Timeline of events in Japan

The strongest earthquake ever recorded in Japan at a magnitude of 8.9 struck the country on March 11. Below is a timeline of events following the earthquake and tsunami and the effect on nuclear power plants in Japan.


  • The temperature inside of Unit 2 dropped to 210.9 F, the last damaged reactor to fall below the boiling point of 212 F, parent company Tokyo Electric Power Co. (TEPCO) said.
  • On September 7, Unit 1's temperature was 186 F and Unit 3 was 205.5 F.
  • TEPCO said it would not declare the plant for cold shutdown until other criteria are met, but said the plant could be shutdown by the end of the year instead of January 2012 as originally planned.


  • A core spray helped the temperature inside of the reactor vessel of Unit 3 at the Fukushima plant reach 205.5 F, lower than the 212 F necessary for cold shutdown, according to parent company Tokyo Electric Power Co. (TEPCO). Unit 1's temperature is 186 F, while Unit 2 remains the highest at 235.2 F as of September 6.
  • Prior to September 1, Unit 3's core was cooled only by steam rising from a pool of water at the bottom of the reactor vessel.


  • TEPCO reports a quarterly loss of $7.4 billion for cleanup at the Fukushima Daiichi nuclear power plant and compensation of victims from the disaster.
  • The utility said in a statement that it had booked a one-time loss of $6.5 billion in charges associated with the disaster. In May, the company reportedly said it had booked a loss of $16.2 billion for the year through March.
  • TEPCO has reportedly paid out more than $917.3 million in compensation to victims of the crisis from a Parliament-approved fund. The company also said it plans to raise an additional $7.8 billion by cutting costs and selling assets.


  • Japan's parliament approved a plan to help TEPCO compensate victims of the nuclear disaster at the Fukushima plant.
  • The BBC reports that a new fund will be set up to pay damages. The government will give an initial investment of $26 billion, and nuclear power operators around Japan will contribute annually.
  • TEPCO may have to pay more than $100 billion to 80,000 people and business owners affected by the disaster. In return for the government's help, TEPCO must restructure the company and allow the government to take over for an unspecified number of years.


  • TEPCO officials reported their second high reading of radiation at the Fukushima plant in as many days, according to reports.
  • The utility reported a reading of 5 sieverts per hour inside the Unit 1 reactor building. The high readings will keep workers from entering the area.


  • TEPCO officials said radiation levels reached 10 sieverts per hour near a ventilation stack between units 1 and 2 at the Fukushima Daiichi nuclear power plant, according to news reports. The previous record was between 3 to 4 sieverts per hour.
  • TEPCO reportedly said melted fuel in the No. 1 reactor might have collected inside the duct after leaking from the containment vessel during venting early in the crisis. TEPCO also said radiation levels around the plant were not rising, a sign that the duct was not leaking, reports said.


  • TEPCO scrambles to put a makeshift roof over the Unit 3 turbine building in preparation for Typhoon Ma-on, according to news reports. The roof would cover a hole caused by a hydrogen blast back in March.
  • Fears of high waves forced officials to desconnected a hose from a reactor to a barge that contains relatively low-level radioactive water.
  • The storm reportedly had sustained winds of 100 mph with gusts to 120 mph and was moving north-northwest at 12 mph. Flooding conditions are possible and warnings of high surf and strong winds have been issued for areas along the storms projected path.
  •  It was expected to make landfall as a Category 1 or 2 storm near Shikoku, about 173 miles southwest of Daiichi.


  • TEPCO began construction on a temporary airtight structure to cover the exposed roof of Unit 1 at the Fukushima Daiichi plant.
  • The roof is expected to be completed by August and last two or three years, according to news reports. It is made to keep rainwater out and stop some radiation from being carried out, although TEPCO officials said the covering is not radiation-proof.
  • The cover is made of a polyester fabric with a vinyl chloride resin coating supported by a steel frame 154-feet wide and 177-feet tall.
  • Unit 1 was given priority because the roof collapsed into the structure, making it easier for cranes to maneuver around the perimeter, reports said.


  • TEPCO officials suspended a second test run of a water decontamination pump after it stopped working at the Fukushima Daiichi nuclear power plant.
  • The pump stopped about five hours into full operation June 17, according to news reports. Workers said the pump was overburdened by excessive liquid flow and that equipment needed changing more frequently than previously estimated.
  • TEPCO also said that a plant worker was found to have been exposed to radiation above the official limit, bringing the number of over-exposed workers to nine, according to the Kyodo Times.


