The ongoing cleanup at Japan’s disabled Fukushima Daiichi nuclear power station has focused on removal of fuel rods, melted fuel and radioactive debris from the three reactors. These localized remediation efforts may not be adequate, as the areal extent of the radiocontamination resulting from the March 2011 earthquake and tsunami appears to be far-reaching.
High levels of radioactive cesium-137 released from the event have been detected in sands and brackish groundwater beneath beaches up to 60 miles away. Researchers from Woods Hole Oceanographic Institution, Massachusetts, and Kanazawa University, Japan, contend that this poses no primary public health concern as no one is exposed to or drinks these water resources. The finding does reveal an unexpected pathway for the storage and release of radionuclides to the ocean which should be considered in the management of coastal areas where nuclear power plants are sited. Of the 440 operational nuclear reactors in the world, about half are situated along coastlines.
Sampling conducted during 2013-2016 documented cesium levels in the groundwater to be up to 10 times higher than the levels found in seawater within the harbor of the nuclear power plant itself. The total amount of cesium retained more than 3 feet deep in the sands is higher than what is found in sediments on the seafloor offshore of the beaches.
The radiocontaminants are theorized to have been transported along the coast by ocean currents. The cesium was eventually absorbed by the surfaces of sand grains and is being released back into the ocean as a result of wave and tidal action.
The amount of contaminated water flowing into the ocean from this brackish groundwater source below the sandy beaches is estimated to be as large as the input from two other known sources: ongoing releases and runoff from the nuclear power plant site itself, and outflow from rivers that continue to carry cesium from the fallout on land in 2011 to the ocean on river-borne particles. Cesium-134, a radioactive form of cesium that can only come from the 2011 Fukushima accident, was also detected.