Rosenergoatom reported that turbine blades broke at the plant where the Russian state-owned company installed two reactors of the type it is building in Turkey and plans to build in Hungary, Reuters reports.

Rosenergoatom, which operates Russia’s nuclear power plants, said it was unclear what caused the blades to break, which shut down the unit at the Leningrad nuclear power plant on Sunday.

“The main thing now is to understand the reason for the destruction of the blades. This is a new phenomenon,” said Oleksandr Shutikov, head of Rosenergoatom. According to him, the repairs should be completed by December 22.

The facility where the problem occurred was built in 2018 and houses the state-of-the-art VVER 1200 pressurized water reactor. Units of this type are being built by Russia at the Akkuyu nuclear power plant in Turkey and are planned for the Paksh-2 installation in Hungary. Russia has already supplied them to Belarus.

Shutikov said the blades that failed were part of a 1,200-megawatt high-speed steam turbine. Turbines are manufactured by the Power Machines company of businessman Oleksiy Mordashov, which did not respond to a request for comment.

Rosatom, the parent corporation of Rosenergoatom, reported that similar models of turbines are operating at another plant in Leningrad and Voronezh. The company said it always investigates and fixes any malfunction.

“As the turbines are not part of the plant’s ‘nuclear island’, their failure does not affect nuclear safety as all reactor equipment is working as intended,” the statement said.