U.S. doubts Korean test was nuclear

U.S. intelligence agencies say, based on preliminary indications, that North Korea did not produce its first nuclear blast yesterday.

U.S. officials, speaking on the condition of anonymity, said that seismic readings show that the conventional high explosives used to create a chain reaction in a plutonium-based device went off, but that the blast’s readings were shy of a typical nuclear detonation.

“We’re still evaluating the data, and as more data comes in, we hope to develop a clearer picture,” said one official familiar with intelligence reports.

“There was a seismic event that registered about 4 on the Richter scale, but it still isn’t clear if it was a nuclear test. You can get that kind of seismic reading from high explosives.”

The underground explosion, which Pyongyang dubbed a historic nuclear test, is thought to have been the equivalent of several hundred tons of TNT, far short of the several thousand tons of TNT, or kilotons, that are signs of a nuclear blast, the official said.

The official said that so far, “it appears there was more fizz than pop.”

A successful nuclear detonation requires a properly timed and triggered conventional blast that splits atoms, setting off the nuclear chain reaction that produces the massive explosions associated with atomic bombs.

White House spokesman Tony Snow said assessing the validity of North Korea’s claim of a successful nuclear test could take several days.

“We need to find out precisely what it is that took place yesterday, and that is something that’s going to take awhile for the scientists and others to work through,” Mr. Snow said.

“Nobody could give me with any precision how long it will take until they can say with certainty what happened.”

Nuclear bombs make big waves, with clear signatures that make them fairly easy to detect, analyze and confirm that they were caused by splitting atoms. But smaller blasts — as North Korea’s appears to have been — are trickier to break down, scientists told the Associated Press.

“It takes days, dozens of lab hours, to evaluate results. Now we can have only a rough estimate,” said Russian nuclear physicist Vladimir Orlov of the Moscow-based Center for Policy Studies in Russia, a nonproliferation think tank.

Elements of the blast were detected by U.S. and allied sensors as it was set off in an underground tunnel in the north-central part of North Korea. U.S. intelligence agencies have been monitoring several tunnels thought to be nuclear test facilities and have not ruled out Pyongyang’s conducting another test.

U.S. officials said the test was timed to coincide with several anniversaries in North Korea, including the end of mourning for the death of North Korean leader Kim Jong-il’s father, Kim Il-sung. The test was thought to have been linked to the commemoration.

North Korea’s military thinks that joining the world’s seven other acknowledged nuclear powers is key to preserving the power of the communist regime.

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