September 9 (SeeNews) - Bulgaria's sole nuclear power plant Kozloduy said it shut down on Sunday its 1,000-megawatt Unit Six for planned annual maintenance, after reconnecting to the power grid its other 1,000-megawatt unit, Unit Five, earlier in the day. Unit Five was shut down on September 1 following an electrical circuit failure, the plant said in a statement. No radiation leaks were invlolved in the accident.