Fukushima nuclear accident cleanup

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.

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.

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 (equivalent to roughly 5.6 kilograms or 12 pounds), 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 equivalent to roughly 9 milligrams or 0.14 grains) of caesium 137 and the same amount (in terms of activity, not in terms of mass – the mass of 90Sr amounts to roughly 5.8 milligrams or 0.090 grains) of strontium 90 into the ocean daily.

[4] Efforts to control the flow of contaminated water have included trying to isolate the plant behind a 30-metre-deep (98 ft), 1.5-kilometre-long (0.93 mi) ice wall of frozen soil, which has had limited success.

[6][7] In November 2016, Japan's trade ministry put the cost of the clean up of radioactive contamination and compensation for victims at US$180 billion (20 trillion yen).

[13][a] 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.

[15] 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;"[16] (5) using radio-controlled equipment to clean up the site;[16] and (6) using silt fences to limit ocean contamination.

[25] 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).

On the evening of 9 October, two holes were drilled into a pipe to install a filter for radioactive substances inside the containment vessel; this was 2 weeks behind the schedule TEPCO had set for itself.

Landysh was built by Russia with funding from Japan to process liquid wastes produced during the decommissioning of nuclear submarines.

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.

[39] In order to remove decay heat of the severely damaged cores of Units 1–3, TEPCO injected cooling water into the reactors.

[further explanation needed] At that time the turbine buildings of units 2 and 3 contained 5000 and 6000 cubic meters of radioactive water respectively.

Hiroshi Kishi, the president of JF Zengyoren, the headman of many fishermen cooperatives, 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.

Cooling the reactors with recirculated and decontaminated water from the basements proved successful, but as a consequence, this radioactive waste was accumulating in the temporary storage facility at the plant.

[89] Because the monsoon season begins in June in Japan, it became urgent to protect the damaged reactor buildings from storms, typhoons, and heavy rainfall.

Considered a last-ditch effort since it would not provide cooling, such a plan would require massive reinforcement under the floor, as in the Chernobyl Nuclear Power Plant sarcophagus.

[93] On 28 October 2011, the Japanese Atomic Energy Commission presented a timetable in a draft report, titled "how to scrap the Fukushima reactors".

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.

[94][95] After discussions were started in August 2011, on 9 November 2011, a panel of experts of Japan's Atomic Energy Commission completed a schedule for scrapping the damaged reactors.

[96][97] Since the disaster, TEPCO has installed sensors, a fabric cover over the reactors and additional filters to reduce the emission of contaminants.

[96][98] On 20 September 2011, the Japanese government and TEPCO announced the installation of new filters to reduce the amount of radioactive substances released into the air.

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 2011.

[99] An effort has been undertaken to fit the three damaged reactor buildings with fabric covers and filters to limit radioactive contamination release.

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.

In addition, despite being allowed to return home, some residents say the lack of an economy continues to make the area de facto unlivable.

[110] Compensation payments to those who have been evacuated are stopped when they are allowed to return home, but as of August 2013[update], decontamination of the area has progressed more slowly than expected.

Kirby opined that the effort would be better called "transcontamination" because it was moving the contaminated material around without long-term safe storage planned or executed.