Unit 6 of Kozloduy Nuclear Power Plant (NPP) in Bulgaria has been switched on again on Thursday with new Russian fuel, a nuclear watchdog official has said.

The unit will now operate using a mix of the new improved fuel and the one used previously, gradually phasing out the old combustible over the next four years, Borislav Stanimirov, of the Nuclear Regulatory Agency, has told the Bulgarian National Radio.

In addition, an upgrade of the reactor's electricity generation capacity is being conducted to 1040 MWh, Stanimirov has said.

The VVER-1000 reactors used in Kozloduy NPP have a capacity of 1000 MWh. While some VVERs in Russia have already been upgraded accordingly, Kozloduy's Unit 6 is the first Bulgarian reactor to be given such a boost during its annual repair.