Some scientists say the long-term impact on marine life from low-dose exposure to such large volumes of water is unknown. Under the basic plan adopted by the ministers, TEPCO will start releasing the water in about two years after building a facility under the regulatory authority's safety requirements.
It said the disposal of the water cannot be postponed further and is necessary to improve the environment surrounding the plant so residents can live there safely. TEPCO says its water storage capacity of 1. Also, the area now filled with storage tanks will have to be freed up for building new facilities that will be needed for removing melted fuel debris from inside the reactors, a process expected to start in coming years.
In the decade since the tsunami disaster, water meant to cool the nuclear material has constantly escaped from the damaged primary containment vessels into the basements of the reactor buildings. To make up for the loss, more water has been pumped into the reactors to continue to cool the melted fuel. In October a member IAEA mission reported on remediation and decontamination in the special decontamination areas. Its preliminary report said that decontamination efforts were commendable but driven by unrealistic targets.
Also, there is potential to produce more food safely in contaminated areas. The total area under consideration for attention is 13, km 2. Summary : There have been no harmful effects from radiation on local people, nor any doses approaching harmful levels. However, some , people were evacuated from their homes and only from were allowed limited return.
As of July over 41, remained displaced due to government concern about radiological effects from the accident. Permanent return remains a high priority, and the evacuation zone is being decontaminated where required and possible, so that evacuees can return.
There are many cases of evacuation stress including transfer trauma among evacuees, and once the situation had stabilized at the plant these outweighed the radiological hazards of returning, with deaths reported see below. The government said it would consider purchasing land and houses from residents of these areas if the evacuees wish to sell them.
In November the NRA decided to change the way radiation exposure was estimated. Instead of airborne surveys being the basis, personal dosimeters would be used, giving very much more accurate figures, often much less than airborne estimates.
Measurement was by personal dosimeters over August-September Disaster-related deaths are in addition to the over 19, that died in the actual earthquake and tsunami. The premature disaster-related deaths were mainly related to i physical and mental illness brought about by having to reside in shelters and the trauma of being forced to move from care settings and homes; and ii delays in obtaining needed medical support because of the enormous destruction caused by the earthquake and tsunami.
However, the radiation levels in most of the evacuated areas were not greater than the natural radiation levels in high background areas elsewhere in the world where no adverse health effect is evident. The figure is greater than for Iwate and Miyagi prefectures, with and respectively, though they had much higher loss of life in the earthquake and tsunami — over 14, Causes of indirect deaths include physical and mental stress stemming from long stays at shelters, a lack of initial care as a result of hospitals being disabled by the disaster, and suicides.
As of July , over 41, people from Fukushima were still living as evacuees. The money was tax-exempt and paid unconditionally. In October , about 84, evacuees received the payments.
The Fukushima prefecture had 17, government-financed temporary housing units for some 29, evacuees from the accident. The number compared with very few built in Miyagi, Iwate and Aomori prefectures for the , tsunami survivor refugees there.
In April , the first residents of Okuma, the closest town to the plant, were allowed to return home. According to a survey released by the prefectural government in April , the majority of people who voluntarily evacuated their homes after the accident and who are now living outside of Fukushima prefecture do not intend to return.
A Mainichi report said that Of the voluntary evacuees still living in Fukushima prefecture, An August Reconstruction Agency report also considered workers at Fukushima power plant. The death toll directly due to the nuclear accident or radiation exposure remained zero, but stress and disruption due to the continuing evacuation remains high. Summary : Many evacuated people remain unable to fully return home due to government-mandated restrictions based on conservative radiation exposure criteria.
Decontamination work is proceeding while radiation levels decline naturally. Removing contaminated water from the reactor and turbine buildings had become the main challenge by week 3, along with contaminated water in trenches carrying cabling and pipework.
This was both from the tsunami inundation and leakage from reactors. Run-off from the site into the sea was also carrying radionuclides well in excess of allowable levels. By the end of March all storages around the four units — basically the main condenser units and condensate tanks — were largely full of contaminated water pumped from the buildings. Some storage tanks were set up progressively, including initially steel tanks with rubber seams, each holding m 3.
A few of these developed leaks in Accordingly, with government approval, Tepco over April released to the sea about 10, cubic metres of slightly contaminated water 0. Unit 2 is the main source of contaminated water, though some of it comes from drainage pits. NISA confirmed that there was no significant change in radioactivity levels in the sea as a result of the 0.
By the end of June , Tepco had installed concrete panels to seal the water intakes of units , preventing contaminated water leaking to the harbour. From October, a steel water shield wall was built on the sea frontage of units It extends about one kilometre, and down to an impermeable layer beneath two permeable strata which potentially leak contaminated groundwater to the sea. The inner harbour area which has some contamination is about 30 ha in area.
