Radioactive cesium levels were much higher in water deep underground at the crippled Fukushima No. 1 nuclear plant than in samples taken closer to the surface, Tokyo Electric Power Co. said on Aug. 1.
TEPCO measured the radioactivity of water samples taken from the vertical shafts of two concrete trenches for pipes each connected to the turbine buildings of the No. 2 and No. 3 reactors.
The samples were collected on July 31 at a depth of 1 meter, 7 meters and 13 meters on the seaward side of the plant.
Cesium-134 levels of 300 million becquerels and cesium-137 readings of 650 million becquerels per liter were found in water samples from a depth of 13 meters in the trench for the No. 2 reactor turbine building, according to TEPCO.
Levels of radioactive materials that emit beta rays, including strontium, were 520 million becquerels at the same site, TEPCO said.
In the trench for the No. 3 reactor turbine building, cesium levels of 39 million becquerels were found in water at a depth of 1 meter.
Immediately after the Great East Japan Earthquake and tsunami struck the plant and triggered the nuclear disaster on March 11, 2011, a huge amount of highly radioactive water leaked from reactor buildings to the trenches.
In April 2011, TEPCO found radioactive water leaking into the sea from somewhere near the quay walls for the No. 2 reactor building. The following month, the utility discovered a similar leak near the water intake for the No. 3 reactor building.
The level of radioactive cesium detected at that time at the plant was 3.6 billion becquerels per liter.
Last month, TEPCO confirmed a level of 2.35 billion becquerels of cesium in water samples collected on July 26 from the power cable trench for the No. 2 reactor turbine building.
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