Open main menu

Wikipedia β

Fukushima disaster cleanup

The Fukushima disaster cleanup is an ongoing attempt to limit radioactive contamination from the three nuclear reactors involved in the Fukushima Daiichi nuclear disaster which followed the earthquake and tsunami on 11 March 2011. The affected reactors were adjacent to one another and accident management was made much more difficult because of the number of simultaneous hazards concentrated in a small area. Failure of emergency power following the tsunami resulted in loss of coolant from each reactor, hydrogen explosions damaging the reactor buildings, and water draining from open-air spent fuel pools. 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.

Automated cooling systems were installed within 3 months from the accident. A fabric cover was built to protect the buildings from storms and heavy rainfall. New detectors were installed at the plant to track emissions of xenon gas. Filters were installed to reduce contaminants from escaping the area of the plant into the area or atmosphere. Cement has been laid near to the seabed to control contaminants from accidentally entering the ocean.

No strontium was released into the area from the accident;[1][needs update] however, in September 2013 it was reported that the level of strontium-90 detected in a drainage ditch located near a water storage tank from which around 300 tons of water was found to have leaked was believed to have exceeded the threshold set by the government.[2]

Decommissioning the plant is evaluated to cost tens of billions of dollars and last 30–40 years.[3][4] Initial fears that contamination of the soil was deep have been reduced with the knowledge that current crops are safe for human consumption and the contamination of the soil was not serious;[5] however, in July and August 2013, it was discovered that radioactive groundwater has been leaking into the sea.[clarification needed]

Contents

OverviewEdit

At the time of the initial event, 50 TEPCO employees remained onsite in the immediate aftermath to work to stabilize the plant and begin cleanup.[6]

Initially, TEPCO did not put forward a strategy to regain control of the situation in the reactors. Helmut Hirsch, a German physicist and nuclear expert, said "they are improvising with tools that were not intended for this type of situation".[7] However, on 17 April 2011, TEPCO appeared to put forward the broad basis of a plan which included: (1) reaching "cold shutdown in about six to nine months;" (2) "restoring stable cooling to the reactors and spent fuel pools in about three months;" (3) putting "special covers" on Units 1, 3, and 4 starting in June;(4) installing "additional storage containers for the radioactive water that has been pooling in the turbine basements and outside trenches;"[8] (5) using radio-controlled equipment to clean up the site;[8] and (6) using silt fences to limit ocean contamination.[8] Previously, TEPCO publicly committed to installing new emergency generators 20 m above sea level, twice the height of the generators destroyed by the 11 March tsunami.[9] Toshiba and Hitachi had both proposed plans for shuttering the facility.[10]

Cold shutdown was accomplished on December 11, 2011. From that point cooling was no longer required, but maintenance was still required to control large water leaks.[11][12] Long term plans for Units 5 and 6 have not been announced, "but they too may need to be decommissioned".[13]

On 5 May 2011, workers were able to enter reactor buildings for the first time since the accident.[14] The workers began to install air filtration systems to clean air of radioactive materials to allow additional workers to install water cooling systems.[14]

Scope of cleanupEdit

Japanese reactor maker Toshiba said it could decommission the earthquake-damaged Fukushima nuclear power plant in about 10 years, a third quicker than the American Three Mile Island plant.[15] As a comparison, at Three Mile Island the vessel of the partially melted core was first opened 11 years after the accident, with cleanup activities taking several more years.

TEPCO announced it restored the automated cooling systems in the damaged reactors in about three months, and had the reactors put into cold shutdown status in six months.[16]

First estimates included costs as high as ¥1 trillion (US$13 billion), as cited by the Japanese Prime Minister at the time, Yoshihiko Noda (野田 佳彦). However, this estimate was made before the scope of the problem was known. It seems that the contamination was less than feared. No strontium is detectable in the soil,[1] and though the crops of the year of the disaster were contaminated, the crops produced by the area now are safe for human consumption.[5]

Japan's economy, trade, and industry ministry recently (as of 2016) estimated the total cost of dealing with the Fukushima disaster at ¥21.5 trillion (US$187 billion), more than twice the previous estimate of ¥11 trillion (US$96 billion). A rise in compensation for victims of the disaster from ¥5.4 trillion (US$47 billion) to ¥7.9 trillion (US$69 billion) was expected, with decontamination costs estimated to rise from ¥2.5 trillion (US$22 billion) to ¥4 trillion (US$35 billion), costs for interim storage of radioactive material to increase from ¥1.1 trillion (US$10 billion) to ¥1.6 trillion (US$14 billion), and costs of decomissioning reactors to increase from ¥2 trillion (US$17 billion) to ¥8 trillion (US$69 billion).[17]

Working conditions at the plantEdit

There has been concern that the plant would be dangerous for workers. Two workers suffered skin burns from radiation, but no serious injuries or fatalities have been documented to have been caused by radiation at Fukushima Dai-ichi.

Unskilled workforce systematically employed on Japanese nuclear power plantsEdit

The disaster in Fukushima has revealed the practice of Japanese nuclear power plants systematically using unskilled laborers with short contracts. These people are paid per day, and are hired per day from questionable agencies and firms. From data provided by NISA, it was concluded that 80 percent of all of the workforce hired in commercial nuclear power plants is done using temporary contracts, In Fukushima this number was even higher, at 89 percent. This had been practiced for decades. Unemployed people gathered in parks in the morning, and were picked up to be taken to the nuclear power plants. They would get a contract for a few months to do unskilled and the most dangerous labor. After the work was finished, these people were supposed to disappear.[18]

Workers in dorms exposed to radiationEdit

Two shelters for people working at the Fukushima-site were not listed as part of the radiation management zones although radiation levels in the shelters exceeded the legal limits. The consequence was, that the workers did not get paid the extra "danger allowance" that was paid to workers in these "radiation management zones". The shelters were constructed by Toshiba Corporation and the Kajima Corporation at a place some 2 kilometers west of the damaged reactors, just outside the plant compound, but quite near to the reactors 1 to 4. The shelters were built after the shelters at the plant-compound became overcrowded. At 7 October 2011 radiation levels in the Toshiba building were between 2 and 16 microsieverts per hour, in the Kajima dorm it was 2 to 8.5 microsieverts per hour. The Industrial Safety and Health Law on the prevention of health damage through ionizing radiation had set the limit for accumulated radiation dosage in radiation management zones at 1.3 millisieverts over three months, so the maximum level is 2.6 microsieverts/hour. In both dorms the radiation levels were higher. However, these doses are well below the level to affect human health. According to the law, the "business operator" is responsible for "managing radiation dosage and the prevention of contamination", Toshiba and Kajima said that TEPCO was responsible. But a TEPCO official made the comment: "From the perspective of protecting workers from radiation, the business operators (that constructed the shelters) are managing radiation dosage and the prevention of contamination" in this way suggesting that Toshiba and Kajima had to take the care for the zone management.[19]

