Fukushima nuclear accident

"Fukushima nuclear disaster" redirects here. For the incidents at Fukushima Daini (Fukushima II), see Fukushima Daini Nuclear Power Plant.

Fukushima nuclear accident

Image on 16 March 2011 of the four damaged reactor buildings. From right to left: Unit 1,2,3,4. Hydrogen-air explosions occurred in Unit 4,3 and 1 causing the building damage, while a vent in Unit 2's wall, with water vapor/"steam" clearly visible, preventing a similar explosion.
Date	11 March 2011 (2011-03-11)
Location	Ōkuma, Fukushima, Japan
Coordinates	37°25′17″N 141°1′57″E
Outcome	INES Level 7 (Major accident)
Non-fatal injuries	37 with physical injuries, 2 workers taken to hospital with radiation burns
File:Japan Nuclear power plants map.gif

External videos
24 hours live camera for Fukushima Daiichi nuclear disaster on YouTube, certified by Tokyo Electric Power Co. Inc.

The Fukushima Daiichi nuclear disaster (福島第一原子力発電所事故, Fukushima Daiichi () genshiryoku hatsudensho jiko) was an energy accident at the Fukushima I Nuclear Power Plant, initiated by the tsunami of the Tōhoku earthquake and tsunami on 11 March 2011. The damage caused by the tsunami produced equipment failures, and without this equipment a loss-of-coolant accident followed with nuclear meltdowns and releases of radioactive materials beginning on March 12. It is the largest nuclear disaster since the Chernobyl disaster of 1986 and the second disaster (along with Chernobyl) to measure Level 7 on the International Nuclear Event Scale, releasing an estimated 10 to 30% of the radiation of the Chernobyl accident.

The plant comprised six separate boiling water reactors originally designed by General Electric (GE) and maintained by the Tokyo Electric Power Company (TEPCO). At the time of the earthquake, reactor 4 had been de-fueled and reactors 5 and 6 were in cold shutdown for planned maintenance. Immediately after the earthquake, following government regulations, the remaining reactors 1–3 shut down their sustained fission reactions automatically, inserting control rods in what is termed the SCRAM event, following this, emergency generators came online to power electronics and coolant systems, which operated right up until the tsunami. The tsunami arrived some 50 minutes after the initial earthquake. The 13 meter tall tsunami overwhelmed the plant's seawall, which was only 10 m high, with the moment of the tsunami striking being caught on camera. The tsunami water quickly flooded the low-lying rooms in which the emergency generators were housed. With the flooded diesel generators failing soon afterwards, cutting power to the critical pumps that must continuously circulate coolant water through a Generation II reactor to keep the fuel rods from melting down following the SCRAM event, the rods remained hot enough to melt themselves down as no adequate cold sink was available. After the secondary emergency pumps (run by back-up electrical batteries) ran out, one day after the tsunami, March 12, the water pumps stopped and the reactors began to overheat due to the high decay heat produced in the first few days after the SCRAM (diminishing amounts of this decay heat continue to be released for years, but with time it is not enough to cause fuel rod melting).

As workers struggled to supply power to the reactors coolant systems and restore power to their control rooms, a number of hydrogen-air chemical explosions occurred, the first in Unit 1, on March 12 and the last in Unit 4, on March 15. It is estimated that the hot zirconium fuel cladding-water reaction in reactors 1-3 produced 800 to 1000 kilograms of hydrogen gas each, which was vented out of the reactor pressure vessel, and mixed with the ambient air, eventually reaching explosive concentration limits in units 1 and 3, and due to piping connections between units 3 and 4, or alternatively from the same reaction occurring in the spent fuel pool in unit 4 itself, unit 4 also filled with hydrogen, with the hydrogen-air explosions occurring at the top of each unit, that is in their upper secondary containment building.

There have been no fatalities linked to short term overexposure to radiation reported due to the Fukushima accident, while approximately 18,500 people died due to the earthquake and tsunami. Future cancer deaths from accumulated radiation exposures in the population living near Fukushima are predicted to be elevated for certain types of cancers such as leukemia, solid cancers, thyroid cancer and breast cancer.

A survey by the newspaper Mainichi Shimbun computed that of some 300,000 people who evacuated the area, approximately 1,600 deaths related to the evacuation conditions, such as living in temporary housing and hospital closures have occurred as of August 2013, a number comparable to the 1,599 deaths directly caused by the earthquake and tsunami in the Fukushima Prefecture in 2011. With the exact cause of the majority of these evacuation related deaths not being specified, as according to the municipalities, that would hinder the deceased relatives' application for condolence money compensation. In terms of the worldwide future cancer burden from accumulated radiation exposures caused by the accident, in the years and decades ahead, Stanford University professor and anti-nuclear advocate Mark Z. Jacobson predicts that there will be an eventual 130 fatalities and 180 additional cancer cases, with the majority of these cases occurring in populations in the most heavily contaminated areas of Fukushima. In 2013, the World Health Organization indicated that the residents of the area who were evacuated were exposed to so little radiation that radiation induced health impacts are likely to be below detectable levels. The negative health effects of the Fukushima nuclear disaster for populations living in the most contaminated areas include a moderately increased risk of thyroid cancer for girls, and a slightly increased risk of other cancers for infants. In particular, a 2013 WHO report predicts that for populations living in the most affected areas there is a 70% higher risk of developing thyroid cancer for girls exposed as infants, a 7% higher risk of leukemia in males exposed as infants, a 6% higher risk of breast cancer in females exposed as infants and a 4% higher risk, overall, of developing solid cancers for females.

A screening program found that more than a third (36%) of children in Fukushima Prefecture have abnormal growths in their thyroid glands, however whether these growths can be attributed to exposure to nuclear radiation has not yet been proven. As of August 2013, there have been more than 40 children newly diagnosed with thyroid cancer and other cancers in Fukushima prefecture as a whole. The government says the recent cases are unlikely to be connected with the Fukushima releases as it generally takes several years after radiation exposure for thyroid cancer to develop and similar rates of cancer occurred before the accident. Data from the Chernobyl accident showed that there was a steady then sharp increase in thyroid cancer rates following the disaster in 1986, however whether this data can be directly compared to the Fukushima nuclear disaster is still yet to be determined.

On 5 July 2012, the Japanese National Diet appointed The Fukushima Nuclear Accident Independent Investigation Commission (NAIIC) submitted its inquiry report to the Japanese Diet. The Commission found the nuclear disaster was "manmade", that the direct causes of the accident were all foreseeable prior to March 11, 2011. The report also found that the Fukushima Daiichi Nuclear Power Plant was incapable of withstanding the earthquake and tsunami. TEPCO, the regulatory bodies (NISA and NSC) and the government body promoting the nuclear power industry (METI), all failed to correctly develop the most basic safety requirements—such as assessing the probability of damage, preparing for containing collateral damage from such a disaster, and developing evacuation plans for the public in the case of a serious radiation release. Meanwhile, the government appointed Investigation Committee on the Accident at the Fukushima Nuclear Power Stations of Tokyo Electric Power Company submitted its final report to the Japanese government on 23 July 2012. A separate study by Stanford researchers found that Japanese plants operated by the largest utility companies were particularly unprotected against potential tsunami.

TEPCO admitted for the first time on October 12, 2012 that it had failed to take stronger measures to prevent disasters for fear of inviting lawsuits or protests against its nuclear plants. There are no clear plans for decommissioning the plant, but there are estimates it will take at least thirty or forty years.

On July 22, 2013, more than two years after the incident, it was revealed that the plant is leaking radioactive water into the Pacific Ocean, something long suspected by local fishermen and independent investigators. TEPCO had previously denied that this was happening and the current situation has prompted Japanese Prime Minister Shinzō Abe to order the government to step in. On August 20, in a further incident, it was announced that 300 metric tons of heavily contaminated water had leaked from a storage tank, approximately the same amount of water as one eighth(1/8) of that found in an Olympic-size swimming pool. The 300 metric tons of water was radioactive enough to be hazardous to nearby staff, and the leak was assessed as Level 3 on the International Nuclear Event Scale. On August 26, the government took charge of emergency measures to prevent further radioactive water leaks, reflecting their lack of confidence in TEPCO.

About the Fukushima Daiichi Nuclear Power Plant

Simplified cross-section sketch of a typical BWR Mark I containment as used in units 1 to 5.
Key:
RPV: reactor pressure vessel.
DW: dry well enclosing reactor pressure vessel.
WW: wet well - torus-shaped all around the base enclosing steam suppression pool. Excess steam from the dry well enters the wet well water pool via downcomer pipes.
SFP: spent fuel pool area.
SCSW: secondary concrete shield wall.

Main article: Fukushima Daiichi Nuclear Power Plant

The Fukushima I (Daiichi) Nuclear Power Plant consisted of six light water, boiling water reactors (BWR) designed by General Electric (GE) driving electrical generators with a combined power of 4.7 gigawatts, making Fukushima Daiichi one of the 25 largest nuclear power stations in the world. Fukushima Daiichi was the first GE designed nuclear plant to be constructed and run entirely by the Tokyo Electric Power Company (TEPCO).

Reactor 1 is a 439 MWe type (BWR-3) reactor constructed in July 1967. It commenced commercial electrical production on 26 March 1971. It was designed for a peak ground acceleration of 0.18 g (1.74 m/s²) and a response spectrum based on the 1952 Kern County earthquake. Reactors 2 and 3 are both 784 MWe type BWR-4. Reactor 2 commenced operating in July 1974, and reactor 3 in March 1976. The earthquake design basis for all units ranged from 0.42 g (4.12 m/s²) to 0.46 g (4.52 m/s²). All units were inspected after the 1978 Miyagi earthquake when the ground acceleration was 0.125 g (1.22 m/s²) for 30 seconds, but no damage to the critical parts of the reactor were discovered.

