Five years on, Fukushima remains a huge challenge for Japan
11 March 2016 Le Figaro
INFOGRAPHICS / VIDEO - The 11 March 2011, a powerful earthquake hit Japan, triggering a tsunami and a nuclear accident whose assessment of the consequences is not over. Five years later, hundreds of thousands of people remain exiled and the technical means to clean the plant and the irradiated areas remain to be imagined.
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Five years after Fukushima, the accident is still ongoing
By Ludovic Dupin Factory New the 11 March 2016
Japan is gathering for the fifth anniversary of the 11 2011 tsunami and the nuclear accident it caused. At the Fukushima site, work continues as the three damaged reactors are barely under control.
The 11 March 2011, an earthquake and a tsunami hit Japan. Flooding in the Fukushima power plant leads to the loss of power and water supply. Hearts heat up, eventually melt, releasing massive quantities of hydrogen. The gas explodes, disemboweling three of the site's six reactors.
Since then, the Tepco operator has been working to stabilize the situation of the site with a view to dismantling it. "Five years after the accident, efforts are continuing to control the installations in a still difficult context linked to a still limited knowledge of the condition of reactors and damaged buildings", judges the Institute for Radiation Protection and Nuclear Safety (IRSN) in an information note compiling the state of knowledge.
He adds : "Groundwater pollution due to degradation of containment barriers still results in diffuse radioactive releases to the environment".
Fuels still cooling
"Reactors 1, 2 and 3 are maintained at a temperature between 20 ° C and 50 ° C by an injection of about 5 cubic meters per hour of fresh water per reactor", assures IRSN, which specifies that an injection of nitrogen is maintained in the containment chambers to avoid any new risk of explosion.
The swimming pools, meanwhile, are cooled by a closed water circuit in order to stay below 30 ° C. The emptying of the spent fuel they contain should have started in 2015, but Tepco had to postpone these operations. "The withdrawal of fuels present in the swimming pools (is planned) from 2017 for the swimming pool of reactor n ° 3, from 2020 for those of reactors n ° 1 and n ° 2", reports IRSN.
As for the removal of degraded fuels in the reactors, it is only expected between 2020 and 2025. The note specifies that these deadlines are to be regarded as indicative because many works of characterization of the state of the installations are still to be done.
Contaminated water volumes that accumulate
For the past five years, the work on contaminated water management - water used for core cooling and natural runoff - is the first battle. "The volumes of water accumulated in storage tanks and building basements reached in early 2016 nearly 900 cubic meters", reports IRSN, the equivalent of 300 Olympic swimming pools.
Some of this water has been treated to extract cesium and strontium. Although traces of radioactivity remain, mainly tritium, Tepco is waiting for a release of these waters. According to IRSN, Tepco would have a storage capacity of 1 million cubic meters today.
In addition to this water stored in around 3 containers, Tepco also has to manage around 000 cubic meters of highly irradiated water in the basements of damaged buildings. "In addition, they are subject to significant inflows of water (around 70 m000 / day) from the water table", adds IRSN.
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