（UPDATE) Video and photos in the latest post.
After successfully drilling a hole through the 1st floor of Reactor 1 building and finding no obstruction, TEPCO sent workers to lower the camera, thermometer, and dosimeter through the hole into the torus room in the basement.
The highest radiation dose was right above the water, at 920 millisieverts/hour.
It took 20 workers 2 hours and 25 minutes to do the first day of work, with maximum radiation exposure of 1.78 millisievert. From TEPCO's February 14, 2013 handout (see my post), the air radiation level at the hole on the first floor of the reactor building is 10 millisieverts/hour, and at 1.2 meter above the hole it is 2 millisieverts/hour.
From TEPCO's Handout for the Press, 2/20/2013: