How to Make a Bomb

Oct. 9. 2006 — -- North Korea's Central News Agency, trumpeting the country's entry into the exclusive club of nuclear powers, said, "The nuclear test was conducted with indigenous wisdom and technology."

Indigenous wisdom -- in other words, homegrown knowledge.

That's what has the rest of the world worried.

"It took the might of the entire United States, the leading nation at the time 60 years ago. But technology progresses, knowledge progresses, and even a country like North Korea can do it today," said Ashton Carter, co-director of the Preventive Defense Project, a research collaboration of Harvard's Kennedy School of Government and Stanford University.

Carter was an assistant secretary of defense in the Clinton administration.

The United States developed the first atomic bombs during World War II. Much of the research was done at Los Alamos National Laboratory in New Mexico.

Dr. Siegfried Hecker is director emeritus of Los Alamos. He is also the last Westerner to have visited North Korea's nuclear-research laboratories.

In 2004, Hecker was given rare access to North Korea's Yongbyon radiochemical laboratory, where he says the North Koreans were making plutonium metal -- the key ingredient for many types of nuclear bombs.

"So they turned to me," he said to ABC News, "and they said, 'Well, Dr. Hecker, how would you like to see our product?' And I was somewhat startled, and I said, 'You mean the plutonium?' And they said, 'Well, yes.' And so I held the plutonium, and it turns out it was reasonably heavy and it was also slightly warm."

In other words, it was probably genuine, Hecker says.

Plutonium -- an element that does not exist naturally -- is heavier than the 92 natural elements, and some of its radioactivity escapes in the form of heat.

The North Koreans created their plutonium the same way other countries have, by mining uranium that is found abundantly in the ground.