The 5 Worst Nuclear Disasters Of All Time – BGR

The Chernobyl disaster is probably the most memorable nuclear disaster in history due to the explosion and all the deaths caused by severe radiation poisoning. Research that shows the dogs of Chernobyl may be evolving at a different rate due to the radiation illustrating the complex nature of radiation. But other great disasters like the Three Mile Island partial meltdown and the Fukushima disaster have contributed to society’s fear of nuclear power as well.

Radiation has a unique power over our imagination. Its reach is invisible, and its presence is lingering. On top of that, we don’t know all the long-term effects it can have on humans. All this feeds a deep, instinctive fear in us. We grow up with the stories of meltdowns, irradiated ghost towns, and genetic mutations that shape how we think of nuclear disasters. Yet, when set against the broader landscape of energy production, nuclear energy causes fewer deaths per unit of electricity generated than many of its alternatives. In fact, nuclear power fatality is remarkably low, even when the worst accidents are accounted for. That said, nuclear accidents and their consequences are frightening, so we pay attention to them.

The figures speak for themselves. Coal causes around 24.6 deaths per terawatt hour, oil around 18.4, while nuclear is as low as 0.03. Energy from fossil fuels kills through chronic air pollution, mining disasters, and long-term health impacts, all of which nuclear power is free from. Nonetheless, it’s radiation we fear. Perhaps because it feels like a threat from beyond, a threat over which we have no control. This lack of control can easily be seen in some of the worst nuclear disasters in human history.

The partial meltdown that occurred at Three Mile Island in 1979 is still considered the worst nuclear disaster in U.S. history. Although the event was severe, there were no deaths or acute radiation injuries. Long-term health studies found that local communities weren’t exposed to any harmful substances. Still, the psychological impact of this accident was enormous. This is when public trust in nuclear power began to decline in the U.S.

The incident happened on the early morning of March 28, 1979, when a failure in the feedwater system shut down the pumps that normally cool the reactor. The reactor itself immediately shut down, but heat continued to build up. As intended, the pressure-relief valve opened. However, it malfunctioned and remained open for a prolonged period of time, allowing the coolant to escape.

Unfortunately, the indicators in the control room gave off the false impression that the valve had closed. The operation team thus believed that the coolant levels were adequate. As if that wasn’t enough, the auxiliary feedwater valves, which are needed for exactly this type of emergency, were left closed after recent maintenance. The loss of coolant resulted in parts of the reactor overheating. Later, a hydrogen bubble formed in the reactor vessel, raising further concerns.

Luckily, only small quantities of radioactive gas were released into the environment. Subsequent monitoring found these levels to be far below any harmful thresholds. But the Three Mile Island accident prompted major reforms in how nuclear plants are operated, how training of personnel is performed, and what emergency response to a nuclear disaster should be.

On October 8, 1957, a fire broke out at the Windscale (now Sellafield) nuclear site in Cumbria, United Kingdom. This incident is regarded as Britain’s worst nuclear accident. The reactors at the Windscale site were graphite-moderated, air-cooled production units that provided plutonium for the British nuclear weapons program. Such reactors need regular “annealing” operations to release stored energy in the graphite. This is a routine maintenance process that restores the properties of the nuclear pressure vessel. But this time, something went wrong. The second application of nuclear heating was applied too soon, and the fuel rods overheated.

When the temperatures started climbing, the cans of the uranium fuel elements failed and exposed uranium to oxygen. The fire broke out in both graphite and fuel, and it burned for approximately three days. Operators tried to extinguish the fire by poking the reactor core with metal poles to knock the burning uranium out. When this didn’t work, they tried injecting carbon dioxide into the core. Eventually, they decided to shut off the air flow and starve the fire of oxygen. To cool off the core, they flooded it with water.

Unfortunately, the fire released a mix of radioactive materials, especially iodine-131, polonium-210, and xenon. The contamination spread across the U.K. and into continental Europe, causing a public health emergency due to what nuclear radiation can do to the human body. The government of the U.K. imposed a milk ban over about 500 square kilometers (~200 square miles) around Windscale, claiming that it was the only contamination that occurred during the Windscale fire. Long-term estimates suggest this incident is responsible for 240 cancer cases. Thyroid cancer among the exposed children was especially studied, and the findings were concerning due to high radiation doses measured in the thyroid.

