Leakage of Coolant Water from Nuclear-Powered Submarine USS Houston
(Information Provided Based on Investigation by the U.S. Side)
August 7, 2008
- In the morning of August 7, Mr. James P. Zumwalt, Deputy Chief of Mission
of the Embassy of the United States of America, orally informed Mr. Shinichi
Nishimiya, Director-General of the North American Affairs Bureau, Ministry
of Foreign Affairs (MOFA), concerning the leakage of coolant water from
nuclear-powered submarine USS Houston, of the progress of the investigation
by the U.S. side and the summary of the present status which was confirmed
after it had given the leakage information to the Government of Japan, stating
this was a prior notice of an official notification to be made later. Around
1:30 p.m. on the same day, August 7, the U.S. Embassy sent an information
sheet to the Ministry of Foreign Affairs as an official notification. The
following is the gist of the information.
(1) The U.S. conducted an investigation after it notified the Government of Japan of the leakage on August 1. This is additional information on the results of the investigation. At first, on August 1, the U.S. informed Japan that it did not know when the leakage had started. However, subsequent investigation newly confirmed that the valve has been steadily leaking a small amount above the stringent design specification from June 2006 until USS Houston was placed in dry dock in July 2008. The list of port visits from June 2006 to present, and the estimated amount of radioactivity released into the environment for each of these port visits is attached.
(2) 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 total amount of radioactivity released into the environment as a result of all the attached foreign port visits is less than the amount of radioactivity contained in a common household smoke detector.
- MOFA double-checked with the Ministry of Education, Culture, Sports, Science and Technology (MEXT) with regards to the amount of radioactivity at each port and date shown in the attachment to the information sheet, and confirmed that when the USS Houston called at Sasebo, Yokosuka and Okinawa since June 2006, no abnormal amount of radioactivity was found in the monitoring by the Japanese side. According to MEXT, there was no leakage of radioactivity that could have affected the safety of human beings and the environment as no abnormal amount has been detected in the investigation which has been carried out up to the present.
(END)
Related Information (Japan-U.S. Relations)
Related Information (Japan-U.S. Security Arrangements)