In July-August only 0. Tepco built a new wastewater treatment facility to treat contaminated water. A supplementary and simpler SARRY simplified active water retrieve and recovery system plant to remove caesium using Japanese technology and made by Toshiba and The Shaw Group was installed and commissioned in August The NRA approved the extra capacity in August ALPS is a chemical system which will remove radionuclides to below legal limits for release.
However, because tritium is contained in water molecules, ALPS cannot remove it, which gives rise to questions about the discharge of treated water to the sea. Collected water from them, with high radioactivity levels, was being treated for caesium removal and re-used.
Apart from this recirculating loop, the cumulative treated volume was then 1. Almost m 3 of sludge from the water treatment was stored in shielded containers. ALPS-treated water is currently stored in tanks onsite which will reach full capacity by the summer of As of February , more than 1.
Some of the ALPS treated water will require secondary processing to further reduce concentrations of radionuclides in line with government requirements. Disposal will be either into the atmosphere or the sea. In November the trade and industry ministry stated that annual radiation levels from the release of the tritium-tainted water are estimated at between 0.
The clean tritiated water was the focus of attention in A September report from the Atomic Energy Society of Japan recommended diluting the ALPS-treated water with seawater and releasing it to the sea at the legal discharge concentration of 0. The WHO drinking water guideline is 0. The government had an expert task force considering the options.
In April the Japanese government confirmed that the water would be released into the sea in This is fed through a catalytic exchange column with a little water which preferentially takes up the tritium. It can be incorporated into concrete and disposed as low-level waste. The tritium is concentrated to 20, times. The MDS is the first system to be able economically to treat large volumes of water with low tritium concentrations, and builds on existing heavy water tritium removal systems.
Each module treats up to litres per day. Earlier in a new Kurion strontium removal system was commissioned. This is mobile and can be moved around the tank groups to further clean up water which has been treated by ALPS. Apart from the above-ground water treatment activity, there is now a groundwater bypass to reduce the groundwater level above the reactors by about 1.
This prevents some of it flowing into the reactor basements and becoming contaminated. In addition, an impermeable wall was constructed on the sea-side of the reactors, and inside this a frozen soil wall was created to further block water flow into the reactor buildings.
In October guidelines for rainwater release from the site allowed Tepco to release water to the sea without specific NRA approval as long as it conformed to activity limits. Summary: A large amount of contaminated water has accumulated onsite and has been treated to remove radioactive elements, apart from tritium. In April , the Japanese government confirmed that the water would be released into the sea. Some radioactivity has already been released to the sea, but this has mostly been low-level and it has not had any significant impact beyond the immediate plant structures.
Concentrations outside these structures have been below regulatory levels since April In particular, proposals were sought for dealing with: the accumulation of contaminated water in storage tanks, etc ; the treatment of contaminated water including tritium removal; the removal of radioactive materials from the seawater in the plant's 30 ha harbour; the management of contaminated water inside the buildings; measures to block groundwater from flowing into the site; and, understanding the flow of groundwater.
Responses were submitted to the government in November. In December IRID called for innovative proposals for removing fuel debris from units about It works with IRID, whose focus now is on developing mid- and long-term decommissioning technologies.
They were in 'cold shutdown' at the time, but still requiring pumped cooling. They were restored to cold shutdown by the normal recirculating system on 20 March, and mains power was restored on March. In September Tepco commenced work to remove the fuel from unit 6. Prime minister Abe then called for Tepco to decommission both units. Tepco announced in December that it would decommission both units from the end of January They entered commercial operation in and respectively.
It is proposed that they will be used for training. Tepco published a six- to nine-month plan in April for dealing with the disabled Fukushima reactors, and updated this several times subsequently. Remediation over the first couple of years proceeded approximately as planned. In August Tepco announced its general plan for proceeding with removing fuel from the four units, initially from the spent fuel ponds and then from the actual reactors.
At the end of Tepco announced the establishment of an internal entity to focus on measures for decommissioning units and dealing with contaminated water. In June the government revised the decommissioning plan for the second time, though without major change. It clarified milestones to accomplish preventive and multi-layered measures, involving the three principles of removing the source of the contamination, isolating groundwater from the contamination source, and preventing leakage of the contaminated water.
It included a new goal of cutting the amount of groundwater flowing into the buildings to less than m 3 per day by April The schedule for fuel removal from the pond at unit 1 was postponed from late FY17 to FY20, while that for unit 2 was delayed from early FY20 to later the same fiscal year, and that at unit 3 from early FY15 to FY Fuel debris removal was to begin in , as before.
