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U.S. May Have Trouble Gauging North Korean Nuclear Test U.S. May Have Trouble Gauging North Korean Nuclear Test
(about 4 hours later)
SEOUL, South Korea — Even if North Korea follows through with its threat to conduct a third nuclear test, Washington and its allies will have difficulty determining whether the device detonated is made of plutonium or uranium, a prominent American nuclear scientist and South Korean officials said on Tuesday.SEOUL, South Korea — Even if North Korea follows through with its threat to conduct a third nuclear test, Washington and its allies will have difficulty determining whether the device detonated is made of plutonium or uranium, a prominent American nuclear scientist and South Korean officials said on Tuesday.
Whether North Korea will set off a uranium bomb is a question high on the minds of policy makers and analysts in the region. A failure to answer it would complicate their efforts to assess North Korea’s nuclear weapons capabilities. Whether North Korea will set off a uranium bomb is a question high on the minds of policy makers and analysts in Northeast Asia. A failure to answer it would complicate their efforts to assess North Korea’s nuclear weapons capabilities.
Until a few years ago, North Korea’s atomic bomb fuel had been believed to be composed solely of plutonium gleaned from its small nuclear reactor in Yongbyon, north of the capital, Pyongyang. That reactor was partially dismantled in 2008 and remains offline after yielding enough plutonium for half a dozen bombs, according to American estimates. Until a new reactor North Korea is building in Yongbyon goes online, its plutonium stockpile is limited.Until a few years ago, North Korea’s atomic bomb fuel had been believed to be composed solely of plutonium gleaned from its small nuclear reactor in Yongbyon, north of the capital, Pyongyang. That reactor was partially dismantled in 2008 and remains offline after yielding enough plutonium for half a dozen bombs, according to American estimates. Until a new reactor North Korea is building in Yongbyon goes online, its plutonium stockpile is limited.
A uranium detonation, however, would indicate that North Korea might be well on its way to substantially expanding its nuclear arsenal through uranium enrichment, a harder-to-detect means of making bomb fuel. That would also make the North’s nuclear program more menacing, its government probably more recalcitrant and its neighbors more anxious, as seen in South Korea’s recent decision to extend the range of its missiles.A uranium detonation, however, would indicate that North Korea might be well on its way to substantially expanding its nuclear arsenal through uranium enrichment, a harder-to-detect means of making bomb fuel. That would also make the North’s nuclear program more menacing, its government probably more recalcitrant and its neighbors more anxious, as seen in South Korea’s recent decision to extend the range of its missiles.
Ever since North Korea announced late last month that it would conduct a new nuclear test, officials and analysts in the region have suspected that North Korea might soon detonate a uranium device. Two earlier tests, in 2006 and 2009, were believed to have used plutonium. Ever since North Korea announced late last month that it would conduct a new nuclear test, officials and analysts in the region have suspected that North Korea would soon detonate a uranium device. Two earlier tests, in 2006 and 2009, were believed to have used plutonium; both were conducted in tunnels at its main underground nuclear test site, Punggye-ri.
But to find out which type of bomb is used, “you have to be very lucky,” said Siegfried S. Hecker, a former director of the Los Alamos National Laboratory in New Mexico and now a professor at Stanford University in California. He was speaking on the sidelines of a forum organized by the South Korean news agency Yonhap and Stanford’s Shorenstein Asia-Pacific Research Center. But to find out which type of bomb is used, “you have to be very lucky,” said Siegfried S. Hecker, a former director of the Los Alamos National Laboratory in New Mexico and now a professor at Stanford University in California. He was speaking on the sidelines of a forum organized by the South Korean news agency Yonhap and the Shorenstein Asia-Pacific Research Center at Stanford.
While scientists can determine the size of the explosion from its seismic signals, differentiating between a plutonium bomb and a highly enriched uranium bomb requires the quick detection and analysis of the different types of xenon gases produced in an atomic explosion. While scientists can determine the size of the explosion from its seismic signals, differentiating between a plutonium bomb and a highly enriched uranium bomb requires quick detection and analysis of the different types of xenon gases produced in an atomic explosion.
“The problem with xenon gases is that 10 to 20 hours after the detonation, it gets extremely difficult to tell their ratio difference between a plutonium and atomic bomb,” said a nuclear scientist affiliated with the South Korean military, speaking on the condition of anonymity because he was not allowed to talk to reporters on the record. “Since North Korea conducts its nuclear tests underground, it takes two to four days for the gases to get out, if they do at all. By then, it would be too late to tell the difference.”“The problem with xenon gases is that 10 to 20 hours after the detonation, it gets extremely difficult to tell their ratio difference between a plutonium and atomic bomb,” said a nuclear scientist affiliated with the South Korean military, speaking on the condition of anonymity because he was not allowed to talk to reporters on the record. “Since North Korea conducts its nuclear tests underground, it takes two to four days for the gases to get out, if they do at all. By then, it would be too late to tell the difference.”