  • TEPCO said it plans to build a polyester shroud around Unit 1 at the Fukushima Daiichi plant to help limit radiation emissions, according to The Daily Telegraph.
  •  Construction will begin June 27 on the steel frame, a spokesperson was quoted as saying in the article. The entire structure will be put together by remote controlled cranes and other vehicles to minimize exposure to radiation.
  • The cover will stand 177-feet high and 154-feet long with a roof that can be opened to give cranes access to the inside. It will also be fitted with filters that will scrub the air of radioactivity, enabling workers to enter the building.
  • TEPCO will use the operation to test the construction methods and effectiveness of the shroud and, eventually, build shrouds around units 3 and 4 at the plant.
  • Officials said they are not sure how effective the covers will be in limiting radiation emissions but say it will prevent more rainwater from entering the buildings and becoming contaminated.


  • Japan approved a $124 billion plan to help TEPCO compensate tens of thousands of victims, but political maneuvering could delay payments, according to The Guardian.
  • Under the bill, the government would set up a fund and issue special bonds to enable TEPCO to pay compensation for the nuclear disaster at the Fukushima Daiichi plant. Other utilities would be asked to contribute and TEPCO is expected to repay the full sum over an unspecified number of years. In return for state help, TEPCO must cut costs and turn its management over to the government for a period of time.
  • However, some government and opposition groups oppose the use of public funds for the plan, and Japan's Prime Minister Naoto Kan is still under pressure to resign immediately.
  • The current parliamentary session will end on June 22, but the Kan Administration is pushing to extend it in hopes of passing the compensation package, as well as an emergency budget to fund post-tsunami reconstruction.


  • Japan's Nuclear Emergency Response Headquarters said reactors 1, 2 and 3 experienced full meltdowns, according to CNN. An evaluation from the agency goes futher than previous statements describing the extent of the damage following the March 11 earthquake and tsunami.
  • TEPCO officials said May 24th that extra fuel rods in reactors 2 and 3 may have partially melted during the first week of the disaster but did not call it a full meltdown. However, a Japanese nuclear engineer told a panel of U.S. scientists on May 27 that nuclear fuel began melting just hours after the earthquake struck. Staff members of the U.S. Nuclear Regulatory Commission were quoted by Bloomberg as saying that they believed the cores were melting early on in the crisis.


  • TEPCO said wastewater levels at the Fukushima Daiichi nuclear power plant rose 2 in. inside the turbine building of reactor 2 and in its utility tunnel during a 24-hour period through June 2, according to news agency NHK. The water level in the utility tunnel was 11 in. from the surface outside of reactor 2 and 9 in. from the surface outside of reactor 3, NHK said. Water level increases were also seen inside the turbine buildings of reactors 3 and 4.
  • TEPCO said it plans to resume removal of radiation-contaminated water flooding the turbine building of reactor 3 by securing additional outside storage capacity, company officials were quoted by the Kyodo News as saying. TEPCO recently stopped transferring contaminated water from reactors 2 and 3 to a waste-disposal facility after the water reached the facility's capacity. The company also plans to transfer water in a condenser to a temporary storage tank and then fill the condenser with contaminated water.
  • Water temperatures in the spent fuel pool of reactor 2 have reportedly been falling steadily since a water circulation system started to operate May 31. Reactor 2's water temperature, which stood at 153 degrees F May 31 dropped to 108 degrees F June 2, according to the Nuclear and Industrial Safety Agency.


  • The International Atomic Energy Agency (IAEA) reported that Japan underestimated the risk of a tsunami hitting a nuclear power plant, according to the BBC. The response to the nuclear crisis that followed, however, was "exemplary." The IAEA's draft report also said a "hardened" emergency response center was needed to deal with accidents.
  • The inspectors pointed out a key failure, which Japan already admitted to, to plan for the risk of waves crashing over the sea wall. The wall at Fukushima was less than 6m (20 ft.) tall, but the wave that hit the plant was 14m (46 ft.) tall.
  • The report also emphasized the importance of independent regulators in the country's nuclear industry. The Nuclear Safety Agency in Japan is part of the industry ministry, which promotes nuclear power.


