of cancer as a result of radioactive contamination, because it accumulates iodine-131; The risk is especially high for children. Between 1990 and 1998, more than 4,000 cases of thyroid cancer were reported among those who were under 18 years of age at the time of the accident.
An increase in the number of congenital pathologies was found in various regions of Belarus between 1986 and 1994. Infant mortality is very high in all three countries affected by the Chernobyl accident.
Other diseases Cataract Cardiovascular diseases Decreased immunity
Dead city 25 years later
In memory of the victims
This must not happen again!
Geographical location of the Chernobyl nuclear power plant The Chernobyl nuclear power plant is located in the eastern part of the Belarusian-Ukrainian Polesie in northern Ukraine, 11 km from the border with Belarus, on the banks of the Pripyat River, which flows into the Dnieper. To the west of the three-kilometer sanitary protection zone of the nuclear power plant is the abandoned city of Pripyat, 18 km southeast of the station is the former regional center of the abandoned city of Chernobyl, 110 km to the south of the city of Kiev.
Chernobyl accident Chernobyl accident destruction on April 26, 1986 of the fourth power unit of the Chernobyl nuclear power plant, located on the territory of the Ukrainian SSR (now Ukraine). The destruction was explosive, the reactor was completely destroyed, and a large amount of radioactive substances were released into the environment. April 26, 1986 Chernobyl nuclear power plant Ukrainian USSR Ukraine reactor
Causes of the Chernobyl accident, the reactor did not meet safety standards and had dangerous design features; low quality of operating regulations in terms of safety; the ineffectiveness of the regulatory and safety oversight regime in nuclear energy, the general lack of safety culture in nuclear matters at both the national and local levels; there was no effective exchange of safety information both between operators and between operators and designers, personnel did not have a sufficient understanding of the plant features that affect safety; the personnel made a number of mistakes and violated existing instructions and the testing program.
Medical consequences of the Chernobyl accident Thyroid cancer and other thyroid pathologies Leukemia Solid cancers other than thyroid cancer Non-cancer and non-thyroid effects: – Mortality that is attributed to the Chernobyl accident – Psychiatric and psychological consequences and effects in the central nervous system – Reproductive effects and children's health – Cataracts – Cardiovascular diseases – Immunological effects
The four main mechanisms of public exposure are external dose from the passage of a radioactive cloud, internal dose from inhalation of radioactive materials from the cloud and resuspended particles, external dose from radioactive material deposited on soil and other surfaces, internal dose from ingestion of food food and water
Radiation-induced effects on plants and animals Acute radiation effects (death of plants and animals due to radiation, loss of reproduction, etc.) and long-term effects (change in biodiversity, cytogenetic abnormalities) were observed in affected areas
Radioactive pollution of the environment The main emissions from the fourth power unit of the Chernobyl nuclear power plant lasted ten days and included radioactive gases, condensed aerosols and a large number of fuel particles.
Agricultural environment Various types of agricultural plants, particularly leafy vegetables and leafy greens, were also contaminated with radionuclides to varying degrees depending on deposition levels and growth stage. Direct fallout onto plant surfaces has been a problem for almost two months.
RESULTS The results of the implementation of the Chernobyl programs show that the problem of overcoming the consequences of the Chernobyl disaster is objectively long-term in nature: A large amount of work has been completed to clarify the radiation situation, environmental, medical-demographic, economic and social characteristics of the territories and contingents affected by the accident. Currently, it is possible to reliably predict the situation in contaminated areas. Work has been carried out to protect the population, including measures in the field of agriculture and forestry, sanitary protection, decontamination and improvement of populated areas. At the same time, programs were implemented to improve medical care for the population, provide specialized medical care, and social protection for citizens affected by the accident. Thanks to natural processes and the work performed, there was an objective improvement in the radiation situation in all areas affected by radioactive contamination. In the lightly polluted territories of Belgorod, Voronezh, Kursk, Lipetsk, Leningrad, Penza, Ryazan, Tambov, Ulyanovsk regions and Mordovia, it can be considered normalized.
