The cover was installed after the March 2011 nuclear accident to prevent radioactive dust from dispersing. The reactor experienced a hydrogen explosion at the time of accident.
Tokyo Electric Power Company plans to remove the cover in order to clear away radioactive debris on the upper part of the building and remove spent nuclear fuel still stored inside. It is part of an effort to decommission the reactor.
For about one week, workers will spray chemicals over the debris inside the cover by using a remote-controlled crane to prevent radioactive dust from spreading.
They will proceed with the work to remove the cover over the period of about one year. Company officials say they will enhance monitoring of radiation levels during the procedure.
TEPCO says a preliminary test last year showed no scattering of radioactive materials when dismantling the cover.
The utility initially planned to start dismantling the cover on the No.1 reactor building in July of last year. But the work was delayed after the removal of debris from the No. 3 reactor in 2013 caused radioactive dust to spread, sparking fear among local residents. The death of workers at the plant also affected the plan.
On the first day of the work, TEPCO, the plant operator, sprayed a chemical agent in the reactor building to prevent radioactive dust in the building from being released into the air when the cover is removed.
On May 15, a large crane lifted a spraying machine to insert a thin, long nozzle into the building through holes created on the top cover to spray a glue-like chemical to contain dust and other materials generated by a hydrogen explosion triggered by the March 2011 Great East Japan Earthquake and tsunami.
The agent will be sprayed through the nozzle at 48 points. After it completes the spraying, TEPCO plans to begin retracting the roof cover on May 25 at the earliest to remove debris from the upper part of the building.
When the utility was removing debris from the No. 3 reactor building in the summer of 2013, a large amount of radioactive substances was released into the environment, fostering the public's distrust in the process.
Subsequently, TEPCO has cautiously been proceeding with preparations for removing the cover around the No. 1 reactor building, such as testing anti-scattering agents in advance last October.
Because it is currently rice planting season around the Fukushima plant, TEPCO has pledged to suspend its work and inform surrounding local governments within 30 minutes when amounts of released dust and radiation exceed certain levels.
Source: Asahi Shimbun