  • Workers at the Fukushima Daiichi nuclear power plant reported a small explosion and an oil leak, according to the Guardian newspaper.
  • The explosion may have come from a gas tank near reactor 4 and did not cause any radiation leaks or major damage, the article said.
  • Workers discovered the oil spill in the sea near reactors 5 and 6, which were shut down during the earthquake and tsunami. An oil fence contained the spill, a TEPCO spokesperson was quoted as saying.
  • TEPCO also finished its preliminary compensation payment of 1 million yen ($12,300) for 50,000 households affected by the nuclear crisis.


  • Nuclear fuel at the Fukushima Daiichi nuclear power plant began melting just five hours after the March 11 earthquake, according to the Washington Post.
  • Naoto Sekimura, a Japanese nuclear engineer with the University of Tokyo, reportedly told a committee of the National Academy of Sciences that 11 hours later, all of the uranium in the Unit 1 reactor had slumped to the bottom of its inner containment vessel, boring a hole through the thick steel lining.
  • Independent scientists, along with staff members of the U.S. Nuclear Regulatory Commission (NRC), thought the cores melted early on in the crisis. That drove the NRC to evacuate Americans within 50 miles of the plant, far larger than the 12.5-mile evacuation zone set by the Japanese government.
  • Scientists with the National Cancer Institute said radioactive material from the plant could cause 120 cases of leukemia in Japanese children over the next 10 years.
  • An official with the U.S. Department of Energy said at the meeting that high salt levels could cause protective components at the facility to crack which could cause a "massive failure" of steel in the "lower head" of the containment vessel, the article said. The official also said TEPCO would have to continue pumping water into the damaged reactors and venting radioactive steam for a year or more.


  • TEPCO officials said nearly 60 tons of radioactive water may now be leaking from a wastewater storage facility at the Fukushima Daiichi nuclear power plant, according to ABC News.
  • The leak was discovered while workers were moving contaminated water from units 2 and 3 to an improvised storage facility. The water level in the facility dropped nearly two inches in 20 hours, which suggested a leak.


  • TEPCO has confirmed the meltdown of extra fuel rods in reactors 2 and 3 at the Fukushima Daiichi nuclear power plant, according to the BBC. The announcement came the same day that a team from the United Nations' atomic watchdog, the International Atomic Energy Agency (IAEA), visited Japan.
  • Earlier in May, TEPCO said rods at Unit 1 melted down and it was thought a similar problem had occurred in the other reactors but it was difficult to confirm, the article said.
  • The meltdown in Unit 2 took place 100 hours after the 9.0-magnitude earthquake. Unit 3 melted down about 60 hours after the quake, according to TEPCO officials.
  • TEPCO said it is sticking with its nine-month timetable to stabilize the plant and bring it to a cold shutdown.


  • TEPCO failed to follow correct procedures to prevent a hydrogen explosion in Unit 1 at the Fukushima Daiichi nuclear power plant. According to Japanese state media NHK World, which obtained the emergency manual for Unit 1, TEPCO did not release air from the reactor vessel when the pressure rose to 853 kilopascals - double the operating limit - as instructed.
  • The manual showed that the pressure inside the vessel was close to the level that required a venting operation 3 hours before the explosion occurred. But TEPCO did not start the operation until 6-and-a-half hours before the explosion, and the operation was carried out just one-and-a-half hours before the blast because it was hampered by high-level radioactivity.
  • A former nuclear plant engineer said the utility should have released air when the pressure rose close to twice the operating limit. If the company had done that, the amount of hydrogen leaked from the reactor core to the container vessel would have been smaller, reducing the risk of an explosion, according to NHK World.


  • TEPCO President Masataka Shimizu resigned May 20 as the company faces allegations that it mishandled the ongoing crisis at the Fukushima Daiichi power plant. He will be replaced by TEPCO Managing Director Toshio Nishizawa. Shimzu said he was resigning to take personal responsibility for the criticism, a practice known as kejime.
  • Shimizu's resignation comes as the company reported a $15.3 billion net loss for the fiscal year that ended in March. The loss was due to the nuclear crisis at the plant caused by the earthquake and subsequent tsunami. Officials said the financial loss "raises substantial questions about our ability to continue" operations at the company. TEPCO missed making dividend payments for the first time since the utility was established in 1951.
  • TEPCO said it is scrapping plans to build two new nuclear reactors at the Fukushima plant.


