Iran’s Arak Reactor and the Plutonium Bomb

by Gregory S. Jones
If the Iranians are allowed to finish the reactor, a bomb will be a very real possibility.

The P5+1 (the five permanent U.N. Security Council members plus Germany) are set to resume negotiations with Iran regarding its nuclear program on Monday. The talks will likely focus on Iran’s centrifuge enrichment program and its ability to produce highly enriched uranium for nuclear weapons. However, Iran is also constructing a 40-megawatt “research” reactor at Arak that could provide enough plutonium for two to three nuclear weapons per year. This reactor was clearly intended to be a plutonium-production reactor as part of Iran’s structured nuclear-weapons program (which existed up until 2004) and could still be part of an ongoing effort to acquire nuclear weapons. As it is currently designed, the reactor would use heavy water as the moderator and coolant and natural uranium as fuel, producing about 11 kilograms of plutonium per year.

The obvious solution to the concerns about the Arak reactor is for it never to be completed and for its components to be destroyed. This is widely acknowledged to be the preferred solution, but, as in the case of Iran’s centrifuge enrichment program, Western “realists” have objected, saying that Iran would never agree to the reactor’s destruction.

As an alternative, it has been suggested that the heavy water could be replaced with ordinary water and the fuel of the reactor changed so as to reduce the amount of plutonium that it could produce. If, instead of natural uranium, the reactor used 3.5 percent enriched uranium, the amount of plutonium produced would be about 6 kilograms per year — enough to make one or two nuclear weapons. If the fuel were 20 percent enriched uranium, then the reactor would produce only about 1 kilogram of plutonium per year. In this latter case, however, Iran could put natural-uranium target elements into the reactor and still produce about 6 kilograms of plutonium per year.

To further decrease the amount of plutonium that could be produced by the Arak reactor, it has also been proposed to reduce its power level. The amount of plutonium that the reactor could produce is directly proportional to its power level, so if the reactor had an output of 10 megawatts instead of 40, the plutonium-production rate would be only about 1.5 kilograms, for a reactor using either 3.5 percent enriched uranium or 20 percent enriched uranium.

Even with these changes, though, there would still be significant problems. Iran could use this modified reactor to strengthen its claim that it should be allowed centrifuge enrichment; as I have written elsewhere, there are significant dangers in affirming Iran’s “right to enrich.” Additionally, Iran would still have to give up the approximately 100 metric tons of heavy water that it has already produced, and shut down and dismantle the heavy-water-production plant at Arak. Is Iran any more likely to agree to this?

It is a slippery slope when one starts to make concessions in order to get any sort of agreement with Iran. One supporter of such an agreement suggested in December that Iran’s number of centrifuges be limited to “3,000 or fewer,” yet by last month had changed its position to allow about 5,000 centrifuges.

Iran has said that it might be willing to “make some change in the design, in order to produce less plutonium.” However, it is possible that Iran might just agree to reduce the power of the reactor somewhat, while retaining it as a natural-uranium heavy-water reactor. If no substantive changes are made to the reactor’s design, Iran could easily increase the power and plutonium-production rate whenever it desired.

Undersecretary of state for political affairs Wendy Sherman has said, “ [the Iranians] do not need a heavy-water reactor at Arak in order to have a peaceful nuclear program.” The U.S. should follow through on the logic of this statement and insist that Iran never complete the reactor at Arak, and that it destroy the components for this reactor, export the 100 metric tons of heavy water that Iran has already produced, and shut down and dismantle the heavy-water-production plant at Arak. Otherwise the U.S. will be granting Iran a “plutonium option” for acquiring nuclear weapons in addition to the dangers posed by Iran’s centrifuge enrichment program.

— Gregory S. Jones is senior researcher at the Nonproliferation Policy Education Center.

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