35 years of the accident at the Chernobyl nuclear power plant: the consequences of the largest nuclear disaster

Chernobyl nuclear power plant

The Chernobyl nuclear power plant named after V.I.Lenin is located on the territory of Ukraine, 3 km from the city

Pripyat, 18 km from the city of Chernobyl, 16 km from the border with Belarus and 110 km from Kiev. The power of the Chernobyl NPP was 12,800 MW (thermal) and 4,000 MW (electric).

By the time of the Chernobyl accident, foura power unit based on RBMK-1000 reactors (high-power channel-type reactor) with an electric power of 1000 MW (thermal power - 3200 MW) each. Two more similar power units were under construction. The fifth power unit was 80% complete. A pit was dug for the sixth power unit. The Chernobyl nuclear power plant produced about a tenth of the electricity of the Ukrainian SSR.

The Chernobyl nuclear power plant was shut down forever on December 15, 2000.

  • Accident

At 01:23:47 on Saturday 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 death of the operator of the main circulation pumps Valery Khodemchuk. A fire broke out in various rooms and on the roof.

Employee of the commissioning enterprise VladimirShashenok died from his injuries at 6:00 the same day. Subsequently, the remains of the core melted, a mixture of molten metal, sand, concrete and fuel fragments spread over the under-reactor rooms.

As a result of the accident, there was a release into the surroundingenvironment of radioactive substances, including isotopes of uranium, plutonium, iodine-131 (half-life - 8 days), cesium-134 (half-life - 2 years), cesium-137 (half-life - 30 years), strontium-90 (period half-life - 28.8 years).

  • Accident causes and investigation

There are at least two different approaches to explaining the causes of the Chernobyl accident, which can be called official, as well as several alternative versions of varying degrees of reliability.

The state commission, formed in the USSR to investigate the causes of the disaster, assigned the main responsibility for it to the operating personnel and management of the Chernobyl nuclear power plant.

The IAEA has established its advisory group,known as the Advisory Committee on Nuclear Safety Issues, which, based on materials provided by the Soviet side, and oral statements of specialists (among whom the group was advised by A.K. Kalugin and V.F. Demin, and the delegation of Soviet specialists was headed by Valery Legasov, First Deputy Director Kurchatov IAE) in its 1986 report also generally supported this point of view.

It was alleged that the accident was a consequence ofthe unlikely coincidence of a number of violations of rules and regulations by operating personnel, and acquired catastrophic consequences due to the fact that the reactor was brought into an irregular state.

According to this point of view, gross violations of the NPP operation rules committed by its personnel are as follows:

  • conducting an experiment "at any cost", despite the change in the state of the reactor;
  • decommissioning of serviceable technological protections, which would simply shut down the reactor even before it entered a dangerous mode;
  • the silence of the scale of the accident in the early days by the leadership of the Chernobyl NPP.

However, in 1990, the Commission of the USSR Gosatomnadzorre-examined this issue and came to the conclusion that "the Chernobyl accident, which began as a result of the actions of the operational personnel, has acquired an inadequate catastrophic scale due to the unsatisfactory design of the reactor."

In addition, the commission analyzedregulatory documents in force at the time of the accident and did not confirm some of the earlier accusations against the station personnel. Despite the widespread misconception that the accident occurred due to tests of the turbo generator run-out, in fact, the tests only facilitated the investigation, since an external one, with a high temporal resolution, also worked together with the standard control systems.

In 1993, INSAG published an additionala report that updated “that part of the INSAG-1 report that focused on the causes of the accident” and focused more on serious problems in reactor design.

It is mainly based on dataGosatomnadzor of the USSR and on the report of the "working group of experts of the USSR" (these two reports are included as appendices), as well as on new data obtained as a result of accident modeling. In this report, many of the conclusions reached in 1986 are invalidated and “some details of the INSAG-1 scenario” are revised and some “important findings” are changed.

According to the report, the most likely cause of the accident was errors in the design and construction of the reactor, these design features had a major impact on the course of the accident and its consequences.

INSAG-7 considers the following to be the main factors that contributed to the occurrence of the accident:

  • the reactor did not meet safety standards and had hazardous design features;
  • low quality of the operating regulations in terms of ensuring safety;
  • the ineffectiveness of the regulatory and oversight regime for safety in nuclear power, the general inadequacy of a safety culture in nuclear matters at both the national and local levels;
  • there was no effective exchange of information onsafety both between operators and between operators and designers, personnel did not have a sufficient understanding of plant features that affect safety;
  • the staff made a number of mistakes and violated the existing instructions and test program.