Units 1–5 have a Mark 1 type (light bulb torus) containment structure; unit 6 has Mark 2 type (over/under) containment structure. From September 2010, reactor 3 has been partially fueled by mixed-oxides (MOX).

At the time of the accident, the units and central storage facility contained the following numbers of fuel assemblies:

Location	Unit 1	Unit 2	Unit 3	Unit 4	Unit 5	Unit 6	Central Storage
Reactor Fuel Assemblies	400	548	548	0	548	764	0
Spent Fuel Assemblies	292	587	514	1331	946	876	6375
Fuel	UO2	UO2	UO2/MOX	UO2	UO2	UO2	UO2/MOX
New Fuel Assemblies	100	28	52	204	48	64	N/A

Causes

Cooling requirements

Diagrammatic representation of the cooling systems of a BWR.

See also: Decay heat – Power reactors in shutdown and Nuclear reactor safety systems

Power reactors work by splitting atoms, typically uranium, in a chain reaction. The reactor continues to generate heat after the chain reaction is stopped because of the radioactive decay of unstable isotopes, fission products, created by this process. This decay of unstable isotopes, and the decay heat that results, cannot be stopped. Immediately after shutdown, this decay heat amounts to approximately 6% of full thermal heat production of the reactor. The decay heat in the reactor core decreases over several days before reaching cold shutdown levels. Nuclear fuel rods that have reached cold shutdown temperatures typically require another several years of water cooling in a spent fuel pool before decay heat production reduces to the point that they can be safely transferred to dry cask storage vessels.

To safely remove this decay heat, reactor operators must continue to circulate cooling water over fuel rods in the reactor core and spent fuel pond. In the reactor core, circulation is accomplished by use of high pressure systems that pump water through the reactor pressure vessel and into heat exchangers. These systems transfer heat to a secondary heat exchanger via the essential service water system, taking away the heat which is pumped out to the sea or site cooling towers.

To circulate cooling water when the reactor is shut down and not producing electricity, cooling pumps can be powered by other reactors on-site, by other units off-site through the grid, or by diesel generators. In addition, boiling water reactors have steam-turbine driven emergency core cooling systems that can be directly operated by steam still being produced after a reactor shutdown, which can inject water directly into the reactor. Steam turbines results in less dependence on emergency generators, but steam turbines only operate so long as the reactor is producing steam. Some electrical power, provided by batteries, is needed to operate the valves and monitoring systems.

If the water in the unit 4 spent fuel pool had been heated to boiling temperature, the decay heat has the capacity to boil off about 70 tonnes of water per day (12 gallons per minute), which puts the requirement for cooling water in context. On 16 April 2011, TEPCO declared that cooling systems for units 1-4 were beyond repair and would have to be replaced.

The reason that cooling is so essential for a nuclear reactor is that many of the internal components and fuel assembly cladding is made from zircaloy. At normal operating temperatures (of approximately 300 degrees Celsius), zircaloy is inert. However, when heated to above 500 degrees celsius in the presence of steam, zircaloy undergoes an exothermic reaction where the zircaloy oxidises, and produces free hydrogen gas. The reaction between the zirconium cladding and the fuel can also lower the melting point of the fuel and thus speed up a core melt.

The reactor's emergency diesel generators and DC batteries, crucial components in powering the reactors' cooling systems in the event of a power loss, were located in the basements of the reactor turbine buildings. The reactor design plans provided by General Electric specified placing the generators and batteries in that location, but mid-level engineers working on the construction of the plant were concerned that this made the back-up power systems vulnerable to flooding. TEPCO elected to strictly follow General Electric's design in the construction of the reactors.

Safety history

1967: Changing the layout of the emergency-cooling system

Fukushima reactor control room.

On 27 February 2012, NISA ordered TEPCO to report by 12 March 2012 regarding its reasoning in changing the layout for the piping for an emergency cooling system. These changes were made from the plans originally registered in 1966, before construction of the reactor began.

In the original papers submitted – in July 1966 – for government approval of the plans to set up the reactor, the piping systems for two reactors in the isolation condenser were separated from each other. But in the application for the construction plan of the reactor – submitted in October 1967 – the piping layout was changed by TEPCO, and the two piping systems were connected outside the reactor. The changes were not reported in violation of legal regulations.

After the plant was hit by the tsunami, the isolation condenser should have taken over the function of the ordinary cooling pumps, by condensing the steam from the pressure vessel into water to be used for cooling the reactor. But the condenser did not function properly, and TEPCO could not confirm whether a valve was opened.

1976: Falsification of safety records by TEPCO

The Fukushima Daiichi nuclear power complex was central to a falsified-records scandal that led to the departure of a number of senior executives of TEPCO. It also led to disclosures of previously unreported problems at the plant, although testimony by Dale Bridenbaugh, a lead GE designer, purports that General Electric was warned of major design flaws in 1976, resulting in the resignations of several designers who protested GE's negligence.

In 2002, TEPCO admitted it had falsified safety records at Fukushima Daiichi unit 1. As a result of the scandal and a fuel leak at Fukushima Daini, the company had to shut down all of its 17 nuclear reactors to take responsibility. A power board distributing electricity to a reactor's temperature control valves was not examined for 11 years. Inspections did not cover devices related to cooling systems, such as water pump motors and diesel generators.

1991: Back-up generator of reactor 1 flooded

On 30 October 1991, one of two backup generators of reactor 1 did fail, after it was flooded in the basement of the reactor buildings. Seawater used for the cooling of the reactor was leaking into the turbine-building from a corroded pipe at a rate of 20 cubic meters per hour, as reported by former TEPCO employees to the Japan Broadcasting Corporation news-service in December 2011. An engineer was quoted as saying that he informed his superiors about this accident, and that he mentioned the possibility that a tsunami could inflict damage to the generators in the turbine-buildings near the sea. However, instead of moving the generators to higher ground, TEPCO installed doors to prevent water from leaking into the generator rooms. The Japanese Nuclear Safety Commission commented that it would revise the safety guidelines for designing nuclear plants and would enforce the installation of additional power sources. On 29 December 2011, TEPCO admitted all these facts: its report mentioned, that the emergency power system room was flooded through a door and some holes for cables, but the power supply to the reactor was not cut off by the flooding, and the reactor was stopped for one day. One of the two power sources was completely submerged, but its drive mechanism had remained unaffected.

2008: Tsunami study ignored

In 2007, TEPCO set up a department to supervise all its nuclear facilities, and until June 2011 its chairman was Masao Yoshida, the chief of the Fukushima Daiichi power plant. An in-house study in 2008 pointed out that there was an immediate need to improve the protection of the power station from flooding by seawater. This study mentioned the possibility of tsunami-waves up to 10.2 metres (33 ft). Department officials at the company's headquarters insisted that such a risk was unrealistic and did not take the prediction seriously. Yomiuri News paper reported that Mr.Okamura of the Active Fault and Earthquake Research Center urged TEPCO and the Nuclear and Industrial Safety Agency (NISA) to review their assumption of a height of possible tsunami based on earthquake occurred 1100 years ago but it was not seriously considered at that time. Bloomberg reported that the U.S. Nuclear Regulatory Commission warned of a risk of losing emergency power 20 years ago (NUREG-1150) and NISA referred to the report in 2004. No action, however, to mitigate the risk was taken.

Location

The plant was located in Japan, which, like the rest of the Pacific Rim, is in a high seismic zone, and more vulnerable to natural disasters like earthquake or tsunami. The International Atomic Energy Agency (IAEA) had expressed concern about the ability of Japan's nuclear plants to withstand seismic activity. At a meeting of the G8's Nuclear Safety and Security Group, held in Tokyo in 2008, an IAEA expert warned that a strong earthquake with a magnitude above 7.0 could pose a "serious problem" for Japan's nuclear power stations. The region had experienced three earthquakes of magnitude greater than 8 in the past, including the 869 Jogan Sanriku earthquake, the 1896 Meiji-Sanriku earthquake, and the 1933 Sanriku earthquake.

Regulation

Regulatory capture may have contributed to the cascade of failures which were revealed after the tsunami receded. Regulatory capture may have also contributed to the current situation. Critics argue that the government shares blame with the regulatory agency for not heeding warnings, for not ensuring the independence of the nuclear industry's oversight while encouraging the expansion of nuclear energy domestically and internationally. World media have argued that the Japanese nuclear regulatory system tends to side with and promote the nuclear industry because of amakudari ('descent from heaven') in which senior regulators accept high paying jobs at the companies they once oversaw. To protect their potential future position in the industry, regulators seek to avoid taking positions that upset or embarrass the utilities they regulate. TEPCO's position as the largest electrical utility in Japan led it to be the most desirable position for retiring regulators, typically the "most senior officials went to work at Tepco, while those of lower ranks ended up at smaller utilities" according to the New York Times.

In August 2011, several top energy officials were fired by the Japanese government; affected positions included the Vice-minister for Economy, Trade and Industry; the head of the Nuclear and Industrial Safety Agency, and the head of the Agency for Natural Resources and Energy.

Events

Further information: Timeline of the Fukushima I nuclear accidents and 2011 Tōhoku earthquake and tsunami

• Position of Japanese nuclear power stations as they relate to the epicenter of the quake and the tsunami that followed. Fukushima I was the second closest power station to the epicenter of the earthquake, after Onagawa Nuclear Power Plant.
  Position of Japanese nuclear power stations as they relate to the epicenter of the quake and the tsunami that followed. Fukushima I was the second closest power station to the epicenter of the earthquake, after Onagawa Nuclear Power Plant.
• 
  The height of the tsunami that struck the station approximately 30 minutes after the earthquake. A:Power station buildings B:peak height of tsunami C:Ground level of site D:average sea level.
• 
  Fukushima Daiichi I nuclear powerplant site close-up.
• 
  Map of Japan's electricity distribution network, showing incompatible systems between regions. Fukushima is in the 50 Hertz Tohoku region.

