Bulgaria shut down one of two reactors at its only nuclear power plant on Tuesday after a generator control problem, the operator said, adding that there was no radiation leak.

"Kozloduy's 1,000-megawatt reactor number six was disconnected from the country's electricity grid at 9:24 am (0624 GMT) due to failure of a control element of the unit's turbogenerator ... that triggered the reactor's shutdown," the plant said.

The glitch in the non-radioactive, secondary circuit of the reactor came just three days after it had been reconnected to the grid following maintenance and refuelling work. It was also shut down in May due to generator problems.

Kozloduy's other 1,000-megawatt reactor remains in operation. Four other reactors at the plant were shut down in 2002 and 2006 as conditions for Bulgaria's entry into the European Union.

The power plant generates around 30 percent of Bulgaria's electricity. In March the government scrapped a deal with Russia's state-owned Atomstroiexport to build a new 2,000-megawatt plant.