Direct effect of the 2011 earthquake and tsunami
The 9.0 MW Tōhoku earthquake occurred on 11 March 2011 at 14:46 Japan Standard Time (JST) off the northeast coast of Japan and resulted in maximum ground accelerations of 0.52 g (5.07 m/s2) (well above the design basis of 0.45 g (4.14 m/s2)) at Unit 3 and values below the design basis at Units 4 and 6.
When the earthquake occured, reactor units 1, 2, and 3 were operating, but units 4, 5, and 6 had already been shut down for periodic inspection. When the earthquake was detected, units 1, 2 and 3 underwent an automatic shutdown (called scram).
After the reactors shut down, electricity generation stopped. Normally the plant could use an external electrical supply to power cooling and control systems, but the earthquake caused major damage to the regional power grid. Emergency diesel generators started but stopped abruptly at 15:41, ending all AC power supply to the reactors. The plant was protected by a seawall which was designed to withstand a tsunami of 5.7 metres (19 ft), but the wave that struck the plant was estimated to be more than twice that height at 14 metres (46 ft). It easily topped the seawall, flooding the low-lying generator building.
Article 10 of the Japanese law on Special Measures Concerning Nuclear Emergency Preparedness, heightened alert condition requires authorities to be informed of such an incident: TEPCO did so immediately and also issued a press release declaring a "First Level Emergency".
After the diesel generators failed, emergency power for control systems was supplied by batteries that were designed to last about eight hours. Batteries from other nuclear plants were sent to the site and mobile generators arrived within 13 hours, but work to connect portable generating equipment to power water pumps was still continuing as of 15:04 on 12 March. Generators are connected through switching equipment in a basement area of the buildings, but this basement area had been flooded.
After subsequent efforts to bring water to the plant, plans shifted to a strategy of building a new power line and re-starting the pumps, eventually resulting in cable emplacement reported at approximately 08:30 UTC.
TEPCO had not anticipated a tsunami as large or a quake as severe as the one that damaged the plant. In addition to concerns from within Japan, the International Atomic Energy Agency (IAEA) had previously expressed concern about the ability of Japan's nuclear plants to withstand seismic activity.
Fukushima I nuclear accidents (福島第一原子力発電所事故 Fukushima Dai-ichi ( pronunciation) genshiryoku hatsudensho jiko ) are a series of ongoing equipment failures and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the 2011 Tōhoku earthquake and tsunami at 14:46 JST on 11 March 2011. The plant comprises six separate boiling water reactors maintained by the Tokyo Electric Power Company (TEPCO). Reactors 4, 5 and 6 had been shut down prior to the earthquake for planned maintenance. The remaining reactors were shut down automatically after the earthquake, but the subsequent 14 metres (46 ft) tsunami flooded the plant, knocking out emergency generators needed to run pumps which cool and control the reactors. The flooding and earthquake damage prevented assistance being brought from elsewhere.
Evidence arose of partial core meltdown in reactors 1, 2, and 3; hydrogen explosions destroyed the upper cladding of the buildings housing reactors 1, 3, and 4; an explosion damaged the containment inside reactor 2; and multiple fires broke out at reactor 4. In addition, spent fuel rods stored in spent fuel pools of units 1–4 began to overheat as water levels in the pools dropped. Fears of radiation leaks led to a 20 kilometres (12 mi) radius evacuation around the plant. Workers at the plant suffered radiation exposure and were temporarily evacuated at various times. On 18 March, Japanese officials designated the magnitude of the danger at reactors 1, 2 and 3 at level 5 on the 7 point International Nuclear Event Scale (INES). Power was restored to parts of the plant from 20 March, but machinery damaged by floods, fires and explosions remained inoperable.