The 9.0 M_W Tōhoku earthquake occurred at 14:46 JST on Friday, 11 March 2011 with epicenter near the island of Honshu. It resulted in maximum ground accelerations of 0.56, 0.52, 0.56 g (5.50, 5.07 and 5.48 m/s²) at units 2, 3, and 5 respectively, above their designed tolerances of 0.45, 0.45 and 0.46 g (4.38, 4.41 and 4.52 m/s²), but values within the design tolerances at units 1, 4, and 6. The Fukushima I facility had not initially been designed for a tsunami of the size that struck the plant, nor had the reactors been modified when later concerns were raised in Japan and by the IAEA. When the earthquake occurred, the reactors in units 1, 2, and 3 were operating, but those on units 4, 5, and 6 had already been shut down for periodic inspection. Reactors 1, 2, and 3 underwent an automatic shutdown (called SCRAM) when the earthquake struck.

When the reactors shut down, the plant stopped generating electricity, stopping the normal source of power for the plant. TEPCO reported that one of the two connections to off-site power for units 1–3 also failed so 13 on-site emergency diesel generators began powering the plant's cooling and control systems. There are two emergency diesel generators for each of the units 1–5 and three for unit 6.

The earthquake was followed by a 13–15 m (43–49 ft) maximum height tsunami arriving approximately 50 minutes later which topped the plant's 5.7 m (19 ft) seawall, flooding the basement of the Turbine Buildings and disabling the emergency diesel generators located there at approximately 15:41. At this point, TEPCO notified authorities, as required by law, of a "First level emergency". The Fukushima II plant, which was also struck by the tsunami, incorporated design changes which improved its resistance to flooding and it sustained less damage. Generators and related electrical distribution equipment were located in the watertight reactor building, so that power from the grid was being used by midnight. Seawater pumps for cooling were given protection from flooding, and although 3 of 4 failed in the tsunami, they were able to be restored to operation.

In the late 1990s, three additional backup generators for units 2 and 4 were placed in new buildings located higher on the hillside, to comply with new regulatory requirements. All six units were given access to these generators, but the switching stations that sent power from these backup generators to the reactors' cooling systems for units 1 through 5 were still in the poorly protected turbine buildings. All three of the generators added in the late 1990s were operational after the tsunami. If the switching stations had been moved to inside the reactor buildings or to other flood-proof locations, power would have been provided by these generators to the reactors' cooling systems.

After the diesel generators located in the turbine buildings failed, emergency power for control systems was supplied by batteries that were designed to last about eight hours. Further batteries and mobile generators were dispatched to the site, delayed by poor road conditions with the first not arriving until 21:00 JST 11 March, almost six hours after the tsunami struck.

Attempts to connect portable generating equipment to power water pumps were eventually discontinued after numerous attempts, as the connection point in the Turbine Hall basement was flooded and because of difficulties finding suitable cables. TEPCO switched its efforts to installing new lines from the grid to the cooling systems. One generator at unit 6 was restored to operation on 17 March, and external power returned to units 5 and 6, on 20 March, allowing cooling equipment to be restarted.

Units 1, 2 and 3

See also: Fukushima Daiichi nuclear disaster (Unit 1 Reactor), Fukushima Daiichi nuclear disaster (Unit 2 Reactor), and Fukushima Daiichi nuclear disaster (Unit 3 Reactor)

In the active reactors (1, 2 and 3), overheating caused a reaction between the water and the zircaloy, creating hydrogen gas.

On the afternoon of Saturday, March 12, a powerful explosion occurred in the building housing Reactor 1, caused by the ignition of the hydrogen. The upper part of the building was destroyed.

Monday morning, March 14, a similar explosion occurred in the Reactor 3 building, blowing off the roof and injuring eleven people.

Finally, early on Tuesday the 15th, an explosion took place in the Reactor 2 building. Part of the Reactor 4 building was damaged.

Units 4, 5 and 6

Main article: Fukushima Daiichi units 4, 5 and 6

Aerial view of the station in 1975, showing separation between units 5 and 6, and 1-4.
・Unit 6, not completed until 1979, is seen under construction.

When the Fukushima Daiichi nuclear disaster began on 11 March 2011, reactor 4 was shut down and all fuel rods had been transferred to the spent fuel pool on an upper floor of the reactor building. On 15 March, an explosion damaged the fourth floor rooftop area of unit 4. Japan's nuclear safety agency NISA reported two large holes in a wall of the outer building of unit 4 after the explosion. It was reported that water in the spent fuel pool might be boiling. Radiation inside the unit 4 control room prevented workers from staying there permanently. Visual inspection of the spent fuel pool of unit 4 on 30 April showed that there was no significant visible damage to the fuel rods in the pool. A radiochemical examination of the water from the pond confirmed that little of the fuel in the pond had been damaged.

Reactors 5 and 6 were also not operating when the earthquake struck although, unlike reactor 4, they were still fueled. The reactors had been closely monitored, as cooling processes were not functioning well.

In October 2012, the former Japanese Ambassador to both Switzerland and Senegal Mitsuhei Murata said that ground under Fukushima unit 4 was sinking, and the structure may collapse.

On 19 September 2013, Japanese Prime Minister Shinzo Abe ordered Tokyo Electric Power Co. to scrap all six reactors at the site instead of just four already slated for decommissioning and to concentrate on issues such as radioactive water leaks.

Central fuel storage areas

Used fuel assemblies taken from reactors are initially stored for at least 18 months in the pools adjacent to their reactors. They can then be transferred to the central fuel storage pond. This contains 6375 fuel assemblies and was reported "secured" with a temperature of 55 °C. After further cooling, fuel can be transferred to dry cask storage, which has shown no signs of abnormalities. On 21 March, temperatures in the fuel pond had risen slightly, to 61 °C and water was sprayed over the pool. Power was restored to cooling systems on 24 March and by 28 March temperatures were reported down to 35 °C.

Contamination

Main article: Radiation effects from Fukushima Daiichi nuclear disaster

Sub article: Comparison of Fukushima and Chernobyl nuclear accident with detailed tables inside

Map of contaminated areas around the plant (22 March – 3 April 2011).

Fukushima dose rate comparison to other incidents and standards, with graph of recorded radiation levels and specific accident events from 11 to 30 March.

Radiation measurements from Fukushima Prefecture, March 2011

Seawater-contamination along coast with Caesium-137, from 21 March until 5 May 2011 (Source: GRS)

Radiation hotspot in Kashiwa, February 2012.

Radioactive material has been released from the Fukushima containment vessels as the result of deliberate venting to reduce gaseous pressure, deliberate discharge of coolant water into the sea, and accidental or uncontrolled events. Concerns about the possibility of a large scale release of radioactivity resulted in 20 km exclusion zone being set up around the power plant and people within the 20–30 km zone being advised to stay indoors. Later, the UK, France and some other countries told their nationals to consider leaving Tokyo, in response to fears of spreading radioactive contamination. The Fukushima accident has led to trace amounts of radiation, including iodine-131, caesium-134 and caesium-137, being observed around the world (New York State, Alaska, Hawaii, Oregon, California, Montreal, and Austria). Small amounts of radioactive isotopes have also been released into the Pacific Ocean.

A monitoring system designed to detect nuclear explosions, operated by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), tracked the dispersion of radioactivity from the crippled nuclear reactor on a global scale. Radioactive isotopes originating from Fukushima were picked up by over 40 CTBTO radionuclide monitoring stations. The CTBTO makes its monitoring data and analysis results available to all its 183 Member States. Around 1,200 scientific and academic institutions in 120 countries currently make use of this offer.

On 12 March, radioactive releases first reached a CTBTO monitoring station in Takasaki, Japan, around 200 km away from the troubled power plant. The dispersion of the radioactive isotopes could then be followed to eastern Russia on 14 March and to the west coast of the United States two days later. By day 15, traces of radioactivity were detectable all across the northern hemisphere. Within one month, radioactive particles were also picked up by CTBTO stations in the southern hemisphere, located for example in Australia, Fiji, Malaysia and Papua New Guinea.

According to one expert, the release of radioactivity is about one-tenth that from the Chernobyl disaster and the contaminated area is also about one-tenth that of Chernobyl. A March 2012 report by the Ministry of Education, Culture, Sports, Science and Technology agreed that radioactive debris from the damaged reactors had dispersed about one-eighth to one-tenth of the distance as those in the Chernobyl disaster. According to a study conducted by Norwegian Institute for Air Research, the release of the particular isotope caesium-137 was about 40 percent of the total from Chernobyl.

In March 2011, Japanese officials announced that "radioactive iodine-131 exceeding safety limits for infants had been detected at 18 water-purification plants in Tokyo and five other prefectures". As of July 2011, the Japanese government has been unable to control the spread of radioactive material into the nation's food. Radioactive material has been detected in a range of produce produced in 2011, including spinach, tea leaves, milk, fish and beef, up to 200 miles from the nuclear plant. Crops produced in 2012 did not show signs of radioactivity contamination, cabbage, rice and beef were tested before reaching market and showed insignificant levels of radiation. A Fukushima-produced rice market in Tokyo was accepted by consumers as safe.

On 24 August 2011, the Nuclear Safety Commission (NSC) of Japan published the results of the recalculation of the total amount of radioactive materials released into the air during the accident at the Fukushima Daiichi Nuclear Power Station. The total amounts released between 11 March and 5 April were revised downwards to 130 PBq (petabecquerels) for iodine-131 and 11 PBq for caesium-137, which is about 11% of Chernobyl emissions. Earlier estimations were 150 PBq and 12 PBq.

On 8 September 2011 a group of Japanese scientists working for the Japan Atomic Energy Agency, the Kyoto University and other institutes, published the results of a recalculation of the total amount of radioactive material released into the ocean: between late March through April they found a total of 15 PBq for the combined amount of iodine-131 and caesium-137. This was more than triple the figure of 4.72 PBq estimated by the plant-owner. TEPCO made only a calculation about the releases from the plant in April and May into the sea. The new calculations were needed because a large portion of the airborne radioactive substances would enter the seawater when it came down as rain.

