Fears of a possibly nuclear-armed Iran took center stage early in Thursday night 's vice presidential debate between incumbent Democrat Joe Biden and his Republican challenger , Paul Ryan . `` When Barack Obama was elected , they had enough fissile material , nuclear material , to make one bomb . Now they have enough to make five , '' Ryan said . `` They 're racing toward a nuclear weapon . They 're four years closer toward a nuclear weapons capability . '' The Wisconsin congressman said Iran 's progress has sped along `` because this administration has no credibility on this issue . '' Biden hit back by criticizing what he called `` bluster '' and `` loose talk '' about the issue , saying international sanctions are crippling the Iranian economy and that U.S. and Israeli officials believe Iran is `` a good way away '' from getting the bomb . Fact Check : What about security in Benghazi ? The facts : . Iran has greatly expanded its ability to produce nuclear fuel in the past four years , revealing a second uranium enrichment plant in 2009 and continuing to defy U.N. demands that it halt work until questions about its intentions are resolved . A bit of tech talk here : About three-quarters of 1 % of naturally occurring uranium is uranium-235 , the radioactive isotope used to produce a nuclear reaction . To produce fuel for nuclear power plants , that concentration has to be increased to 3 to 5 % , while research reactors use fuel with a U-235 concentration of about 20 % . To make a nuclear weapon , that concentration has to be increased to more than 90 % . As of May , Iran had produced about 6,200 kilograms ( 13,640 pounds ) of power plant-grade uranium and 146 kilograms ( 320 pounds ) of fuel at 20 % concentration , according to the International Atomic Energy Agency , the U.N. nuclear watchdog . Based on those figures , the Washington-based Institute for Science and International Security , estimated that Iran could produce enough weapons-grade uranium for five nuclear bombs . The organization , led by former U.N. weapons inspector David Albright , says Iran could build a crude bomb with 20-25 kg ( 44-55 pounds ) of highly enriched uranium . However , it would take Iran more than two months to produce that amount if it started with 20 % -grade uranium , and `` several months '' to make enough for a bomb using low-enriched uranium . That would give the world community enough time to detect the operation and organize a response , ISIS noted in June . And there 's more to building a bomb than just having the uranium , as Biden noted . ISIS estimated last week , that Iran would need `` many additional months '' to develop a device that could be tested `` and even longer to make a reliable warhead for a ballistic missile . '' Fact Check : Wind power , electric cars and the stimulus . Iran has denied conducting any nuclear weapons research , insisting its nuclear program is for civilian purposes . The IAEA has verified that Iran has not diverted any of its declared uranium stock , but cautions that Iran `` is not providing the necessary cooperation '' to verify that all nuclear work is peaceful . Israel has accused Iran of working toward a nuclear weapon , raising concerns that it could launch a preventive attack on Iranian nuclear facilities . Israel is believed to have its own nuclear arsenal , but has never disclosed whether it has the bomb -- and Iran has accused Israel and the United States of trying to sabotage its nuclear facilities . As for the United States , American intelligence agencies believe Iran `` is keeping open the option to develop nuclear weapons '' but has not made the decision to build a bomb , Director of National Intelligence James Clapper told a Senate committee in January . Conclusion : According to at least one widely circulated estimate , Iran could produce enough uranium for five bombs , as Ryan says . But the same estimate notes that it would draw attention if it did so , and that 's only part of the work necessary to make a weapon . Complete coverage of CNN 's Fact Checks .
Ryan says Iran is `` racing '' toward the bomb . Biden says Tehran is `` a good way away '' from having nuclear weapons.