Dr. Hecker shared the concern.Dr. Hecker shared the concern.
“If a next test is well contained, then we may learn nothing about the device detonated,” he said in an article posted on the Web site of Foreign Policy magazine on Tuesday. “However, one of the risks Pyongyang takes in trying to demonstrate a test at a higher level is that they may produce fissures that allow radioactive seepage, or possibly cause a major blowout from the tunnel.”“If a next test is well contained, then we may learn nothing about the device detonated,” he said in an article posted on the Web site of Foreign Policy magazine on Tuesday. “However, one of the risks Pyongyang takes in trying to demonstrate a test at a higher level is that they may produce fissures that allow radioactive seepage, or possibly cause a major blowout from the tunnel.”
In the 2006 test, American officials said they relied on offshore airborne monitors and radiological monitoring stations around the world to detect leaking gases, but without specifying whether it was a plutonium or uranium device. In the 2009 test, when the tunnel used at the time was believed to have been sealed, there was no report of leaked gases. American officials said they relied on offshore airborne monitors and radiological monitoring stations around the world to detect leaking gases in the 2006 test, but did not specify whether it was a plutonium or uranium device. In the 2009 test, when the tunnel used at the time was believed to have been sealed, there was no report of leaked gases.
After the United Nations Security Council voted on Jan. 22 to tighten sanctions against North Korea as punishment for its Dec. 12 rocket launching, the North vowed to expand its nuclear program “both quantitatively and qualitatively” and conduct a third nuclear test at a “higher level.”After the United Nations Security Council voted on Jan. 22 to tighten sanctions against North Korea as punishment for its Dec. 12 rocket launching, the North vowed to expand its nuclear program “both quantitatively and qualitatively” and conduct a third nuclear test at a “higher level.”
After years of denial, North Korea revealed a modern centrifuge facility to Dr. Hecker, who was visiting its Yongbyon nuclear complex in 2010. He said he believed that in addition to the facility made public, North Korea must have a hidden facility. A former U.S. defense secretary, William J. Perry, speaking during the forum in Seoul on Tuesday, said there were “at least two” uranium-enrichment facilities in the North. Dr. Hecker visited the North’s Yongbyon nuclear complex in 2010, and after years of denying its existence, North Korea revealed to him a uranium enrichment facility. He said he believed that North Korea must have another such facility, still hidden. A former United States defense secretary, William J. Perry, speaking during the forum in Seoul on Tuesday, said there were “at least two” uranium enrichment facilities in the North.
Unlike a plutonium program, which involves a highly visible nuclear reactor, centrifuge plants can be easily hidden in North Korea’s estimated 8,000 underground military installations, South Korean military officials said.Unlike a plutonium program, which involves a highly visible nuclear reactor, centrifuge plants can be easily hidden in North Korea’s estimated 8,000 underground military installations, South Korean military officials said.
Another possibility is that North Korea could detonate two or more nuclear devices at the same time, Lee Myung-bak, the South Korean president, told the South Korean daily Chosun Ilbo in an interview published Tuesday.Another possibility is that North Korea could detonate two or more nuclear devices at the same time, Lee Myung-bak, the South Korean president, told the South Korean daily Chosun Ilbo in an interview published Tuesday.
The North Koreans have been active around two of the three known portals to underground tunnels in their Punggye-ri nuclear test site in northeastern North Korea, David Albright and Robert Avagyan said in an analysis of recent satellite imagery posted on the Web site of the Institute for Science and International Security on Monday. The North Koreans have been active around two of the three known portals to underground tunnels at Punggye-ri, in northeastern North Korea, David Albright and Robert Avagyan said in an analysis of recent satellite imagery posted on the Web site of the Institute for Science and International Security on Monday.
The North’s two previous bomb tests were considered less than successful, and it needed more tests for information for miniaturizing bombs to mount on its missiles, analysts said. The North’s two previous bomb tests were considered less than successful, and it needed to conduct more tests for information on miniaturizing bombs to mount on its missiles, analysts said.
“By a ‘nuclear test of higher level,’ the North Koreans meant their efforts to miniaturize their nuclear devices,” Mr. Lee told Chosun. “They become a real threat if they send such miniaturized nuclear weapons to Iran or mount them on intercontinental ballistic missiles.”“By a ‘nuclear test of higher level,’ the North Koreans meant their efforts to miniaturize their nuclear devices,” Mr. Lee told Chosun. “They become a real threat if they send such miniaturized nuclear weapons to Iran or mount them on intercontinental ballistic missiles.”