Fukushima disaster: what happened 10 years ago at the Fukushima Daiichi Nuclear Power Plant

Exactly ten years ago, on a Friday afternoon, March 11, the most powerful earthquake ever recorded in Japan struck off the country’s eastern coast. The 9.0-magnitude quake was so forceful it shifted the Earth off its axis, triggered a tsunami which swept over the main island of Honshu, killing more than 18,000 people and wiping entire towns off the map.
At the Fukushima Daiichi Nuclear Power Plant, in the town of Okuma, Fukushima Prefecture (on the country’s east coast, about 220km north-east of the capital Tokyo), the gigantic wave surged over defences and flooded the reactors, causing a major disaster, the most severe nuclear accident since the Chernobyl disaster in 1986.
Authorities set up an exclusion zone which grew larger and larger as radiation leaked from the plant, forcing more than 150,000 people to evacuate from the surrounding zone.
A decade later, that zone remains off-limits and many residents have not returned. Authorities believe it will take up to 40 years to finish the work, which has already cost Japan over a trillion of yen.

The facility, operated by the Tokyo Electric and Power Company (TEPCO), was made up of six boiling-water reactors constructed between 1971 and 1979. At the time of the accident, only reactors 1–3 were operational, and reactor 4 served as temporary storage for spent fuel rods.
The earthquake occurred at 14:46 local time, with the epicenter near Honshu, the largest island of Japan and struck east of the city of Sendai, 97km north of the plant. Residents had just 10 minutes warning before the tsunami hit the coast.
When the earthquake struck, units 1, 2, and 3 were operating, but units 4, 5, and 6 had been shut down for a scheduled inspection.
Systems at the nuclear plant detected the earthquake and automatically shut down the nuclear reactors. Emergency diesel generators turned on to keep coolant pumping around the cores, which remain incredibly hot even after reactions stop.
However, the earthquake had also generated a tsunami 14 metres high that arrived shortly afterwards. The water overwhelmed the defensive sea wall, flooding the plant and knocking out the emergency generators.
Workers rushed to restore power, but the resultant loss of reactor core cooling led to three nuclear meltdowns, three hydrogen explosions, and the release of radioactive contamination.

In the days after the accident, radiation released to the atmosphere forced the government to declare an ever-larger evacuation zone around the plant, culminating in an evacuation zone with a 20 km radius.
Eventually, some 154,000 residents evacuated from the communities surrounding the plant due to the rising off-site levels of ambient ionizing radiation caused by airborne radioactive contamination from the damaged reactors.
Moreover, large amounts of water contaminated with radioactive isotopes were released into the Pacific Ocean during and after the disaster.
In the days that followed, workers at the plant made several attempts to cool the reactors using truck-mounted water cannons and water dropped from helicopters. Those efforts met with some success, which temporarily slowed the release of radiation, but they were suspended several times after rising steam or smoke signaled an increased risk of radiation exposure.
A second, but smaller, nuclear accident took place in August 2013 when approximately 330 tons of irradiated water used in ongoing cooling operations in reactors 1, 2, and 3 was discharged into the landscape surrounding the Fukushima Daiichi facility. TEPCO officials reported that the leak was the result of an open valve in the short barrier wall that surrounded several of the tanks used in radioactive water storage.

Luckily, there were no deaths immediately during the nuclear disaster. At least 16 workers were injured in the explosions, while dozens more were exposed to radiation as they worked to cool the reactors and stabilise the plant.
However, long-term effects of the radiation are a matter of debate still today. The World Health Organization (WHO) released a report in 2013 that said the disaster will not cause any observable increase in cancer rates in the region. Scientists both inside and outside Japan believe that aside from the region immediately around the plant, the risks of radiation remain relatively low.
However, many believe the dangers are far greater, and residents remain wary. Though officials have lifted restrictions in many areas most people have not returned to their homes.

Investigation Commission (NAIIC) found that the causes of the accident had been foreseeable, and that the plant operator, Tokyo Electric Power Company (TEPCO), had failed to meet basic safety requirements such as risk assessment, preparing for containing collateral damage, and developing evacuation plans.
An independent investigation set up by Japan’s parliament concluded that Fukushima was “a profoundly man-made disaster”.
Either way, following the disaster, the Japanese government began decommissioning many of the nuclear power plants, reducing its nuclear output. Power production switched to other sources, including coal, natural gas, oil and some renewable sources.
However, nuclear energy provides 10 percent of the world’s electricity and is steadily increasing. On current days, 30 countries generated electricity from 440 nuclear power reactors, and a further 55 reactors are currently under construction in 15 countries.