  • Workers with Chubu Electric Power Co. discovered five tons of seawater that appeared to have entered the reactor core of Unit 5 at the Hamaoka nuclear power plant. This follows the discovery of an estimated 400 tons of seawater that flooded the reactor's main steam condenser, according to the Jiji Press.
  • Workers found the water while shutting down the reactor as requested by the government. The utility will not decommission the reactor, but will dilute and desalinate the water to prevent any corrosion by pumping fresh water into the pressure vessel.


  • TEPCO said it dropped initial plans to stabilize the reactors at the Fukushima Daiichi nuclear power plant by flooding them in water after workers discovered a leak in Unit 1, according to Reuters. The company also said it would stick with a plan to safely shutdown the plant within nine months.
  • TEPCO said it would try to cool the reactors by continuously circulating the water already there starting in July, and use new methods that would focus on how to clean up the large amounts of water contaminated by radiation.
  • Uranium fuel rods in reactors 1, 2 and 3 were uncovered for between six and 14 hours after the earthquake, rapidly heated and melted to the bottom of the steel pressure vessel intended to contain the fuel, according to TEPCO. Officials had previously assumed that the suppression chamber in Unit 2 was damaged and now believe Unit 3 has problems.


  • The Japanese government widens evacuations outside of a 20 km (12 mile) government exclusion zone around the Fukushima Daiichi nuclear power plant, according to The China Post.
  • In related news, Chubu Electric Power Co. said all reactors at the Hamaoka nuclear power plant are in a state of cold shutdown, the article said.


  • Fukushima Daiichi reactor No. 1 is leaking water from the center of the reactor, which may delay plans to stabilize the unit, according to Reuters. TEPCO repaired a gauge in the No. 1 reactor when workers noticed water levels dropped 16 feet below targeted levels to cover the fuel under normal operating conditions.
  • "The fuel pellets likely melted and fell, and in the process may have damaged ... the pressure vessel itself and created a hole," Junichi Matsumoto, a general manager at the plant, was quoted as saying.
  • Based on the amount of water remaining, Matsumoto said it is likely that at one point following the earthquake and tsunami, the rods had been entirely exposed to the air.
  • Officials said they will review its timetable for stabilizing the plant on May 17 and that initial progress targets could change, the article said.


  • Japan's Prime Minister Naoto Kan said the country would abandon plans for new nuclear reactors and "start from scratch" in creating a new energy policy, according to The New York Times.
  • Japan currently has 54 reactors and had a plan to build 14 more by 2030 and increase the share of nuclear power in the country's energy mix to 50 percent.
  • PM Kan said Japan would keep nuclear and fossil fuels as energy sources but will add renewable energy and conservation.
  • TEPCO has asked the Japanese government for support in paying compensation for damages caused by the disaster at the Fukushima Daiichi plant, according to the Wall Street Journal. Tepco said it is having fundraising difficulties and will continue restructuring and selling assets.
  • TEPCO may report a net loss of more than 1 trillion yen (US$12.46 billion) for fiscal year 2010 because of the nuclear crisis, according to Reuters. The company estimated the cost of decommossioning at US$7.4bn and it plans to book the amount as an extraordinary loss. The government will provide Tepco with $1.4bn in support under a nuclear accident insurance program.
  • A new body including TEPCO and eight other regional electric companies with nuclear reactors will be formed to support Tepco with loans and, if necessary, buy preferred shares in the company.


  • Chubu Electric Co. agreed to shut down the five reactors at the Hamaoka nuclear power plant southwest of Tokyo after the Japanese government asked Chubu to do so, according to Forbes. Two of the reactors are being decommissioned, one is undergoing inspection and two more are working.
  • Japanese Prime Minister Naoto Kan asked Chubu to shut down the plant until earthquake and tsunami protections can be built, according to CNN.
  • Kan said the plant's location on the Pacific Coast makes it vulnerable and can lead to damage similar to the crisis at the Fukushima Daiichi nuclear power plant.
  • Chubu agreed to build a 40-foot seawall over the next two years.


  • A dozen workers entered the damaged reactor building of Unit 1 at the Fukushima Daiichi power plant for the first time since the March 11 earthquake, according to The New York Times. The workers were trying to install a ventilator to help lower radiation levels inside the reactor building. If the ventilator works as expected, workers should be able to enter the rest of the building within three days to install a new cooling system which was damaged in a hydrogen explosion March 12.
  • TEPCO must install cooling systems at three of the six reactors to stay on its current timetable of stabilizing the plant within six to nine months.


