Friday, 1 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
TEPCO says (
Fukushima Nuclear Plant Time Line 2011) that groundwater near unit 1 contains radioiodine at levels 10,000 times normal, but NISA later disputes the numbers. The Japanese government is reported to be considering injecting nitrogen into the reactor vessels. Two more concrete pumping trucks, used initially to pump cooling water, are shipped to Japan from the Putzmeister factory in Germany.
Saturday, 2 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
TEPCO observes for the first time that contaminated water from the unit 2 is flowing into the sea.Workers discover a crack about 20 cm (8 inches) wide in the maintenance pit, which lies between the reactor 2 and the sea, and holds cables used to power seawater pumps. Workers were preparing to pour concrete into the crack to stop the water, which was emitting radiation at 1 Sv/h.
Sunday, 3 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
The attempt to plug the leak near unit 2 fails when the concrete fails to set. TEPCO then reattempts to plug up the trench that leads to the damaged storage pit with a combination of superabsorbent polymer, sawdust and shredded newspaper, which also fails.[104] Radioactive water continues to leak into the sea. Radiation levels around the plant are estimated at 1 Sv/h and continue to decrease.
TEPCO confirms the first deaths at the Fukushima facility, two workers who had been missing since 11 March and appear to have died in the basement of reactor 4 from bleeding due to multiple injuries inflicted by the tsunami.
Monday, 4 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
TEPCO begins dumping water from storage tanks tainted with low levels of radioactivity into the Pacific Ocean on Monday night. Officials say this is needed to make room in a central waste facility to store water with a higher radioactive level. This more highly radioactive water is preventing workers from making progress on restoring the cooling and other systems to reactors 1–4. Samples of seawater near the plant reveal radioactive caesium at 1.1 million times the legal limit.
Tuesday, 5 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
It is determined that the leak into the cable storage pit from unit 2 was likely due to a faulty joint where the pit meets a duct. The pit leads to a gravel layer beneath, resulting in highly radioactive water pouring directly into the sea. Levels of radioactive iodine-131 in seawater near the facility are found to be 7.5 million times the legal limit. TEPCO drills a hole into the pit near reactor 2, from which highly radioactive water is leaking, and inject water glass (sodium silicate) into the pit to prevent further leaking.
Wednesday, 6 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
TEPCO announces that an injection of 6,000 litres (1,600 USgal) of polymer coagulant into the pit mitigated the leaking; however, the IAEA and others credit additional factors. Sodium silicate ("water glass") and additives are injected into the ground in order to stop the leakage of radioactive water. The residual heat carried by the water used for cooling the damaged reactors accelerates the setting of the injected mixture.
Despite protests from the South Korean government, Russian scientists, and Japanese fishermen, Japan authorizes the release of 11,500 tonnes (12,700 tons) of less radioactive water into the ocean to make room to store the more highly contaminated water.
Thursday, 7 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Nitrogen injection into the pressure containment vessel of unit 1 commences at 01:31. Workers are evacuated following a magnitude 7.1 aftershock off the north-eastern coast of Japan, 118 kilometers from the plant. TEPCO reports communications and power were not affected and no additional damage was observed as a result. A tsunami warning is also issued, but is lifted after 90 minutes. Most of the workers at the nuclear plant were evacuated. Official measures at Fukushima I reactor unit 1, however, show a rise in temperature following the aftershock and a spiking amount of radiation in the Dry Well, which exceeds the instrument maximum of 100 Sv/h.
Friday, 8 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Before the crisis evaluation was elevated by Japanese authorities to level 7, the highest level, experts already recognized that Fukushima is the most complicated nuclear accident ever.
Saturday, 9 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Japan is still struggling to keep water on the reactors to cool them and prevent further meltdown. Russian Antonov An-124 cargo planes fly out of Atlanta and Los Angeles, each carrying a huge concrete boom pump. The two 95-ton boom pumps, which TEPCO purchased for $2million each, can be operated from two miles away by remote control. Each boom pump can direct focused streams of water into the damaged reactors. Currently TEPCO does not plan to take a Chernobyl approach to resolving the nuclear power plant crisis by entombing the radioactive material in concrete. If this decision were to change, the boom pumps could be retrofitted to deliver concrete for that purpose. A survey of radiation in seawater outside unit 2 shows radioactive isotope concentrations (iodine-131, caesium-134 and caesium-137) falling for the third consecutive day since the leak was plugged. However, the levels are still high at several thousand times legal levels.
