Tokyo Electric Power Company Holdings (Tepco) on Thursday suspended experimental work to recover nuclear fuel residues from reactor 2 of the Fukushima 1 nuclear power plant, which was affected by a meltdown.

The suspension is due to an error discovered by the company during preparatory work for the installation of debris removal equipment.

Tepco will not resume test work on Thursday and has not yet made a decision on how to proceed from Friday.

Thursday’s work was actually the company’s first time removing debris from a reactor container since the nuclear meltdown that occurred at the power plant in March 2011 following a major earthquake and tsunami.

According to Tepco, preparatory work began at around 7:25 a.m. on Thursday.

Although a remote-controlled, telescopic device in the shape of a fishing rod was brought up to the connection to the reactor vessel, a worker discovered an error in the installation of the device, which led to a work stoppage.

Tepco had originally planned to insert the device into the reactor vessel and spend about two weeks recovering up to three grams of debris that had accumulated at the bottom of the vessel.

An estimated 880 tons of rubble have accumulated in reactors 1 to 3 of the power plant following the meltdown. However, the exact condition of the rubble is unclear.

The recovery of the rubble, a compacted mixture of nuclear fuel and parts of the nuclear reactor that melted as a result of the high temperatures of the accident, is considered the most difficult part of the decommissioning work.

Tepco was supposed to start trial work to recover the debris in 2021, but had to postpone the plan three times, partly due to delays in developing appropriate equipment abroad in the wake of the Covid-19 pandemic.