The operator of the wrecked Fukushima nuclear power plant said it plans to begin a trial retrieval of debris containing melted nuclear fuel from one of its three meltdown-hit reactors on Thursday.
Tokyo Electric Power Company Holdings Inc said Monday it aims to retrieve a few grams of debris from the No. 2 unit in its first attempt, with plans to gradually expand the process to the No. 3 unit, where large-scale removal is expected in the early 2030s.
Removing the radioactive debris is considered one of the most challenging tasks in decommissioning the Fukushima Daiichi plant, whose reactors were severely damaged following the loss of cooling functions in the wake of a massive 2011 earthquake and tsunami in northeastern Japan.
How to remove an estimated 880 tons of debris from Nos. 1, 2 and 3 reactors, which suffered meltdowns, as well as where to store the retrieved debris until disposal, remains unclear.
TEPCO plans to retrieve up to 3 grams of debris using a telescopic device equipped with a gripper tool. The device can extend up to 22 meters and access the debris through a penetration point into the primary containment vessel.
Since debris emits strong radiation, the retrieval device will be shielded by the connection structure and an isolation valve.
It is expected to take around a week for the device to reach the debris and about two weeks to complete the retrieval operation, according to the utility.
If the radiation level of the debris exceeds 24 millisieverts per hour, the debris will be returned to the containment vessel to protect workers' health and safety, TEPCO said.
The Nuclear Regulation Authority approved the device on Friday, setting up the start of trial retrieval.
TEPCO had initially planned to start retrieving debris from the No. 2 unit in 2021 but has since postponed it three times due to the coronavirus pandemic and technical difficulties.
