Authorities believe it will take up to 40 years to finish the work, which has already cost Japan trillions of yen. It sits on the country's east coast, about km miles north-east of the capital Tokyo. On 11 March at local time GMT the earthquake - known as the Great East Japan Earthquake, or the Tohoku earthquake - struck east of the city of Sendai, 97km north of the plant.
Residents had just 10 minutes warning before the tsunami hit the coast. Overall almost half-a-million people were forced to leave their homes as a result of the earthquake, tsunami and nuclear accident. 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.
But soon after a wave over 14 metres 46ft high hit Fukushima. The water overwhelmed the defensive sea wall, flooding the plant and knocking out the emergency generators. Workers rushed to restore power, but in the days that followed the nuclear fuel in three of the reactors overheated and partly melted the cores - something known as a nuclear meltdown.
The plant also suffered a number of chemical explosions which badly damaged the buildings. Radioactive material began leaking into the atmosphere and the Pacific Ocean, prompting the evacuations and an ever-widening exclusion zone. 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. Three people were reportedly taken to hospital after high-level exposure. Long-term effects of the radiation are a matter of debate. The World Health Organization WHO released a report in 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.
On 9 March , ahead of the year anniversary, a UN report said there had been "no adverse health effects" documented among Fukushima residents directly related to the radiation from the disaster. TEPCO and government officials say tritium, which is not harmful in small amounts, cannot be removed from the water, but all other selected radionuclides can be reduced to levels allowed for release.
Some scientists say the long-term impact on marine life from low-dose exposure to such large volumes of water is unknown. Under the basic plan adopted by the ministers, TEPCO will start releasing the water in about two years after building a facility under the regulatory authority's safety requirements. It said the disposal of the water cannot be postponed further and is necessary to improve the environment surrounding the plant so residents can live there safely.
TEPCO says its water storage capacity of 1. Also, the area now filled with storage tanks will have to be freed up for building new facilities that will be needed for removing melted fuel debris from inside the reactors, a process expected to start in coming years.
In the decade since the tsunami disaster, water meant to cool the nuclear material has constantly escaped from the damaged primary containment vessels into the basements of the reactor buildings. The weekend after the workers' accident, TEPCO scrambled to drain water storage tanks to make room for the radioactive water.
But by March 28 the situation had gotten worse. TEPCO officials announced that radioactive water had been found in concrete tunnels that house cables and pipes alongside the reactor buildings.
On Monday April 4 TEPCO began dumping 11 tons of water contaminated with low levels of radioactive iodine into the Pacific Ocean to make room in the storage tanks for highly radioactive water from the turbine buildings. The waste water released had about times the legal limit for radiation, while the water that TEPCO was so desperate to store had about 10 times the limit. The deliberate discharge of radioactive water wasn't the only source of ocean pollution. After several days of unsuccessful attempts, TEPCO finally plugged the leak on April 6 by injecting liters of liquid glass into the ground near the leak.
These three reactors were offline at the time of the earthquake, but they still became a source of concern. Fires broke out in reactor building No. In these three buildings, spent fuel is stored in water-filled tanks, which keep them cool. In reactor building No. It's likely that the fuel rods overheated, causing the zirconium alloy cladding to partially melt and react with water or steam.
That would have produced volatile hydrogen gas, which could have sparked a blast. According to reports, the actual substance burning in building No. The fires in building No. The smoke from the fire in building No. While Japanese emergency response teams have not focused on building No. On March 17, the head of the U. Nuclear Regulatory Commission told a congressional committee that building No. Water-spraying trucks hosed down building No.
A photo from the No. The storage pools in buildings No. They're not currently considered a threat. The Japanese government evacuated all residents living within 20 kilometers from Fukushima Dai-1 early in the crisis, and advised people living between 20 and 30 kilometers of the plant to stay indoors. Later the government issued a voluntary evacuation advisory for all those living within 30 kilometers of the plant. But by early April it had become clear that radioactive materials would continue to leak from the plant for some time, making the situation more dangerous for residents who would receive a low but steady dose.
