Around 4:25am on Sep. 5th, there was a power outage in part of the site including the main gate. Five hours later,TEPCO announced that the outage was caused by a defect in the switchboard located west of Unit 4, and some still remain out of power. The outage affected both the main and west gage, corporate welfare building and the dusting monitor which measures the dust containing radioactive material. All workers were instructed to wear full-protective masks accordingly. Nuclear and Industrial Safety Agency says there is no safety concern on coolant system and other significant equipment.
Fuji Sankei News 05, 09, 2012
TEPCO Press Release, Sept 05, 2012
At 4:25 AM on September 5, the alarm which indicated an overload trip at the station power source went off at the Main Anti-Earthquake Building, and we confirmed that the power sources for the main gate, west gate and corporate welfare building were turned off. Since we could not use the continuous dust monitor at the main gate due to this, the operations of omission of full face mask wearing was temporarily suspended. We switched to an alternate power source, and the continuous dust monitor was recovered. We restarted the omission of full face mask wearing at 6:15 AM. For reference, there was no impact on Unit 1 - 6 plants, and there was no effect on the values of each parameter and monitoring post.
TEPCO News 05, 09, 2012