Radioactive cesium levels at a well on the premises of the Fukushima No. 1 nuclear power plant on July 9 were more than 100 times higher than those measured at the same site just four days earlier, Tokyo Electric Power Co. said.
TEPCO said July 10 that 33,000 becquerels of cesium levels per liter, compared to 309 becquerels on July 5, were detected in water samples collected on July 9 from a well on the seaward side of the No. 2 reactor building. The figure means that cesium levels increased by an additional 20 percent from 27,000 becquerels measured a day earlier.
It is the highest level found since the onset of the March 2011 nuclear disaster.
TEPCO has said cesium levels have likely surged because radioactive water that leaked from reactors at the time of the disaster spread underground and only reached the well recently.
But the Nuclear Regulation Authority has questioned TEPCO’s explanation. During a meeting on July 10, NRA officials pointed out the possibility that contaminated water has continued to leak from somewhere, such as side ditches connecting turbine buildings with the sea.
On July 8, TEPCO began to inject a sealing agent into the ground near the shore protection to prevent radioactive water from leaking into the sea.
The high radioactivity levels were detected at the No. 1-2 observation well, located near the water intake for the No. 2 reactor, from which highly radioactive water leaked into the sea in April 2011.
The 33,000 becquerels consist of 11,000 becquerels of cesium-134, 180 times the legally permitted level, and 22,000 becquerels of cesium-137, 240 times the legally allowed level.
The levels of strontium and other radioactive substances in the well were 900,000 becquerels, just slightly higher than 890,000 becquerels on July 8.
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