The story

Fukushima Timeline: How an Earthquake Triggered Japan’s 2011 Nuclear Disaster

Fukushima Timeline: How an Earthquake Triggered Japan’s 2011 Nuclear Disaster


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

The 2011 disaster at the Fukushima Daiichi Nuclear Power Plant was the worst nuclear event since the meltdown at Chernobyl in the former Soviet Union 25 years prior.

It started with an earthquake. It resulted in 465,000 evacuations, $360 billion in economic losses and increased radiation levels in Tokyo, 140 miles away.

As with most disasters, several things had to go wrong to produce such a catastrophic outcome. Below is a detailed account of how the devastation unfolded.

March 11, 2011: An Earthquake Precipitates Crisis

2:46 pm: The westward moving Pacific Plate, an oceanic tectonic plate, lurches downwards beneath the North American plate, causing an earthquake 43 miles off the northeastern coast of Honshu, Japan’s most populous island. The earthquake has a magnitude of 9.1, making it the largest earthquake in Japan’s history—and one of the five most powerful earthquakes globally recorded since modern record-keeping began.

3:27 p.m.: The earthquake sets off a tsunami. The first wave arrives at the Fukushima Daiichi Nuclear Power Plant in the form of a 13-foot-high wave, which is deflected by a sea wall built to withstand waves up to 33 feet high.

3:35 p.m.: A second wave, this one over 50 feet high, breaches the wall. It destroys seawater pumps, drowns power panels that distribute energy to water pumps, and surges into basements where backup generators are housed. In five of the six reactors, AC power is lost; without the power, water pumps can’t provide the steady flow of cool water to the reactors’ intensely hot cores. Without the regular flow of cooling water, a meltdown will inevitably follow.

READ MORE: Chernobyl Timeline: How a Nuclear Accident Escalated to a Historic Disaster

3:37 p.m.: With flooding having destroyed the generator’s backup batteries, Unit 1 loses DC power as well. The control room for Units 1 and 2 goes dark, depriving power plant operators any capacity for monitoring the two reactors.

Just before 6 p.m.: A work crew goes to the 4th floor of the Unit 1 reactor building without protective clothing. Their dosimeters read off-the-scale levels of radiation, indicating that the core of Unit 1 is exposed and its fuel rods ruptured.

7:03 p.m.: Prime Minister Naoto Kan declares a nuclear emergency.

9:00 p.m.: The Japanese government issues evacuation orders for the several thousand residents living within a 1.9-mile (3 kilometer) radius of the power plant.

March 12: Evacuation Area Expands, the Roof Blows

Shortly before 6 a.m.: Prime Minister Kan decides to go to Fukushima. He orders authorities to widen the evacuation zone to 6.2 miles (10 kilometers). With the loss of coolant, temperature and pressure builds inside the reactors.

10:09 a.m.: The Tokyo Electric Power Company (TEPCO) announces they have vented some steam from Unit 1 in an attempt to lower the temperature and pressure. The venting means that some radioactive material has been released into the air.

10:58 a.m.: Unit 2, it is announced, has likewise been vented.

3:36 p.m.: A hydrogen explosion blows the roof off Unit 1, collapsing concrete walls and leaving behind only the steel framework. Four workers are injured in the explosion. In addition to the harm to the workers, the explosion damages electric cable that workers had been laying for the purposes of restoring power to Units 1 and 2. The explosion also damages fire hoses that workers had arranged, hampering the plant’s ability to deliver coolant to the reactor core.

Just before 6:30 p.m.: The evacuation area is expanded to a 12.4- mile (20 kilometer) radius.

8:20 p.m.: TEPCO begins injecting seawater into Unit 1, as a substitute coolant. The decision to use seawater is the death knell to Reactor 1: Unlike fresh water, it irreparably corrodes pumps and pipelines. Around the same time, Japan’s Nuclear and Industrial Safety Agency (NISA) detects harmful radiation levels of cesium 137 and iodine 131 near the plant.

READ MORE: The Chernobyl Coverup: How Officials Botched Evacuating an Irradiated City

March 13

6:23 a.m.: A NISA official announces that the emergency cooling system in the Unit 3 reactor has failed.

10:05 p.m.: TEPCO begins injecting seawater into Unit 3.

10:09 p.m.: TEPCO announces a plan to inject seawater into Unit 2, the first acknowledgement of emergency at that reactor.

March 14: Explosions Continue

11:01 a.m.: There’s a hydrogen explosion at the Unit 3 reactor. 11 workers are injured, and the building’s structure is severely damaged.

March 15

6:14 a.m.: A hydrogen explosion occurs at the Unit 2 reactor.

Throughout the day: Seawater pumping continues at Units 1, 2 and 3. Near the plant, radiation levels are measured at 400 millisieverts per hour. By comparison, the average person is exposed to about 2.4 millisieverts of radiation per year, meaning that radiation at Fukushima is 1.46 million times stronger than it would be in an average environment.

March 17

The military begins using helicopters to dump seawater onto Unit 3, where radiation levels are at 17 millisieverts per hour.

March 19

Replacement diesel generators are successfully implemented at Units 5 and 6, pumping water back into those reactor cores. Elsewhere, the extent of damage becomes clearer: Milk and water in the greater Fukushima Prefecture show excessively high levels of radioactive iodine.

READ MORE: Chernobyl: 7 People Who Played a Crucial Role in the World's Worst Nuclear Disaster

March 20: Things Start to Stabilize

Temperatures stabilize at Units 5 and 6, bringing about the safe harbor of “cold shutdown” conditions. Electrical power is restored to Unit 2.

March 22

Eleven days after the initial disaster, electrical power is restored to the control rooms of Units 1 and 2. In the wastewater just south of the plant, radioactive iodine is measured at 126.7 times higher than the legal limit.

March 25

The Unit 1 Reactor temperature is brought down to 204.5 degrees Celsius, safely inside its design limits. The Japanese government advises those residents who are between 20 and 30 kilometers away from the the plant to voluntarily evacuate the area.

READ MORE: How the Three Mile Island Accident Was Made Even Worse by a Chaotic Response

March 26

Seawater that’s tested near the plant has 1,250 times the legal limit of iodine 131.

April 11

A new earthquake, of magnitude 7.0, rocks eastern Japan. For 50 minutes, Fukushima loses power, preventing cooling water from reaching Units 1, 2, and 3.

April 12: Atomic Disaster Declaration

The International Atomic Energy Agency rates the Fukushima Crisis a disaster magnitude of 7, the highest of their scale.

May 11

Evacuees who have abandoned homes within 20 kilometers of Fukushima are given two hours to return for important documents or belongings left behind in the initial haste of their evacuation.