On 25 March, Japan's nuclear regulator announced a likely breach and radiation leak in the containment vessel of the unit 3 reactor, the only one at the plant using MOX fuel. New Scientist reported that measurements taken by the Japanese science ministry and MEXT in areas of northern Japan "far from the Fukushima Daiichi nuclear plant" showed the radioactive caesium fallout levels rival those from the Chernobyl disaster. Previously the publication had reported that world wide measurements of radioactive fallout released from the reactors were "nearing Chernobyl levels". It reported that the preparatory commission of the Comprehensive Test Ban Treaty Organization had measured levels of iodine-131 at 73% and caesium-137 at 60% the levels released from Chernobyl. Food grown in the area was banned. Tokyo officials declared its tap water unsafe for infants for a short time. Plutonium contamination has been detected in the soil at two sites in the plant.
The IAEA announced on 27 March that workers hospitalized as a precaution on 25 March had been exposed to between 2 and 6 Sv of radiation at their ankles when standing in water in unit 3. The international reaction to the accidents was also concerned. The Japanese government and TEPCO have been criticized for poor communication with the public. On 20 March, the Chief Cabinet Secretary Yukio Edano announced that the plant would be closed once the crisis was over. On 30 March 2011, the president of Tepco, Masataka Shimizu, was hospitalised with symptoms of dizziness and high blood pressure in the wake of an increasingly serious outlook for the Fukushima plant and increasingly dangerous levels of radiation leaking from the stricken plant.
On 22 March, the Australian military flew in Bechtel-owned robotic equipment for remote spraying and viewing of the pool. The Australian reported this would give the first clear view of the pool in the "most dangerous" of the reactor buildings.
On 23 March, black smoke billowed from unit 3, prompting another evacuation of workers from the plant, though Tokyo Electric Power Co. officials said there had been no corresponding spike in radiation at the plant. "We don't know the reason for the smoke", Hidehiko Nishiyama of the Nuclear Safety Agency said.
On 23 March, it was reported that low level neutron radiation (reported as "neutron beam") was observed several times. The measured neutron radiation may have originated from leaked uranium or plutonium through nuclear fission.
On 23 March, it was reported that the cooling pump at reactor No 5 stopped working when it was transferred from backup power to the grid supply. This was repaired and the cooling restarted approximately 24 hours later. RHR cooling in unit 6 was switched to the permanent power supply on 25 March.
Possible breachOn 25 March, officials announced the reactor vessel might be breached and leaking radioactive material. High radiation levels from contaminated water prevented work. Japan's Nuclear and Industrial Safety Agency (JNISA) reiterated concerns about a unit 3 breach on 30 March.  NHK World reported the JNISA's concerns as "air may be leaking," very probably through "weakened valves, pipes and openings under the reactors where the control rods are inserted," but that "there is no indication of large cracks or holes in the reactor vessels."
Radioactive material was released from containment on several occasions after the tsunami struck, the result of deliberate venting to reduce gaseous pressure, deliberate discharge of coolant water into the sea, and accidental or uncontrolled events. Using Japanese Nuclear Safety Commission numbers, Asahi Shimbun reported that by 24 March the accident might have emitted 30,000 to 110,000 TBq of iodine-131. On the INES scale, the accident would rate 6 rather than the official level 5, according to the newspaper. The radiation dose rate at one location between reactor units 3 and 4 was measured at 400 mSv/h at 10:22 JST, 13 March, causing experts to urge rapid rotation of emergency crews as a method of limiting exposure to radiation. 1 Sv/h were reported (but not confirmed by the IAEA) close to the leaking reactor units on 16 March, prompting a temporary evacuation of plant workers, with radiation levels subsequently dropping back to 800–600 millisieverts. At times, radiation monitoring was hampered by a belief that some radiation levels may be higher than 1000 mSv/hr, but that "authorities say 1,000 millisieverts is the upper limit of their measuring devices."  The maximum permissible dose for Japanese nuclear workers was increased to 250 mSv/year, for emergency situations after the accidents.
The Japanese Ministry of Health, Labour and Welfare announced that levels of radioactivity exceeding legal limits had been detected in milk produced in the Fukushima area and in certain vegetables in Ibaraki. Measurements made by Japan in a number of locations have shown the presence of radionuclides on the ground. On 23 March, Tokyo drinking water exceeded the safe level for infants, prompting the government to distribute bottled water to families with infants. World wide measurements of wind-born radioactive iodine and caesium vented from reactors suggest that levels have reached around 2/3 those during the Chernobyl disaster, though in that case other radioactive material was also released.
