(Reuters) - The U.S. military took new steps to shield personnel from radiation spread by Japan's crippled nuclear plant on Tuesday, redirecting arriving warships to safer waters and telling some forces to limit time outdoors.
Here are the latest details from the Pentagon on the mobilization of American forces to aid Japan after its devastating tsunami and earthquake.
All times are local to Japan.
* Two U.S. naval bases detected above normal levels of radiation: the Yokosuka Naval Base, located about 200 miles south of the plant, and the Naval Air Facility Atsugi, which is about 150 miles from the plant.
* Rear Admiral Richard Wren, commander of U.S. Naval Forces Japan, said the additional radiation exposure for the past 12 hours at the two bases was about 20 millirem, less than one month's exposure to naturally occurring background radiation. He is recommending personnel and their families limit outdoor activity and shut down external ventilation systems.
* A day after saying 17 Americans on helicopter missions had been exposed to a month's worth of normal radiation, the Navy acknowledged several more crew members had been similarly exposed to low levels of radiation. But it said there was no risk to their health and that operations would continue.
* The Navy said some arriving warships will be stationed off the west coast of Honshu, Japan's largest island, instead of heading to the east coast as planned because of "radiological and navigation hazards."
* The ships are the USS Essex, a large amphibious assault ship; USS Harpers Ferry, a dock-landing ship; and USS Germantown, an amphibious dock-landing ship. They are expected to arrive on March 17.
* The USS Ronald Reagan Carrier Strike Group, which includes the cruiser USS Chancellorsville, the destroyer USS Preble and the combat support ship USNS Bridge, is conducting operations off the east coast of Honshu at a safe distance northeast of the Fukushima nuclear complex.
* The strike group flew 29 sorties on Tuesday to bring humanitarian aid ashore, delivering 17 tons of supplies including food, water and blankets. A total of 25 tons has been delivered so far, providing assistance to 2,000 people.
* The guided-missile destroyers USS Fitzgerald, USS John S. McCain, USS McCampbell and USS Curtis Wilbur are in the same area as the carrier strike group.
* The guided missile destroyer USS Mustin is at sea south of the disaster site.
* U.S. Navy P-3 "Orion" aircraft flew two missions to survey and assess the debris field at sea.
* USS Tortuga, an amphibious dock landing ship, loaded two heavy-lift MH-53 helicopters on Saturday in South Korea. It was due to arrive on the Japanese island of Hokkaido on Tuesday to pick up 300 Japan Ground Self Defense Force personnel and 90 vehicles bring them to Aomori, Japan.
Reporting by Phil Stewart; editing by Todd Eastham