  • Eight workers are scheduled to enter Unit 1 at the Fukushima Daiichi nuclear power plant on Thursday for the first time since a hydrogen explosion damaged the building, according to TEPCO. The workers are part of a plan to cool the reactor by filling the containment vessel with water.
  • Workers must first verify that the water gauge in the pressure vessel and the pressure gauge in the containment vessel are working properly and radiation must be filtered from the air.
  • TEPCO then plans to set up air coolers outside the reactor building to cool the water in the containment vessel before replacing the old cooling system. Once the new system is in place and working as planned, TEPCO said the temperature will drop to under 100 degrees in several days, achieving cold shutdown.


  • Tepco said it detected high levels of radioactive substances in seabed samples gathered April 29 between 9 and 12 miles from the Fukushima Daiichi nuclear power plant, according to The Japan Times. At a location 9 miles north of the plant, 1,400 becquerels/kg of cesium-137 and 1,300 becquerels/kg of cesium-134 were detected, more than 1,000 times higher than what is considered normal. About 190 becquerels/kg of radioactive iodine was also detected.


  • Tepco will not have a limit placed on the amount of compensation paid over the crisis at the Fukushima Daiichi nuclear power plant, according to Reuters.
  • Workers were preparing to install air decontamination equipment in the turbine building of Unit 1 at the power plant. The four purifiers are expected to be ready by Thursday and should remove 95 percent of the radioactive substances in the air of the turbine building.
  • Robots found radiation levels in the pump room of 1,120 millisieverts per hour, indicating a possible leak from the reactor core, according to Tepco.


  • An official at the Korea Electric Power Corp. (KEPCO) told Reuters that the disaster at the Fukushima Daiichi nuclear power plant could set the nuclear power reactor market back two to three years.
  • "Japan's crisis may affect the market in the next two to three years but in a few decades nuclear power demand will rise due to a lack of alternative energy," Byun Jun-yeon, executive vice president and chief nuclear project officer at state-run utility KEPCO, told Reuters in an interview.


  • Hitachi and Mitsubishi Heavy Industries have started discussions on sharing specific roles and defining actual procedures for jointly implementing measures to support recovery efforts at the Fukushima Daiichi nuclear power plant.
  • Immediately following the March 11 earthquake, MHI established as "Emergency Operation Centre," which included provisions of emergency supplies such as radiation shields and conversion work on the Mega-Sloat to be used to store large volumes of contaminated water. MHI also proposed mediaum- and long-term plans that include a contaminated water treatment system, cooling system and measure to enclose the plant buildings.
  • Concurrently, Hitachi established a 24-hour "Emergency Response Center for Nuclear Power," which has dispatched nearly 500 engineers and other workers to the Fukushima site.


  • Tepco says it will cut the total remuneration of its president, chairman and other top executives by half and will cut the annual salary of general employees by 20 percent in order to provide compensation to those affected by the nuclear disaster at the Fukushima Daiichi nuclear power plant. The government will be sharing responsibility for compensation with the utility. As part of a broader restructuring of the company, job cuts and asset sales are also expected.
  • Dai-ichi Mutual Life Insurance Co., Tepco's largest shareholder, said it expects to fall 62 percent short of net profit estimates for the year ended in March because of a roughly $2 billion valuation loss on its share portfolio, including a write down of Tepco Holding by $1.2 billion.
  • Standard & Poor's downgraded three Japanese electric power companies' outlooks from stable to negative. The companies are Chubu Electric, Shikoku Electric and Electric Power Development. The companies either own nuclear power plants that are functioning normally or are building a nuclear power plant.
  • Standard & Poor's said that Japanese power companies "face increased operational and financial risks in building, operating and maintaining nuclear power plants" in light of the nuclear disaster, according to Platts.com.


  • The Japanese government made it illegal to enter a 20 km (12 mile) evacuation zone around the Fukushima Daiichi nuclear power plant. People were urged to leave the area after the earthquake and tsunami hit but the order was not enforced by law.
  • The BBC reports that brief re-entry will be allowed to the area's 80,000 former residents to collect belongings.


  • Tepco accepted a solution from Areva to treat most of the contaminated water from the Fukushima Daiichi nuclear power plant. The solution is based on a co-precipitation concept that uses special chemical reagents to separate and recover the radioactive elements. The treated water could then be reused in the plant's cooling systems.
  • Areva also will be working with Veolia Water to deliver a large-capacity treatment plant equipped with the co-precipitation process to the Daiichi plant.