Accident ratingThe severity of a nuclear accident is rated 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. The Chernobyl disaster is the only level 7 accident on record, while the Three Mile Island accident was a level 5 accident.
The Japan Atomic Energy Agency initially rated the situation at Unit 1 below both of these previous accidents; on 13 March it announced it was classifying the event at level 4, an "accident with local consequences". On 18 March it raised its rating on Unit 1 to level 5, an "accident with wider consequences", and also assigned this rating to the accidents at Units 2 and 3. It classified the situation at Unit 4 as a level 3 "serious incident".
The Wall Street Journal reported on 25 March that authorities were considering raising the event to level 6, a "serious accident," one level above the Three Mile Island accident, and second only to Chernobyl. On the same day, Asahi Shimbun supported this upgrading, based on the amount of radioactive contamination.
Several parties have disputed the Japanese classifications, arguing that the situation is more severe than they are admitting. On 14 March, three Russian experts stated that the nuclear accident should be classified at Level 5, perhaps even Level 6. One day later, the French nuclear safety authority ASN said that the Fukushima plant could be classified as a Level 6. As of 18 March 2011, the French nuclear authority—and as of 15 March 2011, the Finnish nuclear safety authority—estimated the accidents at Fukushima to be at Level 6 on the INES. On 24 March, a scientific consultant for Greenpeace, a noted anti-nuclear environmental group, working with data from the Austrian ZAMG and French IRSN, prepared an analysis in which he rated the total Fukushima I accident at INES level 7.
Previous safety lapses
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. In 2002, TEPCO admitted it had falsified safety records at the No. 1 reactor at Fukushima Daiichi. As a result of the scandal and a fuel leak at Fukushima, the company had to shut down all of its 17 nuclear plants to take responsibility.
Close ties between the regulator and power utilitiesIn 2010 Toru Ishida, the former director general of Ministry of Economy, Trade and Industry (METI) of which responsibilities include regulating nuclear industry, left the agency and joined TEPCO a few months later to become a senior adviser. He followed Susumu Shirakawa, another METI veteran who was a board member and executive vice president at TEPCO until retiring in June 2010.
Regulatory capture may have contributed to the cascade 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 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
What Is Regulatory capture?
In economics, regulatory capture occurs when a state regulatory agency created to act in the public interest instead advances the commercial or special interests that dominate the industry or sector it is charged with regulating. Regulatory capture is a form of government failure, as it can act as an encouragement for large firms to produce negative externalities. The agencies are called Captured Agencies.
For public choice theorists, regulatory capture occurs because groups or individuals with a high-stakes interest in the outcome of policy or regulatory decisions can be expected to focus their resources and energies in attempting to gain the policy outcomes they prefer, while members of the public, each with only a tiny individual stake in the outcome, will ignore it altogether. Regulatory capture refers to when this imbalance of focused resources devoted to a particular policy outcome is successful at "capturing" influence with the staff or commission members of the regulatory agency, so that the preferred policy outcomes of the special interest are implemented.
Regulatory capture theory is a core focus of the branch of public choice referred to as the economics of regulation; economists in this specialty are critical of conceptualizations of governmental regulatory intervention as being motivated to protect public good. Often cited articles include Bernstein (1955), Huntington (1952), Laffont & Tirole (1991), and Levine & Forrence (1990). The theory of regulatory capture is associated with Nobel laureate economist George Stigler, one of its main developers.
Likelihood of regulatory capture is a risk to which an agency is exposed by its very nature. This suggests that a regulatory agency should be protected from outside influence as much as possible. Alternatively, it may be better to not create a given agency at all lest the agency become victim, in which case it may serve its regulated subjects rather than those whom the agency was designed to protect. A captured regulatory agency is often worse than no regulation, because it wields the authority of government.