Tokyo Electric Power Co. must stop using sunken reservoirs to store radioactive water accumulating at the crippled Fukushima No. 1 nuclear plant once it has enough storage tanks, Economy, Trade and Industry Minister Toshimitsu Motegi said Wednesday.
Three of the seven reservoirs, which are basically lined trenches with surface covers, have been found to be leaking radioactive water, including seawater, leading Tepco to consider transferring some of the contents to more reliable tanks above ground. The water was cycled through reactors 1, 2 and 3, which suffered core meltdowns in 2011, to keep the units cool to prevent further massive fallout.
The utility has said it cannot empty all the sunken reservoirs currently in use because there is not enough alternative storage capacity on the site now. Tepco plans to install tanks that can hold 15,000 tons by mid-April.
Motegi told a Diet committee that the radioactive water will be “swiftly” moved to tanks above ground and “after that, sunken reservoirs should not be used.”
The situation regarding radioactive water leaks has been worsening since Tepco first announced it earlier this month, with more sunken cisterns found with problems increasing. There is speculation there may have been flaws in the construction of the reservoirs. All were built by Maeda Corp.
Tepco also said Wednesday that it confirmed a small amount of radioactive substances outside the water-containment lining sheets laid between reservoir No. 1, the latest one found with leaks, and the soil. Radioactive water leaks to soil have already been reported around reservoirs Nos. 2 and 3.
The utility said it has detected 0.11 becquerel of radioactive substances per cubic centimeter of water in soil outside the three lining layers of reservoir No. 1.
Radioactive water that escaped from that cistern may have seeped into the ground, according to Tepco.
To boost oversight at the plant, which also recently saw the halt of its cooling system for spent-fuel pools, the Nuclear Regulation Authority said it will increase the number of on-site inspectors from eight to nine.
The continued injections of water into reactors 1-3 is causing the massive accumulation of radioactive water.
Water used to cool the damaged reactors is recycled as coolant after radioactive cesium and other substances have been removed in a processing facility. But the total amount of tainted water is rising because the existing water flow allows an influx of about 400 tons of groundwater a day.