Sailors aboard the U.S.S. Ronald Reagan scrubbed the aircraft carrier this week down after radiation detectors found traces of contamination.
The U.S. Navy reported the ship hit a radioactive plume from the damaged Fukushima Dai-Ichi nuclear plant in Japan during its mission.
The chief engineer for the vessel said the radiation doesn't pose any significant health risk, but it must be removed.
The aircraft carrier remains off the Pacific coast of Japan delivering supplies to disaster victims.