Chernobyl: How the disaster shaped Bulgaria and Eastern Europe

At 1:23 a.m. on April 26, 1986, a catastrophic nuclear meltdown and explosion occurred in Reactor No. 4 of the Chernobyl nuclear power plant in the USSR, destroying part of the facility. The reactor core was exposed and released large amounts of radioactive substances into the atmosphere. In the following months, more than 200,000 people from the surrounding areas were evacuated.

The radioactive fallout, dispersed by the wind, contaminated large parts of Europe, with Ukraine, Belarus, and Russia being the most affected. The emissions continued until May 5 and formed clouds of cesium-137 and other isotopes, whose concentration decreased with increasing distance but still affected wide areas. The fallout reached the Balkans on May 1.

At that time, Dimitar Vatsov was a 15-year-old high school student in Sofia. "Shortly after the radioactive rains, the Komsomol [the youth organization of the Communist Party] sent my class to work in the fields," he recalls. "Every morning, a bus picked us up to harvest spinach and chives."

By May 7, Bulgarian authorities had not issued a public statement about the disaster. In later official statements, it was claimed that environmental pollution was minimal and did not require special measures. Four of Vatsov's classmates later died of cancer.

This experience left deep scars on him. Today, he is a philosopher and professor at the New Bulgarian University in Sofia. Last autumn, he launched a seminar that deals exclusively with the consequences of the Chernobyl disaster in Bulgaria and brings together historians, journalists, and nuclear physicists.

"Bulgaria was the only country in the socialist bloc that took no measures after the disaster," he explains. Although Bulgaria ranks only eighth among the most radiation-affected countries according to a United Nations report, it exhibited the highest rate of thyroid cancer in children outside the former USSR. "As a philosopher, this peculiarity prompted me to think about the truth, the ethics of political discourse, and, more generally, about the cynicism of the communist regime at that time."

Just don't panic! – Bulgarian silence

Bulgarian stands out as the country where information was most heavily censored and no meaningful measures were taken.

After the Chernobyl accident, information in Eastern Bloc countries was carefully filtered to minimize perceived risks of the disaster while maintaining the reputation of the USSR. In Czechoslovakia, for example, the word katastrofa ("disaster") was deliberately avoided in the early phase, while the term havárie ("accident") was used sparingly and usually without further clarification. Official reports highlighted Soviet expertise and heroism, the rapid containment of the accident, and the alleged exaggeration of events by "Western imperialist media." Nevertheless, Bulgaria stands out as the country where information was most heavily censored and no meaningful measures were taken.

"Ceaușescu – one of the most authoritarian dictators of that time – warned the Romanians on May 2 about the danger of contamination. In Yugoslavia, pregnant women and children were advised to stay at home, and basic precautions such as washing fresh produce were recommended. In Bulgaria, there was a complete information blackout," says Vatsov.

Physicist Georgi Kaschiev, who worked at the Kozloduy nuclear power plant in northwest Bulgaria, vividly remembers those days: "The only information we received was that there had been a fire at Chernobyl and that it had been extinguished." Thanks to a large antenna installed on his building, Kaschiev was able to receive Yugoslavian TV broadcasts. "Reports from Sweden and Finland quickly indicated that the incident was far more serious than officially admitted. Western media showed satellite images from the United States of the destroyed reactor, maps tracking the radioactive cloud, and reports that Yugoslavia had sent planes to evacuate its students from Kiev."

By the end of April, Kaschiev and his colleagues realized that the cloud was moving toward Bulgaria. Between May 1 and 2, radiation levels rose to ten times the natural background, especially after rainfalls. As authorities continued to remain silent, panic spread among the population: engineers warned their relatives to take basic precautions. Often, these warnings were met with disbelief. Subsequent analyses of food samples, including milk from Bulgarian farms, confirmed extreme contamination.

Analyses of food samples, including milk from Bulgarian farms, confirmed extreme contamination.

From today’s accessible archive documents, it appears that the Bulgarian government closely monitored the development of the disaster and the extent of contamination in Europe and within Bulgaria. This included analyzing foreign press reports, intelligence reports, and daily radiation measurements across the country. According to Vatsov, the Politburo of the Bulgarian Communist Party feared that revealing the true extent of contamination would trigger panic and possibly lead to political unrest and protests, as had happened in Poland. "Furthermore, I can only describe it as a form of moral weakness on the part of the ruling elites, who expressed contempt for the rest of the population."

Petko Kovachev, an environmental activist who completed his military service in 1986, recalls that the army acted quickly: "Suddenly, we no longer received fresh food, only canned goods in the canteen. Outdoor activities were canceled, and we were instructed to measure radiation levels around the base with Geiger counters." However, these safety measures did not bring much clarity. "We were never told what was really happening, and we were expected to follow orders without questions. Only years later did I fully realize the extent of the disaster."

