Photo/Illutration The No. 2 reactor of the Fukushima No. 1 nuclear power plant in October (Asahi Shimbun file photo)

Tokyo Electric Power Co. announced on April 23 that it had removed a sample of melted nuclear fuel from the No. 2 reactor at the crippled Fukushima No. 1 nuclear power plant for analysis.

This marked the second time that debris was collected on a trial basis, following the first retrieval in November 2024.

This time, the tiny chunk was gathered from a location 1 to 2 meters closer to the center of the containment vessel than the first time.

The removal work began on April 15.

As in the previous effort, TEPCO inserted a 22-meter-long “fishing rod-type” device through a hole in the side of the containment vessel and collected the debris at the bottom with the tip of the device.

The device was pulled out of the containment vessel, and at 10:15 a.m. on April 23, the debris was placed in a special container to complete the recovery.

The pebble-shaped debris will now be sent to a research institute in Ibaraki Prefecture for analysis of its composition and other factors.

The total debris in the nuclear plant’s No. 1, No. 2 and No. 3 reactors, where the core meltdowns occurred following the 2011 Great East Japan Earthquake and tsunami, is estimated at 880 tons.

However, details of its composition and distribution within the containment vessel are not yet known, and experts have pointed out that the previous sample alone did not provide enough data to show the entirety of the debris.

TEPCO said that it will analyze the differences in the properties and distribution of the two debris samples to help determine the future extraction method. 

Koji Okamoto, professor of nuclear engineering at the University of Tokyo, said that it is significant in that the newest sample was collected from 1 to 2 meters away from the first.

“Just knowing how much difference there is or isn’t is a great achievement,” he said.

The central government and TEPCO are aiming to complete decommissioning of the plant by 2051, and debris removal is considered to be the most difficult task.

Initially, a trial removal operation was scheduled to begin in 2021 using a robotic arm developed at government expense.

However, development did not proceed as planned, and the work was postponed three times.

The first attempt to use a fishing rod-type device was repeatedly interrupted due to a series of connection errors and problems with the camera.

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