  • Tepco said it would take up to nine months to bring the six nuclear reactors at the Fukushima Daiichi power plant into cold shutdown, according to the New York Times. The goals are part of a two-part blueprint for controlling the reactors and improving safety conditions at the plant.
  • The first part of the plan is expected to take three months, and would include building a new cooling system and filling the containment vessels of units 1 and 3 with water to stabilize their reactor cores. Tepco then plans to cover three badly damaged reactor buildings and install filters to reduce contamination being released into the air over the next nine months. The company also plans to seal the containment vessel of the No. 2 reactor by filling damaged parts with stucky cement.
  • The government announced that residents who were forced to evacuate near the plant will be able to return in six months after the land is decontaminated.


  • Japan has ordered Tepco to pay compensation to 48,000 families who lived within 18 miles of the Fukushima Daiichi plant. Provisionally, one household will receive 1 million yen (US$12,000).
  • JP Morgan Chase has estimated that Tepco may face claims of up to 2 trillion yen (US$24 billion) by the end of the year.
  • Engineers continue to pump water into three reactors to cool fuel rods.
  • Water must still be removed from the basements of reactors 1,2 and 3 before vital work on the cooling systems can begin.


  • Tepco says reactors at the Fukushima Daiichi nuclear power plant will take at least until June to stabilize, according to Bloomberg. The company said it will soon present a schedule for dealing with the crisis.
  • Engineers at the plant have rejected a proposal to flood reactors at the plant, which could lower the temperature in days instead of months, to avoid increasing the amount of contaminated water that could flow into the ocean. Instead, they are opting to "feed and bleed," a method in which they pump in water and vent off the steam.
  • Decommissioning and clean up of the plant could take decades and cost more than $12 billion.
  • Water levels inside reactor No. 1. the primary danger, dropped Wednesday, leaving 1.65 metres of fuel rods exposed to air, where they can heat up and melt and release radiation into the pressure vessel. Tepco's data shows that pumping efforts have failed to waise the water level more than 20 cm in the 35 days since the crisis started.


  • Because of an ongoing release of radiation from the plant, Japanese authorities notified the International Atomic Energy Agency of their decision to raise the rating of the nuclear crisis from Level 5 to Level 7, the same level as the Chernobyl disaster in 1986. Level 7 ranks as a "major accident."
  • A batch of eight safety-related incidents were recorded on the International Nuclear Event Scale (INES) in the days after the earthquake and tsunami at both the Daiichi and Daiini plants. They include the overall effect on the nuclear plants (Level 3), two losses of cooling function (Level 5), one covering radiological release (Level 5), one on loss of cooling to a fuel pool (Level 3) and three more on loss of reactor cooling (Level 3).
  • EPA's RadNet radiation monitoring program shows there are very small amounts of iodine, cesium and tellurium in air samples in the U.S. The largest amounts were found in Alaska on March 19 and 24, 2011 but they are still below levels of concern
  • Drinking water samples taken at various locations throughout the U.S. during the week of April 4, 2011 ranged from non-detects to 1.6 picocuries per liter of iodine-131. Early precipitation samples indicate low levels of radioactivity, and milk samples taken March 28, 2011 in Phoenix and Los Angeles detected 3 pCi/L of iodine-131, more than 1,500 times lower than the Derived Intervention Level set by the U.S. Food and Drug Administration.


  • The Japanese government said they will widen the evacuation area around the Fukushima Daiichi power plant outside the current 20 km (12 mile) zone within one month, according to AFP.


  • The 7.1-magnitude earthquake that struck off the coast of Japan on April 7 caused water to slosh out of spent fuel pools at the Onagawa nuclear power plant, according to Reuters. Plant owners Tohoku Electric Power Co. said water leaked out of units 1, 2 and 3 at the plant, which had been shut down after the 9.0-magnitude earthquake on March 11. Company officials also said two out of three lines supplying off-site power to the plant were lost Thursday.
  • Cooling operations of spent pool fuels resumed after they stopped due to the quake and there was still an emergency backup generator to fall back on.


  • A 7.1-magnitude aftershock hits 90 miles from Fukushima and 25 miles underwater, triggering new tsunami warnings for waves up to 3 feet. There were no reports of additional damage at the plant.
  • Tepco officials say an operation to reduce the risk of a hydrogen explosion at Fukushima Daiichi's nuclear reactor No. 1 by injecting it with nitrogen has been a success.
  • Workers continue to dump low-level radioactive water into the Pacific Ocean to make room for more highly radioactive water. Officials said most of the water will be released by Thursday and the remaining amount will be discharged by Saturday.


