Causes and consequences: briefly about the Chernobyl accident
Causes and consequences: briefly about the Chernobyl accident

The accident at the Chernobyl nuclear power plant occurred on April 26, 1986. According to the international scale of events at nuclear power plants, it corresponds to the highest seventh level. The accident occurred due to imperfections in the design of the RBMK-1000 reactor and significant deviations in its operation mode.

Reference: The accident occurred due to a sudden increase in the neutron flux, an increase in energy release, which in turn led to a sharp increase in temperature, destruction of the reactor core, and the release of a significant part of graphite and nuclear fuel. It should be noted that so far there is no final and unified version of the causes of the accident, with which the entire international expert community of experts in the field of reactor physics and technology would agree.

Powerful explosions destroyed both the reactor and its protective structures. The release of radioactive substances into the environment began, from which a “radioactive mushroom” was formed. It is a powerful jet, with a height of 1.5 to 2 km. This “mushroom” had a high temperature at the exit from the red-hot mass of nuclear fuel and acted as a kind of thermochemical column in which the separation of radionuclides took place. At different altitudes from the radioactive jet, the wind tore off air masses that were unequal in composition of radionuclides, and spread in all directions in the form of radioactive clouds. Radionuclides from these clouds fell to the surface of the earth, thereby polluting it.

The most intense emissions occurred during the first 10 days, until the mouth of the reactor, through which a stream of radioactive substances came out, was properly filled with various chemical materials.

Up to 100% of radioactive noble gases, 20-50% of iodine isotopes, 12-30% of cesium 134 and 137, uranium, plutonium, strontium, and other, less volatile radionuclides that were in the reactor at the time of the accident got into the atmosphere. Radionuclides released into the atmosphere at the time of the Chernobyl accident were discovered almost all over the world, on all continents. The maximum infection is localized in Ukraine, Belarus and Russia.

Precipitation of radionuclides formed the so-called radioactive traces. The western track became the clearest – a narrow strip that stretches from Chernobyl to Poland and further to the west. The northern trace stretched to the countries of Scandinavia. It is the second most intense radioactive contamination. The formation of the eastern footprint is associated with pollution in several regions of the Russian Federation. Precipitation of radionuclides on the surface of the earth was more intense in places where rains fell during the passage of radioactive clouds, so the pollution is spotty in nature.

In order to stop further emissions of uranium fission products, transuranium elements, the emergency unit’s mouth was filled with a mixture of various materials, including dolomite and lead.

Confinement: 100 years of security

In the fall of 1986, a protective structure, a sarcophagus, was built over the ruins of the explosion of the 4th Chernobyl NPP power unit, which isolated the remains of the fuel mass and weakened the effect of radiation. This building received the official name “Shelter”.

The sarcophagus was designed for 20-30 years, in 2019, with the help of international partners. A modern project of a new defense was designed and put into operation: safe confinement. Over the next 100 years, this facility will inhibit the penetration of the remains of the reactor core into the atmosphere. This will happen until a technology is developed for the safe dismantling of fuel masses for the corresponding disposal of radioactive waste.

The disposal of radioactive waste is an extremely complex problem, the optimal solution of which has not been found yet. The intentions to turn the Chernobyl zone into an ecologically safe one remain realized so far only in words, since a significant amount of radioisotopes of plutonium and other transuranium elements are concentrated on the territory of the former Chernobyl nuclear power plant site. Over time, radionuclides that got into water bodies, vegetation, soil, joined the substances involved in biochemical transformations. This led to an increase in the dose rate of external and internal exposure of people living in areas contaminated with radionuclides.

External radiation is caused, first of all, by an increase in the concentration of cesium-137, with the decay of which gamma radiation is associated, internal radiation is caused by the influx of radioactive substances into the human body along with drinking water, food, and their air.

Irreversible consequences

In the first weeks after the accident, significant exposure of people was caused by radionuclides of iodine, in particular its isotopes. 4 zones of radioactive contamination are identified on the territory of Ukraine:

  • Exclusion Zone,
  • compulsory resettlement zone,
  • voluntary resettlement area,
  • zone of constant radiological control.

