An American nuclear-powered submarine leaked radiation for over two years, releasing most of the material in its home port of Guam and at Pearl Harbor, Japanese and U.S. officials said Thursday.
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 U.S. Navy released a detailed chronology of the leaks over the past two years, showing the cumulative radioactivity released was less than 9.3 micro curies – with 8 micro curies released in Guam alone. By comparison, according to the U.S. Environmental Protection Agency, the average amount of radioactivity in a smoke detector is about 1 micro curie, or 1 millionth of a curie.
Navy Cmdr. Jeff Davis said the Houston is still in Hawaii being repaired and the reactor is turned off. Once the leak was discovered last month, the Navy provided detailed data to the Knolls Atomic Power Laboratory – a government facility – to determine how much radiation had leaked over the two-year time period, Davis said.
The amount is so small, he said, that the Navy terms it a “weepage” rather than a leak. The problem was discovered July 17, when about a gallon of water spilled onto a crew member when a fitting came loose. The water had previously come in contact with the reactor, but no radioactivity was detected on the sailor.
The 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 subs 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.”
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, south of Tokyo.
Davis said the problem would not affect the USS George Washington's move.
“This goes to show the people of Japan and the government of Japan that they can be reassured that the United States Navy will be forthright in disclosing details about any inadvertent release of radioactivity, even when it is extremely small.”
The carrier's arrival, originally set for August, was delayed until late September because of a fire on the vessel in May, another incident that has caused safety concerns in Japan.