February 2, 2012

Nearly a year after the disaster, the village of Kawauchi—one of nine evacuated municipalities less than 20 kilometers from the plant—announces plans to reopen in the spring.


How is the clean up going?

Ten years later, several towns in north-eastern Japan remain off limits. Authorities are working to clean up the area so residents can return.

Major challenges remain. Tens of thousands of workers will be needed over the next 30 to 40 years to safely remove nuclear waste, fuel rods and more than one million tons of radioactive water still kept at the site.

But some residents have decided never to return because they fear radiation, have built new lives elsewhere or don't want to go back to where the disaster hit.

Media reports in 2020 said the government could start to release the water - filtered to reduce radioactivity - into the Pacific Ocean as early as next year.

Some scientists believe the huge ocean would dilute the water and that it would pose a low risk to human and animal health. Environmental group Greenpeace however said that the water contains materials that could potentially damage human DNA.

Officials have said no final decision has been taken about what to do with the liquid.


Timeline of Japan’s 2011 quake, tsunami and nuclear disaster

TOKYO (AP) — Thursday marks the 10th anniversary of a massive earthquake, tsunami and nuclear disaster that struck Japan’s northeastern coast. Here is a timeline of events:

— March 11, 2011: A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m., triggering a towering tsunami that reaches land within half an hour. The tsunami smashes into the Fukushima Daiichi nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors.

— March 12: A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days.

— April 12: Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from an earlier 5, based on radiation released into the atmosphere.

— April 24: The government designates a 2-kilometer (1.25-mile) exclusion zone around the nuclear plant spanning nine municipalities.

— Dec. 16: After workers struggle for months to stabilize the plant, Japan declares a “cold shutdown,” with core temperatures and pressures down to a level where nuclear chain reactions do not occur.

— July 23, 2012: A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by the plant’s operator, Tokyo Electric Power Co., lax oversight by nuclear regulators and collusion.

— April 1, 2014: The evacuation order is eased for a city west of the wrecked nuclear plant. Parts of at least eight other municipalities are allowed to reopen over the next three years, though the number of returnees remains low due to a lack of jobs and lingering radiation concerns.

— Dec. 22:TEPCO completes the removal of all spent nuclear fuel rods from the No. 4 reactor cooling pool, an initial milestone in the plant’s decades-long decommissioning.

— 2015-2019: Small robots equipped with cameras and sensors are sent into the damaged reactors but provide only limited views of the highly radioactive melted fuel debris. That makes plans for its removal more difficult.

— Feb. 10, 2020: A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. TEPCO says its 1.37 million ton storage capacity will be full in fall 2022.

— Dec. 10: Police say the death toll from the disaster, mostly from the tsunami, reaches 18,426, including 2,527 whose remains have not been found.

— Feb. 13, 2021: A magnitude 7.3 earthquake hits off the Fukushima coast, leaving one dead and injuring more than 180 people. It causes minor damage at the nuclear plant.

— March 6: Prime Minister Yoshihide Suga visits Fukushima and pledges to accelerate decontamination efforts so all remaining no-go zones can be reopened, but doesn’t give a timeframe.


Japan earthquake and tsunami: Timeline

(CNN) -- Here's a minute-by-minute look at the devastating earthquake and tsunami that hit Japan on Friday and subsequent worries over damage at nuclear power plants. (All times and dates are local Japanese time).

Magnitude 8.9 earthquake 231 miles northeast of Tokyo, Japan at a depth of 15.2 miles.

Quake is fifth largest in the world (since 1900) and the largest quake ever to hit Japan.

Pacific Tsunami Warning Center issues tsunami warning for the Pacific Ocean from Japan to the U.S. west coast. Tsunami alerts sound in more than 50 countries and territories. .

Within an hour after the quake a wall of water up to 30 feet high washes over the Japanese coast.

Cars, boats and trains are swept away. Buildings collapse. Roads and highways are severed. Fires break out in many locations.

Casualty reports begin to come in. Kyodo News Service reports at least 32 dead.

Japanese government declares emergency for nuclear power plant near Sendai, 180 miles from Tokyo. Japan has 54 nuclear power plants.

4 nuclear power plants closest to the quake are shut down.

Cooling system at Fukushima nuclear report are reported not working: Authorities say they are "bracing for the worst.

Several thousand people living within a mile-and-a-half of the plant are ordered to evacuate.

Japan resident describes nuke evacuation 83 aftershocks in 21 hours in Japan Gallery: Massive quake hits Japan

Police report finding 200 -- 300 bodies in coastal city of Sendai.

60,000 -- 70,000 city residents evacuated to shelters.

National Police up the confirmed death toll to 93.

A fire at Onagawa nuclear plant is extinguished, according to the International Atomic Energy Agency.

Fires are reported in at least three Japanese prefectures (Hakodate, Chiba, Miyagi). An oil refinery was ablaze near Tokyo.

A dam breaks in Fukushima prefecture, washing away scores of homes.

4 million homes in Tokyo and surrounding areas are without power.

Kyodo News Service puts number of confirmed deaths at 137.

Delta cancels 29 flights into and out of Tokyo.

American Airlines diverts six flights en route to Tokyo to other airports.

US Navy announces movement of seven ships toward Japan to assist relief efforts.

Radiation level in Fukushima No. 1 nuclear power plant reported rising.

President Obama says Japan's prime minister told him no evidence of radiation leaks from his country's nuclear power plants.

Japanese trade minister Banri Kaieda says small radiation leak could occur at Fukushima nuclear plant.

National Police up confirmed death toll to 151.

Japan's streets unrecognizable after quake

Secretary of State Hillary Clinton announces US Air Force planes are headed to Japan carrying coolant for the Fukushima nuclear power pant. The report that the planes carried coolant is later found to be erroneous.

6.2 magnitude earthquake hits Nagano and Niigata prefectures, according to the US Geological Survey.

Power company officials announced they will vent possibly radioactive air from the Fukushima nuclear plant to avoid a breakdown of the reactor's containment vessels.

Nuclear emergency declared at Fukushima Daiichi nuclear power plant.

Officials report the earthquake and tsunami cut off the plant's electrical power and that backup generators had been disabled by the tsunami.

Coming of dawn reveals miles of highways closed by the quake.

13,000 people reported stranded at Narita airport, another 10,000 at Tokyo's Haneda airport.

National Police now put death toll at at least 184.

Another earthquake --- one of a series over the past 24 hours --- hits west coast of Honshu. The quake had a strength of 6.3 magnitude.

Tokyo Electric Power IC. says radioactive substances could have leaked at the Fukushima No, 1 nuclear plant. Japan's Nuclear and Industrial Safety Agency says radiation near the plant's main gate is more than eight times normal level.

Tsunamis continue to awash ashore on Japan's northeast coast.

Death toll now put at at least 427.

