Tepco will open a very humid nuclear reactor airlock, at the Fukushima Daiichi nuclear plant, the company said on Sunday.
The company said work on Reactor 2 is necessary on the unit to improve the working environment in the reactor building for workers.
Humidity in the building was 99.9 percent, Tepco said.
The company said it will install an ambient air filtration system and circulate air inside the building to reduce the density further.
Subsequently, we will open the airlock of the Reactor Building for the workers to enter the building and undertake the necessary work, Tepco said.
Workers would measure the radioactive substances in the building to confirm that the impact to the outside environment is sufficiently low.
Tepco said humidity would be reduced when the airlock opens.
Tepco has also submitted an impact evaluation to the Japanese government.