On 29 September 1957, at the Mayak Production Association site near Kyshtym, a nuclear disaster occurred. A cooling system failed in a tank of a highly radioactive, chemically reactive waste. The radioactive decay caused a heat buildup, which in turn led to a chemical explosion. A massive concrete lid that encapsulated the waste tank was blown off, and large amounts of radioactive materials leaked into the atmosphere.

This incident caused what we now call the East Ural Radioactive Trace (EURT), a contamination zone stretching across thousands of square kilometers of land. Significant amounts of radioactive substances were dispersed into the environment, causing the government to evacuate 1,100 people from the nearby villages.

Soviet officials claimed this accident caused no deaths whatsoever, but even though the historical accounts note there were no immediate casualties, some world institutions claim the Kyshtym disaster likely caused hundreds of radiation-exposure fatalities. Russia has a history of officials staying silent while radiation from super weapons leaks and other accidents happen under their watch. Over the following years, 21,400 people in the EURT zone were studied for the health effects of this disaster. One study found that the average blood cell counts significantly dropped among the exposed individuals. Only later retrospective studies of the death records revealed that the cancer mortality in this area had a two-fold rise after the incident.

On March 11, 2011, a 9.0 magnitude earthquake struck off Japan’s northeast coast, triggering a massive tsunami. This huge wave of water flooded the Fukushima plant’s diesel generators, knocking down the cooling systems. Without cooling, the cores of units 1, 2, and 3 overheated quickly, although it took several days for them to partially melt. Unfortunately, units 1, 3, and 4 experienced a hydrogen buildup inside the reactor buildings, which caused explosions.

Large amounts of radioactive iodine and cesium were released into the atmosphere and into the sea. In response, the Japanese government quickly evacuated people within an approximately 18 mile radius of the plant. Remarkably, there were no deaths caused by acute radiation sickness. The World Health Organization estimated that most of the local residents received a radiation dose of 1 to 10 millisieverts in the following year. That’s well under the levels that could cause harm to the human body.

However, the long-term cleanup and decommissioning effort remains enormous to this day. It involves stabilizing melted fuel, treating contaminated waters, and managing environmental contamination. It also doesn’t help that researchers fear Japan’s plan to dump nuclear meltdown water into the ocean may have some unknown effects on human DNA. It’s estimated it will be a decades-long effort, and the process is still ongoing.

The Chernobyl disaster is still regarded as the most catastrophic nuclear accident in human history. It all happened when, on the night of April 26, 1986, a planned safety test spiraled out of control at reactor 4 of the Chernobyl Nuclear Power Plant. But that was just a trigger for a series of catastrophic events. The plan was to simulate a power loss and see if the turbine’s residual momentum would be enough to power the coolant pumps long enough for the emergency diesel generator to kick in.

However, the reactor had a design flaw which, coupled with the disabled safety systems, allowed a sudden surge of reactivity. A massive steam explosion tore off the roof of the reactor.  A second blast, probably caused by a hydrogen buildup, ignited the graphite and sent radioactive smoke into the skies. The disaster was of catastrophic proportions. Winds carried radioactive particles across Belarus, Russia, and Ukraine. Eventually, the radioactive contamination from Chernobyl affected over 40% of the European continent.

In the immediate aftermath of the disaster, 30 workers and emergency responders died directly in the explosion or of acute radiation exposure. Dozens more succumbed later to the effects caused by the disaster. However, it is estimated that Chernobyl contributed to anywhere between 93,000 and 200,000 deaths across Europe. Chernobyl did more than just expose the design flaw of the particular type of reactor. It reshaped how the world thinks about nuclear power. The results were international safety reforms, stricter nuclear regulations, but also public distrust in this source of energy. Nonetheless, progress is being made with coming next-gen nuclear reactors.