Radioactive contamination of the environment due to the accident at the nuclear plant is not over in Fukushima Japan. Far from it. Seven months after the disaster, the marine environment in particular and all people living in this environment are still high levels of radioactive elements.
The peak of radioactive contamination of the marine environment around the plant, occurred between March 11 and April 8 last. The direct discharge of contaminated water, in fact, could not be stopped until that date. Result in early April “concentrations of sea water reached (…) up to tens of thousands of becquerels per liter (Bq / l) for cesium-134 and 137, and exceeded 100,000 Bq / l for Iodine 131, “says the Institute for Radiological Protection and Nuclear Safety (IRSN).
In hindsight, experts have even been calculated that the total amount of cesium-137 released into the ocean between the date of the accident and mid-July, was “the largest one-time contribution of artificial radionuclides to the marine environment ( that has) never (been) seen. ” An elegant way to describe the catastrophe of historical drama.
Over time, most of these levels have declined. And since mid-July, “the concentrations of cesium 134 and 137 are placed below the detection limits,” notes the IRSN. However, despite the natural decline and the presence of one of the most important currents of the world, which favored a more rapid dispersion of effluents, “significant pollution of sea water on the coast near the plant could persist over time. ”
If a direct discharge of contaminated water is out of date, radioactive substances contained in the soil are transported to the sea by runoff of surface waters. Results also show “the persistence of contamination of marine species, particularly fish, caught on these shores,” says the IRSN. The species most affected are the fish at the top of the food chain, like tuna, very sensitive to pollution cesium. IRSN therefore continues to monitor marine species harvested in coastal waters of Fukushima.