Consequences of the accident

  • The first hours

Directly during the explosion on the 4thOne person was killed in the power unit - the operator of the main circulation pumps Valery Khodemchuk (body was not found). Another, an employee of the commissioning enterprise Vladimir Shashenok, died of a spinal fracture and numerous burns at 6:00 the same day in the Pripyat medical unit No. 126. Subsequently, 134 Chernobyl NPP employees and members of rescue teams who were at the station during the explosion developed radiation sickness. 28 of them died over the next few months.

In the first hours after the accident, many, apparently,did not realize how badly the reactor was damaged, so the erroneous decision was made to supply water to the reactor core to cool it. This required work in areas with high radiation. These efforts were useless, since both the pipelines and the core itself were destroyed.

Other actions of plant personnel, such asextinguishing the centers of fires in the premises of the station, measures aimed at preventing a possible explosion, on the contrary, were necessary. Perhaps they prevented even more serious consequences. When performing these works, many of the station's employees received large doses of radiation, and some even lethal.

  • Information and evacuation of the population

The first message about the accident at the Chernobyl nuclear power plantappeared in the Soviet media on April 27, 36 hours after the disaster. The announcer of the Pripyat radio broadcasting network announced the collection and temporary evacuation of residents of the city.

After assessing the extent of radioactive contaminationit became clear that the evacuation of the city of Pripyat would be required, which was carried out on April 27. It was forbidden to take things, children's toys and the like with you; many were evacuated in home clothes. In order not to fan the panic, it was reported that the evacuees would return home in three days. Pets were not allowed with them.

  • Elimination of accident consequences

To coordinate the work, there were also createdrepublican commissions in the Byelorussian SSR, the Ukrainian SSR and in the RSFSR, various departmental commissions and headquarters. In the 30-kilometer zone around the Chernobyl nuclear power plant, specialists began to arrive, sent to carry out work on the emergency unit and around it, as well as military units, both regular and composed of urgently called up reservists. All these people were later called "liquidators".

The bulk of the work was carried out in 1986-1987, about 240 thousand people took part in them. The total number of liquidators, including subsequent years, was about 600 thousand.

... To prevent contamination of groundwater andof the Dnieper River, a protective wall was built in the ground around the station, the depth of which in some places reached 30 meters. Also, within 10 days, the engineering troops dumped dams on the Pripyat River.

According to the Russian Statemedical dosimetry register, over the past years among Russian liquidators with radiation doses above 100 mSv (10 rem) - this is about 60 thousand people - several dozen deaths could be associated with radiation. In just 20 years, about 5 thousand liquidators died in this group from all causes not related to radiation.

Radioactive release

Before the accident in the reactor of the fourth unitthere were 180-190 tons of nuclear fuel. The estimates, which are currently considered the most reliable, were released into the environment from 5 to 30% of this amount. Some researchers dispute this data, citing photographs and eyewitness observations that show that the reactor is practically empty. However, it should be borne in mind that the volume of 180 tons of uranium dioxide is only an insignificant part of the reactor volume. The reactor was mostly filled with graphite. In addition, some of the contents of the reactor melted and moved through the cracks at the bottom of the reactor vessel outside of it.

In addition to fuel, in the core at the time of the accidentcontained fission products and transuranic elements - various radioactive isotopes accumulated during the operation of the reactor. They are the ones that pose the greatest radiation hazard. Most of them remained inside the reactor, but the most volatile substances were released into the atmosphere, including:

  • 100% of the noble gases (krypton and xenon) contained in the reactor;
  • from 50% to 60% iodine in gas and aerosol forms;
  • up to 60% tellurium and up to 40% cesium in the form of aerosols.

As a result of an accident from an agriculturalturnover, about 5 million hectares of land were withdrawn, a 30-kilometer exclusion zone was created around the nuclear power plant, hundreds of small settlements were destroyed and buried (buried with heavy equipment), as well as the personal auto and motor transport of evacuated residents, which was also contaminated and people were not allowed to leave On him.

The impact of the accident on human health

According to World Health Organization data presented in 2005, the Chernobyl accident could ultimately kill up to 4,000 people in total.

Lack of timeliness, incompleteness and inconsistencyofficial information about the disaster has spawned 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.

