The leak was detected by a station employee at 9:00 local time (0:00 GMT) on Wednesday during the inspection of the equipment. The employee found that 10 of the 16 valves of the station that should have been closed were open.
TEPCO estimated that the volume of water is 5.5 tonnes, it contains radionuclides, including radioactive cesium and strontium, and the content of radioactive substances is estimated at 22 billion becquerels. A significant part of the water has been presumably absorbed into the soil. A monitoring point installed next to a nearby sewage channel does not show radiation levels changes.
The leak occurred in the zone of alienation, work will be carried out to remove the soil into which the water has been absorbed, TEPCO said.