Fukushima nuclear accident

On 11 March 2011, a major nuclear accident began at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. This happened after a big Tōhoku earthquake and tsunami, which caused power failures and damaged the plant's backup energy sources. Without power, the plant could not keep its reactors cool, leading to the release of radioactive contaminants into the air and water.

Even though a lot of radiation was released, health checks have shown that no direct health problems in the local people have been linked to the radiation from the accident. However, many people had to leave their homes because of the danger. Over 164,000 people were moved away from the area, and some of them later faced health problems or stress because of the evacuation.

Experts later found that safety rules were not followed well, which contributed to the problems. The cleanup and compensation for those affected by the accident cost a huge amount of money—around 180 billion US dollars. Even years later, some people from the area were still living far away from their homes.

Background

Main article: Fukushima Daiichi Nuclear Power Plant

See also: Boiling water reactor and Boiling water reactor safety systems

The Fukushima Daiichi Nuclear Power Plant had six special types of reactors called boiling water reactors. At the time of a big earthquake on March 11, 2011, three of these reactors were running, but all of them needed cooling for the fuel even after they stopped.

Many parts inside the reactors were made from a special metal called zirconium alloy. This metal stays safe at normal temperatures, but if it gets very hot, it can react with steam and create a gas called hydrogen. These reactions can make the reactor even hotter if not controlled.

In case of emergencies, the reactors had special cooling systems that could work without regular power. These systems used the steam from the reactor to cool it down. However, they needed some power to control them. The plant also had backup power generators that could provide electricity if the regular power stopped working. Most of these generators were placed underground and needed cooling water, while a few were above ground and used air for cooling.

Accident

On March 11, 2011, a big earthquake and tsunami caused a serious problem at the Fukushima Daiichi Nuclear Power Plant in Japan. The earthquake shook the ground very hard, and the tsunami washed away important parts of the power plant. This made it very hard to keep the nuclear reactors cool, which led to some dangerous situations.

The earthquake caused the reactors to shut down right away. But the tsunami damaged the backup power systems that were supposed to keep things running. Without power, the reactors couldn’t stay cool, and this caused some of the radioactive material to spread into the air and water around the plant. Workers worked very hard to fix the cooling systems and prevent more problems, but it was a very difficult situation.

Consequences

Evacuation

In response to the nuclear accident at the Fukushima Daiichi Power Plant, an evacuation was ordered for people living within a 2 kilometer radius. Later, the evacuation zone was expanded to 10 kilometers, and then further to 20 kilometers. Many people had to move multiple times before finding safe places to live.

The evacuation caused a lot of stress and difficulty for many families. Some people had to leave their homes and live far away from their families. Others lost their jobs or had to sell their homes. The evacuation also caused health problems for some people, especially older people and those who were already sick.

Energy policy

Before the accident, Japan got over 25% of its electricity from nuclear power. After the accident, Japan stopped using nuclear power and started using more fossil fuels like coal and oil. This made Japan import more fossil fuels and spend more money on energy.

Radiation effects in humans

The radiation exposure from the accident was very low for most people. The World Health Organization said that the radiation levels were not high enough to cause many health problems. Some people worried about getting cancer from the radiation, but studies showed that the risk was very small.

Radiation effects in non-humans

Some sea animals and fish were found to have small amounts of radiation in them. However, the amounts were very small and not enough to harm people or animals. Some people were worried about eating fish from the area, but tests showed that the fish was safe to eat.

Radiation effects in agriculture

Some vegetables and farmland near the accident site had high levels of radiation. This made it hard for farmers to grow food and sell it. Many farmers lost their jobs and homes because of the radiation. Japan made new rules to make sure that food was safe to eat after the accident.

Investigations

Three studies looked into the accident and found that it was caused by problems within the rules and relationships between the government and the nuclear companies. The rules were not strong enough to keep everyone safe.

The government fired some top energy leaders after the accident. In 2016, three leaders from the power company were blamed for not being careful enough, but they said they were not guilty.

NAIIC

Main article: National Diet of Japan Fukushima Nuclear Accident Independent Investigation Commission

The National Diet of Japan created a special group to look at the accident. This was the first time Japan had done this in many years. The group said the accident could have been avoided if people had been more careful and responsible. They pointed out that many people in Japan do not like to question those in charge, which helped the accident happen.

The group also noted that people living near the accident were still struggling with worries about their health and their lives after the accident.

ICANPS

Main article: Investigation Committee on the Accident at the Fukushima Nuclear Power Stations of Tokyo Electric Power Company

Another group was formed to find out what went wrong and how to prevent it from happening again. This group included experts from different fields. They found that the rules for handling emergencies were not good enough, and there was confusion about who was in charge. They also said that many people felt too comfortable with nuclear power and did not prepare well for emergencies.

Remediation and recovery

The government ordered cleaning in over a hundred places where extra radiation was found. This was to help calm worries, even though the level was much lower than needed for health safety. Education about radiation effects was also improved.

In 2018, tours of the accident area began. In September 2020, a museum opened in Futaba town near the power plant. It shows items and videos about the earthquake and nuclear accident, with explanations in several languages to welcome visitors from other countries.

Fuel removal

The plan is to take out the remaining nuclear fuel from the plants. By December 2014, 1535 fuel pieces were removed from one unit, and by February 2021, 566 were removed from another. All fuel rods will be taken out of four units by 2037, and the melted fuel from three units by about 2050. The cleanup will take 30 to 40 years.

Treating contaminated water

Since 2013, about 400 metric tons of cooling water went into the reactors each day, and another 400 metric tons of groundwater seeped in. About 800 metric tons of water was taken out each day for cleaning. Half was reused for cooling, and half was stored. The cleaned water, except for one type of material, will be released into the Pacific Ocean. An underground wall of ice was built to block groundwater from entering the buildings. In July 2022, Japan approved releasing the cleaned water into the sea, which will happen over 30 years.

Compensation and government expenses

Early estimates said the costs would be over ¥12 trillion ($120 billion). By 2022, ¥12.1 trillion was spent, with ¥7 trillion on payments to people, ¥3 trillion on cleaning, and ¥2 trillion on taking apart the plant and storing waste. In 2017, a court said the government did not do enough to prevent the accident. In 2020, the government and the plant’s operator were told to pay damages. In 2022, four former plant leaders were ordered to pay ¥13 trillion to the plant’s owner.

Equipment, facility, and operational changes

The accident showed that sea walls at tsunami-prone power plants need to be taller and stronger. New safety devices that do not need electricity were added to turn explosive gases into water. Better filtering systems were installed to catch radioactive materials. Backup batteries were improved, and new safety designs were used in newer reactors. Robots were tried but were not always useful in such conditions, leading to new robot development efforts.

Prior warning

In 2012, it was found that the problems at the Fukushima nuclear plant could have been expected. The company running the plant did not follow important safety rules, such as checking for risks or making plans to keep people safe. This led to many people being upset and protesting.

Studies years before the accident warned about the risks of big waves (tsunamis) hitting the plant, but not enough was done to protect it. Even reports suggesting higher waves might hit were not taken seriously. In one case, a key piece of equipment that provides power was flooded with water in 1991, but fixes were only partly made.

Some scientists had suggested safer ways to release air from the reactors years before the accident, but these were not used at the time.