Tokyo Electric Power Co. said Saturday that 250 tons of water tainted with about 20 terabecquerels of radioactive substances leaked into the Pacific Ocean from a pit near the seawater intake for the No. 3 reactor at the troubled Fukushima No. 1 plant earlier this month.
While the figure is far lower than the 4,700 terabecquerels released near the No. 2 reactor in April, it is still about 100 times the permissible level, according to Tepco.
At the time, the water was registering 9.8 terabecquerels of cesium-137, 9.3 terabecquerels of cesium-134 and 0.85 terabecquerels of iodine-131.
The leak is believed to have started at around 2 a.m. May 10 and was stopped at 7 p.m. May 11, Tepco said. The amount of water that escaped in that 41-hour period totaled 250 tons, it said.
The leakage of tainted water raised the concentration of radioactive substances in the port of the power plant but did not significantly change the level beyond it, the utility said.
The leak was reported to the Nuclear and Industrial Safety Agency.