South African power firm Eskom announced that it has shut down a unit of its Koeberg nuclear plant for scheduled maintenance work in mid-April, Reuters reported.

According to Eskom, the unit 2 of the Koeberg power station was shut down on April 17 for a scheduled refueling outage after a record of 492 days of uninterrupted run. Unit 2 is expected to be back to operation by May 2017.

Koeberg Unit 1 is currently operating optimally and is contributing with 930MW to the national grid.

The company stated that the shutdown is scheduled every 15 to 18 months; each of the two units at Koeberg is shut down for refueling, inspection, and maintenance.

This routine maintenance is part of Eskom’s overall maintenance program for its fleet of generation units. The outages are scheduled to avoid shutting down the two units at the same time in case of interruptions and to avoid the winter months in each year.