In the first half of September 2011 the amount of radioactive substances released from the plant was about 200 MBq (megabecquerels) per hour, according to TEPCO, this was approximately one four-millionth of the level of the initial stages of the accident in March. Traces of iodine-131 are still detected in several Japanese prefectures in the months of November and December 2011.

According to a report published in October 2011 by the French Institute for Radiological Protection and Nuclear Safety, between 21 March and mid-July around 27 PBq of caesium-137 entered the ocean, about 82 percent having flowed into the sea before 8 April. This emission of radioactivity into the sea represents the most important individual emissions of artificial radioactivity into the sea ever observed. The Fukushima coast has one of the world's strongest currents (Kuroshio Current) and this transported the contaminated waters far into the Pacific Ocean, causing a high dispersion of the radioactive elements. The results of measurements of both the seawater and the coastal sediments lead to suppose that the consequences of the accident, for what concerns radioactivity, will be minor for marine life as of late 2011 (weak concentration of radioactivity in the water and limited accumulation in sediments). On the other hand, significant pollution of sea water along the coast near the nuclear plant might persist, because of the continuing arrival of radioactive material transported towards the sea by surface water running over contaminated soil. Further, some coastal areas might have less favorable dilution or sedimentation characteristics than those observed so far. Finally, the possible presence of other persistent radioactive substances, such as strontium-90 or plutonium, has not been sufficiently studied. Recent measurements show persistent contamination of some marine species (mostly fish) caught along the coast of Fukushima district. Organisms that filter water and fish at the top of the food chain are, over time, the most sensitive to caesium pollution. It is thus justified to maintain surveillance of marine life that is fished in the coastal waters off Fukushima. Migratory pelagic species are highly effective and rapid transporters of radiation throughout the global ocean. Evidence has shown elevated levels of 134 Cs in migratory species off the coast of California that were not seen pre-Fukushima.

As of March 2012, there had been no reported cases of Fukushima residents suffering ailments related to radiation exposure. Experts cautioned that insufficient data was available so far to make conclusions on the impact on residents' health. Nevertheless, Michiaki Kai, professor of radiation protection at Oita University of Nursing and Health Sciences, stated, "If the current radiation dose estimates are correct, (cancer-related deaths) likely won't increase."

On 24 May 2012, TEPCO released their estimate of radiation releases due to the Fukushima Daiichi Nuclear Disaster. An estimated 538.1 PBq of iodine-131, caesium-134 and caesium-137 was released. 520 PBq was released into the atmosphere between 12–31 March 2011 and 18.1 PBq into the ocean from 26 March – 30 September 2011. A total of 511 PBq of iodine-131 was released into both the atmosphere and the ocean, 13.5 PBq of caesium-134 and 13.6 PBq of caesium-137.

In May 2012, TEPCO reported that at least 900 PBq had been released "into the atmosphere in March last year [2011] alone". In August 2012, researchers found that 10,000 people living near the plant at the time of the accident had been exposed to well less than 1 millisievert of radiation, significantly less than Chernobyl residents.

In October 2012 an article in Science-magazine concluded that at that time radiation was still leaking from the reactor-site into the ocean. Fishing in the waters around the site was still prohibited, and the levels of radioactive ¹³⁴Cs and ¹³⁷Cs in the fish caught were not lower compared with the levels found after the disaster. On 26 October 2012 TEPCO admitted that it could not exclude radiation emissions into the ocean, although the radiation levels were stabilised. Undetected leaks into the ocean from the reactors, could not be ruled out, because their basements remain flooded with cooling water, and the 2,400-foot-long steel and concrete wall between the site's reactors and the ocean, that should reach 100 feet underground, was still under construction, and would not be finished before mid-2014. Around August 2012 two greenling were caught close to the Fukushima shore. They contained more than 25,000 becquerels of caesium-137 per kilogram of fish, the highest caesium levels found in fish since the disaster and 250 times the government's safety limit.

A report by the World Health Organization (WHO) published in February 2013 anticipated that there would be no noticeable increases in cancer rates for the overall population, but somewhat elevated rates for particular sub-groups. For example infants of Namie Town and Iitate Village were estimated to have a 6% relative increase in female breast cancer risk and a 7% relative increase in male leukemia risk. A third of emergency workers involved in the accident would have increased cancer risks.

With the WHO communicating that the values stated in that section of the report were relative increases, and not representative of the absolute increase of developing cancer:

These percentages represent estimated relative increases over the baseline rates and are not absolute risks for developing such cancers. Due to the low baseline rates of thyroid cancer, even a large relative increase represents a small absolute increase in risks. For example, the baseline lifetime risk of thyroid cancer for females is just (0.75%)three-quarters of one percent and the additional lifetime risk estimated in this assessment for a female infant exposed in the most affected location is (0.5%)one-half of one percent.

In 2013, two years after the incident, the World Health Organization indicated that the residents of the area were exposed to so little radiation that it probably won't be detectable. They indicated that for those infants in the most affected areas, the lifetime cancer risk would increase by about 1%.

On July 22, 2013, more than two years after the incident, it was revealed that the plant is leaking radioactive water into the Pacific Ocean, something long suspected by local fishermen and independent investigators. TEPCO had previously denied that this was happening and the current situation has prompted Japanese Prime Minister Shinzō Abe to order the government to step in. On August 20, in a further incident, it was announced that 300 tonnes (300 long tons; 330 short tons) of heavily contaminated water had leaked from a storage tank. The water was radioactive enough to be hazardous to nearby staff, and the leak was assessed as Level 3 on the International Nuclear Event Scale. On August 26, the government decided to take over running the emergency measures to tackle the radioactive water leaks, reflecting a lack of confidence in TEPCO.

As of 2013, about 400 tonnes per day of cooling water is being pumped into the reactors, plus another 400 tonnes of groundwater seeping into the structure, so about 800 tonnes of water per day is removed for treatment, half of which is reused for cooling leaving 400 tonnes to put in storage tanks.

Response

Government agencies and TEPCO were thoroughly unprepared for the "cascading nuclear disaster". The tsunami that "began the nuclear disaster could and should have been anticipated and that ambiguity about the roles of public and private institutions in such a crisis was a factor in the poor response at Fukushima". In March 2012, Prime Minister Yoshihiko Noda said that the government shared the blame for the Fukushima disaster, saying that officials had been blinded by a false belief in the country's "technological infallibility", and were taken in by a "safety myth". Noda said "Everybody must share the pain of responsibility".

According to Naoto Kan, Japan's former prime minister, the country was totally unprepared for the Fukushima disaster, and the crippled Fukushima plant should not have been built so close to the ocean on a tsunami-prone coast. Kan has acknowledged flaws in authorities' handling of the crisis, including poor communication and coordination between nuclear regulators, utility officials and the government. He said the disaster "laid bare a host of an even bigger man-made vulnerabilities in Japan's nuclear industry and regulation, from inadequate safety guidelines to crisis management, all of which he said need to be overhauled".

A national program to develop robots for use in nuclear emergencies was terminated in midstream because it "smacked too much of underlying danger". Japan, supposedly a leader in robotics, had none to send into Fukushima when the crisis began. Similarly, Japan's Nuclear Safety Commission said in its safety guidelines for light-water nuclear facilities that "the potential for extended loss of power need not be considered." But just such an extended loss of power contributed to the Fukushima meltdowns.

Physicist and environmentalist Amory Lovins has said: Japan's "rigid bureaucratic structures, reluctance to send bad news upwards, need to save face, weak development of policy alternatives, eagerness to preserve nuclear power's public acceptance, and politically fragile government, along with TEPCO's very hierarchical management culture, also contributed to the way the accident unfolded. Moreover, the information Japanese people receive about nuclear energy and its alternatives has long been tightly controlled by both TEPCO and the government".

Poor communication and delays

The Japanese government has admitted it did not keep records of key meetings during the Fukushima nuclear crisis, even though such detailed notes are considered a key component of disaster management. Data from SPEEDI (System for Prediction of Environmental Emergency Dose Information) were sent by email to the Fukushima prefecture government, but not shared with others. Data from five crucial days, from 12 March 2011 11:54 p.m. to 16 March 9 a.m – holding vital information for evacuation and health advisories – were in emails from NISA to Fukushima that stayed unread and were deleted afterwards. All was revealed more than a year later, on 21 March 2012. The data was not used, because the disaster countermeasure office regarded the data as "useless because the predicted amount of released radiation is unrealistic."

Japan's response to the crisis at Fukushima Daiichi was flawed by "poor communication and delays in releasing data on dangerous radiation leaks at the facility", a government-appointed investigative panel has found. The Investigation Committee on the Accident at the Fukushima Nuclear Power Stations of Tokyo Electric Power Company was led by University of Tokyo Professor Yotaro Hatamura. The panel's report attaches blame to Japan's central government as well as Tokyo Electric Power Co., "depicting a scene of harried officials incapable of making decisions to stem radiation leaks as the situation at the coastal plant worsened in the days and weeks following the disaster". The 507-page interim report, which resulted from hundreds of interviews with utility workers and government officials, said poor planning also worsened the disaster response, noting that authorities had "grossly underestimated tsunami risks" that followed the magnitude 9.0 earthquake. The 12.1 metres (40 ft) high tsunami that struck the plant was twice as tall as the highest wave predicted by officials, and the erroneous assumption that the plant's cooling system continued to work after the tsunami struck worsened the disaster. "Plant workers had no clear instructions on how to respond to such a disaster, causing miscommunication, especially when the disaster destroyed backup generators. Ultimately, the series of failures led to the worst nuclear catastrophe since Chernobyl".

