In this fifth and final segment of the series on nuclear safety, we examine Iran's facilities at Natanz and Arak, which some say could be used for weapons production.  

Iran's nuclear program includes uranium enrichment and a reactor being built that uses so-called heavy water. Both have raised strong questions and concerns among other nations regarding Iran's ultimate nuclear intentions.  

Peaceful or for war?  

Iran's nuclear program has two faces. One is the peaceful pursuit of electric power generation, while the other raises strong international suspicions that Tehran may be seeking nuclear weapons.

Iran signed the nuclear Non-Proliferation Treaty about 40 years ago, entitling it to build its new nuclear power plant at Bushehr. But the treaty also requires Iran to abide by strict rules, outlined for us by Institute for Science and International Security founder David Albright. "They agreed to not only not seek nuclear weapons, but they also agreed to inspections by the International Atomic Energy Agency.  And, more important in this case, they were caught cheating. They were hiding. They were not fulfilling their obligations to the IAEA.  And then, when they were caught, they tried to cover up." 

Enrichment facilities 

Much of Iran's reluctance about IAEA inspections has centered around a facility near the city ofthat was revealed in 2002 by an Iranian dissident group. The activities there are described by Nuclear Threat Initiative analyst Corey Hinderstein. "Natanz is a uranium enrichment facility based on the technology of uranium enrichment centrifuges. And, what this means is that there will be installed thousands of machines that spin at very high speeds that allow Iran to get the uranium atoms that are good for nuclear weapons, or good for nuclear fuel for a power plant," she explains. 

Hinderstein says Iran cannot justify its uranium enrichment program by claiming it is needed for the Bushehr nuclear power plant.  Russia provides and control's Bushehr's fuel. "At the time they started working on their centrifuge program, or their enrichment capability, they did not have a Bushehr reactor and they had no contract to build a Bushehr reactor. And so, why they were working on enrichment before they had a reactor to match to -- it is a question.? 

Hinderstein and other analysts say much of Natanz is buried under layers of earth and concrete to protect it from attack. 

Additionally, Natanz has strong air defenses. In a satellite photo, one can see what analysts describe as one of the surface-to-air missile batteries that encircle the facility. 

But attacking Natanz, or any other uranium enrichment facility, does not stop that work from proceeding. The former nuclear program inspector in Iraq, David Albright, says, "If you hit [bomb] a centrifuge plant, they still have the capability to make centrifuges -- and, they just make three to six thousand more, put them someplace else.  And so, it is really hard to bomb away a centrifuge program."

A political issue 

Many nations have strongly criticized Iran's uranium enrichment program. This opposition has been exploited by Iran's leaders for domestic politics according to another nuclear proliferation analyst, Joseph Cirincione at the Ploughshares Fund. "President Ahmadinejad has done a very good job of plucking this nationalist string here, of using this issue to prop up his otherwise unpopular regime. As long as this remains an issue of appeal to the Iranian people, you can expect government officials to keep using it,? says Cirincione. 

Natanz is not the only Iranian nuclear facility getting strong international notice and concern. 

Heavy water reactor 

Near the city of Arak, another nuclear reactor is under construction. This reactor uses so-called heavy water, also called deuterium, which has a neutron in each hydrogen atom.  Corey Hinderstein explains the significance of the Arak facility. "The result of this technology, this sort of setup, is that it produces really, really good plutonium for nuclear weapons. And, in fact, facilities almost identical to the Arak facility are in existence in Pakistan." 

Hinderstein adds that like Natanz, Arak has not been fully open to IAEA inspections.  

Many world leaders have called on Iran to fully acknowledge its nuclear activities.  Some have stated Iran will not be allowed to acquire nuclear weapons.