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North Korean Explosion Fuel Concluded to Be Homemade

By Thom Shanker 
and David E. Sanger


American intelligence agencies have concluded that North Korea’s test explosion last week was powered by plutonium that North Korea harvested from its small nuclear reactor, according to officials who have reviewed the results of atmospheric sampling since the blast.

As administration and intelligence officials watched for indications that the North might be preparing a second test, Secretary of State Condoleezza Rice warned North Korea on Monday that it risked even further isolation if took such a provocative action.

The intelligence agencies’ finding that the weapon was based on plutonium strongly suggested that the country’s second, secret path to a bomb — based on uranium and provided to North Korea by Pakistan’s former nuclear head — is not yet ready.

Nuclear experts said the fact the bomb was made with plutonium was important because it suggested that North Korea likely only has one nuclear program mature enough to produce weapons.

“This is good news because we have a reasonably good idea of how much plutonium they have made,” said Siegfried S. Hecker, the former head of the Los Alamos National Laboratory and now a visiting professor at Stanford University. Hecker, who has visited North Korea and is one of the few foreigners to have seen parts of the country’s nuclear infrastructure, said that it was his guess that “they tried to test a reasonably sophisticated device, and they had trouble imploding it properly.”

The supply of plutonium materials is known from the days when international inspectors kept tabs on the fuel rods in the North’s reactor, and intelligence analysts estimate North Korea has enough material to make six to 10 bombs.

Politically, the results of the test may revive last week’s finger-pointing about who is more responsible for the Korean test, Bill Clinton or George Bush.

Clinton negotiated a deal that froze the production and weaponization of North Korea’s plutonium, but intelligence agencies later determined that North Korea began its secret uranium program under his watch. The plutonium that North Korea exploded was produced, according to intelligence estimates, either during the administration of the first President Bush or after 2003, when the North Koreans threw out international inspectors and began reprocessing spent nuclear fuel the inspectors had kept under seal.

Unlike the Clinton administration in 1994, the current Bush administration chose not to threaten to destroy North Korea’s fuel and nuclear reprocessing facilities if they attempted to make weapons.

That threat in 1994, which resulted in the weapons freeze, was made by William Perry, then Defense Secretary. In an interview on Monday, Perry said: “There was a brief window to catch this plutonium before it was made into bomb fuel. It’s gone. It’s out of the barn now.”

After a week of some lingering doubt about whether the test had indeed been a nuclear detonation, the office of John D. Negroponte, director of national intelligence, confirmed that much in a statement issued on Monday.