REPORTED LEAK OF RADIOACTIVE WATER BY THE USS HOUSTON

Column: 2968

REPORTED LEAK OF RADIOACTIVE WATER BY THE USS HOUSTON: 1.

Mr Michael Palmer asked the Minister for Defence (a) whether he will give an account of the reported leak of radioactive water by the USS Houston when it called at Singapore in September 2006; and (b) whether the Government is

Column: 2969

confident that public safety was not compromised.

The Minister for Defence (Mr Teo Chee Hean): Mr Speaker, Sir, on 1st August 2008, the media reported that the US nuclear-powered submarine USS Houston had been found to be leaking trace amounts of radioactive water. The leak had been discovered by the United States Navy during a routine dry dock maintenance of the submarine at Pearl Harbour Naval Shipyard in Hawaii in July 2008. The media noted that the US had informed Japan of the leak, as the United States Navy's investigations had determined that the USS Houston could have been leaking when the USS Houston made its port call in Sasebo, Japan in March 2008.

At that time, there was no information to suggest that the leak went beyond the port visit that the USS Houston had made in Sasebo, Japan. Nevertheless, as a precautionary measure, we had asked the US on 4th August 2008 for information about the leak. The USS Houston had last called at Singapore nearly two years ago from 22nd to 26th September 2006. We also went through our own monitoring records for the period when the USS Houston was berthed in Singapore at Changi Naval Base.

On 7th August 2008, the US informed MINDEF that the USS Houston had been leaking trace amounts of radioactive water since June 2006. This suggested that the USS Houston could have been leaking during her port call at Changi Naval Base in September 2006. During this period, the USS Houston had also called on other ports in the region, besides Singapore, including Japan, Malaysia, and Guam.

The US informed us that after the initial detection of the leak and the report that the submarine had been leaking while in port in Japan, the United States Navy

Column: 2970

had conducted more tests to determine the extent and duration of the leak. The US informed us that through these tests, the United States Navy was able to determine that one of the USS Houston's shut valves was leaking water at a rate slightly above the United States Navy's Nuclear Propulsion Programme's stringent design specifications. The US told us that further tests by a specialised US government nuclear laboratory, Knolls Atomic Power Laboratory (KAPL), were required to determine the extent of radioactive material being leaked, as well as the duration of the leak. KAPL eventually determined that the leak could have begun as early as June 2006. The US also told us that KAPL confirmed that the trace amounts of radioactive water leaked were so low that the monitoring systems onboard the USS Houston itself could not detect the leak.

The US has assessed that the cumulative amount of radioactivity that could have been leaked in Changi Naval Base was approximately 0.095 micro curies. To put things into perspective, the US indicated that this was less than the amount of radioactivity found in a common smoke detector, and would not have any adverse effect on human health, marine life or the environment.

Apart from the information provided to us by the US, MINDEF also has its own independent monitoring system. Since February 2003, MINDEF has put in place a round-the-clock Integrated Environment Monitoring System (IEMS) at Changi Naval Base. The IEMS takes readings of air quality, and water and sea-bed samples to determine the normal background environmental radiation level, and to detect whether there has been any abnormal level of radiation which may be of safety concern. The safety limits are set by our National Environment Agency's Centre of Radiation Protection and Nuclear Science.

Column: 2971

While the USS Houston was in Singapore in September 2006, the IEMS did not show any abnormal readings. After the news of the USS Houston's leak in Japan broke, a review of the IEMS data for the period of the USS Houston's visit also confirmed that there were no abnormal readings recorded. Our IEMS has therefore provided independent verification that public safety was not compromised at any point during the USS Houston's port call in Singapore in September 2006. Our Defence Science Organisation scientists have also assessed that based on the figures provided by the United States Navy, the potential exposure is 100,000 times less than exposure from natural radiation in a year.

With the assurances from the US, verification from the data collected from our own monitoring system and our own experts' assessments, I am confident that there was no adverse impact on public health, marine life or the environment as a result of the USS Houston's port call in Singapore in September 2006, and that the safety of Singaporeans was not compromised by the reported leak.

Mr Michael Palmer (Pasir Ris-Punggol): Mr Speaker, Sir, just three supplementary questions. First, what steps are we taking, going forward, to make sure that this does not happen again, because the next time it may not be a trace leak? Second, why is it that nothing abnormal was picked up by MINDEF's monitoring system even though there were leaks? Is that because it was so low? Third, are we sure that it will pick up any leaks that may occur in the future and has the US assured that none of their other nuclear-powered ships are leaking?

Mr Teo Chee Hean: Mr Speaker, Sir, we continue to engage the United States

Column: 2972

Navy to understand and to ensure that their ships which call in Singapore, particularly their nuclear-powered vessels, are safe. The US Navy has assured us that their nuclear-powered vessels are designed to extremely stringent standards and these standards include being able to operate in a combat shock environment. They tell us that the nuclear material is contained in four ways. First of all, in the fuel itself, so that radioactive material is not likely to escape from the fuel rods. There is the containment vessel, the compartment in which the reactor is mounted, and the hull of the ship itself, be it the submarine or surface vessel. So within these four very strongly built containment systems, the US Navy's assessment is that it is highly unlikely that there will be a leak of radioactive material. That is also our own assessment. The US Navy has operated nuclear-powered vessels for 50 years without incident.

Why has the IEMS not detected radioactive activity in spite of there having been a leak? The reason is that the radioactive leak was so low that it was below the threshold which the IEMS was designed to detect. The IEMS threshold is set at the safety level which has been designed and determined by the National Environment Agency. In fact, the USS Houston, which itself has a radiation detection system, did not detect such a leak. It is my belief that for the submariners themselves, because they are living next to the reactor 24 hours a day, they are the ones who are most keenly interested in whether or not there are radioactive leaks from the reactor. Their own radiation detector did not pick up such a leak. And that is the main reason why the IEMS did not pick up anything.

We will continue to look at the IEMS system to make sure that it remains up-to-date and that it continues to be able to perform the mission that we have set out for it.