Remediation and recovery
To assuage fears, the government enacted an order to decontaminate over a hundred areas where the level of additional radiation was greater than one millisievert per year. This is a much lower threshold than is necessary for protecting health. The government also sought to address the lack of education on the effects of radiation and the extent to which the average person was exposed.
In 2018, tours to visit the accident area began. In September 2020, The Great East Japan Earthquake and Nuclear Disaster Memorial Museum was opened in the town of Futaba, near the power plant. The museum exhibits items and videos about the earthquake and the nuclear accident. To attract visitors from abroad, the museum offers explanations in English, Chinese and Korean.
Fuel Removal
Tokyo Electric Power Company (TEPCO) plans to remove the remaining nuclear fuel material from the plants. TEPCO completed the removal of 1535 fuel assemblies from the Unit 4 spent fuel pool in December 2014 and 566 fuel assemblies from the Unit 3 spent fuel pool in February 2021. TEPCO plans to remove all fuel rods from the spent fuel pools of Units 1, 2, 5, and 6 by 2031 and to remove the remaining molten fuel debris from the reactor containments of Units 1, 2, and 3 by 2040 or 2050. Plant management estimated the ongoing intensive cleanup program to both decontaminate affected areas and decommission the plant will take 30 to 40 years from the accident.
Treating contaminated water
As of 2013, about 400 metric tons (390 long tons; 440 short tons) of cooling water per day was being pumped into the reactors. Another 400 metric tons (390 long tons; 440 short tons) of groundwater was seeping into the structure. Some 800 metric tons (790 long tons; 880 short tons) of water per day was removed for treatment, half of which was reused for cooling and half diverted to storage tanks. Ultimately the contaminated water, after treatment to remove radionuclides other than tritium, has to be discharged into the Pacific ocean. TEPCO created an underground ice wall to block the flow of groundwater into the reactor buildings. A $300 million 7.8 MW cooling facility freezes the ground to a depth of 30 meters. As of 2019, the contaminated water generation had been reduced to 170 metric tons (170 long tons; 190 short tons) per day.
In February 2014, NHK reported that TEPCO was reviewing its radioactivity data, after finding much higher levels of radioactivity than was reported earlier. TEPCO now says that levels of 5 MBq (0.12 millicuries) of strontium per liter (23 MBq/imp gal; 19 MBq/U.S. gal; 610 μCi/imp gal; 510 μCi/U.S. gal) were detected in groundwater collected in July 2013 and not the 900 kBq (0.02 millicuries) (4.1 MBq/imp gal; 3.4 MBq/U.S. gal; 110 μCi/imp gal; 92 μCi/U.S. gal) that were initially reported.
On 10 September 2015, floodwaters driven by Typhoon Etau prompted mass evacuations in Japan and overwhelmed the drainage pumps at the stricken power plant. A TEPCO spokesperson said that hundreds of metric tons of radioactive water entered the ocean as a result. Plastic bags filled with contaminated soil and grass were also swept away by the flood waters.
As of October 2019, 1.17 million cubic meters of contaminated water was stored in the plant area. The water is being treated by a purification system that can remove radionuclides, except tritium, to a level that Japanese regulations allow to be discharged to the sea. As of December 2019, 28% of the water had been purified to the required level, while the remaining 72% needed additional purification. However, tritium cannot be separated from the water. As of October 2019, the total amount of tritium in the water was about 856 terabecquerels, and the average tritium concentration was about 0.73 megabecquerels per liter.
A 2020 committee set up by the Japanese Government concluded that the purified water should be released to the sea or evaporated to the atmosphere. The committee calculated that discharging all the water to the sea in one year would cause a radiation dose of 0.81 microsieverts to the local people, whereas evaporation would cause 1.2 microsieverts. For comparison, Japanese people get 2100 microsieverts per year from natural radiation. IAEA considers that the dose calculation method is appropriate. Further, the IAEA recommended that a decision on the water disposal must be made urgently. Despite the negligible doses, the Japanese committee is concerned that the water disposal may cause reputational damage to the prefecture, especially to the fishing industry and to tourism.
In 2021, Japan's Nuclear Regulation Authority warned that the some of 3,373 waste storage containers for the radioactive slurry were degrading faster than expected. Due to the fact that transferring the slurry to a new container was very time consuming, this posed an urgent problem.
