http://ajw.asahi.com/article/0311dis...AJ201308030015
Photo at link maps the location of other objects found emitting lower doses of radiation. They are believed to be pieces of bark, rubber and wood chips.
Mystery objects with high radiation found on Fukushima coast
August 03, 2013
[snip]
One hypothesis is that the objects flowed down the Idegawa river, but that theory is highly implausible because all four objects were found at least 100 meters from the river.
Another theory is that the objects were swept out to sea from the Fukushima No. 1 plant and eventually washed ashore. The coastal levee that was once located in the area was destroyed by the tsunami that followed the Great East Japan Earthquake on March 11, 2011.
?Rubble likely was blown out into the ocean by the hydrogen explosions that occurred at the Fukushima No. 1 plant,? an official with the Naraha municipal government said. ?There is the possibility that lighter objects were washed back ashore.?
[snip]
The fragile object that looked like part of a black plastic sheet had an extremely high radiation reading of 36 millisieverts per hour when combining beta and gamma rays, TEPCO officials said.
Its ratio of radioactive cesium-134 and -137 was close to 1:2, leading TEPCO officials to conclude that cesium generated by the Fukushima nuclear accident likely attached to the object....
August 03, 2013
[snip]
One hypothesis is that the objects flowed down the Idegawa river, but that theory is highly implausible because all four objects were found at least 100 meters from the river.
Another theory is that the objects were swept out to sea from the Fukushima No. 1 plant and eventually washed ashore. The coastal levee that was once located in the area was destroyed by the tsunami that followed the Great East Japan Earthquake on March 11, 2011.
?Rubble likely was blown out into the ocean by the hydrogen explosions that occurred at the Fukushima No. 1 plant,? an official with the Naraha municipal government said. ?There is the possibility that lighter objects were washed back ashore.?
[snip]
The fragile object that looked like part of a black plastic sheet had an extremely high radiation reading of 36 millisieverts per hour when combining beta and gamma rays, TEPCO officials said.
Its ratio of radioactive cesium-134 and -137 was close to 1:2, leading TEPCO officials to conclude that cesium generated by the Fukushima nuclear accident likely attached to the object....