  • Tepco officials said they have plugged a leak that was sending radioactive water into the Pacific Ocean, according to the Associated Press. Workers injected 400 gallons of sodium silicate, or "water glass," into the crack in a maintenance pit to close it.
  • Officials said they will begin injecting nitrogen into the reactors to stem a buildup of hydrogen gas that previously caused several explosions at the plant.


  • Tepco visually confirmed they had slowed the leak of radioactive water from Unit 2, according to Reuters news service. Samples of the water used to cool reactor 2 were shown to be 5 million times the legal limit of radioactivity.
  • The Japanese government says it is considering radioactivity restrictions on seafood. India has banned food imports from anywhere in Japan.


  • Power supply to the temporary electric pumps for water supply to the reactor pressure vessels of units 1, 2 and 3 was switched from the temporary mobile power supply to the off-site power supply.
  • Polymer was poured into a trench where a leak was found near Unit 2.
  • Tepco said it would start releasing 11,500 tonnes of low-level radioactive seawater into the ocean to make room for more highly contaminated water. The process is expected to take 5 days.


  • According to the IAEA, an external power supply is being used to power units 1, 2 and 3 and the pumps at the Fukushima Daiichi nuclear power plant. Some lighting has also been reactivated in the turbine buildings of the three units as well.
  • Tepco said they may have found a leakage path from the turbine building of Unit 2 via a series of tunnels and trenches used to provide power to the sea water intake pumps. Pouring of the concrete ended as there was no visible difference observed. There is a plan to inject polymer in an attempt to stop the leak.
  • Most of the imposed recommendations on drinking water have been lifted.
  • Tepco reported that two employees missing since the earthquake hit on March 11 were found dead in the -1 Level of Unit 4's turbine building.


  • A crack was found in the sidewall of a pit that houses cables near Unit 2 at the Fukushima Daiichi nuclear power plant in Japan. Water has been leaking from the crack directly into the sea. Tepco plans to use concrete to try and fill the crack and stop the leakage.


  • Japan considers widening exclusion zone around the Fukushima Daiichi nuclear power plant after the IAEA found high radiation levels in a village 25 miles away. Levels ranged from 0.2 to 25 megabecquerels per square metre for iodine-131, and from 0.02 to 3.7 megabecquerels per square metre for caesium-137 in soil samples of between 15 and 36 miles away.
  • Recent measurements of radionuclides in tap water are below Japanese emergency limits, according to the IAEA. However, concentrations of several radionuclides remain far beyond normal regulatory limits at measuring posts near the plant discharge canals.


  • Tokyo Electric Power Co. (TEPCO) said the company would decommission reactor units 1-4 at the Fukushima Daiichi nuclear power plant.
  • TEPCO is considering whether to cover the reactor buildings to stem the spread of radioactive substances.


  • Japan's Prime Minister Naoto Kan said the government is on "maximum alert" over the Fukushima Daiichi nuclear power plant.
  • Plutonium has been discovered in soil around the facility and radioactive water has leaked from a reactor building.
  • The government is also considering temporarily nationalizing the Tokyo Electric Power Co.


  • Fatal radiation levels were detected outside of reactor buildings for the first time. Water in an underground trench had levels exceeding 1 sievert an hour, according to a spokesman with TEPCO. A partial meltdown of fuel rods in Unit 2 probably caused a jump in the readings.


  • Work resumes at reactor 3 of the Fukushima Daiichi nuclear power plant after black smoke was seen coming from the reactor. Officials with TEPCO said they were unsure what caused the black smoke and there was no fire. Radiation levels in the vicinity did not rise, officials said.
  • Two workers at reactor 3 were taken to the hospital after being exposed to radiation.


  • Black smoke rising out of Unit 3 halts work at the nuclear power plant. A radiation spike at Unit 2 forces workers to evacuate.
  • Power cables have been connected to all six reactors, and lighting at Unit 3 has been restored. TEPCO says restoring power to all of the reactors could take weeks or even months.
  • Officials said tap water in Tokyo is unfit for babies to drink after radiation was found.


