As the most recent round of negotiations between Iran and the P5+1 (China, France, Germany, Russia, the United Kingdom and the United States) wound down on November 10, an unlikely player emerged center-stage in the press coverage of the negotiations: the Arak heavy water reactor. The Arak reactor represents a potential second pathway for Iran to produce fissile material for nuclear weapons. Heavy water reactors are particularly well-suited for plutonium production, which must be separated from the radioactive spent fuel of the reactor if it is to be used for weapons. For this reason, the...