The river is carrying large quantities of leaves and other small objects with it, thus diminishing the effectiveness of the secondary cooling system, the nuclear administration said.

Aleš Janežič, the director of the Inspection Service for Radiation and Nuclear Safety at the administration, said that NEK had been brought to a halt even though the water cleaning devices had been running at full capacity.

All systems and equipment functioned properly upon the shut down, he asserted. "There were no unwanted influences on the environment or the people," he pointed out.

After the necessary analyses and inspections of the systems and the equipment are conducted, preparations for bringing the plant back on line will start, Janežič said.

NEK should be reconnected to the grid in the coming days.