Delayed probe of Fukushima No. 1 reactor to push back fuel debris removal

[Translated by the Japan Times]A plan to remove fuel debris from the primary containment vessel of a reactor at the Fukushima No. 1 nuclear power plant is expected to be further pushed back after it became apparent that Tokyo Electric Power Company Holdings Ltd. will not be able to conduct an internal probe — a key step to start removing the fuel debris — by the end of March as planned. The internal probe would involve using remote-controlled robots to collect fuel debris inside the No. 1 reactor so Tepco can examine its composition and form. Tepco’s plan is to open three holes in both the outer and inner doors of the primary containment vessel using pressurized water mixed with a polishing agent. After it succeeded in opening three holes in the outer door, Tepco started drilling a hole in the inner door in June 2019. But that procedure caused the concentration of radioactive dust to increase temporarily, prompting staff to suspend work. On Jan. 14, Tepco resumed the project, which involves drilling roughly 40 percent of a hole 21 centimeters in diameter over the course of 10 days in order to gather data on how to continue with the work without releasing contaminated dust. In order to move on to the internal probe, Tepco needs to finish drilling the hole as well as two more. Not only that, Tepco needs to secure a path for the robot to go inside the primary containment vessel, install cameras and measuring instruments inside, and make sure it can be remotely controlled once the robot is inside. The entire procedure is expected to take at least several months. To get a complete understanding of the situation inside the No. 1 reactor’s primary containment vessel, Tepco hopes to send a robot that can move underwater and take photos of the inside as it swims in the contaminated water. Not only will it measure the physical condition of sediment inside the vessel, it will collect samples as well, and the information will hopefully be useful in the future when Tepco removes the fuel debris. Tepco first planned to conduct an internal probe during the first half of fiscal 2019. This was postponed to the latter half of the fiscal year. On Jan. 16, Nuclear Regulation Authority Chairman Toyoshi Fuketa urged Tepco President Tomoaki Kobayakawa to start discussing ways to dispose of the spent fuel debris and radioactive waste inside reactors at the Fukushima No. 1 nuclear plant in the decommissioning process. Tepco has stated that spent fuel rods at the Fukushima No. 2 nuclear power plant will be transported outside of Fukushima Prefecture, but nothing concrete has been decided for the melted fuel debris, spent fuel and radioactive waste at Fukushima No. 1. “Decommissioning won’t be complete just by clearing up Fukushima No. 1 and leaving (radioactive waste) inside,” Fuketa said. “If we don’t remove what we can, the decommissioning process will be stalled. I want you to work on a concrete plan to remove (the waste).” “To stabilize the power plant and figure out where to store the nuclear waste after it’s removed will take time, which is why its paramount that (work) begins now,” Fuketa said. “That falls under the responsibility of management.”