The cynicism of the nomenklatura

The handling of the aftermath of Chernobyl in Bulgaria revealed glaring inequalities in access to information and health protection. At the top of the hierarchy was the nomenklatura – high-ranking party officials, political police, administrative officials, and military personnel. During the crisis, they had privileged access to meals and supplies distributed through the state-run Rila Hotel in central Sofia. The Politburo was supplied with mineral water from deep sources and imported foods , including lamb from Australia and vegetables from Egypt and Israel, to avoid radioactive contamination.

According to Vatsov, the top leadership of this nomenklatura – about 300 people – was never at risk because the authorities responsible for their safety and well-being had taken special measures. "The military applied less strict measures, which also reduced the risk. The rest of the population was kept completely uninformed."

The top leadership of this nomenklatura was never at risk because the authorities responsible for their safety and well-being had taken special measures.

Symbolic of the government's cynicism was the decision to hold the May Day parade as usual on May 1. Many children marched in Sofia under radioactive rain. That month, numerous propaganda sports events took place across the country, and "volunteer brigades," mainly composed of 15- to 25-year-olds, carried out outdoor tasks such as agricultural work or construction. An estimated 365,000 young people were exposed to radiation in this way.

On May 10, after a meeting at the Ministry of Energy in Sofia, Kaschiev visited his sister-in-law. Children played outside the apartment building while adults casually conversed. When he urged them to keep the children inside and not to let them play in the sandbox, his warning was dismissed. "They accused me of scaremongering," he recalls. "Someone even told me I was probably a Western agent and threatened to inform the authorities."

Despite often inadequate measures, all Eastern Bloc countries, including Czechoslovakia and Hungary, maintained the mandatory May Day parades. Poland also held its celebrations as planned, with the government publicly denying any health risks. At the same time, Polish authorities distributed iodine tablets and limited milk sales. The rapid distribution of iodine, which began on the afternoon of April 29, is often cited as an exemplary response to a radiological emergency. It remains the largest preventive medical measure ever carried out in such a short time: within three days, 18.5 million people, including adults and children, received iodine solution.

Science and environmental activism

Shortly after the fall of the regime, Kovachev learned more about the Chernobyl disaster and its consequences through an exhibition organized by physicists from Sofia University. Even under communism, some of them belonged to informal environmental networks, which later Ecoglasnost emerged from, an organization Kovachev joined as a student.

Ecoglasnost was founded in spring 1989, just a few months before the fall of communism. It was a citizens' movement focused on environmental protection and emerged from the political liberalization inspired by glasnost in the Soviet Union. In autumn, it organized petitions and public demonstrations, including the rally on November 3 in Sofia, widely regarded as one of the first open mobilizations of citizens against the communist regime. The movement soon expanded its demands to include civil liberties and democratic reforms. In December 1989, Ecoglasnost was officially recognized as the first non-communist political organization in Bulgaria and later played a key role in building the democratic opposition by joining the Union of Democratic Forces (a political party uniting several organizations opposing the communist government). It also initiated the first inspections of the Kozloduy nuclear power plant.

The engagement of scientists in environmental struggles contributed to the weakening of the regime in its final years. It initially manifested in Ruse in northern Bulgaria, where air pollution from a chemical plant across the border in Romania led to widespread protests in 1987. From this movement came the Public Committee for the Protection of the Environment of Ruse , an informal organization tolerated under communism that played a crucial role in early national mobilizations and the democratic transition.

Around the same time, the discovery of radioactive particles called "hot particles" in Bulgaria—evidence of the extent of the Chernobyl disaster—prompted several physicists to monitor the crisis closely and study its effects. The Sofia University exhibition that Kovachev visited in December 1989 was the result of this research and observation.

Similar movements also arose in other socialist countries like Hungary and Czechoslovakia. They combined the activism of certain scientists with awareness of ecological and democratic issues.

As radiation levels rose in late April and early May 1986, Hungarian scientists and health experts documented contamination and exchanged information informally, while official communication remained limited and reassuring. The growing gap between expert knowledge and public statements led to moral dissonance among professionals, torn between scientific integrity and loyalty to the state. In this context, environmental concerns became a coded language through which demands for accountability and transparency were expressed. This fed into reformist networks that later shaped Hungary’s transition to democracy.

In the former Czechoslovakia, the Chernobyl disaster also helped mobilize ecological movements that later became key actors in the Velvet Revolution of 1989. Although the regime was among the most repressive in the Eastern Bloc, it tolerated environmental activism more than open political dissent, considering concerns about pollution, water contamination, or landscape destruction relatively harmless and difficult to censor.