In February 2012, an independent investigation into the accident by the Rebuild Japan Initiative Foundation described how Japan's response was hindered at times by a loss of trust between the major actors: Prime Minister Naoto Kan, the Tokyo headquarters of TEPCO, and the manager at the stricken plant. The report said that these conflicts "produced confused flows of sometimes contradictory information in the early days of the crisis". According to the report, Kan delayed the cooling of the reactors by questioning the use of seawater instead of fresh water. Kan further hindered the response to the crisis by micromanaging disaster management efforts and appointing his own nominees to a small, closed, decision-making staff. The report stated that the Japanese government was also slow to accept assistance from U.S. nuclear experts.

A 2012 report in The Economist said: "The reactors at Fukushima were of an old design. The risks they faced had not been well analysed. The operating company was poorly regulated and did not know what was going on. The operators made mistakes. The representatives of the safety inspectorate fled. Some of the equipment failed. The establishment repeatedly played down the risks and suppressed information about the movement of the radioactive plume, so some people were evacuated from more lightly to more heavily contaminated places".

From 17 to 19 March 2011, US military aircraft, on behalf of the US Department of Energy, measured the radiation within a 45-km radius of the reactors. The data recorded 125 microsieverts per hour of radiation as far as 25 km (15.5 mi) northwest of the plant. The US provided the data, illustrated on detailed maps, to the Japanese Ministry of Economy, Trade, and Industry (METI) on 18 March and to the Ministry of Education, Culture, Sports, Science and Technology (MEXT) two days later. Japanese government officials did not act on the information provided by the maps.

The data were not forwarded to the prime minister's office or the Nuclear Safety Commission, and subsequently not used to direct the evacuation of the people living around the plant. Because a substantial portion of radioactive materials released from the plant went northwest and fell to the ground, and some residents were "evacuated" into this direction, these people could have avoided unnecessary exposure to radiation if the data had been published directly. According to Tetsuya Yamamoto, chief nuclear safety officer of the Nuclear Safety Agency, "It was very regrettable that we didn't share and utilize the information." But an official of the Science and Technology Policy Bureau of the technology ministry, Itaru Watanabe, said it was not Japan, but more appropriate for the United States to release the data.

After the Americans published their map on 23 March, Japan felt itself forced to publish, and the fallout maps – compiled from ground measurements and SPEEDI computer simulation/predictions – were released the same day. On 19 June 2012 science minister Hirofumi Hirano defended the decision not to publish, with the remark, that his "job was only to measure radiation levels on land", and that the government would study whether disclosure of the maps could have helped in the evacuation efforts.

Accident rating

Main article: Accident rating of the Fukushima Daiichi nuclear disaster

Comparison of radiation levels for different nuclear events.

The severity of the nuclear accident is provisionally rated 7 on the International Nuclear Event Scale (INES). This scale runs from 0, indicating an abnormal situation with no safety consequences, to 7, indicating an accident causing widespread contamination with serious health and environmental effects. Prior to Fukushima, the Chernobyl disaster was the only level 7 accident on record, while the Three Mile Island accident was a level 5 accident.

The 2012 analysis of the amount of intermediate and long lived radioactivity released from all the Fukushima Daiichi reactors was about 10-20% of that released from the Chernobyl disaster. The total release from the entire Fukushima disaster, in terms of caesium-137 (which along with strontium-90 are the two primary substances preventing Chernobyl from being inhabited,) is approximately 15 PBq of caesium-137 released; by contrast, the amount released from Chernobyl was approximately 85 PBq of caesium-137. This is the activity that would be produced by 24 kilograms of caesium-137.

Another notable difference between the two accidents is that, unlike Chernobyl, all the Japanese reactors were situated within concrete containment vessels, which contributed to the Japanese accident releasing vastly less strontium-90, americium-241 and plutonium, which were among the radioisotopes released at Chernobyl.

In terms of the most biologically hazardous short lived radioisotope, namely iodine-131, 500 PBq of Iodine 131 were released during the Fukushima disaster. By comparison, approximately 1,760 PBq of iodine-131 were released during the Chernobyl disaster. Iodine-131 has a short half life of 8.02 days; consequently, it decays rapidly to become a stable nucleide. Therefore there is only a short time during which human exposure can occur: after ten half lifes - 80.2 days for Iodine-131 - 99.9% of it has decayed to Xe-131, a stable isotope.

Casualties

Main article: Fukushima Daiichi nuclear disaster casualties

There were no deaths caused by short term radiation exposure, while approximately 18,500 people died due to the earthquake and tsunami. Future cancer deaths from accumulated radiation exposures in the population living near Fukushima are predicted to be, as in the Chernobyl accident, statistically undetectable. After the Chernobyl accident, only 0.1% of the 110,000 cleanup workers surveyed have so far developed leukemia, although not all cases resulted from the accident. Estimated effective doses from the accident outside of Japan are considered to be below (or far below) the dose levels regarded as very small by the international radiological protection community.

Following the power station accident, there have been no reports of short term radiation fatalities reported due to the fukushima accident, in contrast to the 31 to 50 or so that occurred soon after Chernobyl. Stanford University professor Mark Z. Jacobson and his colleague John Ten Hoeve, suggest that according to the linear no-threshold model (LNT model) the accident is most likely to cause an eventual total of 130 cancer deaths. Radiation epidemiologist Roy Shore contends that estimating health effects in a population from the LNT model "is not wise because of the uncertainties". The LNT model did not accurately model casualties from Chernobyl, Hiroshima or Nagasaki; it greatly overestimated the casualties. Evidence that the LNT model is a gross distortion of damage from radiation has existed since 1946, and was suppressed by Nobel Prize winner Hermann Muller in favour of assertions that no amount of radiation is safe.

In 2013 (two years after the incident), the World Health Organization indicated that the residents of the area who were evacuated were exposed to so little radiation that radiation induced health impacts are likely to be below detectable levels. The health risks in the WHO assessment attributable to the Fukushima radiation release were calculated by largely applying the conservative Linear no-threshold model of radiation exposure, a model that assumes even the smallest amount of radiation exposure will cause a negative health effect.

The World Health Organization (WHO) report released in 2013 predicts that for populations in the most contaminated areas there is a 70% higher relative risk of developing thyroid cancer for females exposed as infants, and a 7% higher relative risk of leukemia in males exposed as infants and a 6% higher relative risk of breast cancer in females exposed as infants. With the WHO communicating that the values stated in that section of their report are relative increases, and not representative of the absolute increase of developing these cancers, as the lifetime absolute baseline chance of developing thyroid cancer in females is 0.75%, with the Radiation-induced cancer chance now predicted to increase that 0.75% to 1.25%, with this 0.75% to 1.25% change being responsible for the "70% higher relative risk":

These percentages represent estimated relative increases over the baseline rates and are not absolute risks for developing such cancers. Due to the low baseline rates of thyroid cancer, even a large relative increase represents a small absolute increase in risks. For example, the baseline lifetime risk of thyroid cancer for females is just (0.75%)three-quarters of one percent and the additional lifetime risk estimated in this assessment for a female infant exposed in the most affected location is (0.5%)one-half of one percent.

The WHO calculations determined that the most at risk group, infants, who were in the most affected areas, would experience an absolute increase in the risk of cancer (of all types) during their lifetime, of approximately 1% due to the accident. With the lifetime risk increase for thyroid cancer, due to the accident, for a female infant, in the most affected radiation location, being estimated to be one half of one percent[0.5%]. Cancer risks for the unborn child are considered to be similar to those in 1 year old infants.

The estimated risk of cancer to people who were children and adults during the Fukushima accident, in the most affected area, was determined to be lower again when compared to the most at risk group - infants. A thyroid ultrasound screening programme is currently[2013] ongoing in the entire Fukushima prefecture, this screening programme is, due to the screening effect, likely to lead to an increase in the incidence of thyroid disease due to early detection of non-symptomatic disease cases.

As of August 2013, there have been more than 40 children newly diagnosed with thyroid cancer and other cancers in Fukushima prefecture as a whole. However whether these incidences of cancer are due to exposure to nuclear radiation is unknown at this stage. Data from the Chernobyl accident showed that there was a steady then sharp increase in thyroid cancer rates following the disaster in 1986, however whether this data can be directly compared to the Fukushima nuclear disaster is unknown.

As a point of comparison, thyroid cancer incidence rates after the Chernobyl accident of 1986 did not begin to increase above the prior baseline value of about 0.7 cases per 100,000 people per year, until 1989 to 1991, 3 to 5 years after the accident in both the adolescent and children age groups, therefore data from Chernobyl suggests that an increase in thyroid cancer around Fukushima is not expected to begin to be seen until at least 3 to 5 years after the accident.

A 2013 article in the Stars and Stripes asserted that a Japanese government study released in February of that year had found that more than 25 times as many people in the area had developed thyroid cancer compared with data from before the disaster.

As part of the ongoing precautionary ultrasound screening program in and around Fukushima, (36%) of children in Fukushima Prefecture in 2012 were found to have abnormal growths in their thyroid glands, but whether this is due to the effects of nuclear radiation is still yet to be determined. This screening programme is, due to the screening effect, likely, according to the WHO, to lead to an increase in the incidence of the diagnosis of thyroid disease due to early detection of non-symptomatic disease cases. For example, the overwhelming majority of thyroid growths prior to the accident, and in other parts of the world, are overdiagnosed (that is, a benign growth that will never cause any symptoms, illness, or death for the patient, even if nothing is ever done about the growth) with autopsy studies, again done prior to the accident and in other parts of the world, on people who died from other causes showing that more than one third (33%+), of adults technically has a thyroid growth/cancer, but it is benign/never caused them any harm.

Thyroid cancer is one of the most survivable cancers, with an approximate 94% survival rate after first diagnosis, and that rate increases to a 100% survival rate with catching it early. For example, from 1989 to 2005, an excess of 4000 children and adolescent cases of thyroid cancer were observed in those who lived around Chernobyl, of these 4000 people, nine have died so far, a 99% survival rate.

