Workers trying to restore the Fukushima No. 1 nuclear power plant on Wednesday entered the building of the troubled No. 2 reactor for the first time since it suffered an explosion in the early days of the nuclear crisis.
Plant operator Tokyo Electric Power Co. has already sent workers into the No. 1 reactor building to lay the groundwork for a system to more stably cool the nuclear fuel. Similar work is expected to take place in No. 2′s building, such as checking equipment and adjusting or repairing any malfunctioning gauges.
According to the road map drawn up by the utility, it plans to place crippled reactors 1, 2 and 3 into more stable cooling situations by mid-July and put them into cold shutdown by January at the latest.
In an updated version of its road map unveiled Tuesday, Tepco did not change the broad restoration time frame but said it plans to engineer a system to cool the three reactors by recycling the massive amounts of radioactive water now flooding the reactors’ basements and adjacent turbine buildings.
The water, which is likely highly dangerous, may be leaking out of the reactors’ damaged containment vessels.
The reactors, which lost their cooling systems in the quake and tsunami on March 11, are in turn leaking the water that is being injected into them as an emergency step to keep the fuel in the cores from melting further.
The latest findings suggest the No. 1 reactor core melted down shortly after being rattled by the earthquake, and government officials have emphasized the need to act on the assumption that the cores of reactor Nos. 2 and 3 experienced something similar.
On Wednesday morning, four Tepco workers entered the No. 2 reactor building for about 15 minutes.
They were exposed to radiation between 3.33 and 4.72 millisieverts, Tepco said.
The environment inside the No. 2 building is tough for workers not only because of the high radiation level there, but also because of the high humidity caused by steam rising from a pool above the reactor used to store spent nuclear fuel, it said.
Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency, said Tepco plans to install a device to cool the water in the spent fuel pool in the near future, and that operating the system is expected to help lower the humidity.