Tokyo Electric Power Co. said Saturday it has detected high levels of radioactive substances, including strontium, emitting beta rays in groundwater taken from a well at the port of the Fukushima No. 1 nuclear plant.
Tepco said 3,000 becquerels of radioactive substances per liter were recorded in groundwater from the well, located just 6 meters from the Pacific. That concentration is 100 times higher than the maximum legal limit.
As levels of radioactive tritium have been rising in seawater around the port, radioactive substances are suspected to have leaked into the ocean.
“It is true that radioactive contamination has been found from groundwater near the sea, but we do not know whether tainted water has made its way into the Pacific,” a Tepco official said.
The contamination was found in a water sample collected Friday. The well is the nearest to the shore among the four wells used for observation purposes at the plant, according to Tepco, and the radiation levels from its groundwater also were the highest detected.
Also Friday, Tepco recorded 1,400 becquerels of beta ray-emitting radioactive substances such as strontium in groundwater from another of the wells, situated 25 meters from the sea.
The latest revelations came after readings of tritium and strontium-90 were found to be eight to 30 times higher than the permissible limit in ground water from that well in May. After that discovery, Tepco expanded the area it surveys and drilled an additional observation well nearer to the Pacific.
Over the last few months, levels of radioactive tritium in seawater near the water intakes of reactors 1 to 4 at the crippled complex soared to 1,500 becquerels per liter at one point. A member of the Nuclear Regulation Authority earlier said it is “highly likely” that contaminated groundwater has leaked into the Pacific.
Following the triple meltdowns at the Fukushima No. 1 plant, huge amounts of highly radioactive water gushed into the Pacific through a duct containing cables for reactor 2, one of the three wrecked units. Tepco sealed the duct in April 2011, but some of the remaining tainted water is believed to have leaked and become mixed with groundwater, officials at the utility said.