The Nuclear Regulatory Commission has sent a third inspector to the Palisades Nuclear Plant in Van Buren County following word of a minor cooling water leak.
The reactor was shut down Sunday for the second time this summer to allow workers to do a visual inspection and find the leak, but plant operators described the move as a conservative measure.
The company said no radioactive material was released outside the plant, which is expected to be returned to service once repairs are completed.
Officials say the leak is not associated with repairs earlier this summer that also forced a shutdown.
The plant was closed for a month in June after another leak in the refueling water storage tank.