Tepco begins long-delayed probe of Fukushima reactor’s interior

Tokyo – Tokyo Electric Power Company Holdings on Friday started inspections of the interior of the meltdown-stricken No. 2 reactor at the Fukushima No. 1 nuclear power plant, inserting a robotic arm into the containment vessel.

The company aims to better understand conditions inside the reactor at the plant in Fukushima Prefecture, as it plans to extract some nuclear fuel debris on a trial basis. The work is expected to take about half a year.

According to Tepco, the latest operation involves cutting some rails and cables that could obstruct the robotic arm’s entry with high-pressure water jets and collecting 3D data and images from inside the containment vessel. This information will be used to develop and design new equipment.

The opening in the containment vessel had been used to remove equipment for inserting and withdrawing control rods, which control the nuclear fission reaction. Rails installed down to the bottom of the reactor pressure vessel are believed to be hindering investigations.

Tepco plans to capture images, including those of the lower part of the pressure vessel, with multiple cameras attached to the robotic arm. Debris removal is expected to begin next year, with the collection amount likely to be several grams. The company has so far removed about 0.9 grams of debris over two rounds.

The company had said that it would begin investigating the inside of the No. 2 reactor around this summer, but the operation was delayed after a malfunction was found in the robotic arm and it took time to replace parts.

Tepco has frequently postponed investigations in order to remove accumulated debris and replace cameras, among other reasons.

The radiation level inside the No. 2 reactor’s containment vessel remains extremely high more than 15 years after the March 2011 meltdowns, making it impossible for workers to enter and conduct work.

The robotic arm is about 22 meters long and weighs 4.6 tons. The arm is operated remotely and can be fitted at the tip with cutting gear, cameras and debris removal equipment, depending on the tasks required in the operation.

Akira Ono, president of Tepco’s Fukushima Daiichi Decontamination & Decommissioning Engineering, told a news conference Thursday that he feels relieved that the effort has “finally reached this point.”