On April 11 the Japanese government expanded the evacuation zone , ordering residents of many towns in the 20 to 30 km zone and some even farther out to leave. Strong aftershocks have also raised fears that the already crippled plants could be further damaged.
On April 12, the Japanese government officially acknowledged the severity of the Fukushima Dai-1 incident by raising its rating on the International Atomic Energy Agency's scale of disaster.
The Fukushima incident is now rated 7, the same rating Chernobyl got, because it involved a major release of radiation with widespread health or environmental affects. But the amount of radiation released at Fukushima is still far less than that emitted by the Chernobyl accident--the highest estimates for Fukushima's emissions to date are about 5 to 10 percent of Chernobyl's. One week after the earthquake, the Japanese Ministry of Health, Labour and Welfare announced that radiation levels exceeding the legal limit had been found in milk and vegetables produced in the Fukushima region.
Shipments of agricultural products from the region were quickly banned. In the second week, the government announced that radioactive substances had been detected in the tap water in Tokyo.
On March 24, levels of iodine in the tap water were declared unsafe for infants, causing the government to distribute bottled water to families.
The next day the government said that the amount of radioactive iodine in Tokyo tap water was again within safe limits. How did those radioactive substances get into cow's milk and Tokyo's tap water? It started with the steam that plant operators vented in the days after the earthquake in an unsuccessful attempt to reduce pressure in the reactor buildings and prevent explosions.
That steam carried small amounts of radioactive substances. The subsequent explosions and the steam that rose up when firefighters sprayed water on the reactor buildings also brought radioactive substances into the air.
Officials think the radiation levels in Tokyo's tap water spiked following a rainfall that brought radioactive substances down from the clouds. Even before the deliberate release of radioactive water into the ocean, Japan's Nuclear and Industrial Safety Agency has reported high levels of radioactive iodine in seawater samples taken 1.
Higher levels of iodine were detected in seawater about meters from the plant on March The iodine level was times greater than the government safety limit. Elevated levels of cesium have also been detected in seawater. When TEPCO announced on April 4 that it would begin dumping low-level radioactive waste water into the ocean, Japan's Nuclear and Industrial Safety Agency announced that it did not consider the ocean contamination to be a health threat, because no fishing is currently permitted within 20 kilometers of the plant.
However, The New York Times reports that marine biologists are worried that radioactive elements will accumulate in big fish as they eat smaller, contaminated fish.
For more than a month after the earthquake and tsunami, TEPCO seemed to be reeling from one urgent crisis to the next. Finally, on April 17, the company announced a "roadmap to restoration," which outlines the steps necessary to stabilize the plant and stop most radioactive emissions.
TEPCO hopes to bring all the plant's reactors to a "cold shutdown" within 9 months, meaning that the water inside the reactor would be below the boiling temperature of degrees Celsius. The plan calls for the installation of new cooling systems for the reactors, as the plant's existing cooling systems may be damaged beyond repair. It proposes the installation of a temporary covering over the damaged reactor buildings to prevent further radiation emissions.
On May 10, Japanese prime minister Naoto Kan suggested that the country should rethink its national energy plan, and should place more emphasis on renewable energy and conservation. Kan had previously requested that the Chubu Electric Power Co. On May 10, the company agreed to close the coastal plant "until further measures to prevent tsunami are completed.
She holds a master's degree in journalism from Columbia University. Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires.
The fire is the second-largest in California history. The fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. And this was on top of a fire season that burned more than , hectares of land in California, and a to wildfire season in Australia that torched nearly 18 million hectares.
While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection Cal Fire calculates that nearly , burned hectares of those California fires were the fault of the electric power infrastructure, including the devastating Camp Fire , which wiped out most of the town of Paradise.
Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure.
Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis. However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires.
In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a year lifespan, are entering their final decade.
