RICHLAND, Wash. — The nuclear power plant near Richland, Washington, began feeding the power grid after being shut down for nearly 13 days.

Energy Northwest’s Columbia Generating Station was operating again Saturday and workers were increasing power generation on Sunday.

The Tri-City Herald reports ( ) the plant was shut down Aug. 20 when an air removal valve in the plant’s turbine building closed.

That caused a loss of vacuum pressure in the system that turns steam back into water for reuse at the plant.

As part of the shutdown, a supporting cooling system was turned on.

Recent maintenance work on that system caused small amounts of iron to enter the reactor water circulation system. Officials say that water must be pure.

The valve was fixed and most of the shutdown was used to filter the iron out of the water system.