Photo/IllutrationThe No. 1 reactor building, left, and the No. 2 reactor building at the crippled Fukushima No. 1 nuclear plant in February (Pool)

The government on Sept. 26 revised its long-term plan to decommission the crippled Fukushima No. 1 nuclear power plant, citing high levels of radiation.

It said the three-year delay concerns the removal of spent fuel rods kept in storage pools at the No. 1 and 2 reactor buildings and will not affect the overall plan to fully dismantle the facility within 30 to 40 years.

A committee of Cabinet ministers involved in the process met Sept. 26 and approved the changes submitted by the government and Tokyo Electric Power Co., operator of the Fukushima plant.

The decommissioning road map was last revised in June 2015.

The spent fuel storage pool in the No. 1 reactor building holds 392 fuel assemblies, while the pools in the No. 2 and No. 3 pools contain 615 and 566 assemblies, respectively.

The upper part of the No. 1 reactor building was destroyed in a hydrogen explosion, spreading rubble and debris throughout the building. Studies earlier this year showed that radiation levels within the building are still high.

The No. 2 reactor building was not damaged, but decontamination work within the building is expected to take longer than initially expected.

For those reasons, the start of removal of the fuel rods from the No. 1 and 2 reactor storage pools will be put off until fiscal 2023.

The start of removal of fuel rods from the No. 3 reactor storage pool remains unchanged from fiscal 2018.

It was decided in February 2017 to delay the start of work from fiscal 2017 by one year. Work to remove melted nuclear fuel from the three reactors' containment vessels will also be delayed.

Remote-controlled robots have been used since the start of the year to study the interior of the vessels, but the state of the melted fuel has only partially been determined.

Further studies will be carried out to assess the dangers.

There is no change as yet in the plan to begin removing melted fuel from one of the three reactors before the end of 2021.

But a decision on which reactor to work on first will be delayed until fiscal 2019. At that time, the specifics of how to accomplish the removal work will also be decided. It was initially envisaged that these two points would be thought through in the first half of fiscal 2018.