Foreign minister says 25 countries, including the US, have offered assistance, including rescue teams and relief supplies.

Tokyo Power Co. says cooling systems at three of the four units of its Fukushima Daini plant have failed.

At least 6 million homes -- 10 percent of Japan's households are without electricity, according to the country's ambassador to the US.

Stores begin to run out of food, water and gasoline as masses of residents of northern Japan stream south from their earthquake-stricken hometowns.

Death toll rises to at least 900, according to the NHK broadcast network.

Rescuers struggle to pull survivors from collapsed homes, food waters, and fires.

A small amount of radioactive Cesium has escaped from a nuclear plant in Fukushima prefecture, according to Japan's Nuclear and Industrial Agency. Officials say the leak could have been caused by the melting of a fuel rod.

Tokyo Electric Company says an explosion at the Fukushima Daiichi plant injured four workers. (Kyodo News Agency will later quote electric company officials as saying the explosion caused the roof of a reactor to collapse.)

Technicians worked to contain temperatures at two Japanese nuclear power plants where cooling systems had been crippled by the disaster.

In the US, nuclear expert Robert Alvarez (Institute for Policy Studies in Washington) says the situation "has the potential for disaster."

US Geological Survey says the quake appears to have moved Japan's main island --- the whole island --- by 8 feet and shifted the earth on its axis.

Evacuation area around Fukushima Daiichi nuclear power plant extended to 20 kilometers (about 12.5 miles.)

Authorities insist no harmful gasses had been emitted by the explosion at Fukushima nuclear plant. They blamed the explosion on "water vapor that was part of the cooling process."

Fires reported at more than 200 locations in 12 of Japan's prefectures.

US Marines aircraft and helicopters are dispatched from bases on Okinawa to help in relief efforts.

Radiation levels at the Fukushima Daiichi plant are reported to have fallen, as officials prepare to flood the containment structure with sea water to bring temperatures down.

Authorities make plans to distribute iodine tablets --- a treatment to prevent radiation poisoning -- to residents near two damaged nuclear plants.

About 9500 people --- half the population -- are reported to be unaccounted for in the town of Minamisanriku on Japan's Pacific coast.

A cabinet official says the collapse of the walls of a building at the Fukushima Daiichi plant did not damage the reactor and its containment system.

Many areas experience blackouts as power plants are shut down for safety reasons. The number of houses without power is down to just over 5 million, according to the power company.

More than 83,000 people living within 3 miles of two power plants begin a government-ordered evacuation.

50,000 Japan Self-Defense Forces personnel, 190 aircraft and 25 ships have been deployed to help with rescue efforts, the Defense Ministry announced.

Broadcaster NHK reports the Defense Ministry had sent a team specializing with radioactive contamination to a command post near the plant where a radiation leak had occurred.

Gasoline sales in Tokyo are limited to 20 liters (5.3 gallons) per car.

Three people (selected at random out of 90) test positive for radiation exposure in Fukushima prefecture.

There is news that Japanese authorities have informed the International Atomic Energy Agency (IAEA) that the explosion at the Fukushima Daiichi plant occurred outside the primary containment vessel. The Tokyo Power Company says the integrity of the containment vessel has not been compromised. Sea water mixed with Boron is being injected in an effort to cool the system.

LATER ON SUNDAY MORNING

A government official says a meltdown may be occurring at the damaged plant, sparking fears of a widespread release of radioactive material . Meanwhile, another reactor at the same facility failed Sunday morning -- bringing to three the number of units there that are experiencing major problems in cooling radioactive material


Timeline of Japan's 2011 quake, tsunami and nuclear disaster

TOKYO (AP) — Thursday marks the 10th anniversary of a massive earthquake, tsunami and nuclear disaster that struck Japan's northeastern coast. Here is a timeline of events:

— March 11, 2011: A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m., triggering a towering tsunami that reaches land within half an hour. The tsunami smashes into the Fukushima Daiichi nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors.

— March 12: A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometer (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days.

— April 12: Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from an earlier 5, based on radiation released into the atmosphere.

— April 24: The government designates a 2-kilometer (1.25-mile) exclusion zone around the nuclear plant spanning nine municipalities.

— Dec. 16: After workers struggle for months to stabilize the plant, Japan declares a “cold shutdown,” with core temperatures and pressures down to a level where nuclear chain reactions do not occur.

— July 23, 2012: A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by the plant's operator, Tokyo Electric Power Co., lax oversight by nuclear regulators and collusion.

— April 1, 2014: The evacuation order is eased for a city west of the wrecked nuclear plant. Parts of at least eight other municipalities are allowed to reopen over the next three years, though the number of returnees remains low due to a lack of jobs and lingering radiation concerns.

— Dec. 22:TEPCO completes the removal of all spent nuclear fuel rods from the No. 4 reactor cooling pool, an initial milestone in the plant’s decades-long decommissioning.

— 2015-2019: Small robots equipped with cameras and sensors are sent into the damaged reactors but provide only limited views of the highly radioactive melted fuel debris. That makes plans for its removal more difficult.

— Feb. 10, 2020: A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. TEPCO says its 1.37 million ton storage capacity will be full in fall 2022.

— Dec. 10: Police say the death toll from the disaster, mostly from the tsunami, reaches 18,426, including 2,527 whose remains have not been found.

— Feb. 13, 2021: A magnitude 7.3 earthquake hits off the Fukushima coast, leaving one dead and injuring more than 180 people. It causes minor damage at the nuclear plant.

— March 6: Prime Minister Yoshihide Suga visits Fukushima and pledges to accelerate decontamination efforts so all remaining no-go zones can be reopened, but doesn’t give a timeframe.


Ten Years Since the Fukushima Nuclear Disaster

March 11, 2011 was a terrible day for Japan. Natural disasters led to a man-made disaster that the country is still dealing with. Today marks 10 years since a tsunami triggered the world’s worst nuclear disaster since 1986.

On that afternoon, the most powerful earthquake in Japan’s history struck in the sea off the country’s east coast. The 9.0 magnitude earthquake caused a series of tsunamis to pound Japan’s east coast. About 18,000 people were killed by these tsunamis.

On March 11, 2011, the most powerful earthquake in Japan’s history struck in the sea off the country’s east coast. The 9.0 magnitude earthquake caused a series of tsunamis to pound Japan’s east coast. About 18,000 people were killed by these tsunamis.
(Source: Maximilian Dörrbecker /Connormah/W.Rebel [CC BY-SA 3.0], via Wikimedia Commons.)

But the tsunamis brought other problems, too. The Fukushima Daiichi Nuclear Power Plant is built right at the edge of the ocean in the town of Ōkuma, in the Fukushima district. The plant creates nuclear energy.

