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Comparisons Don’t Support North Korea’s Claims of a Hydrogen Bomb, Experts Say Comparisons Don’t Support North Korea’s Claims of a Hydrogen Bomb, Experts Say
(about 17 hours later)
Military experts said comparisons of underground nuclear tests over the past several decades suggested that the North Koreans were exaggerating their claim on Wednesday to have successfully detonated their first hydrogen bomb.Military experts said comparisons of underground nuclear tests over the past several decades suggested that the North Koreans were exaggerating their claim on Wednesday to have successfully detonated their first hydrogen bomb.
In 1971, when the United States detonated an H-bomb deep beneath the Alaskan island of Amchitka, the colossal upheaval of earth that it caused was typical for a class of weapons whose destructive power is roughly a thousand times greater than the atom bomb that leveled Hiroshima in 1945.In 1971, when the United States detonated an H-bomb deep beneath the Alaskan island of Amchitka, the colossal upheaval of earth that it caused was typical for a class of weapons whose destructive power is roughly a thousand times greater than the atom bomb that leveled Hiroshima in 1945.
The H-bomb was detonated more than a mile down. Gargantuan shock waves radiated outward, throwing solid rock and dense earth into bizarre states of fluidity for many miles.The H-bomb was detonated more than a mile down. Gargantuan shock waves radiated outward, throwing solid rock and dense earth into bizarre states of fluidity for many miles.
A video of the Alaskan tundra shows hills rising and falling as the giant undulations raced outward. Close-up views show the ground waves throwing rocks and other objects into the air, tearing apart test-site structures, sending cliffs tumbling into the sea and opening wide cracks in roads.A video of the Alaskan tundra shows hills rising and falling as the giant undulations raced outward. Close-up views show the ground waves throwing rocks and other objects into the air, tearing apart test-site structures, sending cliffs tumbling into the sea and opening wide cracks in roads.
The magnitude of the American blast was 6.8. In contrast, South Korea estimated that the bomb detonated on Wednesday had a magnitude of 4.8 — on the logarithmic scale of earthquake magnitude, an enormous drop in explosive power.The magnitude of the American blast was 6.8. In contrast, South Korea estimated that the bomb detonated on Wednesday had a magnitude of 4.8 — on the logarithmic scale of earthquake magnitude, an enormous drop in explosive power.
Kenneth W. Ford, an American physicist who worked on the nation’s first hydrogen bomb and last year published an H-bomb memoir, called the North Korean claim highly suspect. “How could a thermonuclear blast trigger such a weak seismic signal?” he said. “I agree with the suspicion that it was not a true H-bomb.”Kenneth W. Ford, an American physicist who worked on the nation’s first hydrogen bomb and last year published an H-bomb memoir, called the North Korean claim highly suspect. “How could a thermonuclear blast trigger such a weak seismic signal?” he said. “I agree with the suspicion that it was not a true H-bomb.”
The club of nations that possess thermonuclear weapons has only five known members: the United States, Russia, Britain, France and China. All are permanent members of the United Nations Security Council.The club of nations that possess thermonuclear weapons has only five known members: the United States, Russia, Britain, France and China. All are permanent members of the United Nations Security Council.
David Albright, president of the Institute for Science and International Security, a Washington research group, said North Korea “may be bluffing” in making very large claims for what was actually a small atom bomb. “This possibility,” he said, “should be carefully considered.”David Albright, president of the Institute for Science and International Security, a Washington research group, said North Korea “may be bluffing” in making very large claims for what was actually a small atom bomb. “This possibility,” he said, “should be carefully considered.”
South Korean experts put the blast’s energy as equivalent to six kilotons of high explosives. In contrast, the atomic bomb dropped on Hiroshima was nearly three times as powerful, with a force of about 15 kilotons.South Korean experts put the blast’s energy as equivalent to six kilotons of high explosives. In contrast, the atomic bomb dropped on Hiroshima was nearly three times as powerful, with a force of about 15 kilotons.
Many nuclear experts, including Dr. Kim, Dr. Ford and Mr. Albright, suggested that the North Korean test might have involved putting a tiny amount of tritium, or heavy hydrogen, into the core of an atom bomb. Such a technique is known as boosting. Many nuclear experts, including Dr. Ford and Mr. Albright, suggested that the North Korean test might have involved putting a tiny amount of tritium, or heavy hydrogen, into the core of an atom bomb. Such a technique is known as boosting.
But such a boosted device, by definition, is not a true H-bomb, even though the added thermonuclear reactions can modestly increase its destructive power.But such a boosted device, by definition, is not a true H-bomb, even though the added thermonuclear reactions can modestly increase its destructive power.
Philip E. Coyle III, a nuclear expert who directed the Alaskan H-bomb test of November 1971, said the seismic signature of the North Korean test was “low enough so that it will be difficult to tell if the device was boosted, thermonuclear, just fission or whatever.”Philip E. Coyle III, a nuclear expert who directed the Alaskan H-bomb test of November 1971, said the seismic signature of the North Korean test was “low enough so that it will be difficult to tell if the device was boosted, thermonuclear, just fission or whatever.”
The world’s largest and most sensitive network meant to detect nuclear blasts, run out of Vienna by the United Nations, uses hundreds of global sensors to detect underground shock waves, track undersea explosions, sniff the air for telltale radioactivity and listen for loud sounds in the atmosphere.The world’s largest and most sensitive network meant to detect nuclear blasts, run out of Vienna by the United Nations, uses hundreds of global sensors to detect underground shock waves, track undersea explosions, sniff the air for telltale radioactivity and listen for loud sounds in the atmosphere.
The array is designed to detect nuclear blasts as small as one kiloton, or equal to 1,000 tons of high explosives.The array is designed to detect nuclear blasts as small as one kiloton, or equal to 1,000 tons of high explosives.
Deciphering all the signals can take days to weeks, experts say, and even then the clues might not add up to hard conclusions since the work of interpretation is often as much of an art as a science. That uncertainty goes especially to small hydrogen bombs, which seismically can be indistinguishable from atom bombs.Deciphering all the signals can take days to weeks, experts say, and even then the clues might not add up to hard conclusions since the work of interpretation is often as much of an art as a science. That uncertainty goes especially to small hydrogen bombs, which seismically can be indistinguishable from atom bombs.
Nuclear experts say ambiguity also surrounds India’s claims to have developed a true H-bomb, based on an underground test in 1998. The reported energy release of that blast was dozens of kilotons — versus the hundreds of kilotons typical of large H-bombs.Nuclear experts say ambiguity also surrounds India’s claims to have developed a true H-bomb, based on an underground test in 1998. The reported energy release of that blast was dozens of kilotons — versus the hundreds of kilotons typical of large H-bombs.
In all, India claims six nuclear tests. Pakistan also claims six tests. North Korea now claims four tests.In all, India claims six nuclear tests. Pakistan also claims six tests. North Korea now claims four tests.
In an official statement, Pyongyang asserted that its successful H-bomb test meant the nation has now “proudly joined the advanced ranks of nuclear weapons states.”In an official statement, Pyongyang asserted that its successful H-bomb test meant the nation has now “proudly joined the advanced ranks of nuclear weapons states.”