Preventing hydrogen explosionsEdit

On 26 September 2011, after the discovery of hydrogen in a pipe leading to the containment vessel of reactor no.1, NISA instructed TEPCO to check whether hydrogen was building up in reactor no. 2 and 3 as well. TEPCO announced that measurements of hydrogen would be done in reactor no. 1, before any nitrogen was injected to prevent explosions. When hydrogen would be detected at the other reactors, nitrogen injections would follow.[20]

After the discovery of hydrogen concentrations between 61 and 63 percent in pipes of the containment of reactor no. 1, nitrogen injections were started on 8 October. On 10 October TEPCO announced, that the concentrations were at that moment low enough to prevent explosions, and even if the concentration would rise again, it would not exceed 4 percent, the lowest level that would pose the risk of an explosion. On the evening of 9 October two holes were drilled into the pipe to install a filter for radioactive substances inside the containment vessel, this was 2 weeks behind the schedule TEPCO had set for itself. This filter should be in operation as soon as possible.[21]

Investigations inside the reactorsEdit

On 19 January 2012 the interior of the primary containment vessel of reactor 2 was inspected with an industrial endoscope. This device, 8.5 millimeters in diameter, is equipped with a 360 degrees-view camera and a thermometer to measure the temperature at this spot and the cooling-water inside, in an attempt to calibrate the existing temperature-measurements that could have an error-margin of 20 degrees. The device was brought in by a hole at 2.5 meter above the floor where the vessel is located. The whole procedure lasted 70 minutes.[22] The photos showed parts of the walls and pipes inside the containment vessel. But they were unclear and blurred, most likely due to water vapors and the radiation inside. According to TEPCO the photos showed no serious damage. The temperature measured inside was 44.7 degrees Celsius, and did not differ much from the 42.6 degrees measured outside the vessel.[23][24]

Inspections of the suppression chambers reactor no. 2 and 3Edit

On 14 March 2012 for the first time after the accidents six workers were sent into the basements of reactor no. 2 and 3, to examine the suppression chambers. Behind the door of suppression chamber in the no.2 building 160 millisieverts/hour was measured. The door to the suppression chamber in the no. 3 reactor building was damaged and could not be opened. In front of this door the radiation level measurement was 75 millisieverts/hour. For reactors to be decommissioned, access to the suppression chambers is vital for conducting repairs to the containment structures. Because the high levels of radiation, according to TEPCO this work should be done with robots, because these places could be hostile to humans. TEPCO released some video footage of the work at the suppression chambers of the No. 2 and 3 reactors.[25][26]

On 26 and 27 March 2012 the inside of the containment vessel of reactor 2 was inspected with a 20 meter long endoscope. With this a dosi-meter was brought into the vessel to measure the radiation levels inside. At the bottom of the primary containment structure, 60 centimeters of water was found, instead of the 3 meters expected at that place. The radiation level measured was 72.9 Sievert per hour. Because of this, the endoscope could only function a few hours at this place. For reactors number 1 and 3, no endoscopic survey was planned at that time, because the actual radiation levels at these places were too high for humans.[25][dead link][26][27]

Management of contaminated waterEdit

Continued cooling of the melted reactor cores is required in order to remove excess heat. Due to damage to the integrity of the reactor vessels, radioactive water accumulated inside the reactor and turbine buildings. To decontaminate the contaminated water, TEPCO installed radioactive water treatment systems.[28]

The Japanese government had initially requested the assistance of the Russian floating water decontamination plant Landysh to process the radioactive water from the damaged reactors, but negotiations with the Russian government were a extremely slow process and it is unclear if the plant was ever sent to Fukushima. Landysh was built by Russia with funding from Japan to process liquid wastes produced during the decommissioning of nuclear submarines.[29]

As of early September 2011 the operating rate of the filtering system exceeded the target of 90 percent for the first time. 85,000 tons of water were decontaminated by September 11, with over 100,000 tons of waste-water remaining to be treated at the time. However, the nuclear waste generated by the filters had already filled almost 70 percent of the 800 cubic meters of storage space available at the time. TEPCO had to figure out how to cool the reactors with less than 15 tons of water per day in order to reduce the growth of waste-water and nuclear waste to more manageable levels.[30]

Installation of circulating water cooling systemEdit

 
Side view of the Fukushima trenches and tunnels. 1: Reactor building, 2: Turbine generator and associated condenser.

In order to remove decay heat of the severe damaged cores of Unit 1-3, TEPCO injected cooling water into the reactors. As the reactors appear to have holes around the bottom, the water dissolved the water-soluble fission products, which then accumulated in the basement of the turbine building (the adjacent diagram #2) through any leaks from the water-injected reactor buildings (#1). Since the accumulated radioactive water was a risk, TEPCO tried to transfer it.

 
Assembly of hose fittings for Fukushima complex, Yokota AB

As the accumulated water in the basement (see the tunnel below diagram #2) of the turbine building of Units 2 and 3 was radioactive, TEPCO needed to remove it. They had initially planned to pump the water to the condenser (the large black vessel in diagram #1).[31][32] However, TEPCO had to abandon that plan after discovering that the condensers on both units were already full of water.[33] Pumps capable of processing 10–25 tons of water per hour were used to transfer condenser water into other storage tanks, freeing up condenser storage for the water in the basements. However, since both the storage tanks and the condensers were nearly full, TEPCO also considered using floating tankers ships as a temporary storage location for the radioactive water.[34][35] Regardless of the availability of offshore storage for radioactive-contaminated water, TEPCO decided to discharge 11,500 tons of its least contaminated water (with was still approximately 100 times the legal limit for radioactivity) to the sea on April 5 in order to free up storage space.[36][37][38] At the same time, on 5 April, TEPCO began pumping water from the condensers of units 1–3 to their respective condensation storage tanks to free room for the trench water (see below).[38]

 
Leakage route of radioactive water through a gravel layer.
1: Reactor building, 2: Turbine building, 3: Injection of sodium silicate.