Monday, 11 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Coolant injection into reactors 1 and 3 is interrupted for 50 minutes due to a loss of power after a strong earthquake. Workers plan to pump water into turbine condensers, but need to pump water out of them first. Work to transfer water from the unit 2 and unit 1 condensers to a central storage tank was completed on 9 and 10 April. Workers have also knocked holes through the turbine hall buildings of units 2 and 4 to accommodate hoses for the water transfer. At unit 3, work continues to make space for water in the turbine condenser by pumping existing water into other tanks. Japanese news wire NHK reports that workers are laying hoses to transfer water to an LLW waste processing facility, which continues to be inspected. TEPCO says that it cannot start work switching on emergency systems on site until the turbine hall is dry. NHK also reported that radioactive water filling a tunnel near unit 2 has risen 12 cm since a leak in a trench was stopped on Wednesday 6 April.
Tuesday, 12 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Japan officially raises Fukushima to INES Level 7, the same as Chernobyl.[166][167] This new rating considers the accidents as a single event and uses estimated total release to the atmosphere as a justification. At Chernobyl, approximately 10 times the amount of radiation was released into the atmosphere as was released from Fukushima I through 12 April 2011.[170] The total amount of radioactive material still stored at Fukushima is about 8 times that stored at Chernobyl, and leakage at Fukushima continues.
Friday, 15 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Nuclear fuel is reported to have melted and fallen to the lower containment sections of reactors 1, 2 and 3. The melted material is not expected to breach a container (which might cause a massive radiation release). Instead, the melted fuel is thought to have dispersed fairly uniformly across the lower portions of the containers of the three reactors, which would make the resumption of the fission process, to the extent of a recriticality accident, 'most unlikely';[173] however, it is only during future dismantling of the three damaged reactors that it would be possible to verify this hypothesis and to know what really occurred inside the reactor cores.
Saturday, 16 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Plans are announced for a large-scale study on the environmental and health effects of radioactive contamination from the nuclear plant. Academics and researchers from across Japan will work with the Fukushima Prefectural Government starting in May.
Monday, 18 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
The Associated Press is reporting that two PackBot ground robots from iRobot have entered unit 1 and unit 3 of the crippled Fukushima nuclear power plant and performed temperature, pressure, and radioactivity measurements. The remote-controlled robots entered the two reactors over the preceding weekend. The devices opened closed doors and explored the insides of the reactor buildings, coming back with radioactivity readings of up to 49 mSv/h inside unit 1 and up to 57 mSv/h inside unit 3. TEPCO officials say that the radiation data from the robots do not change their plans for shutting down the plant by the end of this year. Though more robots will be used a TEPCO official, Takeshi Makigami, says that robots are limited in what they can do and eventually "people must enter the buildings". Robots also entered unit 2, but the probe was hindered by fogging of the robot's camera lens from the high humidity, over 90%, inside the building.
Tuesday, 19 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
TEPCO begins transferring excess radioactive cooling water from the reactor 2's basement and maintenance tunnels to a waste processing facility. Operations to pump radioactive water in the basements of buildings of units 1, 2, 3 and their associated tunnels start with unit 2.
Friday, 22 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Japanese Prime Minister Naoto Kan states additional towns might be asked to evacuate, which largely involves agricultural lands. The government also plans to build 30,000 temporary homes by the end of May, and an additional 70,000 will follow. The president of the Tokyo Electric Power Company (TEPCO), Masataka Shimizu, formally apologizes at the prefectural government office in Fukushima to the Fukushima Governor Yuhei Sato for the nuclear crisis following the 11 March 2011 earthquake and tsunamis. In response, the Governor requests better working conditions for the workers.
Tuesday, 26 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
To prevent the proliferation of dust, TEPCO initiates spraying a synthetic resin to contain contaminated dust.
Wednesday, 27 April- 2011-Timeline of the Fukushima Daiichi Nuclear Disaster
Junichi Matsumoto, a general manager at Tokyo Electric Power Co., reports that radiation readings taken by two iRobot PackBot robots inside the reactor 1 building are as high as 1120 mSv/h, the highest level disclosed to date.