Nuclear Energy
Nuclear power is created by splitting atoms in a nuclear reaction – the same science behind nuclear weapons. Nuclear power produces toxic waste which must be handled and stored with great care.
The great danger of nuclear power is radiation. If something is “radioactive” that means it gives off radiation. Radiation is energy traveling in waves. High levels of radiation can cause sickness or even death. It can also affect the DNA of humans and animals.
Because nuclear reactions create huge amounts of heat, the nuclear reactors where the reactions happen need to be constantly cooled.

For safety, the Fukushima power plant was shut down as soon as the earthquake was detected. When the electricity went out, the factory had to count on its backup electrical generators to cool the reactors.

When a 46-foot (14-meter) tsunami wave washed over the plant, its backup generators stopped working. The flooded reactors slowly began to overheat. Over the next few days, three of the factory’s reactor cores melted down, and there were three large explosions.
(Source: Digital Globe [CC BY-SA 3.0], via Wikimedia Commons.)

But when a 46-foot (14-meter) tsunami wave washed over the plant, its backup generators stopped working, too. The flooded reactors slowly began to overheat. Over the next few days, three of the factory’s four reactor cores melted down, and there were three large explosions.

Radiation began to escape from the plant. The government closed off an area within 12.5 miles (20 kilometers) of the plant. Over 150,000 people were forced to leave their homes.

Radiation began to escape from the plant. The government closed off an area within 12.5 miles (20 kilometers) of the plant. Over 150,000 people were forced to leave their homes. Above, months after the accident, a scientist studies the damage to reactor 3.
(Source: Greg Webb, IAEA Imagebank [CC BY-SA 2.0], via Wikimedia Commons.)

That was ten years ago. Since then, Japan’s government has spent over $300 billion recovering from the earthquake, tsunamis, and the nuclear accident.

Some areas around the Fukushima plant are still closed, but much of it was re-opened a few years ago. Scientists from the United Nations say the radioactivity from the disaster isn’t likely to cause future health problems for people in the area.

This image has not been loaded because of your cookie choices. To view the content, you can accept 'Non-necessary' cookies.

The government closed off the area around the plant. Over 150,000 people were forced to leave their homes. Some areas around the Fukushima plant are still closed, but much of it was re-opened a few years ago. Above, one of the closed-off areas in 2016.

Still, most people who used to live in the area haven’t returned. In 2019, the company that owns the power plant decided to close it permanently. Cleaning up the site is expected to take 40 years.

The group Greenpeace, which works to protect the environment, says radiation levels are too high in many of the re-opened areas. The group says the region can’t be returned to normal.

This image has not been loaded because of your cookie choices. To view the content, you can accept 'Non-necessary' cookies.

In 2019, the company that owns the power plant decided to close it permanently. Cleaning up the site is expected to take 40 years. The huge piles in this picture are radioactive dirt that has been collected as part of the cleanup effort.

One big question about the cleanup is where all the radioactive material will go. That’s a problem faced by any nuclear plant. The Fukushima plant has an extra problem. There’s so much radioactive water at the plant that there’s not enough room to store much more.

The government says it has filtered most of the radiation from the water and plans to release the water back into the ocean. Fishermen, and groups like Greenpeace don’t like that idea. They’re afraid the radiation will harm sea life, and sooner or later make its way back to humans.

This image has not been loaded because of your cookie choices. To view the content, you can accept 'Non-necessary' cookies.

One big question about the cleanup is where all the radioactive material will go. There’s so much radioactive water at the plant that there’s not enough room to store much more. The government says it plans to release the water back into the ocean.

Though the Fukushima Daiichi disaster happened 10 years ago, its effects continue today, and will be felt far into the future.

Did You Know…?
Many people believe nuclear energy will be an important tool for fighting the climate crisis. When nuclear power works correctly, it creates far less air pollution than coal or oil. But nuclear power always produces radioactive materials. The question is whether humans can safely control, store, and contain these materials, even in the face of huge, unexpected natural disasters.

This map has not been loaded because of your cookie choices. To view the content, you can accept 'Non-necessary' cookies.


Timeline of Japan’s 2011 quake, tsunami and nuclear disaster

TOKYO - Thursday marks the 10th anniversary of a massive earthquake, tsunami and nuclear disaster that struck Japan’s northeastern coast. Here is a timeline of events:

— March 11, 2011: A magnitude 9.0 earthquake strikes off the coast at 2:46 p.m., triggering a towering tsunami that reaches land within half an hour. The tsunami smashes into the Fukushima Daiichi nuclear plant, destroying its power and cooling systems and triggering meltdowns at three reactors.

— March 12: A hydrogen explosion occurs at the plant’s No. 1 reactor, sending radiation into the air. Residents within a 20-kilometre (12-mile) radius are ordered to evacuate. Similar explosions occur at two other reactors over the following days.

— April 12: Japan raises the accident to category 7, the highest level on the International Nuclear and Radiological Event Scale, from an earlier 5, based on radiation released into the atmosphere.

— April 24: The government designates a 2-kilometre (1.25-mile) exclusion zone around the nuclear plant spanning nine municipalities.

— Dec. 16: After workers struggle for months to stabilize the plant, Japan declares a “cold shutdown,” with core temperatures and pressures down to a level where nuclear chain reactions do not occur.

— July 23, 2012: A government-appointed independent investigation concludes that the nuclear accident was caused by a lack of adequate safety and crisis management by the plant’s operator, Tokyo Electric Power Co., lax oversight by nuclear regulators and collusion.

— April 1, 2014: The evacuation order is eased for a city west of the wrecked nuclear plant. Parts of at least eight other municipalities are allowed to reopen over the next three years, though the number of returnees remains low due to a lack of jobs and lingering radiation concerns.

— Dec. 22:TEPCO completes the removal of all spent nuclear fuel rods from the No. 4 reactor cooling pool, an initial milestone in the plant’s decades-long decommissioning.

— 2015-2019: Small robots equipped with cameras and sensors are sent into the damaged reactors but provide only limited views of the highly radioactive melted fuel debris. That makes plans for its removal more difficult.

— Feb. 10, 2020: A government panel recommends the controlled release into the sea of rapidly increasing amounts of leaked radioactive cooling water at the Fukushima plant. TEPCO says its 1.37 million ton storage capacity will be full in fall 2022.

— Dec. 10: Police say the death toll from the disaster, mostly from the tsunami, reaches 18,426, including 2,527 whose remains have not been found.

Loading.

— Feb. 13, 2021: A magnitude 7.3 earthquake hits off the Fukushima coast, leaving one dead and injuring more than 180 people. It causes minor damage at the nuclear plant.

— March 6: Prime Minister Yoshihide Suga visits Fukushima and pledges to accelerate decontamination efforts so all remaining no-go zones can be reopened, but doesn’t give a timeframe.