  • Electricity has been restored to three reactors at the Fukushima Daiichi plant. However, the cooling systems are not yet operating.
  • Residents near the plant have been warned not to drink tap water due to higher levels of radioactive iodine.
  • Some workers were evacuated after smoke was seen rising from Unit 3.


  • Authorities raise the alert level at the nuclear power plant to a level 5 on a seven-point international scale of nuclear accidents. The move places the plant two levels below the Chernobyl disaster in Ukraine in 1986. The head of the IAEA said the crisis was a "race against the clock."


  • Engineers laid an external grid power line cable to Unit 2, which will allow cooling pumps to be restarted.


  • Another fire breaks out in Unit 4 at the crippled Fukushima-Daiichi power plant. Power plant workers say Unit 3 is the "priority," but the situation at Unit 4 is "not so good."
  • Water is now being pumped into Units 5 and 6, which indicates that the entire nuclear plant is in danger of overheating.


  • Radiation leaks from Fukushima Daiichi No. 2 after a third explosion at the plant and a fire in a storage pond for used nuclear fuel.
  • About 200,000 people have been evacuated within a 12 mile radius of the plant.
  • A 6.1 magnitude earthquake aftershock shakes the eastern part of Japan, although authorities are reportedly not anticipating significant damage and the risk of another tsunami is low.
  • The International Atomic Energy Agency has said that all units at Fukushima Daini, Onagawa and Tokai nuclear plants are in a "safe and stable" condition.
  • Implementation of rolling blackouts for periods of up to three hours each.


  • TEPCO reports a rise in radiation levels at its Fukushima Daiichi nuclear power plant to government officials.
  • A hydrogen explosion occurred at Unit 3 at 11:01 am local Japan time at the Fukushima Daiichi nuclear power complex and reportedly has not damaged the plant's No. 3 reactor vessel.
  • The International Atomic Energy Agency says Japan reported the hydrogen explosion at the No. 3 reactor at the Fukushima Daiichi nuclear plan did not damage the primary containment vessel.
  • Jiji news agency says Japanese authorities have safely cooled down two nuclear reactors at the 4,400 MW Fukushima Daini nuclear plant. Fukushima Daini houses four boiling water reactors supplied by Toshiba and Hitachi.
  • TEPCO says water levels inside the Fukushima Daiichi complex's No. 2 reactor are almost empty.
  • Cooling systems at Units 1, 2 and 3 of the Fukushima Daiichi plant fail adding concern over a possible meltdown.
  • Restoration work in reactor cooling function that was conducted to achieve reactor cold shutdown has been completed and cooling of the reactor has been commenced at 7:13 am local time, March 14th at Unit 2 at Fukushima Daini Nuclear Power Station, which makes it the third reactor at this plant to cool down.
  • Earthquake upgraded from an 8.9 to a 9.0-magnitude.


  • Risk of an explosion at a building housing the Fukushima Daiichi complex where an explosion March 12 blew the roof off another reactor building.
  • TEPCO begins injecting sea water into the No.1 and No. 3 units at Fukushima Daiichi to cool down the reactors and reduce pressure inside reactor container vessels. TEPCO prepares to pump sea water into the No.2 reactor at its Fukushima Daiichi nuclear power plant.


  • TEPCO begins releasing pressure from the 460 MW No. 1 reactor at Fukushima Daiichi nuclear plant, the Trade Ministry says.
  • Chief Cabinet Secretary Yukio Edano confirms an explosion (apparently hydrogen) and radiation leak at Fukushima Daiichi.
  • TEPCO plans to fill the leaking reactor with sea water to cool it and reduce pressure in the unit


  • The earthquake took place at roughly 2:46 p.m. locally. The epicenter was located about 130 kilometers off the east coast of the island.
  • Eleven reactors shut down in the quake effected area
  • Cooling problem at TEPCO's 4,600 MW Fukushima Daiichi nuclear plant on the northeast coast of Japan. Fukushima Daiichi is a six-reactor plant that uses GE, Hitachi and Toshiba boiling water reactor technology. TEPCO confirms water levels falling inside reactors at the plant and says it is trying to avert the exposure of nuclear fuel rods by restoring power to its emergency power system so that it can pump water inside the reactors.
  • Fire reported at Tohoku Electricity Co.’s 2,100 MW Onagawa nuclear plant, which has since been extinguished. The Onagawa consists of three boiling water reactor units.

We will have continuing updates on the events in Japan at www.Power-Eng.com

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