TEPCO, the operator of the damaged Fukushima Daiichi nuclear plant, has again begun using a camera probe inside the containment vessel of the No. 2 reactor.
Taking pictures of the molten fuel inside is regarded as an important step towards decommissioning the reactors that melted down.
On Tuesday, workers at the plant tried to insert a camera into a pipe leading into the containment vessel.
But the camera got stuck in the pipe's opening. The rubber, which had shrunk due to cold, blocked it.
In a second attempt on Thursday, workers tried to push the camera into the pipe while warming the rubber with thermal material. They were successful.
Footage from the camera shows a black substance adhering to the surface of metal rails in the vessel. The rails will be used as tracks for a robot to do a survey in February.
TEPCO expects the camera may capture footage of molten fuel for the first time since the 2011 meltdown.