The following categories are distinguished among the people who suffered as a result of the disaster:

  • firefighters and rescuers who put out the fire, and thereby localized the release of radioactive substances from the mouth of the exploding reactor. Some of them died almost immediately of acute radiation sickness;
  • emergency response participants, among which the highest doses were received by those who worked directly near the emergency power unit in the first months after the accident. In particular, in works related to the decontamination of the territory of the industrial site adjacent to the reactor, on filling up the reactor vent from helicopters, at the construction of a temporary shelter for the destroyed power unit. This group is large. It consists of several hundred thousand people. The radiation doses of these people exceeded the exposure of 500 mSv;
  • the liquidators who worked in the exclusion zone at the other Chernobyl reactors, temporary burial and localization sites of radioactive waste, decontaminated the territories, ensured the improvement of roads and hydraulic structures;
  • the population evacuated from the exclusion zone;
  • population residing in a territory contaminated with radionuclides.

76 settlements were evacuated from the exclusion zone, including the cities of Pripyat and the city of Chernobyl. 116 thousand people were resettled. 45 thousand people were evacuated from the compulsory resettlement zone. Over 600 thousand people took part in eliminating the consequences of the Chernobyl disaster in 1986-1987. It was mainly youth. Immediately after the shift to the Chernobyl nuclear power plant, upon returning home, they began to turn into elderly people. Almost everyone received irreversible negative consequences for their health.

Today, there are about 200 people in about 11 settlements of the contaminated zone who are called self-settlers. The administration of the exclusion zone provides them some assistance.

Immediately after the accident, the Soviet government did not warn the population of the danger and did not take measures to minimize the effects of the radiation threat. Despite the fact that the dose rate increased by more than a hundred times in Kiev, neither the May Day demonstration, nor the Peace Bike Race, nor other holiday events were canceled. In order to avoid panic, they did not introduce iodine prophylaxis, as a result of which many people received irradiation of the thyroid gland.

Concealment of information about the disaster from the public was initiated by the country’s leadership.

Until mid-May, it was forbidden to disseminate information on work carried out at the emergency reactor, on protection methods, in particular on radioactive contamination of food and water. The rural population continued to consume food products grown in summer cottages and household plots. Maps of radioactive contamination of the land remained classified until 1990.

Nuclear energy – cheap and cheerful

The Chernobyl accident was a powerful blow to nuclear power, which the world considered environmentally friendly, and most importantly, a cheap industry. Related to this are intentions to decorate the real state of affairs regarding the consequences of the disaster. In particular, this concerned information about the true causes of the accident and the health status of the affected population.

The tendency to conceal information about the true consequences of the catastrophe somewhat weakened with the collapse of the USSR. However, even now, circles interested in the further development of atomic energy carefully continue to biased underestimate the tragic consequences of the Chernobyl disaster. This applies, in particular, to estimates of the number of victims of the accident — persons who have died from diseases caused by radiation, people with disabilities — these statistics vary widely from one source to another.

So, according to the Greenpeace organization, the number of future deaths from cancer caused by radioactive emissions from the Chernobyl nuclear power plant can reach 100 thousand. In a UN report prepared by the World Health Organization with the participation of experts from the International Atomic Energy Agency, the number of victims who could die from cancer related to the Chernobyl disaster is more than 3940 people. According to other organizations, the number of victims varies within 1 million of expected future deaths.

Such a discrepancy in data indicates the excessive politicization of the issue of the consequences of the disaster, as well as the existence of objective difficulties in the epidemiological forecasting of the effects of small doses of ionizing radiation.

The medical institutions of many countries that studied the impact of radiation on humans have found that the most tragic consequence of the disaster is a deterioration in people’s health, as evidenced by the vast majority of epidemiological studies.

Over the years, the index of practically healthy people decreases, and the incidence and mortality rate of the population that fell into the zone of influence of the Chernobyl accident, compared with the population of the rest of Ukraine, is growing annually.

In this case, there is a spread of both malignant and non-malignant tumors, as well as other diseases, among which are diseases of the cardiovascular system, coronary heart disease, hypertension, disorders of the endocrine system, digestive tract pathology and the like.

The greatest harm to health was caused by radioactive iodine, which, concentrating in the thyroid gland, caused its irradiation, as a result of which the incidence of thyroid cancer increased, especially in children. The body’s immune function is disrupted under the influence of radiation. In particular, a deficiency of immune cells is formed, and neuropsychological effects are enhanced, including post-radiation cognitive deficiency, chronic fatigue syndrome. So think now: is Chernobyl our past or our present and future?