Tokyo Electric Power Co, operator of the wrecked Fukushima Daiichi nuclear power plant, on Tuesday recommenced clean-up work after a two-week break due to two fatal accidents at the Daiichi and Daini plants.
All work was halted following the accidents, in order for safety regulation checks to be conducted.
However, TEPCO said it expects delays to continue for up to a month on a project to build an ice wall intended to contain the leaking of contaminated water from reactors at the Daiichi plant, TV Asahi reported.
TEPCO has been fighting a daily battle against contaminated water since Fukushima was wrecked by an earthquake and tsunami in March 2011 and three reactors underwent meltdowns.
Water flushed over the wrecked reactors to keep them cool enough to prevent further radioactive releases is leaking into basements after contact with the melted uranium fuel.
The water mixes with groundwater that seeps into the basements, requiring more pumping, treatment and storage.
Missteps and leaks have dogged the efforts to contain the water, slowing down the overall decommissioning process, which is expected to take decades.