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 that 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. Michio Aoyama, a scientist at Fukushima University's  Institute of Environmental Radioactivity, estimated that the meltdowns and explosions released 18,000 terabecquerel (TBq) of caesium 137, mostly into the Pacific Ocean. He also estimated that two years after the accident, the stricken plant was still releasing 30 gigabecquerel (30 GBq, or approximately 0.8 curie) of caesium 137 and the same amount of strontium 90 into the ocean daily. 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. Efforts to control the flow of contaminated water have included trying to isolate the plant behind a 30-meter-deep, 1.5-kilometer-long "ice wall" of frozen soil, which has had limited success. Decommissioning the plant is estimated to cost tens of billions of dollars and last 30–40 years. While radioactive particles were found to have contaminated rice harvested near Fukushima City in the autumn of 2011, fears of contamination in the soil have receded as government measures to protect the food supply have appeared to be successful. Studies have shown that soil contamination in most  areas of Fukushima was not serious. In 2018, Dr. Aoyama of Fukushima University released a report saying that contaminated water was still flowing into the Pacific Ocean, but at a greatly diminished rate of 2 GBq per day. Overview. 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. 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". On 17 April 2011, however, TEPCO appeared to put forward the broad basis of a plan that 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;" (5) using radio-controlled equipment to clean up the site; and (6) using silt fences to limit ocean contamination. 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. Toshiba and Hitachi had both proposed plans for shuttering the facility. "Cold shutdown" was accomplished on 11 December 2011. From that point active cooling was not needed anymore, but water injection was still required due to large water leaks. Long-term plans for Units 5 and 6 have not been announced, "but they too may need to be decommissioned". On 5 May 2011, workers were able to enter reactor buildings for the first time since  the accident. The workers began to install air filtration systems to clean air of radioactive materials to allow additional workers to install water cooling systems. In 2017, TEPCO announced that remote-controlled robots sent into the destroyed Unit 3 reactor buildings had finally found the reactor's melted uranium fuel, which had burned through the floor of the reactor vessel and settled in clumps on the concrete floor below. Scope of cleanup. 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. 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. First estimates included costs as high as (), as cited by the Japanese Prime Minister at the time, Yoshihiko Noda (野田 佳彦). This estimate was made before the scope of the problem was known, however. It seems that the contamination was less than  feared. No strontium is detectable in the soil, and though the crops of the year of the disaster were contaminated, the crops produced by the area now are safe for human consumption. In 2016, Japan's Ministry of Economy, Trade and Industry estimated the total cost of dealing with the Fukushima disaster at (), almost twice the previous estimate of (). A rise in compensation for victims of the disaster from () to () was expected, with decontamination costs estimated to rise from () to (), costs for interim storage of radioactive material to increase from () to (), and costs of decommissioning reactors to increase from () to  (). Working conditions at the plant. 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. 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. Workers in dorms exposed to radiation. 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 were between 2 and 16 microsieverts per hour in the Toshiba building, and 2  to 8.5 in the Kajima dorm. 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. These doses are, however, 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. Preventing hydrogen explosions. 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. 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. Investigations inside the reactors. 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. 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. Inspections of the suppression chambers reactor no. 2 and 3. 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. According to TEPCO, this work should be done with  robots, because these places with high levels of radiation could be hostile to humans. TEPCO released some video footage of the work at the suppression chambers of the No. 2 and 3 reactors. 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 dosimeter 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  sieverts 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. Management of contaminated water. 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 accumulates inside the reactor and turbine buildings. To decontaminate the contaminated water, TEPCO installed radioactive water treatment systems. 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 an 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. 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. 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. Installation of circulating water cooling system. 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. 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). TEPCO had to abandon that  plan after discovering that the condensers on both units were already full of water. 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. 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. Regardless of the availability of offshore storage for radioactive-contaminated water, TEPCO decided to discharge 11,500 tons of its least contaminated water (which was still approximately 100 times the  legal limit for radioactivity) into the sea on April 5 in order to free up storage space. 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). Removal of accumulated water in seawater piping trench. The Fukushima Daiichi NPS has several seawater piping trenches that 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. Groundwater contamination. On 5 July 2013, TEPCO found 9 kBq/L of Cs and 18 kBq/L of Cs 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. A day later the readings in the first well were 11 kBq/L of Cs and 22 kBq/L of Cs, 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. 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 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. 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. Suggestions of dumping cooling water. In September 2019, the contaminated cooling water had almost  reached storage capacity. Japan's environment minister Yoshiaki Harada suggested, that there was only one recourse: "release it into the ocean and dilute it... there are no other options." A day later, Yoshiaki Harada was taken out of his function, after protests. His successor Shinjiro Koizumi apologized to the fishermen in Fukushima at a meeting in Iwaki City. The new minister promised to take a strong few on the facts, and to push for reconstruction. In 2020, the storage of contaminated water reached over a million tons, stored in large containers at the grounds of the plant. In 2022, the  storage capacity could be exceeded. Therefore, a proposal was made in spring 2020 to start discharging the cooling water into the ocean. Hiroshi Kishi, the president of JF Zengyoren, the headman of many fishermen cooperations, strongly opposed this proposal at a meeting with Japanese government representatives. According to Kishi, any release of cooling water could prompt other countries to reinforce restrictions on imports of Japanese fishery products, reversing a recent trend toward easing. Radioactive waste. 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 backup. 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. Spent fuel pools. 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. Unit 4 spent fuel removal. 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). Debris removal. 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. Proposed building protections. 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. Proposed sarcophagus. On 18 March 2011, Reuters reported 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. Scrapping reactor Daiichi 1, 2, 3, 4. 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. 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. 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. The panel's conclusions were: This scheme was partly based on the experience gained from the 1979 Three Mile Island accident. In Fukushima, however, 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. Protection systems installed. 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 reactions. 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. New filters. 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. Fabric cover over Unit 1. An effort has been undertaken to fit the three damaged reactor buildings with fabric covers and filters to limit radioactive contamination release. 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". 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. 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 September 9th, 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. Metal cover over Unit 3. 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. By February 2018 the dome-shaped roof had been completed in preparation of the removal of the fuel rods. Cleanup of neighboring areas. 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. There is also a concern that washing surfaces will merely move the radioactive material without eliminating it. 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: 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. 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. Compensation payments to those who have been evacuated are stopped when they are allowed to return home, but , decontamination of the area has progressed more slowly than expected. There have also been revelations of additional leaks (see above: storage tanks leaking contaminated water). Cementing the seabed near the  water intake. 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. New definition of the no-entry zones introduced. 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: 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. Costs of the cleanup  operations. 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 cleanup costs were estimated to be between 50.5 and 71 trillion yen ($470 to $660 billion). For the cleanup, 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. 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. Lessons learned to date. 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".