TOKYO — An attempt to use an extendable robot to remove a piece of melted fuel from a destroyed reactor at Japan’s tsunami-hit Fukushima Daiichi nuclear power plant was aborted on Thursday due to a technical problem.

The removal of a tiny sample of debris from the containment vessel of reactor 2 would begin the phase of fuel debris removal, the most difficult part of the decades-long shutdown of the plant, where three reactors were destroyed in the magnitude 9.0 earthquake and tsunami disaster on March 11, 2011.

Work was halted when workers noticed that five 1.5-meter-long pipes used to maneuver the robot were placed in the wrong order and could not be corrected within the allotted time due to radiation exposure, power plant operator Tokyo Electric Power Company Holdings said.

The tubes would be used to push the robot in and pull it out again when the job is finished. Once inside the vessel, the robot would be remotely controlled from a safer location.

The robot can extend up to 22 meters (72 feet) to reach its target area and collect a fragment from the surface of the mound of molten fuel using a device equipped with tongs hanging from the top of the robot.

The mission to recover the fragment and return with it is expected to take two weeks. A new launch date has not yet been set, TEPCO said.

“It seems to me to be a fundamental error,” said TEPCO spokesman Kenichi Takahara of the pipe installation problem. He said authorities were investigating the case and the recovery mission would not resume until the cause had been found and preventive measures had been taken, “so a problem like this should never be repeated.”

TEPCO President Tomoaki Kobayakawa said safety took precedence over rushing the process.

The operation’s goal was to bring back less than three grams (0.1 ounce) of the estimated 880 tons of deadly radioactive molten fuel. The small sample will provide important data for developing future decommissioning methods and the technology and robots needed, experts say.

A better understanding of the melted fuel debris is key to shutting down the three destroyed reactors and the entire power plant.

The government and TEPCO are sticking to the 30- to 40-year cleanup target set shortly after the meltdown. Although this has been criticized as unrealistic, there are still no concrete plans for the complete disposal of the melted fuel or its storage.