23 Août 2016
August 23, 2016
TOKYO (Kyodo) -- Around 10,000 tons of contaminated water have pooled in underground trenches around the Nos. 1 to 4 reactor buildings of the crippled Fukushima Daiichi nuclear power plant, according to the plant operator Tokyo Electric Power Company Holdings Inc.
Tokyo Electric has no immediate plan to remove the water in the trenches where cables run for the nuclear power complex devastated by the March 2011 earthquake and tsunami disaster.
Water that flew into the trenches in the wake of the huge tsunami is believed to have been mixed with highly radioactive water leaking from the basements of reactor buildings and contaminated rainwater.
"Compared with around 70,000 tons of highly contaminated water that remain in the basements of the reactor buildings, (the water in the trenches) has a low level of concentration and thus poses little threat in terms of radiation exposure and the environment," said an official of the utility known as TEPCO.
TEPCO said in a report issued in July -- based on research conducted in fiscal 2015 -- that it has found around 8,000 tons of toxic water in 17 locations in the trenches that connect with reactor buildings where highly radioactive water accumulates, as well as around 3,000 tons of toxic water at 11 locations in trenches that do not connect with reactor buildings.
Of the water in the trenches around the Nos. 1 to 4 reactor buildings, a removal procedure was completed by June for around 500 tons of water in a pipe that measured the highest level of radioactive cesium at 500,000 becquerels per liter.
The level of radioactive cesium in water at other locations in the trenches was mostly measured at several thousands becquerels or below.
The level in toxic water in the basements of reactor buildings has been measured at around dozens of millions becquerels at maximum.
TEPCO has said it will continue to monitor and measure the level of contamination in water in the trenches regularly and consider taking measures to remove the water in the future. But no concrete plan has been created yet.
The electricity firm has so far removed a total of around 10,000 tons of highly radioactive water at three locations in the trenches running in the seaside of the complex and completed the procedure to fill locations concerned with cement to prevent water leaks.
Still, the level of radioactive cesium remains unchecked at 40 locations in the trenches due to high radioactive levels as well as debris and other objects blocking the research operation.
Around 8,000 tons of contaminated water, including those with an extremely low level of contamination, have also been found in the trenches running around the Nos. 5 and 6 reactor buildings. The two units have lower levels of radiation doses than the Nos. 1 to 4 units as there were no nuclear meltdowns or hydrogen explosions there during the nuclear disaster.