The Chernobyl nuclear accident happened in Pripyat, a Soviet city located in present-day Ukraine, on April 26, 1986. The accident occurred when reactor four of the nuclear power plant in that city exploded, leaving the reactor open and releasing a large amount of radioactive material into the atmosphere.
What was the Chernobyl accident?
The Chernobyl accident was a nuclear disaster that happened at the VI Lenin Nuclear Power Plant, a nuclear power plant located in Pripyat, a city located in the Soviet Union , now Ukraine. That accident happened at 1:23 am on April 26, 1986 . At the time, the plant was undergoing maintenance, when a human error led to an explosion in reactor 4.
In addition to human error, the explosion was the result of problems in the design of the RBMK reactor (BolshoMoshchnosty Kanalny Reactor). These reactors were very common in the Soviet Union, but they were considered highly unstable, especially when working at reduced power. With the explosion, two workers at the plant were killed immediately and a fire broke out.
The reactor fire raged for days and local authorities tried unsuccessfully to put it out. With the explosion, the reactor and its radioactive material were exposed, causing this material to be released into the atmosphere. This radiation spread and reached nearby regions like Belarus and Russia (both were part of the Soviet Union), but also places like Sweden, Austria and even Canada.
The Swedes, in turn, were the first to identify that a radioactive accident had happened in the Soviet Union and soon informed the international community. They discovered this because of abnormal levels of radioactivity in the atmosphere. At first the Soviets refused to acknowledge it , but on April 28 they admitted that an accident had taken place in Pripyat.
What caused the Chernobyl accident?
As mentioned, the Chernobyl accident happened due to human failures during a safety test. The objective of this test was to determine the time in which the turbines continued to operate, at low power, after a power outage. At the time, the plant’s operators failed to follow a series of protocols, thus causing the instability of one of the nuclear reactors and, consequently, a large explosion.
Although human action was the main cause of the entire disaster, the nuclear reactors of the RBMK type, which, as we have seen, were used in several nuclear power plants in the Soviet Union, had carbon moderators, which caused the water to overheat when the reactor power was reduced.
How did the Chernobyl accident occur?
In all, two explosions were recorded in reactor 4 at the Chernobyl power plant . The first explosion was strong enough to detach the protective shield installed just above the reactor, which weighed more than 1000 tons, sending some extremely harmful nuclear fission products into the air, such as iodine-131, cesium-137 and strontium-90.
The second explosion, in turn, caused more than 300 kg of graphite blocks, located between the fuel rods, to be thrown out of the plant’s facilities. With that, the reactor started to catch fire, and a huge amount of radioactive elements was released into the atmosphere for about 10 days, until the fire was contained.
Chernobyl accident damage containment
At first, the Soviet authorities’ response was slow and cautious . They did not know the extent of damage caused by the explosion or that the reactor was exposed, but they still avoided carrying out the immediate evacuation of Pripyat. The evacuation work took 36 hours to start and forced the city’s 50,000 inhabitants to leave.
In all, the Soviet government mobilized more than 1000 buses to evacuate the population of Pripyat. People were informed that it would be a temporary removal and, therefore, they did not take personal belongings and everything was abandoned in the city. Throughout 1986, a total of 115,000 people were evacuated from regions close to the affected area.
The total number of people evacuated reached more than 300,000 , as regions in Ukraine, Belarus and Russia were severely affected by radiation . In addition, the Soviet government created an exclusion zone in which the entire region within a radius of 30 kilometers from the plant could not have human presence, except for cases with due authorization. To this day, human presence in this area is prohibited.
Once it was identified that what was happening in Pripyat was serious, the Soviet government set up a committee responsible for containing the damage. One of the decisions of this committee was to send hundreds of thousands of people to the Pripyat region in order to contain the damage from the nuclear accident.
These people were called “liquidators” and included soldiers, firefighters, scientists, and others. It is estimated that 600,000 to 800,000 people were sent to work on damage containment and many of these had no idea of the risks they would be exposed to with their work.
Belarusian writer Aleksana Aleksievitch points out that, in the case of Belarus, for example, more than 115,000 people worked as liquidators and, from 1990 to 2003, around 8,500 died |1|. Many of the people sent to help contain the damage from Chernobyl were motivated to go by promises of good pay and a sense of patriotism .
Scientist Elena Kozlova, for example, worked as a liquidator and, at the end of her services, received a payment 10 times higher than what she usually received |2| . Despite the promised good wages, the risks were greater, and many of the liquidators died after working for a few weeks, as they came into contact with high doses of radiation.
One of the most dangerous jobs was that of the liquidators chosen to sweep up the debris from Reactor 4 that was on the roof of the nuclear power plant. Other liquidators were given missions such as burying everything that was contaminated, killing abandoned domestic animals, measuring radiation levels, etc.
After all the containment work was done, the Soviet authorities began the construction of the structure that encapsulated the reactor 4 , to prevent the reactor from releasing radioactivity into the atmosphere. This structure was named the Chernobyl Sarcophagus.
The Chernobyl sarcophagus was a structure of over 7300 tons and 400,000 m³ of steel and concrete. It was installed around the molten core of the reactor, the most dangerous region in the entire exclusion zone. The purpose of the structure was to cover the reactor, protecting it from weather exposure (rain and wind) so that radioactive isotopes would not spread further into the atmosphere. The sarcophagus covered almost 200 tons of radioactive lava — originating from the material used to contain the reactor fire — 30 tons of contaminated dust and 16 tons of uranium and plutonium.
The sarcophagus had to be replaced with a new type of confinement , as the radiation had almost completely deteriorated the structure. The new cover, in addition to being more resistant and designed to withstand at least 100 years, also filters the radioactive gases that leave the reactor core.
Consequences of the accident
The Chernobyl accident left terrible consequences , mainly for the three most affected countries, which were Ukraine, Belarus and Russia. In the 1980s, the disaster served to demoralize the Soviet government internationally and contributed to Mikhail Gorbachev promoting Soviet nuclear disarmament.
In addition, the impacts of the accident on the Soviet economy, which was already suffering from the expenses of the Afghan War , contributed to exacerbate the economic crisis that had dragged on in the USSR since the 1970s. These impacts on the economy continued after the Soviet Union was split into fifteen new countries in the early 1990s.
The country most affected by the accident was Belarus , a nation that saw more than 20% of its territory contaminated (Belarus has an area the approximate size of the territory of the state of Paraná ). With that, the country lost about ¼ of its arable land and, in the 30 years following the accident, had economic losses of around 235 billion dollars. In addition, the Belarusian government spent about 18 billion on measures against the consequences of the accident|4|.
The Ukrainian and Russian territories were affected to a lesser extent, with 7.5% for Ukraine and 1.5 for Russia|4|. In Ukraine, it is estimated that 5% to 7% of the country’s budget is spent annually on Chernobyl-related expenses. Belarus spent, until 2002, around 22% of its annual budget on consequences of the accident and, since 2002, this figure has dropped to 6%.
The accident also contributed to severely affect the health of the population . Cancer cases have increased considerably in the Ukrainian and Belarusian population, and cases of cardiovascular disease have also increased. Finally, the psychological impact of this accident, which forced more than 300,000 people from their homes, cannot be highlighted. To this day, it is not known for sure how many people died as a result of Chernobyl.