According to the Navy's website, the USS Jacksonville, a Los Angeles-class submarine, hit a vessel while operating in the Arabian Gulf on Thursday.
They say one of the sub's two periscopes was damaged in the collision.
The reactor is still in a safe condition according to the website, and there was no damage to the propulsion plant systems.
No injuries were reported.
Jacksonville is on a scheduled deployment to the U.S. 5th Fleet Area of Responsibility.
This incident is still under investigation.