University of Arizona expert discuss the finer details and possible outcomes of the Iran nuclear deal

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Glen Johnson | State Department

U.S. Secretary of State John Kerry shakes hands with German Foreign Minister Frank-Walter Steinmeier in Vienna, Austria, on November 22, 2014, before a bilateral meeting about the status of the nuclear program negotiations between the P5+1 nations and Iranian officials.

Nuclear power can be used for good, clean energy and scientific research, or it can be used to create the most destructive force known to man. This paradoxical nature of nuclear power has many Americans concerned about the recent Iran nuclear deal.

Only 21 percent of Americans support the Iran nuclear deal, according to a recent Pew Research Center survey. High-profile opponents, ranging from congressional Republicans and GOP presidential candidates to Israelis, are loud and many. On the other hand, supporters include most congressional Democrats and many world leaders.

From the perspective of most scientists, there’s no reason for Americans to fear a nuclear Iran. Surveillance by the International Atomic Energy Agency, collecting nuclear material, building a deployable weapon and testing the weapon discretely are all difficult tasks that will ultimately prevent Iran from becoming a nuclear threat.

Harnessing nuclear power

Nuclear power requires radioactive material, such as uranium. Almost all raw uranium — 99.3 percent — is U-238. Its relative stability makes it unsuitable as fuel for nuclear power, according to Phillip Pinto, an astronomy and physics professor at the UA. Pinto has worked as a consultant for a U.S. nuclear weapons laboratory.

The other 0.7 percent of the raw uranium — U-235 — has three fewer neutrons in its nucleus, making it unstable and, therefore, ideal for nuclear power, Pinto said.

Collection of U-235 requires enrichment. Natural uranium is made gaseous when mixed with hexafluoride gas. This chemical combination is then spun at high speeds in a gas centrifuge, separating the heavier U-238 from the lighter U-235. To make fuel for nuclear power plants, raw uranium must be enriched to about 5 percent U-235. For nuclear weapons, it must be enriched to more than 80 percent.

What’s the deal?

The Iran nuclear deal prohibits Iran from developing nuclear weapons for at least 10 years. By reducing the number of working centrifuges and monitoring enrichment levels, it restricts the production of U-235. The deal encourages compliance by lifting sanctions on Iran and freeing $56 billion for the country. The International Atomic Energy Agency will enforce the treaty framework and monitor Iran’s nuclear facilities.

Since 1968, Iran and 190 other countries signed the Treaty on the Non-Proliferation of Nuclear Weapons. By agreeing to this treaty, Iran is legally allowed to develop nuclear power for peaceful purposes, which it has done.

But opponents of the deal argue that Iran might violate the treaty and easily develop nuclear weapons.

Supporters of the deal are also worried. But they think that the treaty will make violations less likely and easier to detect. Building a deployable weapon is difficult with such restrictions. They believe that the treaty will buy time for the world to work with Iran and ensure peaceful nuclear development in the future.

“There will be at least the possibility of Iran opening up to the world and changing the way they do things” said Timothy Axelrod, UA emeritus astronomer who also used to work for the Lawrence Livermore National Laboratory.

Can Iran keep a secret?

Under this treaty, Iran would have the tools to enrich uranium to levels needed to create a bomb. For this reason, containing and monitoring the enrichment process lies at the heart of all efforts to prevent nuclear proliferation.

For commercial nuclear energy, radioactive uranium is concentrated to levels between 3 and 5 percent. But to build a bomb, enrichment must exceed 80 percent, Pinto said.

The process requires thousands of centrifuges to concentrate U-235 to significant levels.

According to Pinto, to control the amount of enriched uranium, the deal reduces the number of centrifuges in Iran’s possession from about 19,000 to about 6,000.

The International Atomic Energy Agency will monitor Iran’s nuclear facilities more strictly than any previous non-proliferation agreement, said Faten Ghosn, UA associate professor of government and public health policy.

But can it really go BOOM?

If Iran decided to cheat on the treaty and produced weapon-grade uranium, the next step would be to build a deployable weapon.

Building a useful weapon on the first try is difficult, Pinto said. “You and I and six of our best friends could probably figure out how to build a car that drove, but trying to build a Maserati on the first go without ever having built another kind of car — no way.”

Pinto outlined two potential bomb designs. The first calls for a grapefruit-sized ball of U-235. This amount is subcritical, meaning it can’t go “Bang!” But squeezing the sphere by using uniform explosions pushes the atoms closer together and causes it to go supercritical … BOOM! This technique is difficult. If compressed unevenly, the U-235 will squish out like toothpaste in your hand, Pinto said. This was the design for the bomb used over Nagasaki — although it used plutonium.

The other method uses a slightly larger sphere of U-235 but removes a central cylinder. Then, a naval cannon shoots the cylinder back in place, making the sphere supercritical. This method is easier, but the bulkiness of the design makes harder to transport and more expensive to build. This was the design used for the bomb dropped on Hiroshima.

A dead giveaway

These designs are sophisticated but without a testing program or access to classified testing data from other countries, it’s impossible for Iran to build militarily-grade weapons, Pinto said.

It is illegal for Iran to have a nuclear testing program. But if Iran decided to test a weapon, it would be to ensure that the nuclear weapon is deliverable. The delivery system must be light and compact to fit on a missile, rugged enough to survive launch and reliable enough to ensure that it will explode once reaching the target, according to Pinto.

But any above-ground testing would be obvious. Underground tests are also easily detected. Seismic detectors all over the world can differentiate the patterns created by nuclear bombs from those of earthquakes, Axelrod said.

Buying time

Overall, the material required for a nuclear bomb is difficult to produce, especially with surveillance by the International Atomic Energy Agency. Even if Iran somehow produced enough enriched uranium, designing the bomb and reliably detonating it is still a difficult task.

“The Iran agreement, if upheld, does achieve the nonproliferation goals in buying at least another decade to seek other solutions.” Pinto said. “But it’s only a start. Making good use of this time to find such solutions is a difficult task at hand.”

Atoms for Peace

The United States actually introduced Iran to nuclear technologies during its Atoms for Peace program, which began in the 1950s under President Eisenhower. The goal was to spread nuclear technology and education to other countries in the hopes of creating a world that understood the danger of nuclear weapons, as well as the promise of nuclear energy.

Today, the Iran nuclear program, which the United States fostered, is almost 60 years old.


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