TOKYO (AP) – An attempt to use an extendable robot to remove a fragment of melted fuel from a destroyed reactor in tsunami-hit Japan Fukushima Daiichi Nuclear Power Plant was suspended on Thursday due to a technical problem.
The removal of a tiny sample of debris from the containment vessel of reactor unit 2 would begin the phase of fuel debris removal, the most difficult part of the decades-long shutdown of the power plant, where three reactors were destroyed in the magnitude 9.0 earthquake and tsunami disaster on March 11, 2011.
Work was stopped when workers noticed that five 1.5-meter-long pipes were being used to maneuver the robot were placed in the wrong order and could not be corrected within the radiation exposure deadline, said power plant operator Tokyo Electric Power Company Holdings.
The tubes would be used to push the robot in and pull it out again when the job is finished. Once inside the vessel, the robot would be remotely controlled from a safer location.
The robot can extend up to 22 meters (72 feet) to reach its target area and collect a fragment from the surface of the mound of molten fuel using a device equipped with tongs hanging from the top of the robot.
The mission to recover the fragment and return with it is expected to take two weeks. A new launch date has not yet been set, TEPCO said.
TEPCO President Tomoaki Kobayakawa said safety took priority over rushing the process and that he wanted to investigate the cause of the problem with the pipeline’s installation.
“I understand that the decision was to stop and not push when there were concerns,” Kobayakawa told reporters in Niigata Prefecture in northern Central Asia, where he was to talk to local people about another nuclear power plant operated by TEPCO.
The sample retrieval mission is a key first step in the decades-long decommissioning work at Fukushima Daiichi, but the goal of returning less than three grams (0.1 ounces) of the estimated 880 tons of deadly radioactive liquid fuel underscores the enormity of the challenge.
Even though the debris sample contains only a small amount, experts say it will provide important data for the development of future decommissioning methods and the technologies and robots needed to carry them out.
A better understanding of the melted fuel debris is key to shutting down the three destroyed reactors and the entire power plant.
The government and TEPCO are sticking to the 30- to 40-year cleanup target set shortly after the meltdown, although this has been criticized as unrealistic. There are no concrete plans for the complete disposal of the melted fuel or its storage.