Removal of accumulated water in seawater piping trenchEdit

The Fukushima Daiichi NPS has several seawater piping trenches which were originally designed to house pipes and cables running from the Unit 2–4 turbine buildings to their seaside, which doesn't directly connect to the sea. Inside the trench, radioactive contaminated water has been accumulating since the accident. Due to the risk of soil or ocean contamination from these trenches, TEPCO has been trying to remove the accumulated water in the trenches by pumping it back into the turbine buildings, as well as backfilling the trenches to reduce or prevent further incursion of contaminated water.[39]

Groundwater contaminationEdit

On 5 July 2013, TEPCO found 9 kBq/L of 134Cs and 18 kBq/L of 137Cs in a sample taken from a monitoring well close to the coastline. Compared with samples taken three days earlier, the levels were 90 times higher. The cause was unknown. The monitoring well is situated close to another monitoring well that had previously leaked radioactive water into the sea in April 2011. A sample of groundwater from another well situated about 100 meters south of the first well showed that the radioactivity had risen by 18 times over the course of 4 days, with 1.7 kBq/L of strontium and other radioactive substances.[40] A day later the readings in the first well were 11 kBq/L of 134Cs and 22 kBq/L of 137Cs, 111 times and 105 times greater than the samples of 5 July. TEPCO did not know the reasons for the higher readings, but the monitoring was to be intensified.[41]

More than a month after the groundwater contamination was discovered, TEPCO started to contain the radioactive groundwater. They assumed that the radioactivity had escaped early in the beginning of the disaster in 2011, but NRA experts[who?] had serious doubts about their assumption. According to them, other sources could not be excluded. Numerous pipes were running everywhere on the reactor grounds to cool the reactors and decontaminate the water used, and leaks could be anywhere. TEPCO's solution resulted in redirection of the groundwater flows, which could have spread the radioactive contamination further. Besides that, TEPCO had plans for pumping groundwater.[further explanation needed] At that time the turbine buildings of units 2 and 3 contained 5000 and 6000 cubic meters of radioactive water. With wells in contact with the turbine-buildings, this could spread the radioactivity into the ground. The NRA announced that it would form a task force to find the leaks and to block the flow of the groundwater to the coastline, because the NRA suspected that the groundwater was leaking into the sea.[42][43][44]

Tritiated water treatmentEdit

In January 2014 it was made public that a total of 875 terabecquerel (TBq) of tritium is on the site of Fukushima Daiichi; it would take 59 years to safely discharge this amount of tritium to the sea. According to data that TEPCO submitted to the tritium task force (of the Ministry of Economy, Trade and Industry), the 400,000 tonnes of contaminated water stored in tanks at the site contained a total of about 817 TBq of tritium. A further 58 TBq of tritium was contained in water outside of the tanks, e.g. in reactor buildings.[45] According to further data submitted by TEPCO, the amount of tritium concentration water is increasing by approximately 230 TBq per year.[46] This followed a report made public in December 2013 that "Tritium could be separated theoretically, but there is no practical separation technology on an industrial scale."[47][dubious ]

Timeline of contaminated water treatmentEdit

2011
On March 27
TEPCO announced that radioactive water had accumulated in the basement of the Unit 2 turbine building.[48]
On March 28
The Japanese Nuclear Safety Commission advised TEPCO to take all possible measures to avoid the accumulated water in the Unit 2 turbine building leaking into the ground and the sea.[49](hereinafter called "the JNSC advice")
On April 2
TEPCO announced the outflow of fluid containing radioactive materials to the ocean from areas near the intake channel of Unit 2.[50] The fluid source was a 20 cm crack on the concrete lateral of the pit which appeared to have been created by the earthquake. TEPCO attempted to inject fresh concrete, polymeric water absorbent, sawdust, and shredded newspapers into the crack; however, this approach failed to slow the leak. After an investigation of the water flow, TEPCO began to inject sodium silicate on April 5th, and the outflow was stopped on April 6th.[51] The total amount and radioactivity of the outflow from the crack was estimated to be approximately 520 m3 and approximately 4.7 PBq respectively.[52]
On April 17
TEPCO announced the Roadmap towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station.[53]
On April 27
In order to prevent the outflow of the highly radioactive water at the turbine building of Unit 2, the water was transferred to the Centralized Radiation Waste Treatment Facility since April 19th. TEPCO planned to install facilities for processing the stored water and reusing treated water to inject it into the reactors.[54]
On May 11
TEPCO investigated possible leakage of radioactive water to the outside from around the intake canal of Unit 3 in response to the employees' report of water flowing into the pit via power cable pipe lines.[55]
On May 23
Nuclear and Industrial Safety Agency began to use the term "Contaminated Water" as the water with high concentration of radioactive materials.[56]
On June 17
TEPCO began the operation of the cesium adsorption apparatus (Kurion) and the decontamination apparatus (AREVA).[57]
On August 17
TEPCO began the (test) operation of SARRY, which is the second cesium adsorption apparatus (TOSHIBA).[58]
On August 28
2 TEPCO workers at the plant were exposed to radiation by mistake while they were replacing parts of the contaminated water processing system. The next Wednesday 31 August two other workers were sprayed with highly contaminated water when the water splashed from a container with a leaking valve that did not close. It was found that they were exposed to 0.16 and .14 millisieverts. The last man wore a raincoat. No immediate symptoms were found.[59]
On December 21
TEPCO announced Mid-and-long-Term Roadmap towards the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4.[60]
2012
On April 5
A leaking pipe was found at 1.00 AM. The leakage stopped an hour after the valves were closed. 12,000 liters water with high levels of radioactive strontium were lost, according to TEPCO much of this water escaped through a nearby sewer-system into the ocean. Investigations should reveal how much water was lost into the ocean, and how the joint could fail. A similar leakage in at the same facility happened on 26 March 2012.[61]
On September 19
Nuclear Regulation Authority (NRA) was established.[62]
2013 (The year to the social problem)
On March 30
TEPCO began the operation of ALPS, which is the multi-nuclide removal equipment.[63]
On July 22[64]
With announcing the situation on seawater and groundwater,[65] TEPCO admitted that contaminated groundwater had been leaking into the ocean since March 2011.[66]
On July 27
TEPCO announced that extremely high levels of tritium and cesium were found in a pit containing about 5000 cubic meters water on the sea side of the Unit 2 reactor building. 8.7 MBq/liter of tritium and 2.35 GBq/liter of cesium was measured. The NRA was concerned that leaks from the pit could release high tritium levels into the sea and that there was still water flowing from the reactor into the turbine building and into the pit. However, TEPCO believed that this pollution was there from the first days in 2011, and had stayed there. Nevertheless, TEPCO would control the site for leaks, and seal the soil around the pit.[67]
On May 30
The Government of Japan decided the policy to prevent the groundwater flowing in the reactor buildings.[68] A frozen soil wall (Land-side Impermeable Wall) was scheduled for introduction to block the flow of groundwater and prevent its mixing with contaminated water.[69]
On August 19
Contaminated water leakage from a flange type tank was found in the H4 area.[70] The incident was finally evaluated by the NRA as a provisional rating Level 3 on the eight-level INES.[71] In response to this incident, NRA recommended that TEPCO should replace the flange type tank, which is prone to leak water, with a welded type tank.[72]
On August 28
A subcontractor employee was contaminated on his face, head and chest while transferring water from the damaged tank. After decontamination, 5,000 cpm were still measured on his head; the readings from prior to decontamination were not released. The man was released, but ordered to have a whole-body radiation count later.[73][74]
On September 2
It was reported that radiation near another tank was measured at 1.8 Sv/h, 18 times higher than previously thought. TEPCO had initially recorded radiation at about 100 mSv/h, but later admitted that that was because the equipment they were using could only read measurements up to that level. The latest reading came from a more advanced device capable of measuring higher levels. The buildup of water at the site is close to becoming unmanageable and experts say that TEPCO will soon be left with no choice but to release the water into the ocean or evaporate it.[3]
On September 3
The Nuclear Emergency Response Headquarters published "the Government’s Decision on Addressing the Contaminated Water Issue at TEPCO’s Fukushima Daiichi NPS".[75]
On September 9
TEPCO started cleaning the draining ditch at the north side of the leaking tank one day before Tokyo was selected as host of the 2020 Olympic Games. Radiation monitoring data were masked after that day for some time.[76][unreliable source?]
On September 12
Contaminated water leakage from storage tanks was found in the H4 area.[77]