Historically, checking the condition of electrical infrastructure has been the responsibility of men walking the line. A cantilevered structure was built over unit 4 from April to July to enable recovery of the contents of the spent fuel pond. This is a 69 x 31 m cover 53 m high and it was fully equipped by the end of to enable unloading of used fuel from the storage pond into casks, each holding 22 fuel assemblies, and removal of the casks.
This operation was accomplished under water, using the new fuel handling machine replacing the one destroyed by the hydrogen explosion so that the used fuel could be transferred to the central storage onsite. Transfer was completed in December A video of the process is available on Tepco's website. A different design of cover was built over unit 3, and foundation work began in Large rubble removal took place from to , including the damaged fuel handling machine.
An arched cover was prefabricated, 57 m long and 19 m wide, and supported by the turbine building on one side and the ground on the other. A crane removed the fuel assemblies from the pool and some remaining rubble. Spent fuel removal from unit 3 pool began in April and was completed in February Maps from the Ministry of Education, Culture, Sports, Science and Tehcnology MEXT aerial surveys carried out approximately one year apart show the reduction in contamination from late to late Areas with colour changes in showed approximately half the contamination as surveyed in , the difference coming from decay of caesium two-year half-life and natural processes like wind and rain.
Tests on radioactivity in rice have been made and caesium was found in a few of them. Summary : Major releases of radionuclides, including long-lived caesium, occurred to air, mainly in mid-March. The population within a 20km radius had been evacuated three days earlier. Considerable work was done to reduce the amount of radioactive debris onsite and to stabilize dust. The main source of radioactive releases was the apparent hydrogen explosion in the suppression chamber of unit 2 on 15 March.
A cover building for unit 1 reactor was built and the unit is now being dismantled, a more substantial one for unit 4 was built to enable fuel removal during By the end of , Tepco had checked the radiation exposure of 19, people who had worked on the site since 11 March. For many of these both external dose and internal doses measured with whole-body counters were considered.
It reported that workers had received doses over mSv. Of these had received to mSv, twenty-three mSv, three more mSv, and six had received over mSv to mSv apparently due to inhaling iodine fumes early on. There were up to workers onsite each day. Recovery workers wear personal monitors, with breathing apparatus and protective clothing which protect against alpha and beta radiation. The level of mSv was the allowable maximum short-term dose for Fukushima Daiichi accident clean-up workers through to December , mSv is the international allowable short-term dose "for emergency workers taking life-saving actions".
No radiation casualties acute radiation syndrome occurred, and few other injuries, though higher than normal doses, were being accumulated by several hundred workers onsite. High radiation levels in the three reactor buildings hindered access there. Monitoring of seawater, soil and atmosphere is at 25 locations on the plant site, 12 locations on the boundary, and others further afield. Government and IAEA monitoring of air and seawater is ongoing.
Some high but not health-threatening levels of iodine were found in March, but with an eight-day half-life, most I had gone by the end of April A radiation survey map of the site made in March revealed substantial progress: the highest dose rate anywhere on the site was 0. The majority of the power plant area was at less than 0.
These reduced levels are reflected in worker doses: during January , the workers at the site received an average of 0. Media reports have referred to 'nuclear gypsies' — casual workers employed by subcontractors on a short-term basis, and allegedly prone to receiving higher and unsupervised radiation doses. This transient workforce has been part of the nuclear scene for at least four decades, and at Fukushima their doses are very rigorously monitored.
If they reach certain levels, e. Tepco figures submitted to the NRA for the period to end January showed workers had received more than mSv six more than two years earlier and had received 50 to mSv.
Early in there were about onsite each weekday. Summary : Six workers received radiation doses apparently over the mSv level set by NISA, but at levels below those which would cause radiation sickness. On 4 April , radiation levels of 0. Monitoring beyond the 20 km evacuation radius to 13 April showed one location — around Iitate — with up to 0.
