Fukushima : bilan environnemental 8 ans après la catastrophe


Since 2011, we have been studying the redistribution of radioactive fallout on the soils of Fukushima. And in 2013, the Japanese authorities set up a landscape decontamination program. Numerous studies have quantified the effectiveness of these different decontamination methods. The idea of the bibliographic overview that we have just published was precisely to evaluate the effectiveness of these different methods. The objective of the Japanese authorities was to allow people to return home without being exposed to a radioactive dose rate higher than one millisievert per year in addition to the naturally occurring level of radioactivity. These are the dose rates to which the Japanese will be naturally exposed. In France, we have an average value of about two millisieverts per year, with differences depending on where we live, since soils and rocks are naturally more radioactive, for example in the Massif Central than in the Île-de-France region. The decontamination has focused on the treatment of inhabited and cultivated areas. The principal technique was to strip away the top 5 centimeters of soil, which is where the radioactivity is actually concentrated. This was effective since it reduced the levels of radioactivity in the soil by about 80%, corresponding to an area similar to that of Corsica that has been decontaminated around the Fukushima power plant in Japan. This yielded 20 million cubic meters of contaminated soil that must be transported to storage sites, where they will be stored for several decades. It has cost around 20 billion euros to decontaminate these soils, this is equivalent to 4 times the annual budget of the Île-de-France region. But the challenge is in the forests, with three-quarters of the area being forested in the region. The only decontamination operation undertaken was within a radius of 20 meters surrounding the dwellings. They cut the branches and removed the litter. They did not get to the majority of the forest. The main challenge for the future will be to identify techniques for recycling these contaminated soils. In addition, we will need to study the long-term contribution of the forests to the radioactivity that transits through the landscapes when there is erosion, when there are typhoons. This past October there were 2 quite significant typhoons that affected the area impacted by the Fukushima radioactive fallout. In particular, there was a typhoon in mid-October that brought more than 600 millimeters of rain in 1 or 2 days, or the equivalent of what falls during one year in Paris. There were overflowing watercourses, fairly serious floods, and more than 30 deaths in the Fukushima prefecture as a result of these events. And then there are also a whole series of questions about the redistribution of residual radioactivity via the hydrographic network in the area. As this is the first time that we have decontaminated a landscape after a nuclear accident, the CNRS and other organizations such as the CEA as well as many Japanese partners have decided to set up an international research laboratory to study in a multidisciplinary and international way the post-accident situation as it stands today. There will be an environmental aspect in which we will study the transfer of residual radionuclides in the landscape, and there will also be an aspect that focuses more on the perception of populations and the difficulties that they face in reclaiming their living space after all these changes. Thus, the idea is really to bring together researchers from different disciplines including the environmental sciences, sociology, and information sciences – and who come from both France and Japan – to study this particular phenomenon in a rather new context.

4 thoughts on “Fukushima : bilan environnemental 8 ans après la catastrophe

  1. C’est un programme très ambitieux mais la topographie du Japon est, tout de même, assez particulière avec un environnement montagneux qui caractérise l’ensemble de l’archipel. L’état du réseau hydrographique n’a pas été clairement évoqué dans le sujet mais c’est pourtant le point le plus important étant donné les conditions météorologiques habituelles de la région, renforcées par le réchauffement climatique global. J’imagine assez facilement que les eaux de ruissellement, combinées à l’érosion naturelle des sols, doivent se contaminer et se re-contaminer périodiquement, transportant la radioactivité résiduelle au-delà de la zone initiale. Autour de Tchernobyl, par exemple, certains villages ont été repeuplés par leurs habitants et ces derniers doivent composer avec des zones contaminées dont la localisation peut changer, parfois quotidiennement, en fonction de la météo. Des habitants ont été formés à mesurer la radioactivité et à baliser les zones autour de leurs villages au cours de rondes quotidiennes. Les produits potagers sont systématiquement mesurés dans des caissons détecteurs installés dans les mairies. Ce sont les personnes les plus âgées qui sont revenu vivre près de Tchernobyl. Les autres ont déserté les lieux.

  2. merci pour l'information, mais où et comment peut on consulter ces publications ? merci

  3. Ils ont tout gagné !! L'argent qu'ils n'ont pas voulu investir pour d'avantage de sécurité au regard des risques qu'ils ont estimé (ratio le plus bas possible entre sécurité/probabilité d'avoir un tel séisme-investissement), ils l'ont dépensé cent fois plus, d'avantage même !! Et c'est sans compter sur le bilan sanitaire qui va se répercuter un bon moment !!

  4. Vont-ils utilisés des plantes Hyper accumulatrices pour décontaminé les forets et les sols qu'ils n'ont pas décontaminés ?
    => Liste des plantes hyper-accumulatrices :
    https://fr.wikipedia.org/wiki/Hyperaccumulateur

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