The Southern Co. shut down one of the reactors at it Joseph M. Farley Nuclear Plant in southeast Alabama to fix a diesel generator.

The company said the Unit 1 reactor was taken down at 3:30 a.m. Friday.

Company spokeswoman Katherine Weitzman said it was required by federal regulations while workers repaired and tested an engine cooling value on one of five diesel generators that are designed to operate the reactor in case of a power loss.

She said there was no danger to workers or the public, and employees began working to bring the unit back online later Friday morning. She declined to give a timetable for competitive reasons. The plant’s second reactor continued to operate.

The Farley Plant is located in Columbia, about 20 miles east of Dothan.