On Aug. 1, the U.S. Navy notified Japan that the USS Houston had leaked water containing small amounts of radiation during three calls to the southern Japanese ports of Sasebo and Okinawa in March and April this year but caused no threat to people or the environment. The submarine also made stops in Guam and Pearl Harbor.
A new U.S. Embassy report released by the Japanese Foreign Ministry Thursday said the submarine was already leaking during nine earlier port calls in Japan and the amount of radiation leaked was larger than initially reported. It "has been steadily leaking a small amount" of radiation from June 2006 to July 2008 when it entered a drydock in Hawaii, the U.S. report said. It said the total leakage was still negligible.
The radiation leak has caused a stir in Japan where the continued presence of the U.S. military and its nuclear vessels draw complaints from residents about crime, noise and pollution linked to some 50,000 American servicemen based in the country. The presence of nuclear submarines is particularly sensitive, given that Japan is the only country the U.S. ever used atomic bombs against in the closing days of World War II.
"If we add all radiation leaked at every Japanese port, it would be still smaller than the amount of naturally occurring radioactivity found inside home smoke detectors," the Japanese foreign ministry said in a statement accompanying its release of the U.S. report. "Japan also has found no abnormality in its monitoring results during Houston's port calls since June 2006."
U.S. Embassy officials could not immediately be reached for comment.
The USS Houston made three previously undisclosed calls at Sasebo in July 2006, February and April in 2007. The vessel was also leaking during its two port calls in Yokosuka, a large U.S. naval port near Tokyo, in 2007, and four calls in Okinawa in 2007, according to the embassy report.
News of the incident also comes just weeks ahead of the arrival of the nuclear-powered aircraft carrier USS George Washington to be based in Yokosuka, just south of Tokyo.
The carrier's arrival, originally set for August under a Japan-U.S. security alliance, was delayed until late September because of a fire aboard the vessel in May, another incident that has caused safety concerns in Japan.