Read More

The disaster also caused level 7 meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex, situated about 140 miles north of Tokyo.

Here is everything you need to know about it.

What happened?

Damage to the plant had already been caused by the massive earthquake, which sent its three nuclear reactors into automatic shut down as a safety measure.

But the reactors were not prepared for the tsunami waves that followed, and as the diesel generators and battery back-ups that were supposed to cool the reactor cores failed, temperatures began to rise uncontrollably.

Hydrogen gas was released, causing large explosions which sent all three reactors into meltdown, spewing radiation and forcing 150,000 people from their homes, many of whom will never return.

No-one was killed from the explosions themselves, but 35 people were injured and the incident sparked a major nuclear ordeal. The disaster was eventually classified at the same severity level as the 1986 explosion at Chernobyl.

Could the disaster have been prevented?

An official inquiry found that Tokyo Electric Power (Tepco) – the company running the station – had failed to plan for the very foreseeable dangers of earthquakes and tsunamis, and had no evacuation plan in place.

And in 2012, a panel criticised the response of Tepco, regulators and then Prime Minister Naoto Kan, who had resigned the year before after criticism of his handling of the disaster.

“The Fukushima nuclear power plant accident was the result of collusion between the government, the regulators and Tepco, and the lack of governance by said parties,” the panel said.

Regulators had been reluctant to adopt global safety standards that could have helped prevent the disaster: "Across the board, the commission found ignorance and arrogance unforgivable for anyone or any organisation that deals with nuclear power,” said the panel.

It also found evidence that damage from the earthquake, and not just the ensuing tsunami, could not be ruled out as a cause of the incident in one of the world’s most quake-prone nations.

“We have proved it cannot be said that there would have been no crisis without the tsunami,” Katsuhiko Ishibashi, seismologist and panel member, said.

What is the area like today?

Many people still have an image of the negative situation of Fukushima Prefecture shortly after the region was hit by the disaster-caused nuclear plant accident.

This has hindered Fukushima's recovery and prevented various countries and regions from lifting import restrictions on agricultural and other products from Japan.

It took six years and a huge clean-up effort before most of the residents evacuated from the area were allowed to return, and today there remains a “core zone” which is still too dangerous for 50,000 inhabitants to be allowed back.

The mammoth clean-up operation is still ongoing, with a crew of over 5,000 people. Independent estimates put the final bill for the project at over £550 billion, and current predictions suggest it may be another 30 years before the site is fully cleaned up.

But recovery has been steadily progressing, and earlier this month the Reconstruction Agency – a government agency overseeing work on recovery from the Great East Japan Earthquake – opened the Fukushima Updates website.

The aim of the site is to accurately and clearly send out information in English regarding questions and concerns that people may have over the safety of Fukushima and Japan.

Intended as a forefront tool to disseminate the latest information on Fukushima, the site responds in a Q&A format to questions and concerns that people may have over the current situation of Fukushima, and the safety of Japanese food products.


Northern Japan’s nuclear emergency

Of significant concern following the main shock and tsunami was the status of several nuclear power stations in the Tōhoku region. The reactors at the three nuclear power plants closest to the quake’s epicentre were shut down automatically following the temblor, which also cut the main power to those plants and their cooling systems. However, inundation by the tsunami waves damaged the backup generators at some of those plants, most notably at the Fukushima Daiichi (“Number One”) plant, situated along the Pacific coast in northeastern Fukushima prefecture about 60 miles (100 km) south of Sendai. With power gone, the cooling systems failed in three reactors within the first few days of the disaster, and their cores subsequently overheated, leading to partial meltdowns of the fuel rods. (Some plant workers, however, attributed at least one partial meltdown to coolant-pipe bursts caused by the earthquake’s ground vibrations.) Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and burned sizable holes through the floor of each vessel, which partially exposed the nuclear material in the cores. Explosions resulting from the buildup of pressurized hydrogen gas in the outer containment buildings enclosing reactors 1, 2, and 3, along with a fire touched off by rising temperatures in spent fuel rods stored in reactor 4, led to the release of significant levels of radiation from the facility in the days and weeks following the earthquake. Workers sought to cool and stabilize the damaged reactors by pumping seawater and boric acid into them.

Because of concerns over possible radiation exposure, Japanese officials established an 18-mile (30-km) no-fly zone around the facility, and an area of 12.5 miles (20 km) around the plant was evacuated. The evacuation zone was later extended to the 18-mile no-fly radius, within which residents were asked to leave or remain indoors. The appearance of increased levels of radiation in some local food and water supplies prompted officials in Japan and overseas to issue warnings about their consumption. At the end of March, seawater near the Daiichi facility was discovered to have been contaminated with high levels of radioactive iodine-131. The contamination stemmed from the exposure of pumped-in seawater to radiation inside the facility this water later leaked into the ocean through cracks in water-filled trenches and tunnels between the facility and the ocean.

In mid-April Japanese nuclear regulators elevated the severity level of the nuclear emergency at the Fukushima Daiichi facility from 5 to 7—the highest level on the scale created by the International Atomic Energy Agency—placing the Fukushima accident in the same category as the Chernobyl accident, which had occurred in the Soviet Union in 1986. Radiation levels remained high in the evacuation zone, and it was thought that the area might be uninhabitable for decades. However, several months after the accident, government officials announced that radiation levels in five towns located just beyond the original 12.5-mile evacuation zone had declined enough that they could allow residents to return to their homes. Although some people did come back, others stayed away, concerned about the amount of radioactive materials still in the soil. Attempts were made in several of those areas to remove contaminated soil. In December 2011 Japanese Prime Minister Noda Yoshihiko declared the Fukushima Daiichi facility stable after the cold shutdown of its reactors had been completed.

In the years following the accident, numerous leaks at the facility occurred at the site where contaminated reactor cooling water was stored. A significant leak occurred in August 2013 that was severe enough to prompt Japan’s Nuclear Regulation Authority to classify it as a level-3 nuclear incident.


Timeline of Events at Japan's Fukushima Nuclear Reactors

A 9.0-magnitude earthquake (originally estimated at 8.9) struck off the coast of Honshu, Japan, and an enormous tsunami followed shortly after. Eleven nuclear reactors at the four nearest power plants automatically shut down upon sensing ground accelerations, stopping the nuclear fission of uranium in their cores. Nuclear fuel requires continued cooling even after a plant is shut down, though, because residual fission products continue to decay and produce a huge amount of heat. The Japanese plants use continually-pumped water, which absorbs a great deal of heat, to cool their nuclear reactors.

The earthquake knocked out the electricity at the Fukushima Daiichi plant run by Tokyo Electric Power Company (TEPCO). Emergency diesel generators were used to pump water to cool Reactor Units 1, 2 and 3, which had been operating at the time of the quake, but an hour later, the back-up generators were knocked out by tsunami flooding.

