Sampling of melted nuclear fuel at Japan’s damaged reactor halted by robot

An effort to retrieve a sample of melted fuel from a damaged reactor at the Fukushima Daiichi nuclear power plant in Japan was halted on Thursday due to a technical problem with a telescoping robot. The intended collection of a small debris sample within the Unit 2 reactor’s containment vessel marked the beginning of the challenging fuel debris removal phase in the prolonged decommissioning process following the devastating earthquake and tsunami on March 11, 2011.

The operation was paused when workers discovered that five 1.5-meter (5-foot) pipes essential for maneuvering the robot were incorrectly arranged and could not be fixed within the radiation exposure time limits, according to Tokyo Electric Power Company Holdings, the plant’s operator. These pipes were crucial for guiding the robot into and out of the vessel, with remote operation taking place from a safer location once inside.

Equipped with a mechanism featuring tongs to collect a fragment from the melted fuel mound, the robot has the capability to extend up to 22 meters (72 feet) to reach its targeted area. The planned two-week mission to retrieve the fragment and return was suspended, with a new timeline yet to be determined, TEPCO stated. Though the objective is to obtain less than 3 grams (0.1 ounce) of the estimated 880 tons of highly radioactive melted fuel, experts emphasize the significance of the sample in advancing decommissioning methods and necessary technologies.

Gaining insights into the characteristics of the melted fuel debris is crucial for the decommissioning of the Fukushima Daiichi plant’s three impaired reactors. Despite facing criticism over the ambitious 30-40-year cleanup timeline set shortly after the disaster, both the government and TEPCO remain committed to it. Specific strategies for the complete removal or storage of the melted fuel debris have not been finalized as of now.