Radioactive wasteEdit

Cooling the reactors with recirculated and decontaminated water from the basements proved to be a success, but as a consequence, this radioactive waste was piling up in the temporary storage facility at the plant. TEPCO decided in the first week of October to use the "Sally" decontamination system built by Toshiba Corporation and keep the Kurion/Areva system as back-up.

On 27 September after three months operation some 4,700 drums with radioactive waste had piled up at the plant. The Kurion and Sally systems both utilized zeolites to concentrate cesium. After the zeolite was saturated, the vessels with the zeolite were turned into nuclear waste. By now, 210 Kurion-made vessels with a total of 307 cubic meters, each vessel measuring 0.9 meters in diameter and 2.3 meters in height had accumulated at the plant. The Areva-filters used sand to absorb radioactive materials and chemicals were used to reactivate the filters. In this way, 581 cubic meters of highly contaminated sludge were produced.

According to Professor Akio Koyama of the Kyoto University Research Reactor Institute, the density of high-level decontaminated water was believed to contain 10 gigabecquerel per liter, but if this is condensed to polluted sludge and zeolites, this density could increase 10,000 fold. These densities could not be dealt using conventional systems.[78]

Spent fuel poolsEdit

On August 16, 2011, TEPCO announced the installation of desalination equipment in the spent fuel pools of reactor 2, 3 and 4. These pools had been cooled with seawater for some time, and TEPCO feared the salt would corrode the stainless steel pipes and pool wall liners. The Unit 4 spent fuel pool was the first to have the equipment installed, the spent fuel pools of reactor 2 and 3 came next. TEPCO expected to achieve removal of 96% of the salt in the spent fuel pools within two months.[79]

Unit 4 spent fuel removalEdit

On December 22, 2014, TEPCO crews completed the removal of all fuel assemblies from the spent fuel pool of reactor 4. 1331 spent fuel assemblies were moved to the ground-level common spent fuel pool, and 204 unused fuel assemblies were moved to the spent fuel pool of reactor 6 (Unit 4 was out of service for refueling at the time of the 2011 accident, so the spent fuel pool contained a number of unused new fuel assemblies).[80]

Debris removalEdit

On 10 April 2011, TEPCO began using remote-controlled, unmanned heavy equipment to remove debris from around reactors 1–4. The debris and rubble, caused by hydrogen explosions at reactors 1 and 3, was impeding recovery operations both by being in the way and emitting high radioactivity. The debris will be placed into containers and kept at the plant.[81]

Proposed building protectionsEdit

Because the monsoon season begins in June in Japan, it became urgent to protect the damaged reactor buildings from storms, typhoons and heavy rainfall. As a short term solution, TEPCO envisaged to apply a light cover on the remaining structures above the damaged reactors. As of mid-June, TEPCO released its plan to use automated cranes to move structures into place over the reactor. This strategy is an attempt to keep as many people away from the reactors as possible, while still covering the damaged reactors.[82]

Proposed SarcophagusEdit

On 18 March, Reuters reported[83] that Hidehiko Nishiyama, Japan's nuclear agency spokesman when asked about burying the reactors in sand and concrete, said: "That solution is in the back of our minds, but we are focused on cooling the reactors down." Considered a last-ditch effort since it would not provide cooling, such a plan would require massive reinforcement under the floor, as for the Chernobyl Nuclear Power Plant sarcophagus.[84]

Scrapping reactor Daiichi 1, 2, 3, 4Edit

On 7 September 2011, TEPCO president Toshio Nishizawa said that the 4 damaged reactors will be scrapped. This announcement came at a session of the Fukushima Prefectural Assembly, which was investigating the accident at the plant. Whether the six other remaining reactors, (Daiichi 5, 6, Daini 1, 2, 3, 4) should be abolished too, would be decided based on the opinions of local municipalities.[85]


