It took twelve years, between 1967 and 1979, to build the six reactors at the Fukushima plant. The site of decontamination and deconstruction of the site, ravaged by the biggest nuclear disaster at the start of the 21st century, will be much longer: almost half a century.
Almost nine years after the tsunami that devastated the facilities and caused the hearts of three reactors to melt, on March 11, 2011, the cleaning operations became an inextricable puzzle for the Japanese authorities, who have just announced that the dismantling schedule would be staggered, and the contaminated water would no doubt be discharged ... into the sea. While confirming that the surrounding forests will never be cleaned.
Mountains of contaminated land
In the aftermath of the disaster, the Japanese authorities carried out a gigantic site of decontamination of the soils of the areas affected by the plume of radioactive smoke. Eleven municipalities had been evacuated and forty others affected by lower pollution levels. A region of 9000 km2 where it was necessary to strip the soil to eliminate in particular traces of cesium, which can remain for three centuries in the environment!
"This is the first time that such a remediation effort has been made following a nuclear accident, notes Olivier Evrard, 16,000 workers participated." This researcher at the Laboratory of Climate and Environmental Sciences has gathered the results of sixty studies published on the subject, in collaboration with two Canadian and Japanese colleagues. To clean up the cultivated land, the authorities have stripped the surface layer of the soil to a thickness of 5 cm. "This has made it possible to reduce cesium concentrations by around 80% in the treated areas", emphasizes the study.
But this operation was very expensive (24 billion euros) and generated mountains of waste: 20 million m3 or… 8000 Olympic swimming pools! They will be stored for several decades near the power plant before being sent to final storage sites outside of Fukushima prefecture by 2050.
Forests have not been cleared
In the areas further from the power plant, Tokyo has not stripped the soil, but has spread substances known on the ground to fix or replace radiocesium. "Regarding the wooded areas, only those that were within a radius of 20 meters around the dwellings were treated", explains the French study coordinated by the National Center for Scientific Research (CNRS) and the French Atomic Energy Commission (CEA).
The branches were cut and the decontaminators picked up the litter from the dead leaves. Residential areas have also been sieved: cleaning ditches, cleaning roofs and gutters, cleaning up gardens and vegetable gardens. "The decontamination activities mainly targeted agricultural landscapes and residential areas, but the forests have not been cleaned up because of the difficulty and the very significant costs that these operations would represent", note the researchers.
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These forests cover 75% of the areas located at the heart of the radioactive plume. "They therefore constitute a potential long-term reservoir of radiocesium which can be redistributed across landscapes following soil erosion and floods, warns Olivier Evrard. Last October, two very violent typhoons crossed the region causing overflows of rivers and landslides. ”
The "bad reputation" Fukushima
Despite this colossal decontamination site, certain villages, such as Iitaté, which had 7,000 inhabitants before the disaster, found only 10 to 15% of its inhabitants. Mostly elderly people.
"Most of the people evacuated in 2011 have rebuilt their lives elsewhere and the whole issue of the authorities is to restart life in this big agricultural region, by attracting young people, but there is now a bad reputation attached to the name of Fukushima , underlines Olivier Evrard. For the next Olympic Games, baseball events will take place in the prefecture, but the South Korean delegation is afraid that its athletes will be fed with products from the region while they undergo a very strict radiological control ". For the time being, fishing is still prohibited in the rivers of the region.
Contaminated water will be released to the Pacific.
On Christmas Eve, Japanese authorities claimed that discharging contaminated water that contaminates the plant site into the sea or into the air (by evaporation) was the only remaining option, with experts now excluding its storage at long term on the nuclear site.
A huge quantity of contaminated water is present on site, stored in a thousand tanks which will be full within two years. At present, these tanks contain 1,100,000 m3 of contaminated water, the equivalent of 366 Olympic swimming pools! These contaminated liquids come from rain runoff, groundwater that rises in the basements of buildings and water injections necessary to cool the hearts of reactors that have melted. "The option of simple long-term storage is no longer considered," recognizes a state official.
"The company has studied several solutions, such as injecting this water into the ground between two impermeable layers or trapping it in concrete blocks, but discharging it into the ocean after treating it as much as possible by spreading out the releases over ten years is the most technically reasonable solution, ”explains the deputy director general of the Institute for Radiation Protection and Nuclear Safety (IRSN) Thierry Charles. This remains impossible for the time being, as the water is still loaded with radioactive elements dangerous for the food chain. Fishermen and environmentalists are categorically opposed to it. So does South Korea.
Five more years to remove spent fuel
Imagine a giant mikado game but where the sticks nested inside each other would be highly radioactive fuel rods. Well, this is pretty much the puzzle that Tokyo Electric Power (Tepco) faces, which is handling the dismantling.
The operation is so perilous that the Japanese government and the company have decided to postpone for four to five years the withdrawal of spent fuel still present in the storage pool of reactor number 1. Originally scheduled for early 2023, this sequence will not start before 2027 at the earliest. Same choice for reactor number 2. "The removal of spent fuel is underway in the pool of reactor 3 and it is a succession of problems", recognized shortly before the transition to 2020 a spokesperson for Tepco, putting in before a priority: worker safety.
Thierry Charles has visited the industrial site several times, which he compares to a "hive" where several thousand workers meet. The famous building 3 is the one that suffered the strongest explosion during the disaster. "It was necessary to clean the surroundings remotely, with cranes and robots, because there is too much radiation and the superstructure of the building was covered with a pile of rubble," he explains. Interior images released by the Japanese nuclear safety authority show shattered doors, rubble everywhere, jagged piping, and radiation levels are so high that no human intervention has been possible since. 2011.