Plight of evacuees

In the former Soviet Union many patients with negligible radioactive exposure after the Chernobyl disaster displayed extreme anxiety about low level radiation exposure, and therefore developed many psychosomatic problems, including radiophobia, and with this an increase in fatalistic alcoholism being observed. As Japanese health and radiation specialist Shunichi Yamashita noted:

We know from Chernobyl that the psychological consequences are enormous. Life expectancy of the evacuees dropped from 65 to 58 years -- not [predominately] because of cancer, but because of depression, alcoholism and suicide. Relocation is not easy, the stress is very big. We must not only track those problems, but also treat them. Otherwise people will feel they are just guinea pigs in our research.

A survey by the Iitate, Fukushima local government obtained responses from approximately 1,743 people who have evacuated from the village, which lies within the emergency evacuation zone around the crippled Fukushima Daiichi Plant. It shows that many residents are experiencing growing frustration and instability due to the nuclear crisis and an inability to return to the lives they were living before the disaster. Sixty percent of respondents stated that their health and the health of their families had deteriorated after evacuating, while 39.9% reported feeling more irritated compared to before the disaster.

Summarizing all responses to questions related to evacuees' current family status, one-third of all surveyed families live apart from their children, while 50.1% live away from other family members (including elderly parents) with whom they lived before the disaster. The survey also showed that 34.7% of the evacuees have suffered salary cuts of 50% or more since the outbreak of the nuclear disaster. A total of 36.8% reported a lack of sleep, while 17.9% reported smoking or drinking more than before they evacuated.

Experts on the ground in Japan agree that mental health challenges are the most significant issue. Stress, such as that caused by dislocation, uncertainty and concern about unseen toxicants, often manifests in physical ailments, such as heart disease. So even if radiation risks are low, people are still concerned and worried. Behavioral changes can follow, including poor dietary choices, lack of exercise and sleep deprivation, all of which can have long-term negative health consequences. People who lost their homes, villages and family members, and even just those who survived the quake, will likely continue to face mental health challenges and the physical ailments that come with stress. Much of the damage was really the psychological stress of not knowing and of being relocated, according to U.C. Berkeley's McKone.

In August 2012, the evacuation order was partly lifted. Some evacuees were permitted to return, some were still forbidden to return. The area near to the related Fukushima Daini Nuclear Power Plant, such as the 7200 residents Naraha town, was deemed to be safe for return with no protective equipment. No contamination had occurred. Some areas had been evacuated despite no contamination. An additional zone was designated low-risk, with entry permitted for restricted purposes and lengths.

A survey by the newspaper Mainichi Shimbun computed that of some 300,000 people who evacuated the area, approximately 1,600 deaths related to the evacuation conditions, such as living in temporary housing and hospital closures have occurred as of August 2013, a number comparable to the 1,599 deaths directly caused by the earthquake and tsunami in the Fukushima Prefecture in 2011. With the exact cause of the majority of these evacuation related deaths not being specified, as according to the municipalities, that would hinder the deceased relatives application for condolence money compensation.

Insurance

According to Munich Re, a major reinsurer, the private insurance industry will not be significantly affected by the accidents at the Fukushima nuclear power plant. Swiss Re similarly states "Coverage for nuclear facilities in Japan excludes earthquake shock, fire following earthquake and tsunami, for both physical damage and liability. Swiss Re believes that the incident at the Fukushima nuclear power plant is unlikely to result in a significant direct loss for the property & casualty insurance industry."

Reactions

Japanese reaction and evacuation measures

Main article: Japanese reaction to Fukushima Daiichi nuclear disaster

Japan towns, villages, and cities in and around the Daiichi nuclear plant exclusion zone. The 20 km and 30 km areas had evacuation and sheltering orders, and additional administrative districts that had an evacuation order are highlighted.

On 11 March 2011, a nuclear emergency was declared by the Japanese government. The government initially set in place a 4-stage evacuation process: a prohibited access area out to 3 km from the plant, an on-alert area 3–20 km from the plant, and an evacuation prepared area 20–30 km from the plant. On day one of the disaster nearly 134,000 people who lived between 3–20 km from the plant were evacuated. 4 days later an additional 354,000 who lived between 20–30 km from the plant were evacuated. Later, Prime Minister Naoto Kan issued instructions that people within a 20 km (12 mi) zone around the Fukushima Daiichi nuclear plant must leave, and urged that those living between 20 km and 30 km from the site to stay indoors. The latter groups were also urged to evacuate on 25 March 2011.

Japanese authorities have admitted that lax standards and poor oversight contributed to the nuclear disaster. They have come under fire for their handling of the emergency, and have engaged in a pattern of withholding damaging information and denying facts of the accident. Authorities apparently wanted to "limit the size of costly and disruptive evacuations in land-scarce Japan and to avoid public questioning of the politically powerful nuclear industry". There has been public anger about an "official campaign to play down the scope of the accident and the potential health risks". The accident is the second biggest nuclear accident after the Chernobyl disaster, but more complex as all reactors are involved.

The second largest nuclear accident in the history of the world has and will continue to have an impact on the people of Japan. In many cases, the Japanese government's reaction has been judged to be less than adequate by many in Japan, especially those directly affected who were living in the region surrounding the Fukushima plant. New decontamination equipment was slow to be made available and then slow to be utilized. As late as June 2011, even rain fall continue to cause fear and uncertainty fear among the populace of eastern Japan because of its possibility of bringing more radiation down to the ground level that had collected in the atmosphere. In June 2011, TEPCO stated the amount of contaminated water in the complex had increased due to substantial rainfall.

To assuage fears, the government enacted an order to decontaminate over a hundred areas with a level contamination greater than or equivalent to one millisievert of radiation. This is a much lower threshold than is necessary for protecting health. The government also sought to address the lack of education on the effects of radiation and the extent to which the average person was exposed.

Previously a proponent of building more reactors, former Prime Minister Naoto Kan took an increasingly anti-nuclear stance in the months following the Fukushima disaster. In May 2011, he ordered the aging Hamaoka Nuclear Power Plant be closed over earthquake and tsunami fears, and said he would freeze plans to build new reactors. In July 2011, Mr. Kan said that "Japan should reduce and eventually eliminate its dependence on nuclear energy ... saying that the Fukushima accident had demonstrated the dangers of the technology". In October 2013, He said in The Huffington Post that if the worst-case scenario had realized, the evacuation of 50 million people within a 250-kilometer radius of Fukushima had needed.

On 22 August 2011, a spokesman of the Japanese Government mentioned the possibility, that some areas of the evacuation zone around the nuclear plant "could stay for some decades a forbidden zone". According to the Japanese newspaper Yomiuri Shimbun the Japanese government was planning to buy some properties from civilians to store radioactive waste and materials that had become radioactive after the accidents. Chiaki Takahashi, Japan's foreign minister, criticized foreign medias reports over accidents in Fukushima Daichii as overdone and excessive. But Takahashi added that "he can understand the concerns of foreign countries over recent developments at the nuclear plant, including the radioactive contamination of seawater".

Due to frustration with Tokyo Electric Power Company (TEPCO) and the Japanese government "providing differing, confusing, and at times contradictory, information on critical health issues" a citizen's group called "Safecast" has been recording detailed radiation level data in Japan. The Japanese government "does not consider nongovernment readings to be authentic". The group uses off-the-shelf Geiger counter equipment. It is important to note that a simple Geiger counter is a contamination meter and not a dose rate meter, as the response differs so much between different radioisotopes it is not possible to use a simple GM tube for dose rate measurements when more than one radioisotope is present. A thin metal shield is needed around a GM tube to provide energy compensation to enable it to be used for dose rate measurements. For measurements of dose rates due to gamma emitters either an ionization chamber, a gamma spectrometer or an energy compensated GM tube should be used. Members of the Air Monitoring station facility at the Department of Nuclear Engineering at the University of Berkeley, California have been doing extensive tests of environmental samples in Northern California.

International reaction

Main article: International reaction to the Fukushima Daiichi nuclear disaster

The international reaction to the 2011 Fukushima Daiichi nuclear disaster has been diverse and widespread. Many inter-governmental agencies are responding to the Fukushima Daiichi nuclear disaster, often on an ad hoc basis. Responders include International Atomic Energy Agency, World Meteorological Organization and the Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization, which has radiation detection equipment deployed around the world.

Many countries have advised their nationals to leave Tokyo, No notice was taken of the actual risk or radiation levels, many nationals left a lower-radiation area to go to a higher radiation area. International experts have said that a workforce in the hundreds or even thousands would take years or decades to clean up the area. Stock prices of many energy companies reliant on nuclear sources have dropped.

There has been a significant re-evaluation of existing nuclear power programs in many countries. One poll found that what had been growing acceptance of nuclear power in the United States was eroded sharply following the 2011 Japanese nuclear accidents, with 43% approving and 50% disapproving of building new plants. Events at Fukushima "cast doubt on the idea that even an advanced economy can master nuclear safety" said one French magazine. Increased anti-nuclear sentiment has been evident in India, Italy, Germany, Spain, Switzerland, Taiwan, and the United States.

Week from	Tons	Plant- capacity utilisation
29 June	6380	76%
6 July	6130	73%
13 July	4510	54%
20 July	4870	58%
27 July	6190	74%
3 August	6720	80%
10 August	7420	88%

Reactor stabilization and cleanup operations

Main article: Fukushima disaster cleanup

The multiple nuclear reactor units involved in the Fukushima Daiichi nuclear disaster are close to one another. Addressing the parallel, chain-reaction accidents that led to hydrogen explosions blowing the roofs off reactor buildings and water draining from open-air spent fuel pools was complicated by this proximity. This situation was potentially more dangerous than the loss of reactor cooling itself. Because of the proximity of the reactors, plant workers were put in the position of trying to cope simultaneously with core meltdowns at three reactors and exposed fuel pools at three units.

