Hungary's only nuclear power plant says that one of its four reactors has been shut down because of an electrical fault in the control system.

The plant said Thursday that the incident did not pose a nuclear threat and the other reactors are functioning normally. Repairs have begun and the reactor is expected to be restarted around noon Friday.

The Soviet-built plant in the city of Paks provided about half of Hungary's electricity supply in 2014 and is in the early stages of a major expansion expected to boost output by some 20 percent.

The European Union has been vetting several aspects of the expansion plan, which will be carried out by Russia's state-owned Rosatom and is being financed largely with a Russian loan of 10 billion euros ($11.1 billion).