Insufficient power meant that water could not be pumped through the nuclear cores quickly enough. As the water inside the reactors heated up too high and started boiling, the water level dropped inside the cores, and the pressure rose from the steam. TEPCO declared a state of emergency. Japanese authorities ordered the evacuation of residents within a three-kilometer radius of Fukushima Daiichi, and told people within a 10-kilometre radius to remain indoors. This was a precautionary measure because, at that point, there had been no release of radiation from the nuclear power plant. The containment vessels housing the reactor vessels were withstanding the increase in pressure inside.

Workers at Fukushima Daiichi worked desperately to restore the diesel generators, and to hook up mobile power sources in order to pump sufficient water to cool the three hot reactors. Units 1 and 2 were both experiencing water level drops and rises in pressure, but the water level in all three reactor vessels remained above the fuel elements at the end of March 11.

A fire broke out at a nuclear power plant in Oganawa immediately after the earthquake. This was soon extinguished, and that plant saw no further problems.

At 9 am local Japan time, the pressure within the containment vessel of Fukushima Daiichi Unit 1 was as high as 840 kPa, compared to reference levels of 400 kPa. Officials vented the vessel to lower its pressure. The released water vapor was filtered to retain most of the radiation within the containment, but because the vapor had been through the reactor core, a certain release of radioactive substances such as caesium-137 and iodine-131 was inevitable. Tepco was also preparing to relieve pressure for Units 2 and 3.

An explosion occurred at Unit 1, blowing off the roof and walls of the concrete structure built around it and leaving a naked steel structure behind. Four workers were injured. Tepco tamped down initial panic and confusion by explaining that the external building structure does not act as the containment, which is an airtight steel structure within, and that the containment was not damaged in the explosion. Hydrogen gas which had burned off of cladding around the fuel rods inside the reactors was the main substance released.

When radiation levels reached 500 microsieverts per hour around the facility due to pressure venting, non-radioactive potassium iodide tablets were brought into the area, but not distributed. Potassium iodide is quickly taken up by the body and its presence prevents the absorption of iodine-131 should people be exposed to it. The evacuation radius was also incrementally increased, eventually expanding to a 20-km radius around the facility. The injection of seawater into parts of the building near the reactor started at 8.20pm local time and was followed by the addition of boric acid, which inhibits nuclear reactions.

The nearby Fukushima Daini power plant encountered problems for the first time after safely shutting down four operational reactor units the day before. Daini Unit 1's isolation cooling system, supplemented by a back-up water condensate system, had been operating normally, but the back-up system stopped working at 5.32am local time when its suppression chamber reached 100 degrees Celsius. Residents within 10 kilometers of Daini were evacuated in case Tepco were to need to vent the containments of Daini units. The number of evacuees around both sites stood at 185,000.

The containment of Reactor Unit 3 at Fukushima Daiichi was vented again in order to lower the pressure inside. Water levels in all three reactors were continuing to drop. Following the failure of a high pressure injection system and other attempts to cool the plant, injection of water, and later seawater, started.

Japanese officials said they believed a partial meltdown had probably occurred in at least two of the nuclear reactors, due to water levels having fallen below the level of the fuel rods inside them. [Infographic: What Is a Nuclear Meltdown?]

At Fukushima Daini Unit 1, plant operators were able to restore a residual heat remover system to cool the reactor, and workers at Units 2 and 4 were working to restore the same residual heat removal systems. Unit 3 was in a safe, cold shutdown. Radiation dose rate measurements observed at four locations around the plant's perimeter over a 16-hour period on 13 March were all normal.

Throughout the day, all Fukushima Daiichi reactors were still being powered by mobile power generators on site, because power via off-site power supply or backup diesel generators had still not been restored.

A skeleton crew of 50 workers were continuing to inject seawater and boron into the reactor vessel to cool the reactor at Unit 1, while the reactor core in Unit 2 was being cooled through reactor core isolation cooling, a procedure used to remove heat from the core, via mobile power generators. The reactor water level was lower than normal but remained steady.

A seawater-boric acid combination continued to be injected into Unit 3. Water levels inside the reactor vessel increased steadily for a while but later stopped increasing for an unknown reason. The concentration of hydrogen was increasing inside the containment building, and a hydrogen explosion occurred at Unit 3 at 11:01 am local Japan time, injuring 11 workers. The primary containment vessel was not damaged.

Fortunately, prevailing winds were moving away from the Japanese coast to the East, carrying any radioactive materials released by venting and explosions out to sea.

The reactors Units 1, 2 and 3 of the Fukushima Daini nuclear power plant were pronounced to be in cold shutdown status, meaning the pressure of the water coolant in the three reactors was around atmospheric level and the temperature was below 100 degrees Celsius. Under these conditions, the reactors were considered to be safely under control. Unit 4 was not yet in a cold shutdown.

A dose rate of 11.9 millisieverts (mSv) per hour was recorded early on March 15 and a 0.6 millisieverts (mSv) per hour rate was recorded six hours later, suggesting radiation levels were dropping off. Cooling via seawater injections was ongoing in all three units.

The spent fuel storage pond at the Unit 4 reactor of the Fukushima Daiichi nuclear power plant, which was thought to be in a cold shutdown, caught on fire. Radioactivity was being released directly into the atmosphere, and radiation doses of up to 400 millisieverts per hour were briefly reported between Units 3 and 4. That hourly dose is approximately 100 times the amount of background radiation the average person absorbs in a year.

The spent fuel fire was extinguished two hours after it began, and radiation levels dropped off again shortly after. Authorities said the fire may have been caused by an earlier hydrogen explosion. An explosion at the Unit 2 reactor at the Fukushima Daiichi plant had occurred at around 6:20 am local Japan time.

The 400 mSv per hour recorded radiation level caused workers to be temporarily evacuated, but they were later called back in. Officials advised residents within 30 km of Fukushima Daiichi to stay indoors.

It was determined that the hydrogen explosion at Unit 2 may have affected the integrity of its primary containment vessel, which would mean greater radiation leaks to the environment.

By the end of March 15, all units at Fukushima Daini had been brought to a cold shutdown.

The pressure inside Unit 3 suddenly plunged, suggesting that either the gauges were malfunctioning or its containment vessel may have cracked. Radiation doses of about 250 millisieverts an hour had been detected 100 feet above the plant.

Early in the day, the water level in Unit 5 at Fukushima Daiichi, which was loaded with fuel but thought to be in a cold and safe shutdown, was found to be dropping. Diesel generators from Unit 6 were brought over to Unit 5 to pump its cooling system.