On 28 October 2011, the Japanese Atomic Energy Commission presented a timetable in a draft report titled, “how to scrap the Fukushima reactors”. Within 10 years, a start should be made with the retrieval of the melted fuel within the reactors. First, the containment vessels of reactors 1, 2 and 3 should be repaired, then all should be filled with water to prevent radiation releases. Decommissioning would take more than 30 years, because the pressure vessels of the reactor vessels are damaged also. After the accident at Three Mile Island in 1979, some 70 percent of the fuel rods had melted. There, the retrieval of the fuel was started in 1985, and completed in 1990. The work at Fukushima was expected to take significantly longer because of the far greater damage and the fact that 4 reactors would need to be decommissioned all at the same time.[86][87]

After discussions were started in August 2011, on 9 November, a panel of experts of Japan's Atomic Energy Commission completed a schedule for scrapping the damaged reactors - their conclusions were;

  • The scrapping will take 30 years or longer.
  • First, the containment vessels needed to be repaired, then filled with water to block radiation.
  • The reactors should be in a state of stable cold shutdown.
  • Three years later, a start would be made to take all spent fuel from the 4 damaged reactors to a pool within the compound.
  • Within 10 years, the removal of the melted fuel inside the reactors could begin.

This scheme was partly based on the experience gained from the 1979 Three Mile Island accident. However, in Fukushima with three meltdowns at one site, the damage was much more extensive. It could take 30 years or more to remove the nuclear fuel, dismantle the reactors, and remove all the buildings. Research institutions all over the world were asked to participate in the construction of a research-site to examine the removal of fuel and other nuclear wastes. The official publication of the report was planned at the end of 2011.[88][89]

Protection systems installedEdit

Since the disaster, TEPCO has installed sensors, a fabric cover over the reactors and additional filters to reduce the emission of contaminants.

Sensors for xenon and temperature changes to detect critical reactionsEdit

After the detection of radioactive xenon gas in the containment vessel of the No. 2 reactor on 1 and 2 November 2011 TEPCO was not able to determine whether this was a sustained fission process or only spontaneous fission. Therefore TEPCO installed detection devices for radioactive xenon to single out any occurrence of nuclear criticality. Next to this TEPCO installed temperature sensors to control temperature changes in the reactors, another indicator of possible critical fission reactions.[88][90]

New filtersEdit

On 20 September the Japanese government and TEPCO announced the installation of new filters to reduce the amount of radioactive substances released into the air. In the last week of September 2011 these filters were to be installed at reactor 1, 2 and 3. Gases out of the reactors would be decontaminated before they would be released into the air. Mid October the construction of the polyester shield over the No.1 reactor should be completed. In the first half of September the amount of radioactive substances released from the plant was about 200 megabecquerel per hour, according to TEPCO, that was about one-four millionths of the level of the initial stages of the accident in March.[91]

Fabric cover over Unit 1Edit

An effort has been undertaken to fit the three damaged reactor buildings with fabric covers and filters to limit radioactive contamination release.[92] On 6 April 2011, sources told Kyodo News that a major construction firm was studying the idea, and that construction wouldn't "start until June". The plan has been criticized for potential only having "limited effects in blocking the release of radioactive substances into the environment".[93] On 14 May, TEPCO announced that it had begun to clear debris to create a space to install a cover over the building of reactor 1.[94] In June, a large crane was erected near Reactor 1 to begin construction of the fabric cover. From mid August to mid September 2011, a rectangular steel frame entirely surrounding the reactor building was constructed. Starting 9 September, the crane was used to attach polyester panels to the frame. On 20 September 2011, TEPCO announced that within three weeks they hoped to complete the construction of the polyester shield over the No.1 reactor. By that time the steel frame for the fabric cover had been completed. By 7 October, the roof of the structure was being added. On 9 October, the walls of the cover appeared to be placed, and by 13 October the roof had been completed.[91][95][96]

Metal cover over Unit 3Edit

In June 2016, preparation work began to install a metal cover over the Unit 3 reactor building. In conjunction with this, a crane is to be installed to assist with the removal of the fuel rods from the storage pool. After inspection and cleaning, the removed fuel is expected to be stored in the site's communal storage facility.[97]

Cleanup of neighboring areasEdit

Significant efforts are being taken to clean up radioactive material that escaped the plant. This effort combines washing down buildings and scraping away topsoil. It has been hampered by the volume of material to be removed and the lack of adequate storage facilities.[98]

There is also a concern that washing surfaces will merely move the radioactive material without eliminating it.[99]

After an earlier decontamination-plan only to clean all areas with radiation levels above 5 millisievert per year, had raised protests, the Japanese government revealed, on 10 October 2011, in a meeting with experts, a revised decontamination plan. This plan included:

  • all areas with radiation levels above 1 millisievert per year would be cleaned.
  • no-entry zones and evacuation zones designated by the government would be the responsibility of the government.
  • the rest of the areas would be cleaned by local authorities.
  • in areas with radiation levels above 20 millisievert per year, decontamination would be done step by step.
  • within two years, radiation levels between 5 and 20 millisieverts should be cut down to 60%.
  • the Japanese government would help local authorities with disposing the enormous amount of radioactive waste.[100]

On 19 December 2011 the Japanese Ministry of Environment published more details about these plans for decontamination: the work would be subsidized in 102 villages and towns. Opposition against the plan came from cattle-farmers in the prefecture Iwate and the tourist-industry in the city of Aizuwakamatsu, because of fears that cattle sales might drop or tourism would be hurt to the town, when the areas would be labeled to be contaminated. Areas with lower readings complained that their decontamination would not be funded.[101]

In a Reuters story from August 2013, it was noted "[m]any have given up hope of ever returning to live in the shadow of the Fukushima nuclear plant. A survey in June showed that a third of the former residents of Iitate, a lush village famed for its fresh produce before the disaster, never want to move back. Half of those said they would prefer to be compensated enough to move elsewhere in Japan to farm." In addition, despite being allowed to return home, some residents say the lack of an economy continues to make the area de facto unlivable.[102] Compensation payments to those who have been evacuated are stopped when they are allowed to return home, however, as of August 2013 decontamination of the area has progressed more slowly than expected.[103] There have also been revelations of additional leaks (see above: storage tanks leaking contaminated water).

