Tokyo Electric Power Co. announced Oct. 12 that it has detected a rising level of radioactive cesium in seawater sampled from the mouth of the harbor of the devastated Fukushima No. 1 nuclear power plant, measuring a combined 10 becquerels of cesium-134 and cesium-137 per liter.
The level is the highest since the plant operator began sampling water in June at the mouth of the port, which marks the boundary between the harbor around the plant and the ocean.
At the plant, a vast amount of contaminated water that includes radioactive substances has been discharging into the sea since the nuclear disaster following the Great East Japan Earthquake and tsunami on March 11, 2011.
On Oct. 11, TEPCO said that it recorded 2.7 becquerels of cesium-134 and 7.3 becquerels of cesium-137 per liter at the port mouth. Samples taken a day earlier were below the measurable limits of 1.1 becquerels of cesium-134 and 0.9 becquerel of cesium-137 per liter, the company said.
The previous record amount of radioactive cesium detected at the mouth of the harbor was 1.6 becquerels of cesium-134 and 4.7 becquerels of cesium-137 per liter in water sampled on Aug. 19.
World Health Organization guidelines advise the maximum level of radioactivity in drinking water to be 10 becquerels per liter or less. But TEPCO officials said that the environmental impact of the level of cesium detected on Oct. 11 is negligible.
On Oct. 8, the company also detected 1.4 becquerels of cesium-137 from seawater sampled 1 kilometer off the mouth of the port.
Meanwhile, TEPCO measured 320,000 becquerels of tritium, a radioactive isotope of hydrogen, per liter from water sampled from an observation well on Oct. 10 located near a storage tank, from which the leakage of 300 tons of highly contaminated water was discovered in August.
About 1,000 storage tanks are holding the ever-increasing volume of highly toxic water left after being used to cool the reactors.
It marked the first time that water containing 300,000 or more becquerels of tritium per liter was detected from groundwater sampled from the compound of the Fukushima No. 1 plant.
It is more than five times the legally allowed maximum level of tritium contamination--60,000 becquerels per liter--that could be released into the ocean.
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