The Pilgrim nuclear power plant was offline for more than 80 days in 2013, 46 of those days from scheduled refueling and maintenance.
Now, the Nuclear Regulatory Commission has placed the 685-megawatt plant on a list of eight reactors across the country deemed as degraded.
That means more federal inspectors will be at Pilgrim in the coming months.
The latest downgrading of the Plymouth plant comes four months after workers had to make an unplanned shutdown, when the plant lost power from an NStar line that provides electricity to the plant.
That shutdown lasted a week.