Article from Japan Today :
" FUKUSHIMA : Workers dealing with the nuclear crisis at the Fukushima Daiichi power plant entered the No. 1 reactor building early Monday for the first time since high-level radiation forced them to abandon on-site operations there to help stabilize the country’s worst ever nuclear accident.
The move came after plant operator Tokyo Electric Power Co opened the building’s doors to its adjacent turbine building Sunday evening, and confirmed that the resultant release of radioactive materials into the air had not raised radiation levels on the premises, according to the firm.
The workers went inside the building around 4:20 a.m. and measured radiation inside, TEPCO said, without immediately announcing the radiation readings.
If the radiation level is confirmed to be acceptable for workers to operate inside, they will start building a new cooling system for the reactor—the most severely damaged of the six reactors at the plant, which lost cooling functions in the March 11 quake and tsunami.
They are expected to install and adjust equipment including a heat exchanger and instruments to measure the water levels in the reactor’s pressure vessel containing nuclear fuel and the containment vessel shrouding it, the company said.
No rises in the radiation level have been measured at nine observation points in the plant located some 220 kilometers northeast of Tokyo since the double-entry doors were opened shortly past 8 p.m. Sunday, TEPCO said.
The government’s Nuclear and Industrial Safety Agency and the Environment Ministry began measuring the same day radiation levels in debris left by the quake-tsunami disaster in Fukushima Prefecture to consider ways to dispose of it and address the fears of local people."