On 21 December 2011, the Japanese government released a roadmap for the cleanup activities, which predicted that the full cleanup will take 40 years, though Toshiba claims to be able to open up the reactor and finish decommissioning in 10 years. To compare, Three Mile Island took 14 years to clean up. On 10 April 2011, Tokyo Electric Power Company (TEPCO) began using remote-controlled, unmanned heavy equipment to remove debris from around nuclear reactors 1–4. TEPCO announced on 17 April that it expected to have the automated cooling systems restored in the damaged reactors in about three months and have the reactors put into cold shutdown status in six months. TEPCO planned to largely empty the basements of the turbine and reactor buildings of units 1–3 of contaminated water by the end of 2011 to allow workers access to the crucial basement areas of both the turbine and reactor buildings.

When the monsoon season began in June 2011, a light fabric cover was used to protect the damaged reactor buildings from storms and heavy rainfall. On 16 August, TEPCO announced the installation of devices in the spent fuel pools of reactor 2, 3, and 4, which used special membranes and electricity to desalinate the water. These pools were cooled with seawater for some time, and TEPCO feared the salt would corrode stainless steel pipes and the pool walls. Extra sensors were installed and filters to reduce the release of contaminants.

In October 2011, Japanese Prime Minister Yoshihiko Noda said the government might have to spend 1 trillion yen ($13 billion) to clean up vast areas contaminated by radiation from the Fukushima nuclear disaster. Japan "faces the prospect of removing and disposing 29 million cubic meters of soil from a sprawling area in Fukushima, located 240 kilometers (150 miles) northeast of Tokyo, and four nearby prefectures". Hydrothermal blasting is one of several techniques being considered to be included in the effort to clean up radioactivity from Fukushima from as much land as possible. In this process, a slurry of contaminated soil is heated in an autoclave (to dissolve any caesium-137) and then filtered; caesium-137 is then precipitated from the filtrate by adding Prussian blue. This technique will be able to strip out 80 to 95% of the caesium from contaminated soil and other materials. Caesium-137 (30 year half life) is the major health concern in Fukushima. The aim is to get annual exposure from the contaminated environment down to 1 millisievert (mSv) above background. The most contaminated area where radiation doses are greater than 50 mSv/year must remain off limits. However, these fears were not realized, as soil contamination proved to be superficial. Since the majority of caesium was found in the vegetation and litter layer of the forest, the preferred method of disposal is incineration of irradiated organics. This method is preferred because it decreases contaminated sites by tenfold in short amounts of time and it is an easy method to apply. The big challenge is disposing of the caesium-enriched ash that would end up in the atmosphere from burning all of the vegetation and litter layers of the forest ground.

Disposal of materials and safe extraction of caesium

Parajuli et al. focused their study on "safe incineration of contaminated wastes while restricting the release of volatile caesium to the atmosphere". In order for incineration to continue without releasing too many harmful toxic substances into the atmosphere, a modified incinerator was created. Using several types of methods and HEPA filters, the scientists were able to prevent the release of caesium into the atmosphere after the contaminants had been incinerated.

These materials incinerated include wood ash, which came from evergreen trees and deciduous trees, household garbage ash, and also sludge ash. After incineration, the ash had to be disposed of properly and decontaminated of its caesium contents. In order to do this, the scientist experimented to see if the ash could just be rinsed with water to extract caesium. They began with the wood ash first. The scientist varied different amounts of water, different mixing times, and different temperatures. After a few trial and error runs, they come to the conclusion that removing caesium from wood ash was optimal with a 1:25 ash to water ratio, mixing for ten minutes, at 40°C. The percentage of released caesium from the wood ash was about 93%. Another interesting observation was that the water that was used to wash had low concentrations of heavy metals. This meant that the ash that was now caesium-free could be reconstructed back into the environment. Removal of caesium from household garbage also had a few experimental runs. What the scientist discovered was that it could also be washed with water. 95% of caesium content was removed from the garbage by a 1:10 ash to water ratio, mixing for ten minutes at 25-90°C. The difference in increasing temperature was found to be negligible.

Incineration of sludge resulted in sludge ash. This ash was a lot more difficult to deal with and clean that the previous two. Sludge ash, when first attempted to be decontaminated with water, resulted in only negligible amounts of caesium removed, unlike wood and garbage ash. Parajuli et al. theorized that this was due to the presence of clay minerals that trap caesium in the sludge. To decontaminate the sludge, new measures had to be taken. The scientist tried several different types of acids, like HNO₃ and H₂SO₄ to help accelerate the decontamination process. They finally ended up with sludge to acid ratio of 1:100, mixed for one hour, at 95°C with an acid concentration of 0.5M. This combination resulted in an 82.3% caesium release from the sludge.

A few other important observations that were not mentioned is that the wood ash and garbage were able to be washed at ambient temperatures, although they wouldn't have as high of a percent of caesium removed. Also, the fly ash in the bag filters suggested that caesium had precipitated after it had been vaporized. Another important note is that the exhaust gas concentration, released from the machine that was burning the vegetation, of caesium was less than 1.67, which is less than the detectable limit. Most importantly, 95% of the contaminated mass was reduced.

Energy policy implications

Anti-nuclear power plant rally on 19 September 2011 at the Meiji Shrine complex in Tokyo.

By March 2012, one year after the disaster, all but two of Japan's nuclear reactors had been shut down; some were damaged by the quake and tsunami. Authority to restart the others after scheduled maintenance throughout the year was given to local governments, and in all cases local opposition prevented restarting. According to The Japan Times, the Fukushima nuclear disaster changed the national debate over energy policy almost overnight. "By shattering the government's long-pitched safety myth about nuclear power, the crisis dramatically raised public awareness about energy use and sparked strong anti-nuclear sentiment". A June 2011 Asahi Shimbun poll of 1,980 respondents found that 74% answered "yes" to whether Japan should gradually decommission all 54 reactors and become nuclear free. An energy white paper, approved by the Japanese Cabinet in October 2011, says "public confidence in safety of nuclear power was greatly damaged" by the Fukushima disaster, and calls for a reduction in the nation's reliance on nuclear power. It also omits a section on nuclear power expansion that was in the previous year's policy review.

Michael Banach, the current Vatican representative to the International Atomic Energy Agency, told a conference in Vienna in September 2011 that the Japanese nuclear disaster created new concerns about the safety of nuclear plants globally. Auxiliary bishop of Osaka Michael Goro Matsuura said this serious nuclear power incident should be a lesson for Japan and other countries to abandon nuclear projects. He called on the worldwide Christian solidarity to provide wide support for this anti-nuclear campaign. Statements from bishops' conferences in Korea and the Philippines called on their governments to abandon atomic power. Author Kenzaburō Ōe, who received a Nobel prize in literature, has said Japan should decide quickly to abandon its nuclear reactors.

According to Reuters, due to the fact that the closest nuclear power plant to the epicenter of the earthquake and tsunami-Onagawa Nuclear Power Plant, successfully withstood the 2011 Tōhoku earthquake and tsunami, it may now serve as a "trump card" for the nuclear lobby, providing evidence that it is possible for a correctly designed nuclear facility to withstand one of most powerful of megathrust earthquakes and tsunamis ever recorded and to shut down safely, as designed, without incident.

Electricity generation by source in Japan (month-level data). Nuclear's contribution declined steadily throughout 2011 due to shutdowns and has been replaced with thermal power stations such as fossil gas and coal power plants. Units 3 & 4 at Ohi Nuclear Power Plant are the only two Japanese reactors which have so far met the new safety rules and thus continue to operate.

The loss of 30% of the country's generating capacity has led to much greater reliance on liquified natural gas and coal. Unusual conservation measures have also been necessary. In the immediate aftermath, nine prefectures served by TEPCO suffered power rationing. The government asked major companies to reduce power consumption by 15%, and some shifted their weekends to weekdays to even out power demand. If Japan were to convert to a gas and oil energy economy, going completely nuclear-free, the repercussions would cost the people and government tens of billions of dollars in annual fees. Oil and gas would only suffice as a temporary fix to help with the summer months, and could not be the long term answer. At this time the cost of oil and gas has increased exponentially with the war in Iraq still in its peak moments and the US Government asking to stop trade with the Middle East, which would thrust Japan into an economic bind if they implemented this energy policy. It has been estimated that if Japan had never adopted nuclear power, accidents and pollution from coal or gas plants would have caused more lost years of life.

Many energy policy analysts have begun calling for a phase out of nuclear power in Japan, including Amory Lovins who has said: "Japan is poor in fuels, but is the richest of all major industrial countries in renewable energy that can meet the entire long-term energy needs of an energy-efficient Japan, at lower cost and risk than current plans. Japanese industry can do it faster than anyone — if Japanese policymakers acknowledge and allow it". Benjamin K. Sovacool has said that, with the benefit of hindsight, the Fukushima disaster was entirely avoidable in that Japan could have chosen to exploit the country's extensive renewable energy base. Japan has a total of "324 GW of achievable potential in the form of onshore and offshore wind turbines (222 GW), geothermal power plants (70  GW), additional hydroelectric capacity (26.5 GW), solar energy (4.8 GW) and agricultural residue (1.1 GW)."

Environmental activists at a 2011 United Nations meeting in Bangkok used the Fukushima disaster as an example to promote accelerated use of renewable energy. One result of the Fukushima Daiichi nuclear disaster could be renewed public support for the commercialization of renewable energy technologies. In August 2011, the Japanese Government passed a bill to subsidize electricity from renewable energy sources. This legislation, effective 1 July 2012, requires utilities to buy electricity generated by renewable sources including solar power, wind power, and geothermal energy at above-market rates.