In September the government updated the June decommissioning roadmap, with no changes to the framework, and confirming first removal of fuel debris from unit 1 in Treatment of all contaminated water accumulated in the reactor buildings was to be completed by For unit 3, fuel removal was completed in February Fuel debris removal remains scheduled to begin in FY Tepco has a website giving updates on decommissioning work and environmental monitoring.
Storage ponds : Debris has been removed from the upper parts of the reactor buildings using large cranes and heavy machinery. Casks to transfer the removed fuel to the central spent fuel facility have been designed and manufactured using existing cask technology. In July two unused fuel assemblies were removed from unit 4 pond, and were found to be in good shape, with no deformation or corrosion.
Tepco started removal of both fresh and used fuel from the pond in November , 22 assemblies at a time in each cask, with used and new ones to be moved. This was uneventful, and the task continued through By 22 December , all used as well as all new fuel assemblies had been moved in 71 cask shuttles without incident. All of the radioactive used fuel was removed by early November, eliminating a significant radiological hazard on the site. The used fuel went to the central storage pond, from which older assemblies were transferred to dry cask storage.
The fresh fuel assemblies are stored in the pool of the undamaged unit 6. Tepco completed moving fuel from unit 3 in February It will now focus on used fuel assemblies and new ones from unit 1, and then used assemblies and 28 new ones from unit 2 will be transferred. The NRA has expressed concern about the unit 1 used fuel.
Reactors order of work : The locations of leaks from the primary containment vessels PCVs and reactor buildings should first be identified using manual and remotely controlled dosimeters, cameras, etc. Any leakage points will be repaired and both reactor vessels RPVs and PCVs filled with water sufficient to achieve shielding.
Then the vessel heads will be removed. The location of melted fuel and corium will then be established. In particular, the distribution of damaged fuel believed to have flowed out from the RPVs into PCVs will be ascertained, and it will be sampled and analysed.
After examination of the inside of the reactors, states of the damaged fuel rods and reactor core internals, sampling will be done and the damaged core material will be removed from the RPVs as well as from the PCVs. Updated plans are on the IRID website. The four reactors will be completely demolished in years — much the same timeframe as for any nuclear plant.
The water overwhelmed the defensive sea wall, flooding the plant and knocking out the emergency generators. Workers rushed to restore power, but in the days that followed the nuclear fuel in three of the reactors overheated and partly melted the cores - something known as a nuclear meltdown.
The plant also suffered a number of chemical explosions which badly damaged the buildings. Radioactive material began leaking into the atmosphere and the Pacific Ocean, prompting the evacuations and an ever-widening exclusion zone. There were no deaths immediately during the nuclear disaster.
At least 16 workers were injured in the explosions, while dozens more were exposed to radiation as they worked to cool the reactors and stabilise the plant. Three people were reportedly taken to hospital after high-level exposure. Long-term effects of the radiation are a matter of debate. The World Health Organization WHO released a report in that said the disaster will not cause any observable increase in cancer rates in the region. Scientists both inside and outside Japan believe that aside from the region immediately around the plant, the risks of radiation remain relatively low.
On 9 March , ahead of the year anniversary, a UN report said there had been "no adverse health effects" documented among Fukushima residents directly related to the radiation from the disaster. Any future radiation-related health effects were "unlikely to be discernible", it said. But many believe the dangers are far greater, and residents remain wary. Though officials have lifted restrictions in many areas most people have not returned to their homes.
In , the Japanese government announced that one worker had died after exposure to radiation and agreed his family should be compensated. A number of people are however confirmed to have died in the evacuation, including dozens of hospital patients who had to be moved due to fears of radiation. The Fukushima Disaster is classified as a level seven event by the International Atomic Energy Agency, the highest such event and only the second disaster to meet this classification after Chernobyl.
Critics blamed the lack of preparedness for the event, as well as a muddled response from both the plant operator Tokyo Electric Power Tepco and the government.
An independent investigation set up by Japan's parliament concluded that Fukushima was "a profoundly man-made disaster", blaming the energy company for failing to meet safety requirements or to plan for such an event. All the reactors except Unit 3 continued using low enriched uranium LEU. Unit 3 was being fed with mixed-oxide MOX fuel since September The Units were disabled in April , followed by the Units 5 and 6 in January in accordance with the Electric Utility Industry Law article 9.
The six reactors were designed by GE. Ebasco provided the architectural design, and Kajima constructed the nuclear complex. GE also supplied the Units 1, 2 and 6. Units 3 and 5 were supplied by Toshiba and Unit 4 by Hitachi. The earthquake measured 8. The remaining two units 5 and 6 were also shut down for regular inspection.
The emergency onsite generation had failed to provide the necessary backup power needed to support the critical instruments and control systems.
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