Due to ongoing power failures, temperatures at spent fuel pools at Fukushima Daiichi were rising by approximately 1 degree Celsius per day. The hottest was the pool near Unit 4, which was at 84 degrees Celsius. According to IAEA experts, a typical spent fuel pool temperature is kept below 25 ?C under normal operating conditions, which requires a constant power source.

Japanese Defense Minister Toshimi Kitazawa announced that Special Defense Forces helicopters planned to drop water onto the spent fuel rods near Unit 3, and officials were preparing to spray water into Unit 4 from ground positions.

Tepco confirmed that several workers had been injured over the previous few days. At least 17 workers had experienced some radiation exposure, and one worker suffered "significant" radiation exposure while venting a reactor unit. Two workers are missing.

Four helicopters dropped water on the spent fuel rods of Unit 3, but this had little effect on their temperature. Military fire trucks later began spraying cooling water on them. Unit 3 was considered to be a greater threat than Unit 4, because it is the only one loaded with a mixed fuel known as MOX &ndash which contains plutonium-239, a more dangerous radioactive material than depleted uranium-238.

An external grid power line cable was successfully attached to Unit 2. Power will be turned on in Unit 2 as soon as workers finish spraying of water on Unit 3.

For the first time, Japanese officials admit that burying the damaged nuclear power plants in sand and concrete - the method used to seal huge radiation leakages from the Chernobyl meltdown in 1986 - maybe be the only way to prevent a massive radiation release.

"It is not impossible to encase the reactors in concrete. But our priority right now is to try and cool them down first," an official from the plant operator, Tokyo Electric Power Co, told a news conference. Officials said they still hoped to fix a power cable to at least two reactors to restart water pumps needed to cool overheating nuclear fuel rods at the Fukushima Dai-ichi plant.

New reports trickle out that, immediately after the nuclear damage was detected, Japan turned down an offer from the United States to provide technical support for cooling and dismantling the damaged reactors. At that point, Japanese officials said, the government and TEPCO still believed they could handle the situation themselves.

Meanwhile, Japan fallout reaches California but, according to an official, radiation is miniscule, far below health threat levels.

March 19 - 20:

Workers continued spraying Units 1, 2 and 3 with seawater and worked to reconnect the power supply to Unit 2 (which would then act as a hub to power Unit 1) in order to operate their cooling systems.

Unit 1's containment vessel appeared to be intact and pressure inside was restored, but the containments of Units 2 and 3 are both thought to have cracked during explosions in previous days. White smoke was seen to be emerging from both vessels, but seemed to diminish over time.

The spent fuel pools in Units 3 and 4 are still dangerously hot, and helicopters have continued dropping water on them.

The reactor cores and spent fuel pools of Units 5 and 6, which were in a cold shutdown at the time of the March 11 earthquake and had not since been problematic, began to heat up. Workers have turned on generators to pump water through them and have drilled holes in the roofs of their containment buildings to prevent the hydrogen explosions that damaged other units in previous days.

The Japanese government has advised evacuees who live within a 20 km radius of the Fukushima Daiichi plant to take iodide pills after heightened levels of radioactive iodine-31 were found in milk and vegetables grown in the area.

The containment vessels of Reactor Units 2 and 3, which were suspected of having cracked in explosions, have been found to be intact.

Seawater injection is continuing in Units 1, 2 and 3. Plant officials said off-site power was about to be restored to Units 1 and 2, and had already been restored to Units 3 and 4. Restored power will allow normal cooling operations to resume in the reactors. A U.S. Nuclear Regulatory Commission (NRC) official described the situation at the Fukushima plant as "on the verge of stabilizing."

The NRC is planning a 90-day review of reactor safety to assess natural disaster preparations at 104 U.S. nuclear plants, some of which use the same model as the Fukushima plant. A report on the NRC&rsquos initial findings will be released after 30 days. Bill Borchardt, executive director of operations at NRC, said he and his commission do not expect to find any significant weaknesses.

Efforts to restore electricity to the Fukushima Daiichi plant in order to resume normal operation of its cooling system were sidetracked by rising temperatures at Unit 2's spent fuel pool. Steam was seen spewing from the pool. If water were to boil away and leave the spent fuel rods exposed, they would melt, sending radioactive materials into the air, so workers had to focus on cooling the pool down by spraying it with water.

A power line connected to Reactor Units 1 through 4 may be damaged, so technicians are working on fixing it while other workers continue to pump water through the Units via fire hoses.

Elevated levels of radioactive iodine and cesium have also been detected in the seawater near Fukushima, though not elevated enough to pose a direct threat to human health according to experts. The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) have begun carrying out comprehensive measurements of the radioactivity in the marine environment. Sea water sampling from eight locations will be sampled and their radionuclide concentrations and dose rates will be analysed by the Japan Atomic Energy Agency (JAEA). Results will be provided on 24 March.

Radiation levels surpassing 400 times the normal level had been detected in soil about 25 miles from the Fukushima plant, according to the government's Science Ministry. Though drastically higher than normal, this is also said not to pose an immediate health risk.

Workers continue their efforts to reconnect power to the plant, after temporarily evacuating due to higher than normal levels of radioactivity being detected around a smoking fuel pool near Reactor Unit 2. Off-site electricity is connected to a transformer in Unit 2, but technicians must conduct diagnostic tests to determine the integrity of the reactor's electrical systems before turning them on. When Unit 2 is powered up, workers will move to Unit 1, which sustained some damage during a hydrogen explosion and may take more time to get going.

Units 3 and 4 have not been hooked up to power yet, despite previously reports to the contrary. There is concern about the too-hot spent fuel pools at both units. Units 5 and 6 are hooked up to off-site power, and are not causes for immediate concern.

In Tokyo, iodine-131 was detected in water samples at a level of 210 becquerels per liter. The recommended limit for infants is 100 becquerels per liter, and for adults, the limit is 300 becquerels. Japan's Health Ministry said it was unlikely that there would be negative consequences to infants who drank the contaminated water, but that it should be avoided if possible.

Shipment of raw milk and parsley from Ibaraki Prefecture, adjacent to Fukushima, was suspended. Shipments of 11 contaminated vegetables from Fukushima Prefecture ended on Monday (March 21).

Radioactive iodine found in water in Tokyo dropped back to safe levels after being considered dangerous for consumption by infants the day before, according to city authorities. The level fell to 79 becquerels per liter (Bq/L) and is considered safe for consumption by both infants and adults. In Japan, 100 Bq/L is safe for infants and 300 Bq/L is safe for adults. These limits are much stricter than those in the U.S., where infants are allowed to drink water containing radioactivity as high as 300 Bq/L, and adults are allowed to drink water with 3,000 Bq/L of radioactivity.