Tanks used to store the water were expected to be filled in 2023. In July 2022, Japan's Nuclear Regulation Authority approved discharging the treated water into the sea. Japan said the water is safe, many scientists agreed, and the decision came weeks after the UN's nuclear watchdog approved the plan; but critics say more studies need to be done and the release should be halted. In August, Japan began the discharge of treated waste water into the Pacific Ocean, sparking protests in the region and retaliation from China, who blocked all imports of seafood from Japan. Discharges were planned to occur over the subsequent 30 years to release all the water. A US State Department spokesperson supported the decision. South Korea's foreign minister and activists from Japan and South Korea protested the announcement. In April 2023, fishers and activists held protests in front of the Japanese embassy in the Philippines in opposition to the planned release of 1.3 million tons of treated water into the Pacific Ocean.
Compensation and government expenses
Initial estimates of costs to Japanese taxpayers were in excess of ¥12 trillion ($110 billion inflation adjusted). In December 2016 the government estimated decontamination, compensation, decommissioning, and radioactive waste storage costs at ¥21.5 trillion ($200 billion inflation adjusted), nearly double the 2013 estimate. By 2022, ¥12.1 trillion had already been spent, with ¥7 trillion on compensation, ¥3 trillion on decontamination, and ¥2 trillion on decommissioning and storage. Despite concerns, the government expected total costs to remain under budget.
In March 2017, a Japanese court ruled that negligence by the Japanese government had led to the Fukushima accident by failing to use its regulatory powers to force TEPCO to take preventive measures. The Maebashi district court near Tokyo awarded ¥39 million ($400,000 inflation adjusted) to 137 people who were forced to flee their homes following the accident. On 30 September 2020, the Sendai High Court ruled that the Japanese government and TEPCO are responsible for the accident, ordering them to pay $9.5 million in damages to residents for their lost livelihoods In March 2022, Japan's Supreme Court rejected an appeal from TEPCO and upheld the order for it to pay damages of ¥1.4 billion ($12 million) to about 3,700 people whose lives were harmed by the accident. Its decision covered three class-action lawsuits, among more than 30 filed against the utility.
On 17 June 2022, the Supreme Court acquitted the government of any wrongdoing regarding potential compensation to over 3,700 people affected by the accident.
On 13 July 2022, four former TEPCO executives were ordered to pay ¥13 trillion ($95 billion) in damages to the operator of the power plant, in the civil case brought by TEPCO shareholders.
Equipment, facility, and operational changes
A number of nuclear reactor safety system lessons emerged from the incident. The most obvious was that in tsunami-prone areas, a power station's sea wall must be adequately tall and robust. At the Onagawa Nuclear Power Plant, closer to the epicenter of the 11 March 2011 earthquake and tsunami, the sea wall was 14 meters (46 ft) tall and successfully withstood the tsunami, preventing serious damage and radioactivity releases.
Nuclear power station operators around the world began to install passive autocatalytic recombiners ("PARs"), which do not require electricity to operate. PARs work much like the catalytic converter on the exhaust of a car to turn potentially explosive gases such as hydrogen into water. Had such devices been positioned at the top of the reactor buildings, where hydrogen gas collected, the explosions would not have occurred and the releases of radioactive isotopes may have been less.
Unpowered filtering systems on containment building vent lines, known as Filtered Containment Venting Systems (FCVS), can safely catch radioactive materials and thereby allow reactor core depressurization, with steam and hydrogen venting with minimal radioactivity emissions. Filtration using an external water tank system is the most common established system in European countries, with the water tank positioned outside the containment building. In 2013, TEPCO installed additional filters, vents, and other safety systems at Kashiwazaki-Kariwa Nuclear Power Plant.
For generation II reactors located in flood or tsunami prone areas, a 3+ day supply of back-up batteries has become an informal industry standard. Another change is to harden the location of back-up diesel generator rooms with water-tight, blast-resistant doors and heat sinks, similar to those used by nuclear submarines.
Upon a station blackout, similar to the one that occurred after the back-up battery supply was exhausted, many constructed Generation III reactors adopt the principle of passive nuclear safety. They take advantage of convection (hot water tends to rise) and gravity (water tends to fall) to ensure an adequate supply of cooling water to handle the decay heat, without the use of pumps.
As the crisis unfolded, the Japanese government sent a request for robots developed by the U.S. military. The robots went into the plants and took pictures to help assess the situation, but they couldn't perform the full range of tasks usually carried out by human workers. The accident illustrated that robots lacked sufficient dexterity and robustness to perform critical tasks. In response to this shortcoming, a series of competitions were hosted by DARPA to accelerate the development of humanoid robots that could supplement relief efforts. Eventually a wide variety of specially designed robots were employed (leading to a robotics boom in the region), but as of early 2016, three of them had promptly become non-functional due to the intensity of the radioactivity.