Tokyo Electric Power Co. said Tuesday that around 150 liters of water containing strontium and other radioactive substances has flowed into the Pacific from the Fukushima No. 1 nuclear power plant.
Tepco said the amount of radioactive substances is estimated at around 26 billion becquerels. The impact will be "negligible" even if people continue to eat marine products from the area, the utility said.
The water leaked from a water processing facility after undergoing a process to remove radioactive cesium. The facility, however, is not capable of removing strontium, which tends to accumulate in bones and is feared to cause bone cancer and leukemia.
The seawater near the plant has already been contaminated not only by massive radioactive fallout since the March 11 earthquake and tsunami triggered the nuclear crisis, but also by accidental releases of polluted water.
In the latest case, Tepco found Sunday that around 45 tons of water had accumulated inside a building housing part of the water processing facility and some of it was seeping through a concrete crack to a nearby gutter, which leads to the sea about 500 meters away.
According to a Tepco press release, the water contained radioactive materials including about 11 billion becquerels of strontium-89, 15 billion becquerels of strontium-90 and 4.4 million becquerels of cesium-137.
The water processing facility is essential to maintain the water-based cooling of reactors 1, 2 and 3, which lost their key cooling functions in the March disaster.
The water used to cool the reactors contains massive amounts of radioactive substances and is channeled to the water treatment facility so it can be recycled as a coolant.
Tepco said the latest incident has not affected the injection of water into the reactors.