Photo/Illutration The tip of a crane device used to collect melted nuclear fuel at the Fukushima No. 1 nuclear power plant, equipped with two cameras and a gripper (Takuya Tanabe)

Tokyo Electric Power Co. has announced that it will retract a malfunctioning device to collect melted nuclear fuel at the stricken Fukushima No. 1 nuclear power plant, further delaying the start of the project. 

On Sept. 19, TEPCO said it will inspect the two cameras on the tip of a robotic crane device that stopped working two days earlier.

The equipment is designed to remove highly radioactive materials from the plant's No. 2 reactor.

The device is currently positioned inside the reactor's containment vessel, where the fuel debris has collected at the bottom.

It will be withdrawn to a separate area next to the vessel, where it will be inspected using cameras installed in that space.

All the work will be conducted from a remote control room situated 400 meters from the site due to the high levels of radiation.

If the two cameras on the device need to be replaced, the entire instrument will have to be removed to another site, causing further delays in the project.

A government official speculated that the cameras were damaged due to the high humidity within the vessel, where conditions resemble a sauna because water is continuously being pumped in to cool the debris.

However, TEPCO is skeptical of that hypothesis.

“The cameras and cables are waterproof, but we’ll investigate that possibility nonetheless,” said a utility spokesperson.

This month, TEPCO began removing the fuel debris for the first time since the devastating 2011 accident at the plant, triggered by the Great East Japan Earthquake and tsunami. 

It plans to use the crane device that extends up to 22 meters, placing it inside the containment vessel to experimentally retrieve and analyze debris pieces weighing less than 3 grams.

This is just the first step in the larger project to remove an estimated 880 tons of debris that have collected in the plant’s No. 1, No. 2 and No. 3 reactors. 

The removal device was also used in February 2019 when it successfully picked up what are believed to be chunks of fuel debris from the same reactor. However, no debris was removed from the vessel during that operation. 

It was deployed again this time, as the development of another device--a robotic arm partly funded by taxpayer money--has faced difficulties.

However, it remains unclear whether the device will withstand the rigors of the latest undertaking, which will take about two weeks compared to the one-day operation in 2019.

(This article was written by Keitaro Fukuchi and Fumi Yada.)

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