Russia was, at the date, the only country that operates fast neutron reactors for energy production.[citation needed] However issues detected during low power operation required further fuel development work. On 31 July 2015, the unit again achieved minimum controlled power again, at 0.13% of rated power. Commercial operations are expected to start before the end of 2016, now with a power rating of 789 MWe.[3] In December 2015, Unit 4 was connected to the national grid.[4][5]