The Japanese government and the operator of the crippled Fukushima Daiichi nuclear power plant say cleaning up a heavily contaminated reactor building is much harder than they had believed, NHK reported on Friday.
They have decided to conduct additional decontamination work at one of the reactor buildings before they launch a decommissioning process.
Workers have been scraping off flooring material at the upper part of the No.3 reactor building to remove radioactive substances sticking to the surface.
The operator Tokyo Electric Power Company expected the work to lower the radiation level there to 1 millisievert an hour, a level that will allow people to work there for some time.
But estimates by the operator have found that even after the planned cleaning up, radiation could reach 60 millisieverts an hour in some areas, and over 10 millisieverts in many other areas.
The government and Tokyo Electric Power decided to introduce more measures to reduce exposure. They include laying down steel sheets on floors to block strong radiation as well as scraping off more layers of flooring material.
The operator plans to remove nuclear fuel from the storage pool of the No.3 reactor from the next fiscal year. But it says it's not yet known how the delay in decontamination would affect the schedule.
Removal of nuclear fuel from reactor storage pools is a significant part of the decommissioning process. For reactor No.1, the operator plans to delay the schedule by 2 years to fiscal 2019. For reactor No.2, it says it will compile a plan in 2 years.