The operator of the disaster-struck Fukushima No. 1 nuclear power plant will make a new attempt to examine the inside of reactor 1 on Tuesday with a remote-controlled robot.

The move, announced Thursday, follows a botched attempt with another self-propelled robot to look inside reactor 2, which also sustained a meltdown after the March 11, 2011, Great East Japan Earthquake and tsunami. That robot became unable to move when it encountered debris and eventually could not be retrieved.

The attempts are the first by Tokyo Electric Power Company Holdings Inc. to examine the insides of the wrecked reactors since the nuclear disaster unfolded.

For the reactor 1 inspection, Tepco said the new robot will carry out a four-day probe inside the containment vessel. Findings of the survey will be released on March 21.

Deposits of melted fuel in reactor 1 are believed to have penetrated the pressure vessel and melted through the containment vessel, which is supposed to hold the fuel.

The utility said the robot will enter the structure through a pipe connected to the containment vessel, and land on steel grating once used as a walkway for workers.

According to Tepco, as much as 2.5 meters of water — injected into the structure to cool the fuel — has accumulated in the bottom of the containment vessel.

If successful, the robot will drop from the walkway a dosimeter and underwater camera attached to remote control cables, to ascertain the extent of debris. It will also attempt to collect water and examine deposits.

The plant's reactors 1, 2 and 3 suffered core meltdowns due to the loss of cooling water in the world's worst nuclear catastrophe since the 1986 Chernobyl disaster.

The actual condition of the melted fuel remains unknown as radiation levels inside the reactors remain extremely high.