Nuclear accidents

The nuclear establishment vigorously promotes the idea that nuclear energy is safe, but in truth there is a nuclear accident for every day of the year.

The International Nuclear Events Scale (INES) rates nuclear events in increasing severity from one to seven, based on the spread of radioactive material and the impact upon people and the environment.  Levels one to three are incidents; four to seven are accidents.

These are some of the most serious nuclear accidents to date:

Chernobyl, Ukraine, 1986
INES 7: major accident
During the test of a safety system in Unit 4 of the Chernobyl nuclear power station, a series of mistakes by the reactor operators lead to a core meltdown. An explosion blasted off the 1,000-tonne steel and concrete lid of the reactor, and started an ensuing fire in the reactor core.  A radioactive cloud traveled over Europe. Twenty-four countries recorded elevated levels of radioactivity.

It took eight days to contain the fire at Chernobyl, and twelve to extinguish it completely.  Slow to admit to the accident, the Ukrainian government later sent military helicopters to dump huge amounts of lead, boron and other materials into the burning reactor core.  Workers battling the flames had little to no protection from the radionuclides streaming from the ruins of the reactor.  

Over one hundred times more radiation was released in the Chernobyl accident than dropped over Hiroshima and Nagasaki. In Ukraine and Byelorussia, vast areas were contaminated. The long-term effects of the radiation, in particular on children, are only just beginning to show.

Fukushima, Japan, 2011
INES 7: major accident
The world’s worst nuclear disaster after Chernobyl, and the only other accident to be given the top INES rating.  An offshore earthquake on 11th March, followed by a tsunami, damaged the cooling systems at the Fukushima Daiichi nuclear plant.  A series of partial core meltdowns followed, and a fire at a spent fuel storage pond released radioactivity directly into the atmosphere.

Workers pumped both fresh and seawater into the plant in an effort to cool the systems, and were later forced to release 11,500 tonnes of low-radioactivity water back into the ocean.  

At the time of writing, the disaster was still unfolding.  Radioactive material has been released into both terrestrial and marine environments, including through a crack in one of the reactors.  Elevated levels of radioactivity have been found in fish, vegetables and tap water, including in the Tokyo, Japan’s capital city. Up-to-date information on the tragedy can be found here.

Kyshtym, Russia, 1957
INES 6: serious accident
Another failure-of-coolant accident, this time in the Mayak complex that formed the dark heart of the Soviet Union’s nuclear programme during the cold war. A fire began in a liquid waste tank, causing an explosion that blasted the lid from the storage container and released radioactive material into the air - more than half the amount of radioactivity that was released from Chernobyl.  A plume fifty kilometers wide and 1,000 kilometers long emerged.  Two hundred and seventeen towns and at least 272,000 people were exposed to chronic levels of radiation, yet only a few villagers were evacuated. The disaster was kept secret for almost twenty years.Today, around 7,000 people still live in direct contact with the highly polluted Techa river, into which the plant would also freely dump waste, or on contaminated land.

Sellafield, UK, 1957
INES 5: accident with wider consequences
Britain’s most severe nuclear accident was at a nuclear reactor then known as Windscale, used for creating radioactive material for atomic weapons.  The reactor core caught fire and blazed for many hours, pouring smoke and radionuclides into the air.  This radioactive cloud spread across Europe to as far as Switzerland. There was no evacuation, though thousands of litres of milk in Britain were withdrawn and disposed of.

Three Mile Island, US, 1979
INES 5: accident with wider consequences
A stuck valve at a civilian nuclear power station in Pennsylvania lead to a loss of coolant and rising temperatures.  The fuel rods melted into the core of the reactor and began leaking radioactivity into the environment.  The amount of radioactivity released was thought to be relatively low, though an evacuation of pregnant women and young children was ordered.  

The accident had a calamitous effect on the public opinion of nuclear power in the US, and not a single new nuclear power plant has been commissioned there since.

Goiânia, Brazil, 1987
INES 5: accident with wider consequences
A caesium-137 source, left in an abandoned hospital, was stolen for scrap and broken open.  Parts were later sold and the contamination spread quickly in the community, depositing radioactive material up to 100 miles away.  Four people died shortly afterwards, and sixty were killed by the disaster in total, including the police and firemen who helped in the clean-up. Six hundred and twenty-eight people were contaminated, and over 6000 exposed to radiation.