Kyushu Electric Power Co has restarted the No. 1 reactor at its Sendai nuclear plant in southwestern Japan after completing mandatory upgrades to protect the facility against terrorist attacks, a spokesman said.

The utility began booting up the 890-megawatt (MW) reactor on Tuesday after carrying out regular maintenance and refueling, the spokesman said by phone on Wednesday.

With the restart, Japan now has two operating nuclear reactors with a total capacity of 2,070 MW. Many reactors are still going through a relicensing process under new safety standards imposed after the 2011 Fukushima disaster.

Kyushu Electric said it plans to restart the No. 2 reactor at Sendai in late December following upgrades.