The Russian Scientific Commission on Radiation Protection adopted the “Concept of radiation, medical, social protection and rehabilitation of the population of the Russian Federation exposed to emergency exposure,” which creates a scientific basis for rehabilitation work in the recovery phase and involves changing the principles of zoning of affected areas and ongoing activities. High-risk groups have been identified - liquidators and the child population of the most contaminated areas of the Bryansk, Kaluga, Oryol and Tula regions. Long-term medical supervision is necessary for these populations.
The tasks of restoring the Chernobyl zone are health protection and medical rehabilitation of citizens exposed to radiation as a result of the Chernobyl disaster; socio-psychological rehabilitation of citizens exposed to radiation; radiation control in radioactively contaminated areas; reduction of dose loads on the population and environmental improvement of territories; socio-economic rehabilitation of the population of contaminated areas.
The world's worst accident occurred at the Chernobyl nuclear power plant on April 26, 1986. A technological experiment to study the possibility of providing pumps with energy from the station itself (previously this was done from the city network) led directly to the accident. At 1 hour 24 minutes, the nuclear reactor of the fourth block went out of control, exploded and caught fire.
The total release of radioactive substances into the environment is estimated to be 50 MCi, which is 3.5% of the total amount of radioactive substances in the reactor. 96.5% or approximately 1380 MCi remained inside the reactor. Since 1Ci = 3.7*10 10 Bq = 3.7*10 10 decays per second, then immediately after the accident 50*10 6 *3.7*10 10 decays / s =1.85 *10 occurred in the environment 18 rpm/s
According to the Organization for Economic Cooperation in Europe, the following radioactive substances were released into the environment: ElementIsotopeHalf-life CESIUM137 CS30 YEARS CESIUM134 CS2.1 YEARS IODINE131 I8 DAYS XENON133 XE5.3 DAYS MOLYBDENUM99 MO2.8 DAYS ZIRCONONIUM95 ZR64 DAYS RUTHENE I103 RU39 DAYS RUTHENIUM106 RU368 DAYS BARIUM140 BA12 .7 DAYS CERIUM141 CE32.5 DAYS CERIUM144 CE284 DAYS STRONTIUM89 SR59.5 DAYS STRONTIUM90 SR29.2YEARS PLUTONIUM239 PU24000 YEARS
Today, 20 years later, radioactive cesium and strontium with a half-life of 30 years pose a particular danger. Currently, more than 60% of the original amount of these elements are in the environment, participating in the biological cycle of substances. Ultra-long-lived plutonium poses a particular danger. During the fire, plutonium and soot formed “hot particles” that are easily transported by the wind and, once ingested by the human body, settle in the lungs, causing serious internal radiation. Now, 20 years after the accident, about 0.1% of the plutonium released from the reactor has decayed, 99.9% is still in the environment.
As a result of the accident, the territories of Belarus (23%), Ukraine (4.8%), and Russia (0.5%) were affected. 264 thousand hectares of land were taken out of agricultural production. 600 thousand people were directly affected by the Chernobyl accident. The first victims of Chernobyl were the heroes - the firefighters who extinguished the reactor immediately after the explosion. There are 31 of them. At the cost of their lives, they prevented the fire from spreading to the nearby III block. Then the consequences of the accident would be difficult to imagine.
The Chernobyl disaster does not have one single cause. The disaster became possible as a result of a series of mistakes and miscalculations - political, managerial and technical. 1. The dangers of nuclear power were underestimated. This led to the decision to massively build nuclear power plants. 2. A number of miscalculations were made when designing a nuclear power plant. 3. Low qualifications and low discipline of the personnel. The experiment, which failed during the day, was continued at night by young shift supervisors, in the absence of the main specialists of the station, which led to a gross violation of the instructions (in particular, control rods were left in the working area of the reactor much less than the critical norm. ) 4. In addition, untimely notification of people about the accident aggravated the consequences and significantly increased the number of victims.
The consequences of Chernobyl are global and eternal. Global because Chernobyl radiation spread throughout the planet. Eternal, because contaminated lands will remain dangerous for tens and even hundreds of thousands of years. The main lesson of the tragedy is that you cannot rely on technology, no matter how reliable it may seem. Blind faith in the safety of the “peaceful atom” led to disaster.
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