Five years after the accident at the Fukushima Daiichi nuclear plant,
efforts are continuing to control the facilities in a persistently difficult environment linked to a still limited knowledge of the condition of the reactors and of the damaged buildings. These actions are part of a long-term plan that should lead to the dismantling of the plant within 30 to 40 years.
groundwater contamination due to the deterioration of the containment barriers is still producing diffuse radioactive releases into the environment. This situation has forced Tepco, the operator of the Japanese plant, to implement specific provisions, in particular the covering of the buildings of the damaged reactors and the construction of underground barriers.
In the contaminated areas of Fukushima, studies continue in order to monitor
the effects of the releases on the environment and to measure the effectiveness of the decontamination actions, which have resulted in the generation of a large volume of waste. Scientists have already collected enough data to
demonstrate the effects on plant and animal species.
However, the results are often contradictory and different from those observed in the Chernobyl region (Ukraine) in the contaminated exclusion zone following the first major accident in 1986.
One of the main objectives of the study is to
improve post-accident management, in particular taking into account the management of the forest, which has become contaminated over time, and the migration of radioactive deposits via waterways. For example, research programmes are underway to improve the modelling of the contamination of various ecosystems.
The accident has finally resulted in significant health and social consequences. Four epidemiological studies have been initiated to regularly assess the health status of the population of Fukushima Prefecture. They in particular concern the evacuees, who were in the areas most exposed to radioactivity and fallout, and two populations at risk: pregnant women and children.
In parallel, the workers involved in the operations at the Fukushima Daiichi plant undergo a specific monitoring by Tepco, the operator of the facilities.
Unlike the Soviet and Ukrainian authorities after the Chernobyl accident in 1986, Japan decided to "reconquer" the contaminated territories. Five years after the accident, mass decontamination and revitalization is continuing, both in the evacuated areas and in those contaminated but not evacuated.
However, many of the evacuees believe that acceptable conditions for their return are not met. To date, only 900 of the 80,000 evacuees have returned home.
The Fukushima accident also showed the vulnerability of nuclear facilities in the event of extreme and multiple natural aggressions.
Globally, this finding led to the launch of new research programmes and to stricter safety measures. It is within this context that France has defined a "post-Fukushima hardened safety core" aimed at gradually equipping French facilities with an additional line of defence to cope with higher levels of aggression than those previously considered.
Another essential change:
the improvement of the prognostic tools designed to assist governments in their decision making during crisis situations. In Japan, differences have been observed between the dispersion models of radioactive releases into the atmosphere and measurements performed in the environment. The feedback from Fukushima has already reduced uncertainty in simulation tools.