40 years after. Anniversary of the greatest nuclear disaster

Saturday, April 26, 1986, was a day that went down in history in black letters. Shortly after midnight (from Friday to Saturday), the largest nuclear disaster in the history of Europe and nuclear energy occurred, an explosion at the Chernobyl nuclear power plant. On Sunday this year, April 26, it will be exactly 40 years since this disaster, which affected the lives and generations of people not only in Ukraine but also in the entire Eastern part of Europe. Historians even claim that the Chernobyl nuclear disaster in 1986 had a significant role and influence on the fall of socialism in the Soviet Union (which, among other things, was later admitted by M. Gorbachev himself).

The Chernobyl nuclear power plant was built in the 1970s 15 km northwest of the city of Chernobyl, 10 km from the border with Belarus and 110 km north of Kyiv. In its immediate vicinity, three kilometers to the north-west, at that time a completely new housing town of Pripyat was built, which was to serve mainly for the workers of the power plant and their families. The power station and the cities of Pripyat and Chernobyl are located on the banks of the Pripyat River, which flows into the Dnieper.

What actually happened on that fateful night?

During an experiment on the power plant's 4th reactor, it overheated, melted and exploded, releasing radioactive substances into the air. This contaminated the surrounding environment, and to a limited extent, radioactive fallout affected a significant part of Europe.

A radioactive cloud was released into the atmosphere, spreading across the western part of the Soviet Union, Eastern Europe and Scandinavia to the entire Northern Hemisphere. Vast areas of Ukraine, Belarus and Russia were contaminated. The vast area around the power plant, including the nearby city of Pripyat, was evacuated and turned into a closed zone.

The Soviet government first reported the tragedy on Monday, April 28, on Moscow Radio and through the TASS news agency.

At the very beginning, after the explosion and its aftermath, several dozen people died and a huge number of people were irradiated. Some died after a few days, weeks and months from the effects of radioactivity and severe radiation. There is no exact and definitive number of victims of this accident, but the consequences of diseases and mortality are estimated in the thousands.

The trial of the plant workers took place in July 1987. The director of the Chernobyl nuclear power plant, Bryukhanov, the chief engineer Fomin, and the deputy chief engineer, Dyatlov, were sentenced to 10 years in a labor camp. Shift supervisor Rogoshkin received 5 years, the chief of the reactor department Kovalenko 3 years, and the inspector of the Gosatomnadzor Laushkin 2 years. All were released after serving half of their sentences, except for Laushkin, who died in prison.

At first, Chernobyl was a secret disaster. The first evidence that a major nuclear accident had occurred did not come from Soviet sources, but from Sweden. On April 27, workers at the Forsmark nuclear power plant (approximately 1,100 km from Chernobyl) found radioactive particles on their clothes. The search showed that the problem was not in the Swedish power plants, which indicated a serious nuclear problem in the western part of the Soviet Union. On May 1, the usual May Day demonstrations were still held in Kiev, as the population had not been informed about the disaster. The Peace Cycling Race (Warsaw–Berlin–Prague) was even transported from the Czechoslovakian SSR to Kiev for several stages during these days, including the Czechoslovak representatives, by air.

Long-term impacts

Soon after the accident, the greatest health risk was radioactive iodine 131I, with a half-life of 8 days. Today, the greatest concerns regarding soil contamination are caused by the isotopes strontium 90Sr and caesium 137Cs, which have half-lives of around 30 years. The highest concentrations of 137Cs were found in the surface layers of the soil, where it is absorbed by plants, insects and fungi and thus enters the local food chain. Earlier tests (around 1997) showed that the amount of 137Cs in trees in contaminated areas was still increasing. There is evidence that the contamination is moving into underground aquifers and closed water reservoirs such as lakes and ponds. It is assumed that the main way of removing the contamination will be the natural decay of 137Cs to the stable isotope barium 137Ba, as leaching by rain and surface water has proven to be negligible.

Global impact

As the IAEA notes show, although the Chernobyl accident released as much radioactive contamination as 400 Hiroshima bombs, its overall impact was about 100 to 1,000 times less than the contamination caused by atmospheric nuclear weapons tests in the mid-20th century. It can therefore be argued that, although the Chernobyl accident was a huge local disaster, it did not escalate into a global catastrophe.

Impact on nature

According to reports by Soviet scientists at the First International Conference on Biological and Radiological Aspects of the Chernobyl Accident (held in September 1990), the fallout level in the 10 km zone around the plant reached up to 4.81 GBq/m². The so-called “Red Forest” of pine trees, destroyed by the heavy fallout, lies within this 10 km zone and begins immediately behind the reactor complex. The name of the forest comes from the days after the accident, when the trees appeared dark red as they died from the effects of radiation. During the cleanup operations after the accident, most of the 4 km² of the forest was razed to the ground and burned. The territory of the Red Forest remained one of the most contaminated areas in the world. On the other hand, it turns out to be a location rich in the occurrence of many endangered species, since it is not inhabited by humans. However, the soil and forests of the wider area were also affected by the fallout. Therefore, there is still a threat of a forest fire that would spread radioactive elements into the air over Europe.

Long-term impacts on civilians

The results of the studies, especially the reported numbers of affected people, vary greatly depending on which organization prepared them. At the most optimistic end of the spectrum are the reports published by the IAEA. The WHO follows with a slight gap, and then UNSCEAR (the United Nations Commission for the Study of the Effects of Radiation), which report larger numbers of affected people, but remain roughly the same. Much higher numbers of affected people are reported by studies by post-Soviet researchers, studies by the German section of the Physicians for the Prevention of Nuclear War (IPPNW) and the German Society for Radiation Protection (GfS), and studies prepared for the Green Party, or Greenpeace.

First study: at least 30,000 will die

A USSR report (Legasov, 1986) prepared for the Vienna International Conference in August 1986 estimated the number of people who would die from cancer caused by radiocesium isotopes at 30,000 to 40,000. The IAEA called the prediction extremely overestimated and set the maximum number at 25,000, then 10,000 and 5,100. The author of the study, Professor Valery Legasov, was found hanged on 26 April 1988, the 2nd anniversary of the disaster.

The first sarcophagus

The sarcophagus is a reinforced concrete structure that covers the reactor building No. 4. The design of the sarcophagus began on 20 May 1986, and construction lasted from June to the end of November of that year.

However, the sarcophagus cannot permanently and effectively enclose the destroyed fourth reactor. Its construction, in many cases carried out remotely by industrial robots, has resulted in its rapid aging and, if it were to collapse, could release another cloud of radioactive dust.

About 95% of the reactor fuel remained under the sarcophagus after the accident, representing a radioactivity of about 18 MCi = 0.67 EBq. The radioactive material consists of the remains of the reactor core, dust, and lava-like "fuel-containing materials" (FCM) that solidified into a ceramic form. A new mineral, chernobylite, has also been described in the reactor. According to conservative estimates, there are also at least 4 tons of radioactive dust under the reinforced concrete shell.

Water leaked into the sarcophagus, which had to be pumped out and disposed of as radioactive waste. High humidity inside the cover contributes to corrosion of its steel structure and subsequent leakage of radioactivity.

New sarcophagus cover

The new cover is designed to prevent the release of radioactive substances into the environment, protect the reactor from weathering, and enable the safe dismantling of the original sarcophagus and the reactor remains. It is an arched structure with an inverted catenary profile, 108 m high, 162 m long, and 257 m wide. Construction of the cover began in September 2010, and the cover was completed, placed over the original sarcophagus in 2016, and put into operation in late 2018 and early 2019.

Source WT.24, Wikipedia

Photo pexels.com