The fourth reactor at the Oi nuclear power plant in Fukui, Japan, started generating electricity with 15% power output on Saturday after the Fukushima Daiichi nuclear accident in 2011, operator firm Kansai Electric Power Co. said. Power transmission from the 1.18-million-kilowatt reactor will cover Western Japan and areas from Fukui, Japan's official news agency (Kyodo) said. The reactor is the second to go into full operation after all of Japan's commercial reactors were taken offline for checks upon the 2011 nuclear accident of Fukushima Daiichi plant in northeastern Japan. The No 4 reactor was booted up Wednesday night and the following morning reached criticality, the state at which a chain reaction of nuclear fissions becomes self-sustaining. The reactor is expected to start full-capacity generation next Wednesday.