At the end of July the highest level measured within 30km radius was 0. The safety limit set by the central government in mid-April for public recreation areas was 3. In June , analysis from Japan's Nuclear Regulation Authority NRA showed that the most contaminated areas in the Fukushima evacuation zone had reduced in size by three-quarters over the previous two years.
In August The Act on Special Measures Concerning the Handling of Radioactive Pollution was enacted and it took full effect from January as the main legal instrument to deal with all remediation activities in the affected areas, as well as the management of materials removed as a result of those activities. It specified two categories of land: Special Decontamination Areas consisting of the 'restricted areas' located within a 20 km radius from the Fukushima Daiichi plant, and 'deliberate evacuation areas' where the annual cumulative dose for individuals was anticipated to exceed 20 mSv.
The national government promotes decontamination in these areas. Intensive Contamination Survey Areas including the so-called Decontamination Implementation Areas, where an additional annual cumulative dose between 1 mSv and 20 mSv was estimated for individuals. Municipalities implement decontamination activities in these areas.
The doses to the general public, both those incurred during the first year and estimated for their lifetimes, are generally low or very low.
No discernible increased incidence of radiation-related health effects are expected among exposed members of the public or their descendants.
However, the report noted: "More than additional workers received effective doses currently estimated to be over mSv, predominantly from external exposures. Among this group, an increased risk of cancer would be expected in the future. However, any increased incidence of cancer in this group is expected to be indiscernible because of the difficulty of confirming such a small incidence against the normal statistical fluctuations in cancer incidence.
These workers are individually monitored annually for potential late radiation-related health effects. By contrast, the public was exposed to times less radiation. Most Japanese people were exposed to additional radiation amounting to less than the typical natural background level of 2. The Report states: "No adverse health effects among Fukushima residents have been documented that are directly attributable to radiation exposure from the Fukushima Daiichi nuclear plant accident.
People living in Fukushima prefecture are expected to be exposed to around 10 mSv over their entire lifetimes, while for those living further away the dose would be 0. The UNSCEAR conclusion reinforces the findings of several international reports to date, including one from the World Health Organization WHO that considered the health risk to the most exposed people possible: a postulated girl under one year of age living in Iitate or Namie that did not evacuate and continued life as normal for four months after the accident.
Such a child's theoretical risk of developing any cancer would be increased only marginally, according to the WHO's analysis. The man had been diagnosed with lung cancer in February Eleven municipalities in the former restricted zone or planned evacuation area, within 20 km of the plant or where annual cumulative radiation dose is greater than 20 mSv, are designated 'special decontamination areas', where decontamination work is being implemented by the government.
A further municipalities in eight prefectures, where dose rates are equivalent to over 1 mSv per year are classed as 'intensive decontamination survey areas', where decontamination is being implemented by each municipality with funding and technical support from the national government.
Decontamination of all 11 special decontamination areas has been completed. In October a member IAEA mission reported on remediation and decontamination in the special decontamination areas.
Its preliminary report said that decontamination efforts were commendable but driven by unrealistic targets. Also, there is potential to produce more food safely in contaminated areas. The total area under consideration for attention is 13, km 2. Summary : There have been no harmful effects from radiation on local people, nor any doses approaching harmful levels.
However, some , people were evacuated from their homes and only from were allowed limited return. As of July over 41, remained displaced due to government concern about radiological effects from the accident.
Permanent return remains a high priority, and the evacuation zone is being decontaminated where required and possible, so that evacuees can return. There are many cases of evacuation stress including transfer trauma among evacuees, and once the situation had stabilized at the plant these outweighed the radiological hazards of returning, with deaths reported see below.
The government said it would consider purchasing land and houses from residents of these areas if the evacuees wish to sell them. In November the NRA decided to change the way radiation exposure was estimated.
Instead of airborne surveys being the basis, personal dosimeters would be used, giving very much more accurate figures, often much less than airborne estimates. Measurement was by personal dosimeters over August-September Disaster-related deaths are in addition to the over 19, that died in the actual earthquake and tsunami.
