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Friday, Aug. 8, 2008

U.S. details sub Houston's radiation leaks

Staff writer

The U.S. government notified Japan Thursday that trace amounts of radioactivity leaked from the nuclear submarine USS Houston at a port in Kanagawa Prefecture and one in Okinawa between July 2006 and this April.

The U.S. earlier admitted that a similar leak occurred when the Los Angeles-class fast-attack sub made a port call in Sasebo, Nagasaki Prefecture, in March.

In all, the submarine made 11 port calls in Japan during the period, according to a report provided to the Foreign Ministry by the U.S. Embassy in Tokyo. Details of the leak, first made public last week.

The total amount of radioactivity released in Japanese ports — 0.605 microcuries — "is less than the amount of radioactivity contained in a common household smoke detector," the report said. It also disclosed that the Houston had been leaking radioactivity between June 2006 and last month.

No abnormalities showed up in monitoring results at the three ports during the sub's visits, the Foreign Ministry said.

The ministry's North American Affairs Bureau was notified Thursday morning by the U.S. Embassy's deputy chief of mission, James Zumwalt, of the investigation update.

Extensive analysis by the U.S. Navy determined that a valve was "steadily leaking a small amount above the stringent design specification." Because the leak was extremely small, it required a computational analysis to determine.

According to the report, the sub leaked a cumulative 0.34 microcuries of radioactivity in Sasebo, 0.095 microcuries in Yokosuka, Kanagawa Prefecture, and 0.170 microcuries at a U.S. base in Uruma, Okinawa Prefecture.

The navy did not disclose the specifics of the valve design "in order to protect the details of the technology."

"At no time was there a risk to the reactor plant, the safety of the crew, the safety of the public, marine life, or the environment as a result of these port visits," the report said.

The Foreign Ministry did not publicize the incident when it was first informed by the U.S. of the possible leak at Sasebo port on Aug. 1.

Foreign Minister Masahiko Komura had said he found out about the leak while watching a CNN program the next morning.

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The Japan Times

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