The government and the operator of the Fukushima Daiichi nuclear plant decided Tuesday to delay by three years to fiscal 2023 the start of work to remove spent fuel from reactor buildings housing two stricken reactors.
In the revised road map for scrapping the damaged reactors, run by Tokyo Electric Power Company Holdings Inc., the 40-year time frame to complete the process was maintained. It is the fourth time the document has been revised, demonstrating the lingering uncertainty in the aftermath of one of the world's worst nuclear disasters.
Tepco's chief decommissioning officer Naohiro Masuda played down the impact of the partial delays, telling a press conference that "the important thing is that we seek to optimize the decommissioning work as a whole."
"It's not the whole plan that is being moved back," he said.
Top officials from the towns of Futaba and Okuma that host the Fukushima plant expressed disappointment over the delay, but recognized the need to proceed carefully.
"The progress of decommissioning is a prerequisite for the town's reconstruction. The delay is regrettable," said Isamu Kaneda, deputy mayor of the town of Futaba, most of which is still under access restrictions due to the high level of radiation.
But he said the work at the Fukushima plant is something "no other country has gone through" and that "we can't just say 'hurry up.'"
Okuma Mayor Toshitsuna Watanabe added that, to a certain extent, delays "could not be helped if safety is a priority."
The road map to recovery was first crafted in December 2011 after the government declared that the Fukushima crisis had been brought under control, outlining the process of scrapping the Nos. 1 to 4 units by around 2051 at the latest.
In the Fukushima crisis, triggered by a huge earthquake and tsunami in March 2011, the Nos. 1 to 3 reactors, all in operation at the time, suffered meltdowns and the reactor buildings of the Nos. 1, 3 and 4 units were damaged by hydrogen explosions.
The No. 4 reactor, offline at the time of the accident for periodic maintenance work, had all of its fuel stored in the spent fuel pool. Its fuel assemblies have already been removed from the crumbling building, with the work completed in late 2014.
In the latest version of the road map, endorsed by the government on Tuesday, fuel will be extracted from the Nos. 1 and 2 units' spent fuel pools starting in fiscal 2023 instead of fiscal 2020. The government said new technical issues and the need to take safety precautions led to the schedule change.
It is the third time that the schedule for spent fuel removal at the Nos. 1 and 2 units has been postponed.
For the No. 3 unit, the schedule to remove spent fuel in the mid-fiscal year 2018 is unchanged after having already been pushed back earlier this year.
Removing fuel inside the spent fuel pools is one of the key steps in the process before Tepco moves on to the most challenging task of defueling the Nos. 1 to 3 reactors.
The road map retained 2021 as the year in which debris extraction will start. But the deadline to decide the specific approach to remove the melted fuel debris from one of the three reactors was postponed to fiscal 2019, from the earlier planned first half of fiscal 2018.
Attempts have been made to confirm internal conditions of the damaged reactors using robots. A survey robot captured images of what is likely to be melted nuclear fuel at the bottom of the No. 3 reactor for the first time in July this year.
A debris removal method currently considered feasible by the government involves accessing the side of the three crippled reactors by partially filling them with water.
Measures will also be taken to slow the daily pace of contamination of water at the complex to around 150 tons in 2020 from the current 200 tons, according to the road map.
Currently, toxic water is building up at the plant partly because groundwater is seeping into the reactor buildings to mix with water made radioactive in the process of cooling the damaged reactors.
The toxic water undergoes a process to remove radioactive materials and is kept in massive tanks set up at the plant. Regulatory authorities have called for the water to be drained into the sea, but the act is controversial among local people, especially fishermen, as the water still contains radioactive tritium, which is difficult to remove.
The road map did not mention a specific schedule for the disposal of the processed, but still tritium-contaminated water, only saying that the matter will be considered while taking into account "social aspects such as reputation damage (of the area)."