Sunday, April 26, marks the 40th anniversary of the world’s worst nuclear power plant accident at the Chernobyl nuclear power station in the Soviet Union.
Five worst nuclear reactor disasters
1. Chernobyl Nuclear Disaster
Ukraine 1986 (INES Level 7)
The Chernobyl disaster is the worst nuclear power plant accident ever in terms of death toll and cost. One of only two Level 7 accidents, when a steam explosion destroyed reactor number four at the Ukrainian plant. Resulting fires spread huge amounts of radioactive waste across Western Europe, killing 32 people from acute radiation poisoning in the immediate aftermath and raising long-term fears of increased instances of thyroid cancer. An estimated 5,000 Soviet citizens eventually died from cancer and other radiation-induced illnesses. The World Nuclear Association says, “The nuclear disaster was the product of a flawed Soviet reactor design coupled with serious mistakes made by the plant operators.”
In 2000, the last working reactors at Chernobyl were shut down and the plant was officially closed.
2. Fukushima Nuclear Disaster
Japan 2011 (INES Level 7)
On Friday, March 11, 2011, the Great East Japan Earthquake, which measured 9.0 on the Richter scale, caused a 49-foot tsunami that disabled the power supply and prompted three reactor meltdowns at the Fukushima Daiichi plant. Official figures suggest that more than 1,000 deaths occurred as a result of an evacuation process that displaced more than 100,000 people. Subsequent investigations have suggested that the infrastructure and risk forecasting were inadequate for such a devastating natural disaster.
3. Kyshtym Nuclear Disaster
Russia 1957 (INES Level 6)
The third most serious nuclear accident in history happened at the secretive Mayak plant, near the Russian town of Kyshtym – part of the Soviet Union’s attempt to match the U.S. for weapons-grade plutonium production. After a faulty cooling system was left to disrepair, rising temperatures resulted in an explosion with the equivalent force of 70-100 tons of TNT. Nuclear fallout reached more than 185 miles away and, due to the classified nature of the plant, it was only a week later that 10,000 locals were evacuated from the area.
4. Windscale Fire Nuclear Disaster
Sellafield, UK 1957 (INES Level 5)
On October 10, 1957, a raging inferno swept through the core of Unit 1 nuclear reactor at Windscale, Cumberland (now Sellafield, Cumbria) for three days. The Level 5 accident dumped radioactive contamination across Europe and it is thought that traces of isotope iodine-131 may have caused several hundred cancer diagnoses. Windscale’s two piles had been hastily built during the British atomic bomb project. It was the UK’s worst ever nuclear accident.
5. Three Mile Island Nuclear Accident
Pennsylvania, USA 1979 (INES Level 5)
The Three Mile Island Unit 2 (TMI-2) reactor, near Middletown, Pennsylvania, suffered a partial meltdown on March 28, 1979. The most serious accident in U.S. nuclear power plant history was caused by a relief valve failure, after an unplanned shutdown, causing severe damage to the core. Better instrumentation, training programs and public information would have vastly improved matters but luckily there were no injuries or discernible health impacts.
Reactors in the U.S.
There are 54 nuclear power plants operating in the United States.
Electricity generation from commercial nuclear power plants in the United States began in 1958. As of April 30, 2024, the United States had 94 operating commercial nuclear reactors at 54 nuclear power plants in 28 states.
The average age of these nuclear reactors is about 42 years old. The oldest operating reactor, Nine Mile Point Unit 1 in New York, began commercial operation in December 1969. The newest reactor began operating in the state of Georgia in 2023.
On December 2, 1942, under the bleachers of the football stadium at the University of Chicago, Dr. Enrico Fermi initiated the first controlled nuclear chain reaction. The experiment, conducted as part of the wartime atomic bomb program, also led to peaceful uses of the atom, including construction of the first U.S. commercial nuclear power plant at Shippingport, Pennsylvania, in 1958.
U.S. nuclear statistics
Data as of the end of 2021, except where noted.
Total operable nuclear reactors: 93
Nuclear total annual net electricity generation: 778,188 million kilowatt hours
Nuclear percentage of total annual electricity generation: 18.9%
Nuclear net summer electricity generation capacity: 95.55 million kilowatts
Share of total U.S. utility-scale electricity: 8.3% (net summer capacity)
Nuclear average annual capacity factor: 92.7%
Largest nuclear power plant Palo Verde (3 nuclear reactors): 3,937 megawatts
States with operating commercial nuclear power plants: 28
Uranium expenditures: $72.5 million
Uranium concentrate (U3O8) production: 21,000 pounds
Average price for purchased uranium concentrate U3O8: $33.91 per pound U3O8
Fuel cost: nuclear vs. fossil steam: 0.61 cents/kilowatt hour vs. 2.46 cents/kilowatt hour
Sources: Nuclear Energy Institute, U.S. Energy Information Administration, U.S. Nuclear Regulatory Commission, World Nuclear Association, Process Industry Forum