Cementing the seabed near the water-intakeEdit

On 22 February 2012 TEPCO started cementing the seabed near the plant to prevent the spread of radioactive materials into the sea. Some 70000 square meters of seabed around the intake of cooling water would be covered with 60 centimeters thick cement. The work should be finished within 4 months time, and prevent the spread of contaminated mud and sand at that place for at least 50 years.[104]

New definition of the no-entry-zones introducedEdit

On 18 December 2011 Fukushima Gov. Yuhei Sato and representatives of 11 other municipal governments near the plant were notified at a meeting at the city of Fukushima the three ministers in charge of handling the crises, Yokio Edano, minister of Economy, Trade and Industry, Goshi Hosono, nuclear disaster minister, and Tatsuo Hirano, minister in charge of reconstruction of the government plan to redesign the classification of the no-entry-zones around the Fukushima nuclear plant. From 1 April 2012 a three level system would be introduced, by the Japanese government:

a) no-entry zones, with an annual radiation exposure of 50 millisieverts or more

at these places habitation would be prohibited

b) zones with annual radiation exposures between 20-50 millisievert,

here former residents could return, but with restrictions.

c) zones with exposures of less than 20 millisievert per year

in these zones the residents would be allowed to return to their houses.

Decontamination efforts were planned in line with this newly designed order, to help the people to return to places where the radiation levels would be relatively low.[105]

Costs of the clean-up operationsEdit

Mid December 2011 the local authorities in Fukushima had spent already around 1.7 billion yen (21 million$) on the costs of decontamination-works in the cities of Fukushima and Date and the village of Kawauchi. The total clean-up costs were estimated around 420 billion yen (~ 5.2 billion$).[citation needed] For the clean-up only 184.3 billion yen was reserved in the September supplementary budget of prefecture Fukushima, and some funds in the central government's third supplementary budget of 2011. Whenever needed the central government would be asked for extra funding.[106]

In 2016, University of Oxford researcher and author Peter Wynn Kirby wrote that the government had allocated the equivalent of US$15 billion for the regional cleanup and described the josen (decontamination) process, with "provisional storage areas (kari-kari-okiba) ... [and] more secure, though still temporary, storage depots (kari-okiba)". Kirby opined the effort still would be better called "transcontamination" because it was moving the contaminated material around without long-term safe storage planned or executed. He also saw little progress on handling the more intense radiation waste of the destroyed power-plant site itself; or on handling the larger issue of the national nuclear program's waste, particularly given the earthquake-risk of Japan relative to secure long-term storage.[107]

Lessons learned to dateEdit

The Fukushima Daiichi nuclear disaster revealed the dangers of building multiple nuclear reactor units close to one another. This proximity triggered the parallel, chain-reaction accidents that led to hydrogen explosions blowing the roofs off reactor buildings and water evaporating from open-air spent fuel pools—a situation that was potentially more dangerous than the loss of reactor cooling itself. Because of the proximity of the reactors, Plant Director Masao Yoshida "was put in the position of trying to cope simultaneously with core meltdowns at three reactors and exposed fuel pools at three units".[108]

See alsoEdit

ReferencesEdit

  1. ^ a b "Survey finds zero Fukushima plant strontium contamination in soil samples - AJW by The Asahi Shimbun". Ajw.asahi.com. Archived from the original on 2013-12-12. Retrieved 2013-12-24. 
  2. ^ The Mainichi Shimbun (13 September 2013) Toxic water has leaked into Pacific Ocean: TEPCO Archived 2013-09-15 at the Wayback Machine.
  3. ^ a b Fukushima radiation levels 18 times higher than previously thought The Guardian 1 September 2013
  4. ^ "Doubts over ice wall to keep Fukushima safe from damaged nuclear reactors". The Guardian. 13 July 2014. Retrieved 14 July 2014. 
  5. ^ a b Kaplan, Karen (2011-07-12). "Japanese soil still safe for planting after Fukushima nuclear power plant disaster, scientists report - Los Angeles Times". Articles.latimes.com. Retrieved 2013-12-24. 
  6. ^ David McNeill (2 March 2013). "'I am one of the Fukushima fifty': One of the men who risked their lives to prevent a catastrophe shares his story". The Independent. London. Retrieved 5 March 2013. 
  7. ^ Veronika Hackenbroch, Cordula Meyer and Thilo Thielke (5 April 2011). "A hapless Fukushima clean-up effort". Der Spiegel. 
  8. ^ a b c TEPCO Announces a "Roadmap to restoration" at Fukushima Dai-1 - IEEE Spectrum. Spectrum.ieee.org. Retrieved on 30 April 2011.
  9. ^ Clenfield, Jason. (14 April 2011) Fukushima radioactive contamination leaks will continue through June, Tokyo Electric says. Bloomberg. Retrieved on 30 April 2011.
  10. ^ NTI: Global Security Newswire – Japan plant emits more radiation after cooling lapse. Global Security Newswire (14 April 2011). Retrieved on 30 April 2011.
  11. ^ Brumfiel, Geoff (December 11, 2011). "Fukushima reaches cold shutdown". Nature. doi:10.1038/nature.2011.9674. Retrieved 10 April 2013. 
  12. ^ "After Nuclear Milestone, a Long Road". Asia Times. Retrieved 10 April 2013. 
  13. ^ Tabuchi, Hiroko Nuclear cleanup plans hinge on unknowns, NY Times, 14 April 2011.
  14. ^ a b Workers enter reactor building, NHK, 5 May 2011
  15. ^ "Japan: Minister in first tour of stricken nuclear plant". BBC News. 9 April 2011. Retrieved 12 April 2011. 
  16. ^ Kyodo News, "Reactor shutdowns nine months away", Japan Times, 18 April 2011.
  17. ^ "2.4 trillion yen in Fukushima crisis compensation costs to be tacked onto power bills". Mainichi Daily News. The Mainichi. 10 December 2016. Retrieved 10 March 2017. At the meeting, the ministry also revealed that the estimated cost of dealing with the disaster has hit 21.5 trillion yen -- nearly double the initial projection of 11 trillion yen.

    Total compensation for people affected by the disaster is estimated to rise from 5.4 trillion yen to 7.9 trillion yen, and decontamination-associated costs are likely to grow from 2.5 trillion yen to 4 trillion yen. The bill for building interim storage facilities for radioactive materials is expected to rise from 1.1 trillion yen to 1.6 trillion yen, while that of decommissioning reactors at the crippled plant will likely surge from 2 trillion yen to 8 trillion yen.
     