The premature disaster-related deaths were mainly related to i physical and mental illness brought about by having to reside in shelters and the trauma of being forced to move from care settings and homes; and ii delays in obtaining needed medical support because of the enormous destruction caused by the earthquake and tsunami. However, the radiation levels in most of the evacuated areas were not greater than the natural radiation levels in high background areas elsewhere in the world where no adverse health effect is evident.
The figure is greater than for Iwate and Miyagi prefectures, with and respectively, though they had much higher loss of life in the earthquake and tsunami — over 14, Causes of indirect deaths include physical and mental stress stemming from long stays at shelters, a lack of initial care as a result of hospitals being disabled by the disaster, and suicides.
As of July , over 41, people from Fukushima were still living as evacuees. The money was tax-exempt and paid unconditionally. In October , about 84, evacuees received the payments. The Fukushima prefecture had 17, government-financed temporary housing units for some 29, evacuees from the accident. The number compared with very few built in Miyagi, Iwate and Aomori prefectures for the , tsunami survivor refugees there.
In April , the first residents of Okuma, the closest town to the plant, were allowed to return home. According to a survey released by the prefectural government in April , the majority of people who voluntarily evacuated their homes after the accident and who are now living outside of Fukushima prefecture do not intend to return.
A Mainichi report said that Of the voluntary evacuees still living in Fukushima prefecture, An August Reconstruction Agency report also considered workers at Fukushima power plant. The death toll directly due to the nuclear accident or radiation exposure remained zero, but stress and disruption due to the continuing evacuation remains high. Summary : Many evacuated people remain unable to fully return home due to government-mandated restrictions based on conservative radiation exposure criteria.
Decontamination work is proceeding while radiation levels decline naturally. Removing contaminated water from the reactor and turbine buildings had become the main challenge by week 3, along with contaminated water in trenches carrying cabling and pipework. This was both from the tsunami inundation and leakage from reactors. Run-off from the site into the sea was also carrying radionuclides well in excess of allowable levels.
By the end of March all storages around the four units — basically the main condenser units and condensate tanks — were largely full of contaminated water pumped from the buildings. Some storage tanks were set up progressively, including initially steel tanks with rubber seams, each holding m 3.
A few of these developed leaks in Accordingly, with government approval, Tepco over April released to the sea about 10, cubic metres of slightly contaminated water 0.
Unit 2 is the main source of contaminated water, though some of it comes from drainage pits. NISA confirmed that there was no significant change in radioactivity levels in the sea as a result of the 0.
By the end of June , Tepco had installed concrete panels to seal the water intakes of units , preventing contaminated water leaking to the harbour. From October, a steel water shield wall was built on the sea frontage of units It extends about one kilometre, and down to an impermeable layer beneath two permeable strata which potentially leak contaminated groundwater to the sea.
The inner harbour area which has some contamination is about 30 ha in area. In July-August only 0. Tepco built a new wastewater treatment facility to treat contaminated water. A supplementary and simpler SARRY simplified active water retrieve and recovery system plant to remove caesium using Japanese technology and made by Toshiba and The Shaw Group was installed and commissioned in August The NRA approved the extra capacity in August ALPS is a chemical system which will remove radionuclides to below legal limits for release.
However, because tritium is contained in water molecules, ALPS cannot remove it, which gives rise to questions about the discharge of treated water to the sea. Collected water from them, with high radioactivity levels, was being treated for caesium removal and re-used.
Apart from this recirculating loop, the cumulative treated volume was then 1. Almost m 3 of sludge from the water treatment was stored in shielded containers. ALPS-treated water is currently stored in tanks onsite which will reach full capacity by the summer of As of February , more than 1.
Some of the ALPS treated water will require secondary processing to further reduce concentrations of radionuclides in line with government requirements. Disposal will be either into the atmosphere or the sea.
In November the trade and industry ministry stated that annual radiation levels from the release of the tritium-tainted water are estimated at between 0.
The clean tritiated water was the focus of attention in
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