At the Fukushima Daiichi plant, 140 miles north of Tokyo, workers are still pumping seawater onto spent fuel pools at all six nuclear reactors, using a combination of sprayhoses, pump trucks, and water injection through functional cooling lines. The temperature of the fuel pool at Unit 2, the most worrisome of them all, climbed to 52 degrees Celsius on March 23 but has since dropped back to 47 degrees C. Spent fuel pools are normally kept under 25 degrees C.

Three contracted workers at Unit 3 were exposed to elevated levels of radiation, and were taken to hospital with beta-radiation burns on their feet and legs. The workers purportedly ignored the readings of their dosimeters while treading through contaminated water, believing the meters to be giving inaccurate readings.

The number of workers at the Fukushima Daiichi nuclear power plant found to have received more than 100 millisieverts of radiation dose totalled 17. These include the three contract workers, and fourteen Tepco employees.

Japanese officials have begun assisting the evacuation of citizens in a larger radius around the Fukushima nuclear plant. They are now encouraging people living within 19 miles to leave. The mandatory evacuation radius remains at 12 miles around the plant, but the new extended radius for assisted evacuations suggests the officials do not consider the situation at the plant to be on the verge of stabilizing.

An official said there is evidence that the reactor vessel housing Unit 3 is damaged. Unit 3 is the reactor that burns mox fuel, a mix of uranium and plutonium, so there are grave concerns that these two dangerous substances could be released to the environment.

Fortunately, the effects of iodine-131 leaked to the environment appears not to have done significant thyroid damage in the first round of tests conducted March 24 and announced March 25. The thyroid glands in 66 children were examined at the Kawamata Town Health Center (40-50 km from Fukushima Daiichi) and Kawamata Town Yamakiya Branch Office (30-40 km from Fukushima Daiichi NPP). According to a press release form the Nuclear and Industrial Safety Agency, the results indicate that the dose rate "of all the 66 children including 14 infants from 1 to 6 years old had no big difference from the level of background and was at the level of 'no problem' in the view of the Nuclear Safety Commission."

The three contracted workers who were admitted to hospital March 24 for radiation exposure will be released on Monday. Rethy Chem, human health director at the International Atomic Energy Agency (IAEA), told a news conference that this means they were probably not seriously harmed.

With power not yet back on at the plant, manual seawater injection is continuing into Units 1, 2, 3 and into the spent fuel pool of Unit 3. The spent fuel pool of Unit 4 is being sprayed with seawater. Workers are still attempting to restore the cooling systems in the reactors.

March 26 - 27:

Over the weekend, workers switched from pumping sea water through the reactor cooling lines to using freshwater, which is less corrosive and leaves less deposits. The temperatures in the reactor pressure vessels of Units 1 to 3 all stabilized. Unit 1 was the hottest at 144 degrees-C. The pressures in the three vessels also stabilized at or around atmospheric pressure. Units 5 and 6 stayed in a cold shutdown with approximately stable temperatures and pressures. (The reactor vessel in Unit 4 contained no fuel rods at the time of the earthquake.)

White smoke was seen emanating from the spent fuel pools at Units 3 and 4, possibly carrying with it radioactive materials. Workers continued spraying the spent fuel pools with seawater.

Technicians managed to get all six units hooked up to off-site power. The lights are on in several of the units' control rooms, but individual components still needed to be checked before the electric cooling system could be energized.

Gamma radiation dose-rates, measured in the Tokyo region at 8 locations, ranged from 0.08 to 0.15 microsievert per hour, which is within or slightly above the normal background according to the International Atomic Energy Agency (IAEA). At distances of 30 to 41 km from the Fukushima nuclear power plant, the dose-rates ranged from 0.9 to 17 microsievert per hour - higher than the normal background.

Radiation levels in the Pacific Ocean were also assessed at several locations. According to the IAEA, the contamination at these locations is influenced by aerial deposition of fallout as well as by the migration of contaminated seawater from the discharge points at the reactor. The measured radiation doses rates above the sea remain consistently low (between 0.04 and 0.1 microsievert per hour).

The state of the reactors themselves is much the same as on preceding days, as are efforts to restore electricity to the reactors. Before switching on full power, workers must remove water from the reactor turbine buildings. Unfortunately, in doing this, they discovered some bad news.

Radiation measuring 1,000 millisieverts per hour was detected in water in an overflow tunnel outside Unit 2's turbine building. (For comparison's sake, the maximum dose allowed for workers at the plant is 250 millisieverts per year). The tunnel leads to an opening just 180 feet from the sea, according to Hidehiko Nishiyama, deputy director-general for the Nuclear and Industrial Safety Agency. Contaminated water was also found at tunnels leading from the Unit 1 and 3 reactors, though with much lower levels of radiation.

The nuclear safety agency also reported that radioactive iodine 131 was detected March 27 at a concentration 1,150 times the maximum allowable level in a seawater sample taken about a mile north of the drainage outlets of Units 1 through 4. The amount of cesium 137 found in water 1,000 feet from plant was 20 times the normal level, the same level as readings taken a week ago.

No fishing has been allowed in this area since the earthquake, so, presumably, no contaminated food has entered the food chain via the sea.

Yukiya Amano, IAEA Director General, says that the situation at the Fukushima nuclear power plant remains very serious. Workers are focusing on removing water that had previously been sprayed on the containment vessels and spent fuel pools, and safely storing it. The reactor buildings must be dried out before electrical cooling systems can be powered back up. Because the water inside them has become contaminated by proximity to the nuclear fuel, it must be stored and slowly decontaminated rather than released to the environment.

Plutonium, one of the most dangerous radioactive substances, has been found in soil samples near the nuclear plant. According to the IAEA, "Traces of plutonium are not uncommon in soil because they were deposited worldwide during the atmospheric nuclear testing era. However, the isotopic composition of the plutonium found at Fukushima Daiichi suggests the material came from the reactor site, according to Tepco officials. Still, the quantity of plutonium found does not exceed background levels . tracked over the past 30 years." [Find out why plutonium is more dangerous than uranium]

Officials publically acknowledged for the first time that Reactor Units 1 through 4 at the Fukushima Daiichi nuclear power plant will have to be permanently scrapped. The multi-billion dollar facilities have sustained too much damage by earthquakes, explosions, and seawater corrosion to ever function again.

They cannot be abandoned yet, however. Workers are still manually cooling the fuel in the facilities via freshwater injection. They are also pumping contaminated water out of the reactors' turbine buildings and into condensed water storage tanks in order to let the turbine buildings try out before restoring electric cooling systems.

This article was provided by Life's Little Mysteries, a sister site to LiveScience. Follow Natalie Wolchover on Twitter @nattyover


Watch the video: Ιαπωνία: Πέντε χρόνια από την καταστροφή στη Φουκουσίμα (May 2022).