Tokyo Electric Power Company (Tepco) said around 10,000t of contaminated water has accumulated in underground trenches around the unit 1-4 reactor buildings at the crippled Fukushima Daiichi NPP. Tepco has no immediate plan to remove the water in the trenches. “Compared with around 70,000t 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,” A Tepco official said.

In a report issued in July, based on research conducted in fiscal 2015, Tepco said it had found around 8,000t tons of contaminated water in 17 locations in the trenches that connect with reactor buildings, as well as around 3,000t at 11 locations in trenches that do not connect with reactor buildings.

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 it in the future. It has so far removed a total of around 10,000t of highly radioactive water at three locations in the trenches running along the sea side of the complex and completed a procedure to fill those locations with cement to prevent water leaks.

Around 8,000t of contaminated water, including some with an extremely low contamination, have also been found in the trenches running around the unit 5 and 6 reactor buildings which suffered no nuclear meltdowns or hydrogen explosions during the 2011 accident.