In September 2011, Mycle Schneider said that the Fukushima disaster can be understood as a unique chance "to get it right" on energy policy. "Germany – with its nuclear phase-out decision based on a highly successful renewable energy program – and Japan – having suffered a painful shock but possessing unique technical capacities and societal discipline – can be at the forefront of an authentic paradigm shift toward a truly sustainable, low-carbon and nuclear-free energy policy".

As of September 2011, Japan plans to build a pilot floating wind farm, with six 2-megawatt turbines, off the Fukushima coast. After the evaluation phase is complete in 2016, "Japan plans to build as many as 80 floating wind turbines off Fukushima by 2020." In 2012, Naoto Kan said the Fukushima disaster made it clear to him that "Japan needs to dramatically reduce its dependence on nuclear power, which supplied 30% of its electricity before the crisis, and has turned him into a believer of renewable energy". Sales of solar cells in Japan rose 30.7% to 1,296 megawatts in 2011, helped by a government scheme to promote renewable energy. Canadian Solar plans to build a factory in Japan and is currently in negotiations with local governments in Fukushima and Miyagi prefectures. The facility is expected to have a capacity of 150 megawatts of solar panels a year, could go online as soon as 2013.

As of September 2012, most Japanese people support the zero option on nuclear power according to the LA Times, and Prime Minister Noda and the Japanese government announced a dramatic change of direction in energy policy, promising to make the country nuclear-free by the 2030s. There will be no new construction of nuclear power plants, a 40-year lifetime limit on existing nuclear plants, and any further nuclear plant restarts will need to meet tough safety standards of the new independent regulatory authority. The new approach to meeting energy needs will also involve investing $500 billion over 20 years to commercialize the use of renewable energy sources such as wind power and solar power. In July, a Commission presented a 450-page report about Fukushima that strongly criticized TEPCO and the former government. It described the NISA ("Nuclear and Industrial Safety Agency") as a toothless tiger. The NISA was subordinated to the Japanese Ministry of Economy (METI). 19 September, the NISA was replaced by an organization called Nuclear Regulation Authority.

On 16 December, there was a general election in Japan. Voters gave the Liberal Democratic Party (LDP) a clear victory. Shinzō Abe (LDP) was elected prime minister of Japan. The LDP has governed Japan almost uninterrupted for half a century. Abe said he wanted more nuclear power. A survey of local mayors by the Yomiuri Shimbun newspaper in January 2013 found that most of them from cities hosting nuclear plants would agree to the reactors being restarted, provided the government could guarantee the safety of the facilities. However, more than 30,000 people marched on June 2, 2013, near the Diet building in Tokyo against the government's plan to restart nuclear power plants. Kenzaburo Oe, a Nobel laureate in literature, attended the march. Marchers had gathered more than 8 million signatures in a petition against Japan's plan to restart nuclear power plants after the Fukushima disaster.

In October 2013, it was reported that Tokyo Electric Power Company and eight other Japanese power companies are paying approximately 3.6 trillion yen, or 37 billion dollars more in combined imported fossil fuel costs this year compared to the year 2010, before the accident, to make up for the electric power output that would otherwise have been supplied by the nations presently idle nuclear power stations.

In late October 2013, Prime Minister Shinzo Abe ruled out the possibility of Japan phasing out its nuclear reactors, stating that those who support such a policy goal are "irresponsible".

Investigations

NAIIC

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

The Fukushima Nuclear Accident Independent Investigation Commission (NAIIC) is the first independent investigation commission by the National Diet in the 66-year history of Japan's constitutional government.

The Fukushima nuclear accident "cannot be regarded as a natural disaster," the NAIIC panel's chairman, Tokyo University professor emeritus Kiyoshi Kurokawa, wrote in the inquiry report. "It was a profoundly man-made disaster -- that could and should have been foreseen and prevented. And its effects could have been mitigated by a more effective human response." "Governments, regulatory authorities and Tokyo Electric Power [TEPCO] lacked a sense of responsibility to protect people's lives and society," the Diet's Fukushima Nuclear Accident Independent Investigation Commission said. "They effectively betrayed the nation's right to be safe from nuclear accidents.

In addition, the Commission recognized that the affected residents are still struggling and facing grave concerns, including the "health effects of radiation exposure, displacement, the dissolution of families, disruption of their lives and lifestyles and the contamination of vast areas of the environment". The decontamination and restoration activities, essential for rebuilding communities, will continue into the long term.

Investigation Committee

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

The determination of the causes of the accident that occurred at Fukushima Daiichi and Daini Nuclear Power Stations of Tokyo Electric Power Company (TEPCO), and those of the damages generated by the accident, and thereby making policy proposals designed to prevent the expansion of the damages and the recurrence of similar accidents in the future was the purpose of the Investigation Committee on the Accident at the Fukushima Nuclear Power Stations (ICANPS). The 10 member, government-appointed panel included scholars, journalists, lawyers and engineers, was supported by public prosecutors and government experts and released its final, 448-pages investigation report on 23 July 2012.

The panel's report faulted an inadequate legal system for nuclear crisis management, a crisis-command disarray caused by the government and TEPCO, and possible excess meddling on the part of the prime minister's office in the early stage of the crisis. The panel concluded that a culture of complacency about nuclear safety and poor crisis management led to the nuclear disaster.

Lessons learned

A number of nuclear reactor safety system lessons have been learned from the Fukushima I accident. The most obvious being that in tsunami prone areas, a power station's sea wall must be adequately tall and robust enough. An example of just how important this can be was exemplified at the Onagawa Nuclear Power Plant, up the coast from Fukushima Daiichi and therefore closer to the epicenter of the March 11 earthquake and tsunami. At this power station the sea wall was 14 meters tall and successfully withstood the vast majority of the impact of the tsunami, preventing the serious damage and radiation releases that occurred at Fukushima. No government mandate required Onagawa's operators to build the sea wall to this height, they simply thought it was a good idea.

Following the accident nuclear power station operators around the world began to install Passive Auto-catalytic hydrogen Recombiners ("PARs"), which do not require electricity to operate. PARs work much like the catalytic converter on the exhaust of a car, and turn potentially explosive gases, like hydrogen gas into harmless water. Had Fukushima I had such hydrogen gas Recombiners positioned at the top of its reactor and containment buildings, where hydrogen gas most likely collects, the devastating hydrogen gas explosions would not have occurred and the releases of radioactive isotopes would arguably have been much less.

The installation of power-free filters on containment building vent lines has also been suggested, for example, in the event that radioactive isotopes are emitted from the reactor or spent fuel pool, the filters would safely catch radioactive materials and thereby allow reactor core de-pressurization, with steam and hydrogen venting while also minimizing environmental radiation emissions. Wet filters, an external water tank system, is the most common in Europe, with the water tank positioned outside the containment building. In October 2013, the owners of Kashiwazaki-Kariwa nuclear power station began installing wet filters and other safety systems, with completion anticipated in 2014.

In generation II reactors in flood or tsunami prone areas like those at Fukushima I, a 3+ day supply of back-up batteries has become somewhat of an industry standard following the accident. Also advised along with this is hardening the location of back-up Diesel generator rooms with the type of water tight and blast resistant doors, and heat sinks, commonly used by nuclear submarines. The oldest operating nuclear power station in the world, Beznau Nuclear Power Plant, which has been operating since 1969, has a 'Notstand' hardened building designed to support all of the power station systems independently for 72 hours if in the event an earthquake or severe flooding hit the power station, this system was built prior to Fukushima by the reactor operators without regulation or government directive forcing them to.

Upon a Station Blackout, which occurred after the back-up battery supply at Fukushima ran low, many already constructed Generation III reactors have been built along the principle of passive nuclear safety, and therefore take advantage of convection(hot water tends to rise) and gravity(water tends to fall) to ensure an adequate supply of water to provide cooling, and do not require large electrical pumps to cool the residual reactor decay heat.

See also

• List of civilian nuclear accidents
• Lists of nuclear disasters and radioactive incidents
• Timeline of the Fukushima Daiichi nuclear disaster
• Comparison of Fukushima and Chernobyl nuclear accidents

External links

• The Fukushima Nuclear Accident Independent Investigation Commission Report website in English
• Executive summary of the Fukushima Nuclear Accident Independent Investigation Commission Report
• Fukushima report: Key points in nuclear disaster report - An outline of key quotes, findings and recommendations from the 88-page executive summary of the Nuclear Accident Independent Investigation Commission's report, as provided by the BBC, 5 July 2012
• Webcam Fukushima nuclear power plant I, Unit 1 through Unit 4
• Investigation Committee on the accidents at the Fukushima Nuclear Power Station of Tokyo Electric Power Company
• Schematic drawing of Unit 1 reactor building
• TEPCO News Releases, Tokyo Electric Power Company
• NISA Information update, Nuclear and Industrial Safety Agency, the nuclear safety authority of Japan
• JAIF Information update, Japan Atomic International Forum
• JAEA Information update, Japan Atomic Energy Agency
• IAEA Update on Japan Earthquake, International Atomic Energy Agency
• Nature Journal – Specials: Japan earthquake and nuclear crisis
• TerraFly Timeline Aerial Imagery of Fukushima Nuclear Reactor after 2011 Tsunami and Earthquake
• Documentary photographs: residential damage within "No Go" Zone
• In graphics: Fukushima nuclear alert, as provided by the BBC, 9 July 2012
• PreventionWeb Japan: 2011 Fukushima Daiichi nuclear disaster
• "What should we learn from the severe accident at the Fukushima Dai-ichi Nuclear Power Plant?" by Kenichi Ohmae, Team H2O Project. 28 October 2011
• "Reassessment of Fukushima Nuclear Accident and Outline of Nuclear Safety Reform Plan(Interim Report)" by TEPCO Nuclear Reform Special Task Force.14 December 2012
• Tatsujiro Suzuki's Fukushima Updates, 2013, Bulletin of the Atomic Scientists