On Tuesday, TEPCO workers investigated the torus room of Fukushima Daiichi Unit 1. A camera, thermometer, and dosimeter were inserted through pipes above the torus room, and down into the torus room between the wall suppression chamber.
The investigation revealed that the area was nearly half full of highly contaminated water, which was 10-15 degrees warmer than the temperature in the Torus room.
The radiation dose measured in the Torus Room was 19.5 millisieverts per hour, but spiked dramatically over 10,000 millisieverts (Equivalent of 10 Sv – 1 Sv = 1000 mSv = 1000000 µSv) just above the surface of the accumulated water. Floating sediment confirmed when the equipment touched the wall or the bottom surface.
The dosimeter seems to have failed during the measurement as the values did not change until the dosimeter was brought back up.
TEPCO had previously determined that similar lethal radiation levels, detected near pipes at the bottom of a duct between Unit 1 and Unit 2, were likely due to vented radioactive materials on March 12th, 2011.
At the time, the science ministry noted that receiving 10,000 mSv (1,000,000 mrem) as a short-term and whole-body dose would cause immediate illness and subsequent death within a few weeks.