Tokyo Electric Power Company Holdings (Tepco) on Thursday halted experimental work to extract nuclear fuel debris from the No. 2 reactor of its meltdown-stricken Fukushima No. 1 nuclear power plant.
The suspension follows an error discovered by the company in procedures to install debris-removal equipment during preparatory work.
Tepco is not resuming the experimental work on Thursday, and has yet to decide what to do from Friday.
Thursday's work was supposed to be the first time the company removes debris from a reactor container vessel since the meltdown that occurred at the plant in March 2011 in the wake of a massive earthquake and tsunami.
According to Tepco, preparatory work began around 7:25 a.m. on Thursday.
Although a remotely operated telescopic-type device — shaped like a fishing rod — was inserted right up to the connection leading to the reactor container vessel, a worker found the error in the procedures to install the device, which resulted in work being stopped.
Tepco had initially planned to insert the device into the reactor container vessel and spend two weeks or so to extract up to 3 grams of debris accumulated at the bottom of the vessel.
About 880 tons of debris is estimated to have piled up at the plant's No. 1 to No. 3 reactors since the meltdown. The exact conditions of the debris, however, are unclear.
Extracting debris, which is a compacted mixture of nuclear fuel and parts of the nuclear reactor melted down as a result of the accident's high temperatures, is said to be the most difficult part of decommissioning work.
Tepco was supposed to begin experimental work to extract the debris in 2021, but postponed it three times, partly due to delays in developing related devices overseas amid the COVID-19 pandemic.