Workers drilled a hole through the 1st floor concrete on February 13 and 14. And unlike in the Reactor 2 torus room the other day (1/28/2013), there was no unexpected pipe blocking the way.
The atmospheric dose level on the 1st floor before the drilling was 1 millisievert/hour. After the drilling, the radiation went up to 2 millisieverts/hour right above the hole, at 1.2 meters off the floor. At the hole, the radiation was 10 millisieverts/hour, and at the end of the hole through to the torus room, it was 210 millisieverts/hour. TEPCO says the investigation will proceed, now that they've found out that the radiation level didn't change much before and after.
The radiation levels inside the Reactor 1 Containment Vessel, measured in October last year, were 4.7 to 11.1 sieverts/hour (or 4,700 to 11,100 millisieverts/hour).
From TEPCO's Photos and Videos, 2/14/2013:
The white dot in the dark in the photo must be the reflection of the camera light on the water.
The atmospheric dose level in the Reactor 2 (about the same location) was much higher, at 4 to 8 millisieverts/hour.