The plutonium bomb was dropped on Nagasaki on August 9th 1945, three days after a uranium bomb had destroyed Hiroshima.
Michael Mullen, the Chairman of the US Joint Chiefs of Staff, acknowledged that Iran has enough uranium for a bomb.
The U.S. scientists who made the first uranium A-bomb, dubbed "Little Boy, " were so sure that it would work they did not bother to test it.
What did happen was that the Enola Gay, an American B-29 bomber, dropped a uranium-based atomic bomb on the Japanese city of Hiroshima.
Mark Fitzpatrick argues that if Pyongyang has perfected the highly-enriched-uranium route to a bomb, then there will be heightened concern about the potential for the proliferation of these weapons or materials.
After Qom, Iran appeared to back off a bit by agreeing in principle to ship abroad much of its uranium stock (a bomb's worth or thereabouts if sufficiently re-enriched) for reworking to provide the needed reactor fuel.
Seemingly contradicting Mullen, Defense Secretary Robert Gates claimed that there is no reason to worry about all that uranium because Iran won't have a bomb for some time, given that the uranium it possesses is not sufficiently enriched to make a weapon.
Israel assesses that Iran will have a sufficient quantity of enriched uranium to make a nuclear bomb by the end of the year.
Notably, also on Wednesday, the US-based International Institute for Strategic Studies released a report concluding that Iran will have a sufficient quantity of highly enriched uranium to make an atomic bomb in a matter of months.
Ukraine, Canada, Chile, Mexico and Kazakhstan were among those promising to dispose of bomb-usable enriched uranium or plutonium on their soil.
Officials trying to stem nuclear proliferation used to congratulate themselves that only a very few of the known incidences of trafficking involved the sort of uranium and plutonium useful for a bomb.
That move prompted Britain, France and Germany to discontinue negotiations aimed at persuading the Iranians to abandon for good their ambitions to enrich uranium and make plutonium (another potential bomb ingredient).
They underlined that their intelligence services agreed on how far the Iranians had got with their programme but Mr Netanyahu made it clear his red line was Iran getting enough depleted uranium to be able to build a bomb whereas the president's is Iran actually deciding to build the bomb and getting near to achieving it.
The United Nation's International Atomic Energy Agency continues debating whether and how to advocate sanctions against Iran for its planned uranium enrichment program that could lead to a bomb.
Iraq constructed centrifuges (which spin uranium to extract the U-235 used in a bomb) before the Gulf War so has the knowledge to do this again.
Loomis backed much of Lawrence's work, not least his uranium fission research, which led to the development of the atomic bomb.
Several times Iran postponed the resumption of uranium conversion, which can be a step towards fashioning a nuclear bomb, while Britain, France and Germany, with American support, worked on a package of economic and political incentives for Iran to give up its nuclear plan.
Representatives of the five permanent members of the UN Security Council plus Germany began a fresh round of talks with Iran over its nuclear plans, this time in Baghdad, hoping to persuade its government to agree to stop enriching its uranium to the high grade that would enable it to make a bomb.
And rather than suspend its own suspect uranium-enrichment efforts (the stuff can be used for power generation or, with further enrichment, abused for bomb-making), Iran insists it will press ahead at all speed, even though it has no nuclear reactors that need the stuff.
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