  18. ^ (dutch) AD (6 September 2011) Slave-labor in Japanese nuclear power-plants
  19. ^ The Mainichi Daily News (31 October 2011) Workers in shelters just outside gates of nuclear complex miss out on allowance Archived October 31, 2011, at the Wayback Machine.
  20. ^ JAIF (26 September 2011)Earthquake-report 216: Hydrogen check ordered at No.2, 3 reactors Archived 2011-10-28 at the Wayback Machine.
  21. ^ JAIF (10 October 2011)Earthquake-report 230: Hydrogen level falls at Fukushima plant Archived 2011-11-06 at the Wayback Machine.
  22. ^ The Mainichi Daily news (19 January 2012)TEPCO uses endoscope to look inside crippled Fukushima reactor Archived 2012-07-15 at Archive.is
  23. ^ JAIF (20 January 2012)Earthquake-report 323: TEPCO fails to clearly see inside damaged reactor Archived 2013-05-16 at the Wayback Machine.
  24. ^ nu.nl (20 January 2012) TEPCO films in reactor 2 (footage comments in Dutch)
  25. ^ a b NHK-world (15 March 2012)Radiation high near suppression chambers
  26. ^ a b JAIF (15 March 2012)Earthquake report 374: Radiation high near suppression chambers[permanent dead link]
  27. ^ The Mainichi Shimbun (28 March 2012)Fukushima No. 2 reactor radiation level up to 73 sieverts per hour
  28. ^ "Tech companies to begin cleaning water at Japan nuclear plants". Gigaom.com. 17 June 2011. Retrieved 13 July 2011. 
  29. ^ "Russia floating nuclear waste plant ready to depart for Japan". ITAR TASS. 8 April 2011. Retrieved 11 April 2011. [dead link]
  30. ^ JAIF (11 September 2011) Earthquake-Report 201: Challenges to contain nuclear accident[permanent dead link]
  31. ^ "Fukushima Daiichi Nuclear Accident Update (27 March, 03:00 UTC)". International Atomic Energy Agency. 27 March 2011. Retrieved 27 March 2011.
  32. ^ Staff (24 March 2007). "Official: Workers touched water with radiation 10,000 times normal". CNN Wire. Retrieved 27 March 2011. , records(2011) pp.249-250
  33. ^ "TEPCO halts work to remove radioactive water". NHK WORLD English. 30 March 2011. Archived from the original on May 11, 2011. 
  34. ^ "Fukushima's radioactive water to be pumped into 'Mega Float'". Gizmodo. 30 March 2011. Retrieved 2 June 2011. 
  35. ^ "TEPCO may use floating island to hold tainted water". E.nikkei.com. 2 April 2011. Retrieved 7 April 2011. 
  36. ^ "Increase your water play pool, use of Mega-Float for fishing". Google. Retrieved 24 April 2011. 
  37. ^ Westall, Sylvia (4 April 2011). "Japan to dump 11,500 metric tons of radioactive water The wastewater facility had 11,500 tons of water stored (by 10 April 8900 tons had been pumped into the sea". Reuters. Retrieved 24 April 2011. 
  38. ^ a b asahi.com(朝日新聞社):Radiation fallout from Fukushima plant will take "months" to stop - English. Asahi.com (4 April 2011). Retrieved on 30 April 2011.
  39. ^ TEPCO:Seawater Piping Trench
  40. ^ The Mainichi Shimbun (08 July 2013) Groundwater contamination level soars at Fukushima plant
  41. ^ The Mainichi Shimbun (10 July 2013)Cesium readings further climb in groundwater at Fukushima plant
  42. ^ The Mainichi Shimbun (11 July 2013) Radioactive water at Fukushima plant 'strongly suspected' of seeping into sea: NRA Archived 2013-07-14 at the Wayback Machine.
  43. ^ The Asahi Shimbun (12 July 2013)Strontium detected in well on seaward side of Fukushima plant Archived 2013-07-16 at the Wayback Machine.
  44. ^ The Asahi Shimbun (13 July 2013) TEPCO's plan to halt spread of radioactive water based on shaky theory Archived 2013-07-17 at the Wayback Machine.
  45. ^ 875,000,000,000,000 Bq of Tritium contained in total contaminated water / Over 60 times much as safety limit – Fukushima Diary
  46. ^ Total Tritium in contaminated water increasing by 330 [sic] Trillion Bq per year / Beyond discharge-able amount – Fukushima Diary
  47. ^ JP Gov “No drastic technology to remove Tritium was found in internationally collected knowledge” Fukushima Diary
  48. ^ Japanese nuclear firm admits error on radiation reading The Guardian, 27 March 2011.
  49. ^ 福島第一発電所2号機タービン建屋地下1階の滞留水について(助言)
  50. ^ Photo, Press Release(TEPCO:2011.4.2)
  51. ^ Press Release (TEPCO:2011.4.6), records(2011) pp.253-256
  52. ^ Press Release (TEPCO:2011.4.21)
  53. ^ Roadmap towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station (TEPCO:2011.4.17)
    TEPCO revised this roadmap many times in 2011 as below.
    May 17th, Jun.17th, Jul.19th, Aug.17th, Sep. 20th, Oct.17th, Nov. 17th
  54. ^ Installation Plan of the Water Treatment Facility (TEPCO:2011.4.27)
  55. ^ Possible leakage of water including radioactive materials to the outside from around the intake canal of Unit 3 (TEPCO:2011.5.11)
  56. ^ Appendix1 (NISA:2011.5.25)
  57. ^ Soramoto(2014) p.9,
    Recovery and processing of radioactive accumulated water at Fukushima Daiichi NPS
  58. ^ Appendix3
  59. ^ Jaif (31 August 2011) 2 workers showered with highly radioactive water Archived 2011-10-11 at the Wayback Machine.
  60. ^ Mid-and-long-Term Roadmap towards the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4, TEPCO (TEPCO:2011.12.21)
  61. ^ NHK-world (5 April 2012) Strontium at Fukushima plant flows into sea[permanent dead link]
  62. ^ 原子力規制委員会の施行に伴う関係政令の閣議決定について 原子力規制委員会設置法の施行日を定める政令要綱 (2012.9.11)
  63. ^ Hot test started for the multi-nuclide removal equipment (ALPS) Announcements (TEPCO:2013.3.30)
  64. ^ On the day before, Japan's Upper House election was held.
