U.S. Navy officials in Japan announced early today that they have repositioned their 7th Fleet after 17 Navy personnel aboard three helicopters tested positive for low levels of contamination from a radioactive plume that rose above the Fukushima Daiichi nuclear plant.
The nuclear-powered aircraft carrier USS Ronald Reagan and its strike group were roughly 100 miles northeast of the plant at the time of the explosion, but three helicopters had flown closer to help with relief efforts, reported the fleet's public affairs office.
Fleet spokesman Cmdr. Jeff A. Davis told The New York Times that the levels of contamination appear so low--described as the equivalent of one month's natural background radiation from the sun, rocks or soil--that the situation "certainly is not cause for alarm."
Kirby Kemper, a nuclear physicist and professor at Florida State University, said in a phone interview that moving the fleet out of the downwind direction of the plume is, indeed, simply a precautionary measure:
One of the advantages, if you can call it that, about radiation is that you can detect extremely low levels. We are all radioactive. Every time you eat a banana you are eating radioactivity. If you've had a chest X-ray in the last year you've had the same amount of radiation. So why not simply take the precaution and just not further expose them at all.
The low-level contamination was no longer detected on the personnel and equipment after surfaces were washed off with soap and water, according to the press release.
The fleet commander also said: "We remain committed to our mission of providing assistance to the people of Japan." The guided-missile cruiser USS Chancellorsville and the destroyer USS Preble are accompanying carrier USS Reagan in what is being called Operation Tomodachi, which is the Japanese word for friends.