A major new leak of highly radioactive water into the ocean near the Fukushima No. 1 nuclear power plant was discovered May 11.
Local authorities and the embassies of the United States and other countries, including neighboring nations, were notified of the latest setback at the stricken plant, which has been out of control since the March 11 Great East Japan Earthquake.
The plant’s operator, Tokyo Electric Power Co., said cesium-134 at levels about 18,000 times above government standards for wastewater discharge into the ocean was detected in the sea near the No. 3 reactor.
Workers discovered highly radioactive water in a pit connected to a trench of the No. 3 reactor around 10:30 a.m. May 11.
The water leaked into the sea through cracks on the side of the pit facing the ocean.
TEPCO stopped the leak at 6:45 p.m. by plugging the crack with concrete.
Checks on seawater outside a silt fence installed by TEPCO last month at an intake of the No. 3 reactor to stop contamination from spreading out to sea found 96 becquerels of iodine-131 per cubic centimeter, 2,400 times above safety standards, according to the utility. The silt fence is a plastic curtain hanging from floats and reaching near the sea bottom.
Inside the pit, the iodine-131 level was 3,400 becquerels per cubic centimeter, 85,000 times the permissible level.
Cesium-134 was measured at 37,000 becquerels per cubic centimeter, 620,000 times the safety limit.
TEPCO said the contaminated water was believed to be from the basement of the turbine building of the No. 3 reactor, where highly radioactive water was discovered earlier.
It is the first major leak of highly contaminated water into the sea since a leak near the No. 2 reactor last month.