Photo/Illutration A retrieval device is deployed in the No. 2 reactor of the Fukushima No. 1 nuclear power plant on Oct. 30. (Provided by Tokyo Electric Power Co.)

The operator of the Fukushima No. 1 nuclear power plant reported on Nov. 5 that the radiation level of retrieved fuel debris from a reactor that melted down in 2011 is within the threshold for safe handling.

Tokyo Electric Power Co. said that the trial removal of debris from the No. 2 reactor will be completed on or after Nov. 7.

On Nov. 2, TEPCO placed the device that collected the fuel debris in an isolation box set up outside the containment vessel.

On Nov. 5, the utility measured the radiation level using a dosimeter placed on top of the isolation box, recording approximately 0.2 millisievert per hour at a distance of 20 centimeters.

This level was below the safety threshold of 24 millisieverts per hour at that distance, which is set to prevent workers from being exposed to excessive radiation.

TEPCO plans to place the debris in a box-shaped container inside the isolation box on Nov. 6.

The utility will then open a window on the side of the isolation box on or after Nov. 7 to place the container into a bucket-shaped container, marking the completion of the trial retrieval.

An estimated 880 tons of fuel debris remain inside the No. 1, No. 2 and No. 3 reactors. They went into meltdowns after the Great East Japan Earthquake and tsunami in March 2011, which knocked out cooling systems at the plant.

In this trial, the government and TEPCO aim to retrieve up to 3 grams of fuel debris from the No. 2 reactor for analysis of its composition and other characteristics, which will help in developing future retrieval methods.

(This article was written by Shoko Tamaki and Keitaro Fukuchi.)

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