The survey of the No. 1 reactor will continue until Oct. 13 and will involve measuring radiation levels and temperatures of gases within the containment vessel. TEPCO will also collect water inside the container to study radioactive concentration levels.

TEPCO inserted a camera, 75 millimeters in diameter, through a piping hole on the side of the containment vessel on Oct. 9 and confirmed the surface of water used to cool the melted fuel, which is believed to have accumulated at the bottom of the vessel. However, TEPCO officials were unable to determine the water level.

source: [link to ajw.asahi.com]