How to Make a Bomb

Oct. 9. 2006 —, 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.

Heavy and 'Slightly Warm'

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.

Making Plutonium

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

They used the uranium to make the fuel rods that power a five-megawatt reactor at Yongbyon. The process generates heat, electricity -- and also plutonium.

"For the reactor design that the North Koreans have," Hecker said, "we believe that they can make about 6 kilograms of plutonium per year."

That's enough plutonium, he says, for one bomb to two bombs annually.

To get this material in the form needed for bombs, the used fuel rods are removed from the reactor, cooled in a pool of water, and then treated chemically to extract the plutonium.

The metal plutonium forms the core of the bomb, surrounded by high explosives and detonators. As the explosives are triggered, the plutonium is driven inward.

A fission reaction follows. The nucleus of the plutonium atom is split, releasing subatomic particles in a chain reaction that splits other plutonium atoms.

The result is a nuclear explosion -- difficult to accomplish, but as the North Koreans appear to have demonstrated, far from impossible.

"A primitive, simple bomb of the nature of just squeezing a plutonium ball," Hecker said, "is sufficiently straightforward for somebody as technologically sophisticated as North Korea."

"One of the alarming things about a development like this," said Carter of Harvard's Kennedy School, "is that once plutonium, which doesn't exist in nature, is made, it has a half-life of 24,400 years, which means that this material, which [North Korean leader] Kim Jong Il and his government has made, will pose a danger to humanity for many, many, many generations."