What It Takes to Make a Nuclear Bomb

Iran is getting closer to creating a nuclear bomb, a new report finds. What's involved and how close are they?

THE GIST

A new report determined that Iran is getting closer to making a nuclear bomb.

Making a nuclear bomb is a complicated process with several steps.

Another big challenge is actually deploying a bomb and the report didn't assess where Iran is in doing that.

Iran is getting closer to building a nuclear bomb, according to a new report from the International Atomic Energy Agency (IAEA) released Tuesday. But how tough is it to make one? And could other nations be planning the same thing?

The IAEA report gave critics of Iran new details about their nuclear program, including evidence of computer modeling of nuclear explosions and technology to make triggers needed to detonate one.

Iran could be hoping to join the world's nuclear weapons club, which includes the United States, Great Britain, France, Russia, India, China, Pakistan, Israel and possibly North Korea. Still, making a bomb from nuclear fuel isn't simple. Experts say there are several challenges for would-be bombmakers.

The first one is getting the fuel. Naturally-occurring uranium comes in two forms, uranium 238 and uranium 235, the isotope used for making both bombs and power. But uranium 235 makes up less than 1 percent of what comes up out of the ground. That means countries have to first separate the two isotopes using a centrifuge, and then enrich the uranium 235 through a process in a nuclear reactor, according to Ivan Oelrich, a disarmament expert and Washington-based consultant.

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"Getting the material is the hard part," Oelrich said. "If you have the material, the rest of the bomb isn't easy, but you've done more than half the work."

Both bomb-making and electricity-making harness the power of the reaction that occurs when a uranium nucleus is bombarded with neutrons and then splits apart, releasing a huge amount of energy and radiation.

"What happens in a bomb in a millionth of a second you spread out in a reactor over years," Oelrich said.

The difference is that nuclear power plants use uranium that is enriched to about 3 to 5 percent, whereas bomb-making requires uranium to be enriched to 90 percent of its mass, according to Sharon Squassoni, senior fellow at the Center for Strategic and International Studies and a former U.S. State Department non-proliferation official.

"Right now Iran is almost at 20 percent (enrichment)," Squassoni said, adding that the first step of enrichment, from 3 percent to 20 percent represents the "lion's share" of the work. After that, she says, getting from 20 to 90 percent, the process is repetitive and not as hard.

Squassoni says a nuclear weapon requires about 25 kilograms (55 pounds) of highly-enriched uranium.

Scientists can also build a nuke using plutonium. As the uranium fuel is burned in a reactor, plutonium is formed.  If the nuclear waste is reprocessed, the plutonium is extracted and it can also be used to power a nuclear bomb. "But it's kind of difficult," Squassoni said.

The second hurdle after fuel is detonation. The bomb that was detonated over Hiroshima was a so-called "gun-assembled" weapon. Scientists smashed two roughly equal pieces of uranium together to start a critical mass of nuclear reactions, a reaction that generates an atomic blast.

These days most weapons are detonated by using conventional explosives to generate a blast that is focused onto the uranium. That shock wave kick-starts the reaction that produces a secondary atomic bomb blast.

The new IAEA report states that Iran has been testing computer simulations of nuclear blasts, and has also been conducting experiments on new kinds of sophisticated triggers.

"Do they have a rational civilian need for that? No," Squassoni said. "You couple that with scores of undeclared activities, clandestine facilities, and supported claims of military involvement in the program. How much more evidence does the international community need to apply the pressure for a satisfactory response from Iran?"

Oelrich disagrees. He says that Iran may not be taking a step-by-step approach to building a weapon, but rather keeping its nuclear options open as it tries to be a regional player.

"If this were a national campaign, then Iran would have a bomb right now," Oelrich said. "The question is how hard and fast are they working."

Both experts say the final challenge is delivering a bomb to its target. The new IAEA report did not address that issue. That problem may be the biggest one for rogue nations like Iran or North Korea, according to Patricia Lewis, deputy director of the James Martin Center for Nonproliferation Studies at the Monterey Institute of International Studies.

"Holding (the uranium) in place for enough iterations of a reaction is hard," said Lewis, a former United Nations disarmament official. "It's all well to understand the physics and engineering, but doing it is another thing all together. Just getting one to fit into a (missile) nose cone is not trivial."

Lewis noted that North Korea failed in its attempt to detonate nuclear weapon in 2006, a so-called "fizzle." There are other nations that have the technological capability to make a nuke, Japan, Canada or Germany, for example but not the political desire.

Others like Syria or Myanmar may not yet have the technology in place, but could be in the hunt. Still, Lewis says she's concerned about the next steps that Iran -- and the U.S. -- may take in the nuclear drama now unfolding.

"I don't know how any one knows what is going on inside Iran," Lewis said. "This is quite worrying. Iran has to spend some time explaining to the IAEA what they are doing."

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