TEPCO replaces faulty motor of robotic arm at Fukushima Daiichi Unit 2

Tokyo Electric Power Company (TEPCO) began replacing the faulty motor of the robotic arm used for fuel debris retrieval trials at Unit 2 of the Fukushima Daiichi Nuclear Power Station on August 26. The robotic arm, approximately 22 meters long, is planned for use in the third fuel debris retrieval trial.

During a previous operational inspection inside the reactor building of Unit 2, TEPCO found that the motor driving the robotic arm had malfunctioned, preventing the brake from releasing and the arm from extending. As the robotic arm is already installed on site, workers will enter the "front chamber" in front of the containment vessel to perform the replacement manually. The company stated that radiation levels in the work area will be strictly controlled to prevent workers from receiving excessive exposure.

After this replacement, TEPCO will also confirm whether the robotic arm can operate normally. The replacement and inspection are expected to take several weeks. The company had originally planned to launch the third fuel debris retrieval trial after July 2026, but the relevant schedule is being reassessed due to the equipment malfunction.

Unit 2 of the Fukushima Daiichi Nuclear Power Station achieved the first retrieval of fuel debris in November 2024, and the second retrieval trial was conducted in April 2025. Because high-temperature molten material solidified after the accident and blocked some pipes leading to the containment vessel, the first two operations used a "fishing rod-type" device capable of passing through narrow spaces. The next operation is planned to use a larger robotic arm, first acquiring three-dimensional data of the inside of the containment vessel before collecting fuel debris, with the entire process expected to take three to four months.

The total amount of fuel debris remaining in Units 1 to 3 of the Fukushima Daiichi Nuclear Power Station is estimated at approximately 880 tons, with about 279 tons in Unit 1, about 237 tons in Unit 2, and about 364 tons in Unit 3. The two retrieval trials conducted to date have collected approximately 0.9 grams of fuel debris in total. As planned, the next phase of the robotic arm operation will also retrieve only a few grams of samples for subsequent analysis and decommissioning planning. With approximately 25 years remaining until the decommissioning target of 2051 set by the Japanese government and TEPCO, fuel debris retrieval remains the core challenge in the decommissioning of the Fukushima Daiichi Nuclear Power Station.