SEOUL, South Korea — The White House said today that initial data from its monitoring stations in Asia were “not consistent” with North Korea’s claim that the nuclear test it carried out earlier in the day was its first test of a hydrogen bomb, a far more powerful weapon than the country previously had built.
The statement by Josh Earnest, White House press secretary, came as the United Nations Security Council condemned the test after a two-hour, closed-door meeting, and after China, Britain, France, Japan and other powers indicated they would consider action against the country.
The seismic wave left by the explosion was smaller than what most experts would expect from the detonation of a true thermonuclear weapon. Some experts said it was possible the North had increased the yield of a more traditional device using tritium, a technique that often has been used in the 70-year history of nuclear weapons.
The true nature of the test might not be revealed until results are back from atmospheric testing.
Officials and analysts in South Korea cast doubt on the North’s claim, saying the seismological data from the test was more in keeping with a simpler uranium- or plutonium-based atomic device.
Lee Cheol-woo, a member of the intelligence committee of the South Korean National Assembly, said his country’s National Intelligence Service estimated the explosive yield from the test was equivalent to 6 kilotons of TNT. (The atomic bomb dropped on Hiroshima in 1945 exploded with 15 kilotons of energy.)
A hydrogen bomb would have yielded “hundreds of kilotons or, even if it is a failed test, tens of kilotons,” Lee told reporters.