The second wave of contamination

Since Bulgarian authorities took no measures, cows, sheep, and goats continued grazing on contaminated pastures until spring 1987 and ate radioactive feed. Products from this food chain remained in circulation, leading to a "second wave" of contamination, accounting for an estimated nearly 30 percent of the total burden. This situation—unique in the history of the Chernobyl disaster—explains the extraordinarily high rates of thyroid cancer among very young children in Bulgaria.

Retired physicist Liliana Prodanova, who was working at the Solid State Physics Institute at the time, only learned in mid-May about the severity of the situation. "My husband was vice-rector of Sofia Technical University. I myself specialized in silicon research, so we understood very well the effects of such contamination. We silently took precautions, such as systematically washing food. We also removed contaminated soil around our country house. That year, we planted nothing."

Prodanova recalls that she and her colleagues were often asked by friends to measure the radioactivity of yogurt for children using the equipment of the Physics Institute. "We did this discreetly, without official permission."

However, the nomenklatura was fully aware of the risk. They tested Bulgarian dairy products they consumed and imported the rest from abroad. Around the Vratsa Palace of the King on the outskirts of Sofia, which was then inhabited by party officials, pastures were mowed in May to prevent contamination. However, the hay was handed over to livestock cooperatives supplying the capital, where contaminated dairy products were produced.

Kaschiev recalls that physicists at the Kozloduy nuclear power plant used a specialized research laboratory to develop their own measuring devices. They designed a device to measure thyroid radiation exposure. "Those who had not taken precautions at the beginning of May, especially people on vacation at that time, were exposed to contamination up to 10,000 times higher than ours. In early May, I bought as much cheese and milk powder as possible. That probably also protected us during the second wave," he says.

The Chernobyl dissidents

According to Vatsov, there were no real dissidents in Bulgaria before the Chernobyl accident. "The awareness that we had been deceived by authorities and exposed to serious health risks shaped the political engagement of an entire generation, especially within the scientific community."

Kaschiev is a good example. Chernobyl influenced both his political activism and his career. His anger over the moral and political failure of the regime prompted him to focus on nuclear safety. From the late 1980s, he shifted from reactor physics to risk assessment, initially as a safety critic within the plant, then as a university lecturer and nuclear inspector. In 1997, he was appointed head of Bulgaria’s national nuclear regulation laboratory.

In other socialist countries, the Chernobyl disaster also triggered resistance against the regime. In Poland, this evolved into a strong anti-nuclear movement. Fears of the disaster quickly led to opposition against the planned Żarnowiec nuclear power plant and sparked nationwide protests involving environmental groups, local activists, and dissidents like Lech Wałęsa, who later became the country’s first democratically elected president. In a referendum held in 1990 alongside local elections, over 86 percent of voters rejected the Żarnowiec project, leading the government to abandon it that same year. As political scientist Kacper Szulecki notes, these mobilizations reflected a broad social and generational shift and accelerated it, while simultaneously further undermining Moscow’s legitimacy in Poland.

The disastrous handling of the Chernobyl disaster revealed mainly the immorality and cynicism of the communist regime, as well as the irrationality of its ideology.

Although the disaster left lasting scars on Bulgarian society, it did not lead to a large-scale anti-nuclear movement. The Kozloduy plant, which was renovated and remains operational today, is widely regarded as a source of national pride and a guarantee of energy independence. The disastrous handling of the Chernobyl catastrophe mainly exposed the immorality and cynicism of the communist regime and the irrationality of its ideology.

In December 1991, after the regime’s fall, the Supreme Court in Sofia convicted former Minister of Health Lyubomir Shindarov and former Deputy Prime Minister Grigor Stoichkov of intentional misleading of the public, sentencing them to prison for negligent homicide. After a lengthy appeals process, their sentences were reduced to three and two years in prison. They are the only high-ranking officials of the Bulgarian regime who were properly prosecuted and sentenced for their handling of the Chernobyl disaster.

Physicist Atanas Krastanov, who in the 1980s as a young researcher witnessed the mismanagement of the disaster by Bulgarian authorities, believes that nuclear energy itself is not the problem. He emphasizes that "the Chernobyl accident was primarily due to human error" and notes that "it was not originally a nuclear explosion but a thermal explosion caused by pressure buildup." Today, Krastanov works as an expert at the Center for Disaster, Accident, and Crisis Prevention in Nadezhda Sofia. Recently, he was co-author of a documentary on this topic, which is scheduled to be released in Bulgaria this fall.