In preparation for the removal of nuclear fuel debris, which is considered to be the most difficult task in the decommissioning of the Fukushima Daiichi Nuclear Power Station, TEPCO plans to start the first trial removal of nuclear fuel debris at Unit 3 by March. However, preparations for the robotic arm inside the containment vessel have been difficult, and the plan may have to be revised.
It is estimated that the total amount of nuclear fuel debris in Units 1 to 3 is approximately 880 tons, which is a mixture of nuclear fuel melted down in the accident at the Fukushima Daiichi Nuclear Power Plant and internal structures.
TEPCO plans to start a trial removal of about a few grams at Unit 2, but due to the extremely high radiation levels at the site and the time it took to develop a robot arm for remote work and internal investigations, it is more than two years behind the original target, and it is expected to start by March.
However, last year, when the lid of the pipe containing the robot arm was opened, it was confirmed that the inside was blocked by sediment.
We plan to start work to remove it on the 2th, but the Nuclear Regulation Authority and others have pointed out that it may not be possible to remove it sufficiently depending on the hardness of the sediment.
If TEPCO is unable to remove the sediment, it is considering an alternative to inserting a telescopic rod-shaped device through the gap created in the previous survey.
In that case, the plan to start by March is expected to be revised due to changes in the process and design, and TEPCO says that it will "scrutinize the process while working carefully."