  65. ^ Increases in the Concentration of Radioactive Materials in Seawater and Groundwater on the Ocean Side of the Site: Current Situation and Countermeasures (TEPCO reference material)
  66. ^ 汚染水の発電所港湾内への流出に関する公表問題について(TEPCO:2013.7.26)
  67. ^ The Asahi Shimbun (28 July 2013) Extremely high tritium level found in water in pit at Fukushima plant Archived 2013-08-01 at the Wayback Machine.
  68. ^ 地下水の流入抑制のための対策 in 汚染水処理対策委員会(第3回) (2013.5.30)
  69. ^ Land-side Impermeable Wall (Frozen Soil Wall)
  70. ^ Contaminated Water Leakage from the Tank in the H4 Area
  71. ^ Background information and Press Release on INES provisional rating on contaminated water leakage from a water tank at Fukushima Daiichi NPS
  72. ^ NRA committee(2013.8.28)
  73. ^ The Fukushima Diary (28 August 2013) Fukushima worker had contamination over head, face and chest on transferring water from the leaking tank
  74. ^ TEPCO (Japanese) Handout 130828 07
  75. ^ Government’s Decision on Addressing the Contaminated Water Issue at TEPCO’s Fukushima Daiichi NPS
  76. ^ The Prime Minister Shinzo Abe's presentation of Tokyo's bid in the International Olympic Committee in Buenos Aires was gotten plenty of attention.
  77. ^ Contaminated Water Leakage from the Tank in the H4 Area
  78. ^ The Mainichi Daily news (3 October 2011) Radioactive waste piles up at Fukushima nuclear plant as disposal method remains in limbo Archived 2011-10-05 at the Wayback Machine.
  79. ^ Jaif (August 16, 2011)Desalinisation of spent fuel pools Archived 2011-08-18 at the Wayback Machine.
  80. ^ "FUEL REMOVAL FROM UNIT 4 REACTOR BUILDING COMPLETED AT FUKUSHIMA DAIICHI". www.tepco.co.jp. Retrieved 30 April 2011. 
  81. ^ NHK, "TEPCO Uses Unmanned Equipment To Remove Rubble", 10 April 2011.
  82. ^ "TEPCO unveils plan to seal Fukushima reactors". The Guardian. London. 15 June 2011. Retrieved 6 August 2011. 
  83. ^ Saoshiro, Shinichi (18 March 2011). "Japan weighs need to bury nuclear plant; tries to restore power". Reuters. Retrieved 18 March 2011. 
  84. ^ Alleyne, Richard (19 March 2011). "Japan nuclear crisis: scientists consider burying Fukushima in a 'Chernobyl sarcophagus'". The Daily Telegraph. London. 
  85. ^ JAIF (7 September 2011) Nishizawa:TEPCO to scrap Fukushima reactors Archived 2012-04-19 at the Wayback Machine.
  86. ^ NHK-world (28 October 2011) Fuel retrieval at Fukushima to start in 10 years Archived 2011-10-28 at the Wayback Machine.
  87. ^ JAIF (29 October 2011) Earthquake-report 249: Fuel retrieval at Fukushima to start in 10 years Archived 2013-05-17 at the Wayback Machine.
  88. ^ a b JAIF (10 November 2011) Earthquake-report 261[permanent dead link]
  89. ^ NHK-world (9 November 2011) Commission releases report on scrapping N-plant Archived 2011-12-13 at the Wayback Machine.
  90. ^ NHK-world (10 November 2011) TEPCO to monitor xenon at Fukushima plant Archived 2011-11-12 at the Wayback Machine.
  91. ^ a b JAIF (20 September 2011 Earthquake-report 211: A new plan set to reduce radiation emissions
  92. ^ "Reactor feared in meltdown, radiation spreads". ABC News. 30 March 2011. Retrieved 30 March 2011. 
  93. ^ Radiation-shielding sheets to be installed in September at earliest, Kyodo News. English.kyodonews.jp. Retrieved on 30 April 2011.
  94. ^ "TEPCO to cover No.1 reactor building". NHK. 14 May 2011. Archived from the original on May 13, 2011. Retrieved 2 June 2011. 
  95. ^ Based on archived video of the plant from TEPCO
  96. ^ JAIF (20 September 2011)Steel Frame for Unit 1 Reactor Building Cover is Complete Archived 2012-04-19 at the Wayback Machine.
  97. ^ "Test run for Fukushima Daiichi 3 cover installation". World Nuclear News. 13 June 2016. Retrieved 14 June 2016. 
  98. ^ Hot-spot cleanups hampered by public resistance to local disposal sites - The Mainichi Daily News Archived August 27, 2011, at the Wayback Machine.
  99. ^ No quick way to remove radioactive substances from soil: experts - The Mainichi Daily News Archived August 27, 2011, at the Wayback Machine.
  100. ^ JAIF (10 October 2011) Earthquake-report 231: Decontamination-plan compiled Archived 2011-11-06 at the Wayback Machine.
  101. ^ JAIF (20 December 2011) Earthquake report 296: Govt to designate nuclear clean-up areas Archived 2012-01-03 at the Wayback Machine.
  102. ^ Knight, Sophie (14 August 2013). "Japan's nuclear clean-up: costly, complex and at risk of failing | Reuters". In.reuters.com. Retrieved 2013-12-24. 
  103. ^ https://archive.is/20130821145939/http://mainichi.jp/english/english/newsselect/news/20130808p2a00m0na013000c.html. Archived from the original on August 21, 2013. Retrieved August 21, 2013.  Missing or empty |title= (help)
  104. ^ NHK-world (22 February 2012)Seabed near nuke plant to be covered with cement Archived November 27, 2012, at the Wayback Machine.
  105. ^ The Daily Yomiuri (18 December 2011) Govt speeds rezoning of contaminated areas
  106. ^ The Mainichi Daily News (21 December 2011) Fukushima local decontamination costs bust estimates Archived December 21, 2011, at the Wayback Machine.
  107. ^ Kirby, Peter Wynn, "Playing Pass the Parcel With Fukushima", New York Times OpEd, March 7, 2016. Retrieved 2016-03-07.
  108. ^ Yoichi Funabashi and Kay Kitazawa (March 1, 2012). "Fukushima in review: A complex disaster, a disastrous response". Bulletin of the Atomic Scientists. 

SourcesEdit

  • 電気新聞, ed. (2011). 東日本大震災の記録 - 原子力事故と計画停電 -. (社)日本電気協会新聞部. 
Management of contaminated water

External linksEdit