TEPCO doesn't know yet what caused the power outage in the Reactors 1 and 2. The power stopped for these reactors from 2:20PM to 5:30PM on June 8.
TEPCO plans to open the double door to the Reactor 2 reactor building after they install the air filtering system and run it for several days to "reduce" the amount of radiation inside the reactor building. The same exercise that they did for the Reactor 1 reactor building.
The air filtering system is scheduled to start operating on June 11, which happens to be the day when big "anti-nuke plant" rallies are planned throughout Japan.
In the meantime, the president of TEPCO, Masataka Shimizu, verbally scolded (without any penalty) the head of Fukushima I Nuke Plant, Masao Yoshida, for not stopping the seawater injection on March 11 as agreed at TEPCO and not reporting it to the TEPCO headquarters.
"Tatemae" at its best (I should say worst.)