Top 5 Largest Nuclear Accidents

Thirty-eight years ago, on the night of April 25-26, 1986, an accident occurred at the Chornobyl Nuclear Power Plant, which went down in history as the largest man-made disaster of the 20th century. Unfortunately, and in some ways fortunately, the tragedy at the Ukrainian Chornobyl Nuclear Power Plant still holds the top spot in the rather long list of nuclear disasters today.

Unfortunately, because the consequences of the accident still affect the radiation picture of the entire region and the lives of the people who inhabited it. Fortunately, because now another Ukrainian nuclear power plant, the Zaporizhzhia Nuclear Power Plant (ZNPP), which is considered the largest in Europe, is currently in the hands of Russian military terrorists. And, fortunately, despite numerous provocations by the Russians, a new nuclear catastrophe has so far been avoided.

An Accident Waiting to Happen

The ZNPP, along with the satellite city of Enerhodar, was seized by Russian occupying forces at the very beginning of the full-scale invasion, during the battles on March 3-4, 2022. Despite the fact that ZNPP was fully shut down in September 2022, two out of six reactors are still in "hot standby" mode, providing heat to Enerhodar. Fortunately, there is currently no confirmed data on radiation leakage or reactor damage, but it is worth remembering that the situation at ZNPP is a classic illustration of the phrase "monkey with a grenade," the meaning of which is understandable even to children.

Despite numerous calls from the IAEA commission for the demilitarization of ZNPP, Russian occupiers, as before, control the captured station, using it as a military base to shell the positions of the Armed Forces of Ukraine and peaceful Ukrainian cities. As a kind of protection against retaliatory strikes, the occupiers have mined the station and placed heavy weaponry and ammunition depots near the reactors and spent nuclear fuel storage. The consequences of such actions can be imagined by watching the HBO series "Chornobyl," but in the event of an accident at the Zaporizhzhia Nuclear Power Plant, the consequences could be orders of magnitude worse. Therefore, in the list of potential catastrophes that could happen at any moment (especially if we continue to do nothing), the crisis at ZNPP holds the top spot in our list.

The First Major Accident in the History of Nuclear Energy

On December 12, 1952, at the Chalk River Nuclear Power Plant in the Canadian province of Ontario, located 180 km from Ottawa, as a result of technical personnel errors and failures (electrical and mechanical) in the emergency shutdown system, the reactor in the laboratory entered a supercritical regime with excess reactivity. The reactor's power exceeded the design level for no more than 1 minute, but this was enough to cause overheating and partial melting of the reactor's active zone.

As a result, 4,500 tons of contaminated water with long-lived radioactive fission products were released into the environment. It is considered lucky that the radioactive waste did not reach the Ottawa River through the soil, which is located just 1.5 km from the station. By the way, among the team that conducted further environmental cleanup of the station was nuclear engineer and future U.S. President Jimmy Carter.

The Kyshtym "Polar Lights"

On September 29, 1957, in the closed city of Chelyabinsk-40 at the Mayak Chemical Combine, due to a violation of the cooling regime, there was an explosion of a tank for storing radioactive waste. This was the first accident at nuclear facilities in the USSR. According to the modern classification of radiation incidents and accidents by the IAEA, the Kyshtym incident received a level 6 rating on the 7-point scale, second only to the future accidents at the Chornobyl NPP and Fukushima-1. It is noteworthy that the nuclear facility in Chelyabinsk-40 was initially built as a plant for the production of atomic bombs, and already in 1948, three years after the start of construction, the first industrial nuclear reactor, A-1, in Eurasia reached its design capacity.

As a result of the explosion of the tank with chemical waste into the atmosphere, about 20 million curies of radioactive substances in the form of gas and dust were released. A kilometer-high column of smoke and dust rose above the damaged facility, shining with orange-red light. As in the case of the Chornobyl accident, the Soviet authorities first tried to cover up the leak and misinform the population. On October 6, 1957, the newspaper "Chelyabinsk Worker" published an article describing the rare “polar lights” in these latitudes. However, later, during the liquidation of the consequences of the radioactive leak, 23 settlements in three regions were resettled and buried.

Tragedy With a "Japanese Character"

On March 11, 2011, as a result of a powerful earthquake and subsequent tsunami, the Fukushima-1 nuclear power plant experienced a radiation accident reaching the maximum Level 7 on the International Nuclear Event Scale (INES). The natural catastrophe led to the flooding of the basements of the power plant, where generators and batteries were located, resulting in the station's power failure and the failure of the reactor cooling system. As a result, the nuclear fuel began to melt down in the reactors of three power units, leading to the accumulation of a critical dose of hydrogen and a powerful explosion. Lightweight radioactive mixtures of iodine and cesium isotopes were released into the environment, with emissions reaching 20% of those during the Chornobyl accident. Over 160,000 people had to be evacuated from the contaminated area, and cleanup efforts at Fukushima are still ongoing, estimated to take another 30 to 40 years according to various assessments.

Despite the external factors that caused the accident at Fukushima-1, the commission investigating the causes of the disaster noted its "man-made" nature. The point is that Fukushima-1 was one of the first Japanese nuclear power plants built at a time when seismology was in its early stages of development. Therefore, risk assessments related to earthquakes were based on... historical chronicles of natural disasters over the previous 400 years. And although deficiencies in the nuclear power plant safety system were identified before 2011, neither TERSO nor the Ministry of Energy took steps to address them, which, according to commission members, was dictated by the very specific nature of Japanese culture, based on obedience, subordination, and adherence to a given program.

Chornobyl

On Saturday, April 26, 1986, an explosion occurred at the 4th reactor of the Chornobyl Nuclear Power Plant (Ukraine), completely destroying the reactor's active zone. A large amount of radioactive substances, including uranium isotopes, plutonium, iodine-131, cesium-134, and strontium-90, was released into the air. The accident became the largest in the history of nuclear energy in terms of both casualties and the extent of economic and environmental damage. The cause of the explosion was a failed reactor test, which, as later established, was initially faulty. The fire at the 4th reactor was only extinguished on May 1, while the liquidators, including helicopter pilots who dropped a special mixture onto the reactor, received high doses of radiation.

Despite the evacuation of residents from the 30-kilometer contamination zone (Prypiat and adjacent villages) the day after the accident, and the radioactive cloud spreading over the territory of Ukraine, Belarus, and Russia, the Soviet leadership remained silent about the catastrophe until April 28. And Mikhail Gorbachev, the General Secretary of the CPSU Central Committee, personally insisted on holding festive demonstrations in Kyiv the next day, allegedly to prevent panic among the population. 

A special concrete sarcophagus was built over the 4th reactor of the Chornobyl NPP, and a 30-kilometer exclusion zone was established, which until the full-scale invasion of the Russian Federation into Ukraine was a pilgrimage site for Ukrainian "stalkers," and later for Western extreme tourists - largely due to the popularity of the HBO series "Chornobyl." It is noteworthy that the Russian occupiers, who seized the Chornobyl NPP at the beginning of the invasion, set up one of the military camps in the radiation-contaminated zone, the so-called "Rusty Forest," (Rudyi Lis) resulting in high doses of radiation exposure.