The decades-long challenge to scrap the Fukushima Daiichi nuclear plant, crippled by the massive earthquake and tsunami disaster that struck northeastern
Decommissioning of the plant, scene of the world's worst nuclear accident since the 1986 Chernobyl disaster, is crucial for
"It is likely that the roadmap will not be completed as scheduled," said
He added the "melted debris is mixed with fractured parts of buildings and concrete material and is highly radioactive, making it hard for robots to clear the debris."
The scrapping of the plant involves the daunting decision on how to dispose of the huge amount of radioactive waste left as a byproduct. This has been made worse as no municipality offered to become the final disposal site when the plant was operating.
Following a magnitude-9.0 earthquake and subsequent tsunami that hit the plant on
Due to the instability of renewable energy,
Of the 33 reactors in
Tsutsui, a former petrochemical complex engineer, points to how the risk of extracting debris has become "clearer" compared to when the roadmap was first compiled in
"Nearly 10 years have passed following the Fukushima accident but with respect to the long decommissioning process, we are still hovering around the start line. We have a long journey ahead," said Fukushima Gov.
"The most difficult step is the safe and stable retrieval of the debris but we don't know what state it is in," he added.
Despite the use of computer simulations and small-scale internal probes using remote cameras, data is scarce about the exact locations and other details of the melted fuel -- crucial information to determine the retrieval methods and develop the appropriate technology and robots.
Robotic probes at the Nos. 2 and 3 units have captured images of large amounts of material that appear to be melted fuel, but attempts so far have been unsuccessful at the No. 1 unit.
In a setback for retrieval efforts, the company said in late December removing melted fuel from the No. 2 unit would be delayed from its initial starting period in 2021 by at least a year as the coronavirus pandemic has stalled the development in
That robotic arm, however, can only extract a few grams of melted fuel debris at a time. To completely remove the hundreds of tons of melted fuel from the reactor larger machinery is required, experts say.
In another development that may affect the decommissioning process, a
The regulator's findings in a new interim report draft on the Fukushima accident came as a shock because it was previously believed that most of the radioactive material remained at the bottom of the reactors in the form of melted nuclear fuel debris.
While industry minister
The utility and the government have also been grappling with the buildup of radioactive water, which is generated in the process of cooling the meltdown reactors.
Part of the water is stored inside massive tanks set up inside the premises, having gone through a system that removes various radioactive materials except tritium, which is difficult to separate from water.
The government is considering dumping the water into the Pacific after diluting it to a radiation level below the legal limit, saying the tanks are filling up. It says space is needed to store debris once it is extracted from the damaged reactors.
But discharging the water remains a sensitive issue especially for the local fishing industry struggling to revive its business following the accident. Neighbors
Releasing it into the ocean could lead to a continued ban on exports from this area or an introduction of new export restrictions, observers say.
According to
"But the roadmap is nothing but pie in the sky," he said.
The commission says it is more logical to keep the debris inside the reactors than to retrieve it and suggests constructing a shield around the reactors and postpone taking out the melted fuel until 100 years or 200 years later when radioactive activity levels have decreased.
==Kyodo
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