Greenpeace and Doctors Againstnuclear war "claim that as a result of the accident, tens of thousands of people died among the liquidators alone, in Europe 10 thousand cases of deformities in newborns, 10 thousand cases of thyroid cancer are recorded, and another 50 thousand are expected.

Children's health of "Chernobyl victims"

Scientists from the United States, Ukraine, Russia and Japan have estimated the number of hereditary mutations in children whose parents were exposed to radiation as a result of the Chernobyl accident in 1986.

The fact is that mutations and other genetic changes in germ-line cells are inherited, unlike somatic cells.

Thanks to the development of the latest methods of genomicsequencing only recently has it become possible to study at the population level the complete triple genome of the father, mother and child, which is necessary for de novo mutation counting.

Scientists today are evaluating DNMs in the population atthe level of 50-100 new mutations per individual in a generation. The results of a new study show that children whose parents were exposed to radiation at the Chernobyl nuclear power plant, this figure does not exceed the population average, and they do not have excessive mutations in the cells of the germ line.

The further fate of the station

After the accident at the 4th power unit, the operation of the power plant was suspended due to a dangerous radiation situation; the 5th and 6th power units planned for commissioning were never completed.

However, already in October 1986, after extensiveworks on decontamination of the territory and construction of the "sarcophagus", 1st and 2nd power units were re-commissioned; in December 1987, the work of the 3rd power unit was resumed. In 1991, a fire occurred at the 2nd power unit caused by faulty insulation of the turbine; after this accident, the 2nd power unit was shut down and closed.

However, over the next two yearsthe remaining power units of the plant - 1st and 3rd - continued to operate and generate electricity. In 1995, the Ukrainian government signed a Memorandum of Understanding with the governments of the G7 countries and the European Union Commission: a program for the closure of the station was prepared. The 1st power unit was shut down on November 30, 1996, the 3rd - on December 15, 2000.

The original reinforced concrete sarcophagus, hastilybuilt in 1986 - "Shelter" - over time began to decay, and in the 2010s a second sarcophagus was built, this time steel - "New Safe Confinement".

The construction, funded by an international fund managed by the European Bank for Reconstruction and Development, was carried out by the French consortium Novarka, a joint venture between Vinci and Bouygues.

Construction started in 2010 several timesdelayed, including due to lack of funding; ultimately the confinement cost more than € 1.5 billion. The arched structure was erected next to the old sarcophagus and in November 2016 pushed onto the reactor building with the help of jacks - thus the New Safe Confinement enclosed both the destroyed reactor and the old sarcophagus around it.

In accordance with the National ProgramUkraine (dated January 15, 2009) for the decommissioning of the Chernobyl nuclear power plant and the transformation of the Shelter object into an ecologically safe system, the process will be carried out in several stages:

  1. Termination of operation (preparatory stage fordecommissioning) - the stage during which the nuclear fuel will be removed and transferred to the spent nuclear fuel storage facility intended for long-term storage. The current stage, during which the main task is carried out, which determines the duration of the stage, is the extraction of nuclear fuel from power units. Completion date - no earlier than 2014.
  2. Final closure and conservation of reactor facilities. At this stage, the reactors and the most radioactively contaminated equipment will be mothballed (approximately until 2028).
  3. Holding of reactor facilities during the period during which a natural decrease in radioactive radiation to an acceptable level should occur (approximately until 2045).
  4. Dismantling of reactor facilities. At this stage, equipment dismantling and site cleaning will be carried out in order to maximize the removal of restrictions and regulatory control (approximately until 2065).

Declassified documents

The Security Service of Ukraine (SBU) on the 35th anniversary of the disaster at the Chernobyl nuclear power plant published the very first report on the incident from the director of the Chernobyl nuclear power plant, Viktor Bryukhanov.

Bryukhanov reported the time of the accident at the fourth power unit and described the consequences of the explosion, and also cited statistics on the injured, dead and missing.

In particular, in 1982 at the first power unitthere was a significant release of radioactive substances. “But the KGB report ends with the usual“ measures have been taken to prevent panic and provocative rumors, ”the SBU said in a statement.

In addition, emergencies occurred in 1984 at the third and fourth power units, the service noted.

Also, the message says that in July 1986a directive appeared, classifying all the details of the accident, including its causes, the nature of the destruction, the composition of the mixture thrown into the air during the explosion, the radiation situation, the scale of liquidation and morbidity.

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